I have some lemon and lime seeds. What kind of advice can you give me on starting them?
chaz-
I have some lemon and lime seeds. What kind of advice can you give me on starting them?
chaz-
I have taken several citrus courses in the past month. I got hooked on oranges. One of the courses said to take the citrus seed from the fruit (fresh)(if you can't plant immediately, put in a plastic bag with some moisture in the refrigerator and wait until you can) and plant in soil, keep moist and warm at a minimum of 65 degrees F. Putting them in an oven (an off oven ) with the door works. I planted:
In 30 days, the Nu Clementine, Pong Koa and Changsha all germinated and are in bright light in a window sill (about 2 1/2 -3 inches tall). They are photosynthesizing and the leaves are getting bigger.
TANGERINE, MANDARIN, TANGELO, SATSUMA
Citrus are evergreen trees and shrubs, with glossy green leaves year-round, and many also offer fragrant blooms. Plant them in an area that receives at least =BD day of sun; citrus do not require full sun as most other fruit trees do. The size of the trees varies depending on the variety, from medium shrub to large tree. They do not need pollinators. Pay close attention to the freeze tolerance of each variety, for freeze tolerance varies. Citrus cannot tolerate standing water. =
Satsumas are a variety of tangerine. Buy early, mid and late season varieties to have months of ripe fruit harvests. All Satsumas are cold tolerant to at least 26 degrees and perhaps more. They grow in a weeping posture and can become about 10' tall and 10' wide. =
J
chaz wrote:
Hi! I read the responses to your post and am I baffled! I would swear that I was taught that you CAN grow the seeds but the plant/tree won't bear, and that it had to be grafted to a base tree in order to have the graft bear. Tell me I'm wrong? Tell me I'm right?
Mike Picture Rocks, AZ
Mike, from the 2 courses I took, one can grow a tree from seed and it will bear fruit. One has to wait till the fruit is evaluated to see if the seed was true. Different species have different characteristics. Grafting can combine good characteristics from different plants. A lot of citrus is grown on "trifoliate rootstock" which is grafted on for its cold tolerance.
Cold Hardy Citrus As citrus trees are basically subtropical or tropical I am often asked for information regarding their cold hardiness. Most citrus will not tolerate temperatures below -2 C. For those of you who live in regions where the winter chill regularly falls below this temperature there are many preventative measures and cultural practices you can follow to grow citrus successfully.
Cold Hardy Variety Selections
Trifoliate orange is an inedible citrus used as a rootstock. It withstands the lowest temperatures of all citrus followed by kumquat, satsuma mandarin, calamondin, mandarin, orange, grapefruit, lemon, lime and citron. Considered cold hardy to about -15=B0F, its range of cultivation can be extended into zone 5 if it is planted in a sheltered location and perhaps given some extra protection. Grapefruit, lemon, lime and citron being cold sensitive. Satsuma and kumquats are the most prominent of the cold hardy citrus.
Cold Hardy Sweet Oranges Hamlin and Navel Oranges are the most cold tolerant of the oranges. If on trifoliate rootstock they exhibit the maximum cold-hardiness, with swingle and sour orange following.
Cold Hardy Mandarins The Sunburst Mandarin is one of the most cold hardy again with maximum cold hardiness being achieved when budded onto trifoliata or sour orange rootstock. Satsuma Mandarins are the most cold-tolerant of commercial citrus, with mature dormant trees having survived temperatures as low as -9C with serious injury. The Satsuma is adapted to regions that are too cold for most other citrus. The Satsuma tree is vigorous, of medium size and very productive. Maximum cold hardiness is achieved when budded onto trifoliate rootstock.
Cold Hardy Kumquats Kumquats exceed even satsuma in terms of cold-hardiness being able to sustain temperatures as low as -12C when dormant. Trifolate is the recommended rootstock when growing kumquats in cold areas.
Planting site When planting in cooler climates give some thought to the planting site. Cold air drains downhill so higher elevations are somewhat warmer than sites at the bottom of a slope. Planting citrus near a house or other building will also offer protection. The building will act as a windbreak, forcing cold air up and over it and therefore over the citrus also. The house itself radiates considerable heat some of which will be absorbed by the plants.
Cultural Practices The soil under and around cold sensitive trees should be free of weeds and mulch. These act as insulators preventing warmth from the sun from entering the soil during the day. This warmth is stores in the soil for release during the night. A clear surface allows maximum heat absorption during the day and maximum heat radiation at night. It is also recommended that soil be kept moist as it will absorb more heat than a dry soil. Keeping your trees strong and healthy through good care will also help them to withstand cold temperatures.
Cold Protection For more information on how to protect your trees during winter visit the July 2001 newsletter. =
Fahrenheit to Celsius Conversion Chart For those of you in cooler climates you may find this chart interesting when referring to text printed in the USA. It is a simple
are any left over they can be used in salads and marinades or as an attractive garnish in desserts.
