When a plant requires full sun, what does that mean? I thought I heard that
meant 6 hours.
A second question, is there some kind of measuring device you can put in
your yard to check for full sun, partial shade, etc.
There is no exact measure, besides nature does not work that way, one
day it is sunny all day and then cloudy for the next week. The 6 hour
rule is about right for most cases. If you live were there are few clouds,
you might get by with 5 and if you live in Seattle you might need 8 hours.
"Full sun" generally means *at least* 6hrs/day of unobstructed
sunlight. That is, a location where, if it's not a cloudy day, the sun
will beam down full strength for that length of time.
The "measuring device" is usually your own observation. Eg., my
east-facing front porch gets early morning (full) sunlight, but it's
in shadow beginning in late morning. NOT full sun. The back side of
the house is in shadow in the morning, and sunny later. At least as
far as the shadow of the house is concerned. Big trees keep most of
the back yard in shade.
"Partial shade" means either full sun for a brief period (usually
morning sun for 3-4 hrs) or filtered sun. That is, a location where a
not-dense canopy of trees blocks much full sun but allows a good
amount of light to pass through. "Shade" is an area little or no
direct sun ever reaches.
If a recommendations for a plant say "full sun to partial shade," it
doesn't mean it'll thrive in partial shade. It means it can *tolerate*
a little shade.
You never get full sun indoors, even in a south facing window. Indoors, the
light intensity is always much less. Glass filters out some of the
wavelengths and transforms some others into heat. That's why you should
never move a plant grown indoors directly into full sun until the plant is
first acclimatized to growing outdoors. A plant grown outdoors in the shade
will often receive more light than one grown in a south facing window. You
can use a light meter to measure the differences.
That's logical. I start most of my vegetables such as tomatoes, peppers, and
okra, as well as numerous flowers from seed under grow lights and in south
facing windows in a sun room. I've learned from experience that one does not
plant seedling directly from the indoor environment into the ground in the
sun without first having the plants grow through a "hardening in" process.
Tomatoes do just fine when going from the house to the outside if the cages
I plant them in are covered with clear plastic - ordinarily in early April.
The clear plastic takes the place of glass. Even tomatoes like afternoon
shade in Zone 6B during the summer.
Full sun is not a good enough term any more. I believe it's another thing the
horticulture industry has to address.
I have plants which require full sun, but if they don't have afternoon shade,
will be fried in one season. I live in south central Texas. The afternoon sun
can give you a blistering sunburn in half hour in high summer. So, for me, full
sun is morning sun to about 2pm, then shade.
When I lived on Long Island, full sun meant all morning and all day long.
However, most full sun plants will do very well with the best sun, which is
morning sun till about 2pm, and that's for anywhere.
Plants can't read books! Much of gardening with plants is trial and error.
Native plants need some fussing for the first year, maybe two years, then they
can take care of themselves with very little watering and virtually no
So, full sun...having worked in the industry as a grower I would say if you buy
a plant which requires full sun, and you have all morning till 2pm sun, that is
plenty sufficient. Roses love heat and sun and can take it all day, provided
you buy the right rose for the right place and provide heavily amended soil with
lots of compost and plenty of water and fertilizer.
As you can see, it's really plant by plant basis, and soil types, etc...which
should all be looked at when planting new plants.
Yes. In the interest of brevity, I decided to omit that local
conditions may make "full sun" intolerable for some plants. However,
sunburn or no, my own most successful (veg and flower) garden was in a
situation where "full sun" meant dawn to dusk, with summer
temperatures often above 90F. My recollection is far from perfect, but
I don't believe I ever had a plant die from excess sunlight. As long
as these full-sun critters had plenty of water, they seemed to thrive.
Oh, wait. The celeriac was a complete failure.
Best sun? Please explain.
This wasn't the question.
Oh, jeez. So no one else's experiences are worthwhile if they haven't
"worked in the industry"?
Which is, what? 4hrs? 6hrs? 8hrs? I see that sunrise in Austin is now
approx. 7am, which would make "morning til 2pm sun" 7 hrs. Probably
Full sun means at least six hours of direct sunlight. However,
as with everything else, your mileage may vary. In the Pacific
Northeast, I found that the only place I could grow roses
successfully was in a spot that got sun from can to can't.
However, here in western NY, the only place the roses have done
well is in a little side-garden that gets about four hours of
direct mid-day sun, and filtered sun the remainder of the time.
So, do consider the guidelines when planting stuff -- something
that likes full sun is never going to be happy in a spot that
never gets direct sunlight, or vice-versa -- however, keep an eye
on how the plant does, and consider moving it if it is showing
signs of getting too much sun, or not enough. Also, remember
that, in general, morning sun is gentler than afternoon.
The best way to figure out light levels in your yard is to look.
Make a plat diagram of the yard. [You can do one in almost any
painting / drawing program on your computer.] Then, at least one
day a week, about once an hour, go out and look at where the
shade is, and what type it is, and mark it on the diagram. Over
the course of a year, you'll get a good feel for the various, and
varying, light levels in the yard. You'll need to update this
occasionally as things grow / change. For example, the olive
bushes I planted are now about six feet tall. They provide a lot
more spring and early summer shade than they did a couple of
years ago. Conversely, in the ice-storm our neighbor's dying
locust split in half [and took out one end of the house -- that
was fun!], so we now have a very large patch of sun in an area
that used to be dense shade all day long. That entailed some
emergency plant relocations this spring.
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