I was advised to use chopped banana peels on my ferns and have had
beautiful results. Are there any other plants, indoor or outdoor, that
would like banana peels? Also, Can I cut back my eupatorium chocolate
now and still get blooms later? Thank you.
All of them. :-) Potassium is especially good for the roots. Nitrogen is
for the stems and leaves (that's why it greens up the lawn), and
phosphorus is good for flowers and fruits. You'll see that fertilisers
formulated for different plants are higher or lower in these nutrients,
depending. This probably doesn't do as much good as one might think. At
best it makes up for lacks in the soil, but temperate climate plants
generally take up only as much as they need, so giving them too much is
a waste. My bro-in-law, who is an agriculturist, uses 20-20-20
agricultural fertiliser, which he buys in 100lb bags at the co-op.
But indoor plants are different: many potting soils are poor in
micronutrients, so giving them some MiracleGro or similar stuff from
time to time is a good thing. Also, the plants will use up all the
nutrients in the pot, after all there isn't that much soil, and there
are no new nutrients being produced as there are in the garden. Potting
soil is (nearly) sterile.
To figure out how much to fertilise, look at the plant's natural
habitat. Eg, dryland and alpine plants don't need much fertiliser, and
may be killed if you over-fertilise. They are adapted to take everything
they can get when they can get it (ie, when it rains.) No restraint.
Some wetland plants are the same - wetlands are poor in nitrogen, for
example, because nitrogen salts are water soluble, so they don't
accumulate in swamps. Eg, Venus flytrap gets its nitrogen from the
insects it catches, so giving it a fertiliser will kill it -- too much
nitrogen. But ferns like to grow in damp duff, although many ferns are
adapted to tolerate quite severe wet-dry cycles. Duff is fertile, hence
ferns like to be fertilised.
Another factor is the acidity of the soil, which affects the solubility
of the fertiliser, and hence the ease with which the plant takes up the
nutrients. Plants are adapted to different acidities, so read the
labels, and group acid-loving plants together, for example.
And so on.
In general, it's better to underfeed than to overfeed. A good rule is to
fertilise at half the recommended rate and see what happens. That's
because soil already has a lot of good stuff in it already. If the plant
doesn't thrive, give it a little more (or a little less). It's also
better to fertilise lightly and often, especially indoor plants. Give
just enough to keep them happy. Some people recommend a little
fertiliser in every watering, at 1/4 or less of the recommended
I probably told you too much. I recommend you buy a gardening book and
absorb new information at your own pace. You sound like a beginner,
there are lots of good books out there for beginning gardeners.
Firstly, my list of what's good for what was in error: fast typing, I
guess. I apologise. Here's the real scoop:
Nitrogen: stems and leaves
Potassium: flowers and fruits.
The sequence of numbers of fertiliser labels is N-P-K (nitrogen,
phosphorus, potassium). Or "shoots, roots and fruits."
Secondly, um, er, all fertilisers are chemicals. In fact, you and me are
made of chemicals. :-)
Compost is a low-level source of pretty well everything (on the order of
0.5-0.5-0.5). But the main value of compost is that it loosens the soil
and increases water retention, as well as introducing all kinds of
beneficial critters into that sandy patch you're trying to change into a
rose garden. :-) Compost is essential for a good garden. But beware:
compost sold in bags at your friendly local box store may be sterilised,
which is both good (doesn't introduce strange critters into your garden)
and bad (doesn't introduce any critters into your garden.) (BTW, peat
moss is nutrionally empty and acidifies the soil. Use it only to improve
water retention, and add limestone or dolomite if necessary.)
Composted manure is somewhat better as a fertiliser source (in the range
of 1-1-1 to about 3-3-3, depending on source). Straight manure tends to
be high in nitrogen, so use it carefully. Fish emulsion is high in
nitrogen and phosphorus. (I've used smelts as fertiliser here - one
year, I grew marigolds in pure gravel laced with dead smelts.)
Downside of composts is that some seeds survive the composting process,
and you will have to do a lot more weeding.
Potassium and phosphorous sources in artificial fertilisers are usually
ground up minerals: crushed rocks, actually. (Potash is mined in
Saskatchewan - most of the potash in North American fertilisers comes
from there. It's dissolved, pumped up as a brine, which is evaporated to
retrieve the mineral for shipment.) Guano (bird s**t) is still a
significant source of phosphorus worldwide, as are bones from our
hamburger animals, and fish, in addition to minerals. Nitrogen sources
in artificial fertilisers are usually ammonia compounds made from
petroleum, but animal byproducts are also used (eg, blood in
blood-and-bone mneal.) Rain (esp. during a thunderstorm) is a
surprisingly significant source of nitrogen.
The major drawback of artificial fertilisers, especially the cheap ones,
is that they tend to be poor in micronutrients. NB that fertilisers
made for agricultural use may have micronutrients (mostly metals) added
- farmers know what they need. MiracleGro is one of many fertilisers
with micronutrients added, which is why it works so well. But you pay
extra for its brand name. Housebrands are just as good. Read the
The notion that "organic sources" are better for plants is a myth.
Plants are mineral eaters. The only advantage (minor, IMO) of organic
sources is that they may contain enzymes, which are sometimes
beneficial, and they may contain those micronutrients. The downside of
organic sources is heavy-metal concentration, especially in animal sources.
But the nitrogen, phosphorus and potassium have to be broken down into
pure mineral salts before the plant can use them. Some plants can do
this to a limited extent themselves, but most rely on bacteria and/or
the effects of water and oxygen to do the decomposition, hence the need
for a healthy soil. If you feed a plant a diet of pure minerals
dissolved in water, it will be very, very happy. Just ask the growers of
hydroponic tomatoes. :-)
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