Meiwa is the sweetest kumquat and has round, sweet tender skin and a sweet tangy centre. Marumi has tiny round, very tart kumquats and nagami has oblong fruits that have a delicious sweet and tart taste. =
The plant itself is highly ornamental as it is almost always covered in either delightfully scented blossoms or bright orange fruit. It is an evergreen shrub with glossy green foliage that make fantastic additions to wreaths and floral arrangements. They are great for planting in containers and can be shaped into topiary forms.
Taxonomy, cultivars. =
The genus Citrus belongs to the Rutaceae family, sub-family Aurantoideae. This family contains many edible species, some distantly related such as White Sapote (Casimiroa edulis Llave & Lex.) and Wampee (Clausena lansium Skeels.). While Citrus is by far the most important genus, two other genera contain commercially important species: =
a. F. margarita Swing. - 'Nagami'. Also called Oval Kumquat. =
b. F. hindsiiSwing. - 'Hong Kong', or 'Hong Kong Wild'. =
c. F. japonica Swing. - 'Marumi'. Also called round kumquat. =
d. F. crassifolia Swing. - 'Meiwa', or Large Round Kumquat.
There is considerable debate over the number of species within Citrus. Some "lumpers" argue that all citrus fruits belong to one large species as they are freely graft and cross-compatible for the most part. On the other extreme, there are taxonomists that give almost each cultivar a species name, which is clearly in error. Biochemical evidence (R.W. Scora, 1988. Proc. 6th Int'l. Citrus Congress) suggests that there are probably four "basic" species of citrus fruits: =
The literature on citrus usually recognizes each economically important type as a species, yielding the following: =
A. C. limon (lemons). Includes the lemons of commerce, such as 'Lisbon' (oval to round, less pronounced stylar end) and 'Eureka' (oval, pronounced stylar end bulge). The 'Meyer' is considered to be a lemon hybrid of unknown parentage. The rough lemon C. jambhiri Tanaka, is used as rootstock, as is C. limonia or the 'Rangpur' lime. =
=B.C. aurantifolia (limes). The two main cultivars include the 'Key' (syn. =91Mexican'), and 'Tahiti' (syn. =91Persian'). The latter is someti= mes given species status as C. latifolia (Tanaka) or Citrus x tahiti (C. Campbell). C. macrophylla is a lime-like fruit used as a rootstock for lemons in California. =
C. C. aurantium (the sour orange). This is allied with limes by some, but is a very important rootstock and ornamental. Cultivars and variants include: Bittersweet, Oklawaha, Vermillion Globe, Paraguay, Trabut, var. myrtifolia (Myrtle), Bergamot, daidai (Japanese), Leaf of Chinnoto, and C. taiwanica Tanaka. =
D. C. sinensis (the sweet oranges). This is a widely accepted name for this group, containing 4 groups of cultivars: =
a. Common or round oranges. Mostly used for juice or fresh market. Cultivars include =91Valencia', =91Hamlin', =91Parson Brown', =91Pineappl= e', and =91Washington Navel'. =
b. Blood oranges. Increasing in importance in the US, these red-juiced variants contain anthocyanin in the peel and juice. =91Torocco' and =91Mo= ro' are the major cultivars. =
c. Navel oranges. This group is unique in that cultivars have a secondary ovary embedded within the usual ovary, giving a small fruitlet at the stylar end of the fruit at maturity; a fruit-within-a-fruit. =91Washington' is a major cultivar, but there are dozens. =
d. Acidless oranges. Insipidly sweet flavor; used mostly in the Mediterranean region.
The term "orange" is used rather loosely, sometimes for fruits that look like oranges but are not C. sinensis. Examples include: 'Temple' and =91Page' oranges ( tangerine hybrids), Satsuma orange (a cold hardy variant of tangerine), and Trifoliate orange (Poncirus trifoliata). =
E. C. reticulata (mandarin, satsuma, or tangerine). As stated above, this is probably a "real" species. Due to the success of breeding with these types, many cultivars and hybrids have been produced or formed naturally, some erroneously given species status. Common cultivars include: 'Dancy', Clementine' or 'Algerian', 'Owari' (a satsuma), =91Cleopatra' (common mandarin rootstock). I prefer to use C. reticulata for all tangerines, but other species names sometimes given in the literature are: X Citrofortunella mitis (Calamondin), C. unshiu (Satsuma), and C. deliciosa (Willowleaf mandarin). =
Tangerine hybrids may be more important economically than pure tangerines. The most important hybrids are tangelos (tangerine x grapefruit), tangors (tangerine x orange), and tangtangelos (tangerine x tangelo). Popular cultivars include: 'Orlando' tangelo, 'Minneola' tangelo, 'Page' orange (actually a tangtangelo), 'Robinson' tangerine (a tangtangelo). "Ugli" fruit from Jamaica is probably a chance seedling from a natural cross between reticulata and paradisi; it is now marketed under the more politically correct name "Unique" fruit. =
F. C. grandis or C. maxima (the pummelo or shaddock). This species originates from southeast Asia where it is used as grapefruit is in the US. It is much larger and thicker-peeled than grapefruit. =
=G. C. paradisi (the grapefruit). This is a relatively recent species (since 1700's) of unknown origin. It probably derives from Caribbean 'Forbidden Fruit', and was introduced to Florida from there. Cultivars include: 'Duncan', 'Marsh', 'Red-blush', and 'Thompson' (syn. 'Pink Marsh'). Hybrids include the tangelos and citrumelos; the latter are used as rootstocks.
Origin, history of cultivation. =
The center of diversity for Citrus ranges from northeastern India eastward through the Malay archipelago and south to Australia. Sweet oranges probably arose in India, the trifoliate orange and mandarin in China, and acid citrus types from Malaysia. Oranges and pummelos were mentioned in Chinese literature in 2400 BC, and later in Sanskrit writings (800 BC) lemons were mentioned. Theophrastus, the Father of Botany, gave a taxonomic description of the citron in 310 BC, classifying it with apple as Malus medica or Malus persicum. At the time of Christ and shortly thereafter, the term "citrus" arose as a mispronounciation of the Greek word for cedar cones, "Kedros". Alternatively, "citrus" may have arose through a condensation of "Callistris", the name for the sandalwood tree. =
At this time, citrus fruits were spread throughout Asia, North Africa, and Europe along trade routes. The dissemination was carried out by many cultures, indicating widespread appeal of the fruits at this time. From the first centuries BC to medievil times, orangeries and citrus "groves" were established in Europe, and cultivation became more sophisticated. Columbus, Ponce de Leon, and Juan de Grijavla carried various citrus fruits to the new world in the late 1400's early 1500's. Citrus culture proliferated in Florida in the late 1700's, when the first commercial shipments were made. Right about this time, citrus was introduced to California, although it was much later that commercial production began in the west. With the advent of large-scale irrigation projects in the 1940's, citrus culture increased greatly in western states. In Florida, citrus acreage peaked in the 1970's at about 1 million acres, but has declined since then due to freezes and Foreign competition. Today, Citrus is grown in Florida, California, Arizona, and to a limited extent in Texas and Louisiana. =
Folklore, medicinal and non-food uses. =
In addition to various food products from pulp, citrus peels are candied, fed to livestock, used to scent perfumes and soap products, and limonene oils from the peel have an insecticidal property recently discovered. Seeds are used to derive a cooking oil, and oils for plastics and soaps. Flowers and foliage are used in perfume manufacture. Nectar is converted to honey by bees, and is a profitable industry itself. =
A. Limonene oils - in peel and leaves may cause contact dermatitis. These are also "photosensitizing compounds", meaning that one may get a sunburn rash if juice gets on skin while exposed to UV light. (agent =3D furocoumarin?). =
B. Citromellal - volatile oil, has mutagenic properties. =
C. Chewing and sucking "quids" - of various tribal peoples; contain lime juice and other alkaloids. May actually cause cancer. Lime juice causes release of alkaloids from other materials. =
D. Cancer therapy - Two citrus relatives being studied for cancer therapy drugs: =
Acronychia baueri (Australia) - Acronycine =
Fagara macrophylla (Nigeria) - 8-methoxy-dihydronitidine. =
=E. Hesperidin (syn. citrin, vitamin P) - a bioflavonoid, up to 8% in dried peel. Strong vasopressor agent (reduces blood pressure). Also in rose hips and black currants, which oddly enough, are used for vitamin C sources like citrus. =
F. Sweeteners - =
G. Volatile oils - in Clausena anisata, anise-scented leaves are used to repel mosquitos in tropical Africa. In many species these oils are used to scent creams, shampoos, etc. =
H. Oral - =
I. General medical - =
=
J. Myth/folklore - Because the orange tree bears flowers and fruits at the same time, it was used in fertility rituals and weddings - the white flower symbolized virginity, and the fruits symbolized fertility. The citron is used in certain religious ceremonies by Hebrews. The word "orange" is said to have derived from the spanish word naranja; english-speaking folks applied the indefinite article to the spanish word to give "a naranja" which was corrupted to "an orange". =
The term "golden apples arose from the myth of Hercules and the golden apples. The Hesperides were Mediterranean islands, where the giant Atlas lived, and were a haven for the golden apples (probably quinces, not citron). This is because the Gods were fearful of the golden apples being stolen. Hercules managed to obtain some of the golden apples as one of his 12 tasks, despite Atlas' attempt to trick him into holding up the sky. Later Perseus visited the Hesperides to obtain some golden apples, and succeeded by turning Atlas to stone using the head of Medusa; the Atlas Mountains of northern Africa now hold up the sky, fortunately. =
There is also the myth of the Grecian Maiden Atlanta, "who was as fleet of foot as she was beautiful". To obtain her hand in marriage, her suitor had to beat her in a foot race; if he lost, he was beheaded. Hippomenes, an apparently slow but sly individual, obtained some golden apples, and during the race rolled them at her feet as she passed. She stopped to pick them up and Hippomenes scooted to the finish line the victor. =
K. Bael Fruit (Aegle marmelos Correa) - Hard-shelled fruit, used for medicinal purposes ranging from laxative, diuretic, treatment of hemorrhoids, diarrhea and dysentery (unripe fruit), purgative. Has antibiotic activity in fruits, leaves, and roots. =
L. Wampee (Clausena lansium Skeels). - Small, peel-able fruit of southeast Asia; eaten out-of-hand or made into jams, desserts, pies, etc. Vietnamese remedy for bronchitis.
Botanical description =
A. Plant: Small, spreading, evergreen trees or tall shrubs. Stems often armed with long thorns, particularly in limes or in all types when young. Current season's shoots are angular, green like the leaves. Older wood has thin, dark grey bark. Leaves are unifoliate (sometimes termed compound unifoliate to indicate the loss of lateral leaflets over time), relatively thick, ovate with acute to obtuse tips, having entire margins and a petiole wing of various width, depending on species (grapefruit =3D=
large, tangerine =3D small). Leaves contain characteristic citrus oils in=
glands ("pellucid dots") which makes them fragrant when crushed. =
B. Flowers: Fragrant flowers are solitary or in short cymes, borne axillary on current flush of growth (then termed "leafy bloom"), and also without leaves from the previous flush of growth (then termed "bouquet bloom). Usually perfect, rarely staminate by pistil abortion. Normally 5 petals and sepals; petals linear, sometimes curved lengthwise, white, waxy, and thick; sepals fused at base to form a small cup. A globular, green ovary subtends a thin straight style which terminates in a pronounced, donut-shaped stigma. Ovary with 10-14 locules in most commercial cultivars, each with potentially 4-8 seeds; axile placentation. Ovary, superior, subtended by raised nectary disc. =
C. Pollination: Most cultivars are self-fruitful through self-pollination, and some are parthenocarpic, setting and maturing commercial crops of seedless fruit without fertilization (but not necessarily without pollination). Examples of parthenocarpic cultivars are 'Marsh' grapefruit, 'Tahiti' or Persian lime, 'Hamlin' sweet orange. 'Marsh' and 'Hamlin' also develop seeds. Fruit size is related to seed # in all cultivars. Pollinizers are necessary for some tangerine (hybrid) cultivars. 'Robinson', 'Nova', and 'Page' (all tangtangelos) require pollination for adequate fruit set. =
D. Fruit: A hesperidium. The endocarp (edible portion) is divided into
10-14 sections, separated by thin septa, each containing up to 8 seeds, but usually only one seed/segment. Placentation is axile. Each segment is composed of juice vesicles ("pulp"), with long stalks attached to the outer wall, containing juice. The mesocarp is the white tissue usually adherent to the outer surface of the endocarp, except for mandarins; it is also called the albedo. The exocarp, or flavedo, is the thin, pigmented outer portion of the rind, with numerous oil glands. The seeds contain both nucellar (maternal) and multiple embryos, except in some tangerines where only 1 zygotic embryo forms. Nucellar embryony and polyembryony are characteristics exploited by nurserymen, but impede breeding efforts, since germination often exceeds 100% in seed lots, yet variation in seedling progeny is non-existent since most seedlings are clones of the maternal parent. =General Culture =
A. Soils and Climate: =
Soils: Citrus is adapted to a wide variety of soil types and conditions. Trees are grown on almost pure sand in central Florida, to organic muck in south Florida, to loamy, heavy soils in the San Joaquin valley of California. =
Climate: Citrus fruit obtains highest internal quality in subtropical humid climates. However, with irrigation, it also grows well in Mediterranean climates, like California, achieving the best external quality. In the tropics, citrus accumulates less sugar and acid, and the peel usually remains green; also, bloom is not synchronized, so several stages of maturity are present on the tree at any given time, causing some immature fruit to be harvested. =
Cold hardiness is the major limiting factor for citrus production in subtropical areas. Fruit are killed by 30 minutes @ 26-28 F; larger fruit are more cold tolerant due to greater thermal mass. Fruit freeze from the stem end to the button, and mildly frozen fruit can be salvaged for juice. Leaves and stems are killed by a few minutes at 20-28=B0 F, depending on stage of acclimation, species, and age of tissue. =
Hardiness increases in the following order: Citron < limes & lemons < grapefruit & pummelo < sweet oranges < tangerines & hybrids < sour orange < satsuma < kumquats < citranges < trifoliate orange. =
Citrus has no chilling requirement, and does not attain a truly dormant state, but becomes quiescent at temperatures below 55=B0F (13=B0C). =
Flowering is induced following emergence from quiescence, and sometimes by drought in tropical species like limes. =
Fruit quality and climate: Internal and external quality of citrus differs in humid subtropical and Mediterranean climates. Heat and humidity are the main environmental factors controlling quality. =
=
B. Propagation: Although citrus seedlings will produce fruit identical to the parent tree, due to nucellar embryony, trees are generally T-budded onto various rootstocks to avoid the long juvenile period for seedlings. Budding can be performed during most of the year, when pencil-sized, round budsticks are available, and bark slips on rootstocks. =
C. Rootstocks: Citrus was grown from seed until the mid-1800s, due to ease of propagation from seed and trueness of type. Phytophthora foot rot appeared in the Azores in 1842 and later in other parts of the world, which stimulated a search for resistant stocks. =
Common stocks: =
D. Orchard design, pruning, training: =
E. Backyard considerations. Citrus trees make excellent containerized plants for the patio or deck; kumquats, =91Meyer' lemon, and calamondin are ornamental and do very well in large pots. They must be brought indoors or covered if temperatures drop below 25=B0F. Of course, trifoliate orange is hardy throughout the southeast, and the =91Flying Dragon' cultivar makes a good rock garden or specimen tree with its striking serpentine stems. In coastal Georgia, I have successfully fruited =91Owari' satsuma, =91Changsha' tangerine, =91Sinton' and =91Thomasville' citrangequat, and a few others outdoors with temperatures=
as low as 17=B0F! =
Harvest, post-harvest. =
A. Maturity. The best indices of maturity for citrus are Brix, acid content, and the Brix/acid ratio. External color is a function of climate more than ripeness, and is a poor indicator of maturity. Legal maturity standards are enforced in major citrus regions. For limes, juice content must be at least 42% to market; diameter must be at least
1 7/8" also. =Brix sugar content (measured with hydrometer or hand refractometer); increases during maturation: =
Oranges - 7-14% =
Grapefruit - 10-12% =
Tangerines - 16-17% =
Lemons/limes - I have some lemon and lime seeds. What kind of advice can you give me= on
This describes when grafting and budding occurs:
A. Grafting for Clonal Selection and Propagation of Otherwise Difficult-to-Clone Plants =
a. Shade tree cultivars of several difficult-to-root species are routinely budded: =
Norway Maple (e.g. Acer platanoides 'Crimson King') =
Green Ash (e.g. Fraxinus pennsylvanica 'Marshall's Seedless') =
Honeylocust (e.g. Gleditsia triacanthos inermis 'Moraine') =
Littleleaf Linden (e.g. Tilia cordata 'Greenspire') =
b. Other ornamental cultivars =
(1) Cultivars of selected Pinaceae (Pine Family) species with unusual growth forms =
Dwarf Pine cultivars =
Blue Spruce cultivars such as Picea pungens 'Pendens' =
(2) Bloodgood Japanese Maple (A. japonicum 'Bloodgood') =
(3) Taxus bacatta 'Repandans' =
(4) Upright Juniper cultivars =
c. Find out about these and other ornamental plants. The Nursery Web has links to many Plant Identification websites
This is a corollary to A.1. above, since if a selection is difficult to root, grafting is usually cheaper than cuttage. =
a. Although labor for grafting per se is usually more costly than cuttage (more time-consuming per unit, and more skilled), the cost of materials and equipment may be lower if cuttage requires long periods in a heated greenhouse, with bottom heating, mist, etc. =
b. Cost analysis: Flowering dogwood cultivars: This is the result of an economic analysis of costs for production of flowering dogwood cultivars by either budding or cuttings ( Badenhop, 1986). =
a. Some species are difficult to root from cuttings, because a conventional cutting cannot stay alive long enough for rooting to occur. Such "cuttings" may be grafted to a piece of root to keep them alive long enough for them to become self-rooted. This is called nurse root grafting. The graft union is planted below the soil line (unlike most grafting), and eventually the scion becomes self rooted. Afterwards, the rootstock can either be deliberately removed or it will die off, especially in cases where the scion and rootstock are not closely related, resulting in a delayed graft incompatibility. Incompatibility is discussed in the section on Compatibility. =
In what way is the process of nurse grafting similar to layering? =
Examples: =
(1) Lilac (Syringe vulgaris), until the advent of micropropagation, was commonly nurse root grafted to California privet (Ligustrum ovalifolium). Both of these genera are in the Oleaceae family. =
The root piece is typically whip and tongue grafted at the bench during winter, stored in a cool place where graft union formation occurs, and then lined out in the field in the spring, where scion rooting occurs. =
Eventually the graft union fails due to delayed incompatibility, and the privet root piece dies. The likelihood, overall (for any kind of plant), of an intergeneric graft like this being a compatible scion/stock combination is low. =
Alternatively lilacs may be nurse root grafted onto one year old root pieces of seedling Green Ash (Fraxinus pennsylvanica, also in the Oleaceae). =
In recent years, most lilacs are propagated by tissue culture (micropropagation). Nurse root grafting has lost popularity because sometimes the graft union fails before the scion becomes self rooted, or it will not fail at all, or the rootsystem will sucker, eventually outgrowing the lilac scion. In the image shown here, this nurse root grafted lilac apparently did not self root, and after several years, the lilac/privet graft union broke apart (delayed incompatibility), killing the lilac. =
(2) Avocado. Nurse seedling graft of avocado rootstocks by the Frolich method and modifications are described by Reuben Hofshi in the
Subtropical Fruit News, (vol. 4, no. 2, Spring, 1997). The method was developed as a means of cloning avocado rootstock varieties. Avocado is very difficult / slow to root from cuttings; hence, grafting. The method involves grafting a scion, from a clone that is ultimately intended to be used as a rootstock, onto a nurse seedling. This nurse seedling will serve as a temporary root system for the scion of this rootstock variety. New growth from the scion is then etiolated, and then air layered, in order to induce its own adventitious root system. The rooted layer is then detached from the nurse seedling and grown on. Subsequently a scion of a fruiting variety is grafted onto the rootstock clone. =
View a good video (with audio) of the Frolich method of nurse seedling grafting of Avocado from the University of California Cooperative Extension.
(3) In the past, apples were sometimes nurse root grafted before the use of size controlling clonal rootstocks became common. This illustration is from Liberty Hyde Bailey's Standard Cyclopedia of Horticulture, written in the early part of the 20th century ( Bailey, 1924). NRG is sometimes still used to "bulk up" (rapidly increase the numbers of) newly selected apple rootstock selections in rootstock breeding programs such as the one at the New York Agricultural Research Station at Geneva. =
(4) Other examples: Large-flowered Clematis hybrids, Peony, and Catalpa cvs. =
B. Grafting for repair =
a. Young bridge graft =
b. Older bridge graft =
c. Bridge grafting described in an MSU Extension bulletin concerning rodent damage and "first aid" for trees. =
d. Guy Witney, WSU Area Extension Faculty, describes the use of Bridge Grafting to repair mouse damage (girdling) of apple trees in Washington State. =
How is bridge grafting like double working (described in the section on Concepts and Definitions)? What time of year (season) is bridge grafting performed? (see Seasonal Considerations in the section on Required for Successful Grafting and Budding)
Inarching, an in-ground version of approach grafting, is described in the University of Georgia Extension Web site, Propagating Deciduous Fruit Plants Common to Georgia =
The picture is from the cover of a 1933 extension bulletin by Thomas & MacDaniels, which described the use of inarching to repair damage caused by freezing. =
C. Grafting to create unusual growth forms - Highworking (see Grafting by Position)
a. Tree (standard) Roses =
Roses that typically grow as low shrubs or climbers can be given an arborescent (tree-like) appearance by grafting them at the top of a long straight interstock which is in turn grafted onto a suitable rose rootstock such as R. multiflora. This would be an example of both highworking and double working . =
Tree Roses FAQ sheet from the Just Roses Web page =
=b. Tree peonies =
Peonies from China Web site =
=c. Weeping Higan Cherry (a cultivar of Prunus subhirtella)
( Picture from Edgar Joyce Nurseries) =
Prunus subhirtella is normally an arborescent (tree) form, but the variety pendula "weeps," and would grow as a prostrate shrub. It is grafted ~ 4 - 6' high on a P. subhirtella understock to give a "weeping tree." =
d. Cariganna aborescens var. pendula
Picture shows high graft union (right), and root suckers from the rootstock (left). =
=Why are these suckers upright instead of weeping? =
e. Bonsai =
This ancient Chinese art is, perhaps, the ultimate in tree "engineering." If the grower wants a branch in a particular location where none exists, it can be grafted into place, as is described at the Bonsai Primer Web page =
=f. Living sculptures created by grafting =
One of the most unusual applications of grafting is its use to create living sculptures such as chairs, tables, and a variety of strange abstractions. =
The Arborsmith Studios has many examples of the work of its owner, Richard Reams, and images of other creative designs from the past. =
D. Grafting to change fruit varieties =
Replacing an old variety on an established tree with an new one for economic or other reasons is known as Reworking, which is a form of topworking (see Grafting by Position spatial diagram) =
Seedling fruit trees can take 7 years or so to flower, and even grafted nursery stock can take several years. An alternative to waiting this long was, and still is, to a limited extent, to cleft graft a new variety up into the crown of an established tree. This could hasten production of the new fruit variety by several years. =
E. Grafting to put multiple scion varieties on a single tree. =
This is an example of Topworking (see Grafting by Position spatial diagram) =
Apple with Macintosh, Granny Smith, & Red Delicious, etc. all on one tree =
Citrus tree with orange, lemon, grapefruit all on one tree. =
Hibiscus with several cultivars differing in flower color. =
b. Cleft grafting would typically be used for this topworking objective. =
F. To provide a pollinizer branch for self-incompatible fruit tree species =
e.g. Macintosh apple will not self-pollinate, but it will cross-pollinate with another domestic apple or a crabapple. =
garden. =
G. Grafting to Influence Growth Phase =
a. Generally a grafted tree will come into bearing sooner than a seedling.
(1) This is because the (adult) growth phase of the scion tends to be maintained; whereas, a seedling is naturally rejuvenated by the process of embryogenesis (seed formation) compared to the seed-bearing parent tree. =
(2) Furthermore, dwarfing rootstocks tend to induce scion precocity, i.e. they cause a scion to come into flowering one or more years sooner than it would on its own roots or grafted onto a non-(or less) dwarfing rootstock. =
b. This avoidance of rejuvenation is exploited by tree fruit growers, to avoid the long delay (several years) associated with orchard establishment from seedlings.
e.g. Avocado would come acceptably true-to-type from seed, but several years of bearing would be lost. Hence top wedge grafting of a scion from a mature bearing tree onto a seedling understock is commonly practiced in the nursery production of this tropical crop. =
See autotutorial slide set on Top Wedge grafting of avocado. =
e.g. Many Citrus varieties would come true-to-type from apomictic seed, since apomixis is a natural form of asexual propagation. Apomictic seedlings, however, like zygotic seedlings, are juvenile, and flowering would be delayed for several years, as explained above. Hence, one reason for T -budding citrus is to avoid seedling rejuvenation. =
see autotutorial slide set on T-budding of citrus. =
It should not be inferred that avoidance of rejuvenation is the only or even the principal reason for grafting fruit trees. Grafting is also practiced simply because m ny fruit tree species (e.g. apple, avocado, etc.) are difficult to root from cuttings (described above), and in order to take advantage of specific rootstock effects (described below) =
a. Ease of rooting is a general property of juvenile compared to adult growth. =
b. Even though a scion from a mature tree tends to retain its adult growth phase. =
As pointed out in the previous section, an adult scion will be slightly rejuvenated by grafting onto a juvenile (seedling) understock. Because this rejuvenating effect is only slight a scion may have to be sequentially regrafted onto a series of juvenile rootstocks before a useful degree of rejuvenation has been achieved. Cuttings taken from this rejuvenated growth tend to root more easily than from mature growth.
c. This rootstock-influenced gradual rejuvenation of the scion is called serial grafting. =
d. Serial grafting is an extreme (last resort) method for facilitating the rooting of cuttings from the mature wood of extremely difficult-to-root species such as 100 year-old Sequoia ( Tranvan, et al., 1991). =
H. Grafting for Virus Detection (Graft indexing) =
Why is it important that the indicator is used as understock, not as the scion? =
Note: for many viruses there are other newer, more specific and/or more sensitive virus indexing techniques such as ELISA (enzyme linked immuno sorbant assay). Hence, graft indexing tends to be used less frequently. =
a. Examples: =
(1) Strawberry - petiole wedge graft - terminal leaflet of trifoliate leaf removed, and small split made, where rachis of suspect terminal leaflet is inserted. =
(2) Prunus subhirtella is used as an indicator for cherry, plum, etc. - compatible union doesn't even form, but virus is transmitted, and detection can be made. =
I. Grafting to achieve independent optimization of component genotypes - Specific Rootstock / Interstock Benefits =
a. The rootsystem and the shoot system of a plant exist in different environments. Each has a different role in plant development and each makes a different contribution to agricultural productivity. Given the long generation time of trees (years), it could take a very long time, using standard plant breeding methods, to breed a tree to genetically optimize both the root and the shoot systems. Grafting, on the other hand, has allowed agriculturists to mix and match different genotypes in the root and shoot systems, resulting in a genetically compound plant that performs better overall than either genotype alone. =
b. Of course, in modern times, genetic engineering, is another way to "construct" a plant with genes from more than one organism. However promising, genetic engineering is still in its infancy with respect to "designer" trees. =
Do you think genetic engineering will ever make traditional grafting obsolete? =
a. "Specific" rootstock (or scion, or interstock) benefits, in the context of this discussion, are advantages gained by grafting that are due to the specific genotype of stock or interstock. For example:
Grafting Macintosh apple (scion) onto an M9 (dwarfing) rootstock, results in size control (dwarfing) of the scion because hormonal or other aspects of M9, under genetic control, are translated to the scion, affecting its vigor. Size control and other specific rootstock benefits in apples discussed in the section on Clonal Apple Rootstocks. =
Grafting Arabica Coffee (Coffea arabica, higher quality but nematode susceptible) onto another species of coffee, C. robusta, which is nematode resistant. =
b. Non-specific rootstock effects would be grafting to achieve an objective that could be achieved by any compatible rootstock, regardless of its genotype. This includes many of the reasons for grafting & budding stated above such as the following examples in which the scion but the rootstock genotype is important: =
Grafting onto a seedling rootstock merely to propagate a difficult-to-root clone. =
Grafting onto a seedling rootstock to produce a plant with an unusual growth form, such as a weeping cherry. =
What are some other non-specific rootstock effects? =
a. Size control of the scion. =
"Size control" in this context refers to some degree of dwarfing (or in some cases invigoration) of the scion by the rootstock, especially in the case of fruit trees. =
Apple - the use of clonal rootstocks for size control (and other reasons) is a major part of modern apple production. The Malling and Malling-Merton apple rootstocks, introduced in the early 20th century, revolutionized apple production. Progress has been made since then by a number of other apple rootstock breeding programs around the world. Since apple is perhaps the best example of crop improvement through selection of clonal rootstocks, this topic is discussed at length in the section on Clonal Rootstocks.
Pears are sometimes dwarfed by grafting them onto quince rootstocks
b. Effects of rootstock on precocity (early flowering) of scion =
Flowering and fruiting of an adult phase scion occurs more rapidly (precociously) when grafted on some rootstock genotypes than on others. In particular, the more dwarfing caused by the rootstock, the sooner the scion will flower and "come into bearing" from the standpoint of fruit production. =
c. Pathogen resistance =
Many rootstocks have been selected for disease or pest resistance but in most cases the resistance is not transmitted to the scion (in contrast to dwarfing). For example:
(1) Fungal pathogens =
Fusarium sp. =
Fusarium causes a wilting disease of many species, caused by fungal plugging of host xylem. =
e.g. Passion fruit (Passiflora edulis), purple-fruited hybrid varieties that are Fusarium wilt-sensitive, are grafted onto resistant seedlings of P. edulis forma flavicarpa =
Phytophthora root rot =
Resistance to root rot is one of the major selection criteria for the apple rootstock breeding program at the NY Agriculture Experiment Station at Geneva, NY. =
=(2) Bacterial pathogens =
Fire blight (Erwinia amylovora) =
A disease of pear, apple, etc. Rosaceous fruits (link to Plant Pathology Online, by Phil Arneson, Cornell University) =
Fireblight resistance is one of several selection criteria in modern apple rootstock breeding program at the NY Agriculture Experiment Station =
Characteristics of Apple Rootstocks and Interstem Combinations by Paul Domoto (including resistance to fireblight) is part of the NC-140 Regional rootstock breeding program Web site. =
=(3) Viral pathogens =
Tristeza virus =
Tristeza causes greening disease in citrus which is a serious problem in Africa and other parts of the world. =
Resistance to tristeza is conferred by rough lemon rootstock. A table of citrus rootstock resistance to Tristeza and other diseases is presented by the Florida Agricultural Information Retrieval System. =
=d. Pest resistance =
(1) Insect pests =
Wooly aphid (WA) (Eriosoma lanigerum) is an insect pest of apple. The Malling-Merton series rootstocks were developed by crossing wooly aphid-susceptible East Malling selections with WA-resistant Northern Spy apple (Information sheet from UC Davis IPM Pest Management project). =
Phylloxera, described in an Information sheet from Univ. of California Integrated Pest Management project, is an aphid-like sucking insect pest of grape which parasitizes the root system. Phylloxera infestation in the wine regions of France in the 19th century virtually destroyed production of European (wines) grapes (Vitus vinifera) until they began grafting them onto resistant American grape rootstocks (Vitus lambrusca). =
=(2) Nematodes =
Nematodes are microscopic "eel worms" which parasitize the root systems of many agricultural crops =
Almond (Prunus amygdala) scions are grafted on Mariana plum 2624 rootstocks which are nematode-resistant. ( Information sheet from University of California IPM Pest Management Project) =
Arabian coffee (Coffea arabica) produces a higher grade of coffee than Canefera coffee (Coffea robusta, the kind used to make instant coffee), but the former is nematode-susceptible while the latter is resistant. Scions from seedlings of C. arabica are grafted onto seedling understocks of C. robusta for coffee plantations in Guatemala and other parts of Latin America. =
=(3) Rodents - the cultivar 'Novole' crabapple rootstock, selected at the NY Agriculture Experiment Station at Geneva, inhibits meadow voles from feeding on the bark during the winter. =
e. Cold hardiness =
(1) Trifoliate orange (Poncris trifoliata) is deciduous (unlike the citrus species cultivated as fruit crops) citrus species. It is sometimes used as a rootstock for citrus. Orange or other citrus grafted on trifoliate rootstock are better suited for more northerly Florida growing conditions because of the cold hardiness of the trifoliate orange. This is one of the few examples of evergreen/deciduous grafting. =
(2) Apple - for a summary of apple rootstock (cold) hardiness consult Paul Domoto's Characteristics of Apple Rootstocks table.
For what (other) reason is it surprising that Poncris trifoliata is used as a rootstock for Citrus sp. (hint, check the section on Requirements for Successful Grafting and Budding)? =
f. Tolerance of specific soil types =
(1) The apple rootstock M7 is tolerant of wet soil conditions; conversely MM104 is tolerant of dry soil conditions. For a summary of apple rootstock soil adaptability consult Paul Domoto's Characteristics of Apple Rootstocks table.
Just as single working (scion/understock grafting) allows the grafter to combine the best possible scion genotype with the best possible rootstock genotype, double working (scion/interstock/understock grafting) allows for further optimization of each of the three components of a tree - root system (nutrition, anchorage, dwarfing, etc.), trunk (support), canopy (fruit). See Grafting by Position =
a. Size control =
(1) A genotype that causes dwarfing when used as a rootstock has a similar dwarfing effect (but to a lesser extent) when used as an interstock.
(2) In addition, the degree of dwarfing by a given interstock genotype is proportional to the length of the interstock, i.e. a relatively long section of M9 used as an interstock has a greater dwarfing effect than a shorter section of the same genotype. =
Why use an interstock for size control of a double worked tree rather than using the same genotype as a rootstock in a single worked tree? (Hint: see Apple Grafting autotutorial slide set)
b. To achieve an arborescent growth form of an otherwise shrubby scion variety (see Grafting to achieve special growth forms in this section, above)
c. Avoid incompatibility of an otherwise incompatible stock / scion combination by inserting a mutually compatible interstock. (see discussion of Bradford pear/Quince incompatibility in the section on Compatibility) =
a. Apple b. Stone fruits =
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