Why don’t my plants flower?

Why don’t my plants flower? by A.




don’t my plants flower? Probably this plaintive

question is raised oftener than any other that

has to do with gardening. As likely as not, too,

the complaining gardener will go on to say that

he gives considerable attention to fertilization,

to watering and to cultivation, but still his

plants do not flower as well as those in his neighbor’s

garden. Why? he asks, and if his morale is low

enough he will probably repeat, with emphasis,



to answer our unhappy questioner with anything

like accurate information we would have to actually

see what his conditions are with respect to type

of soil, kind of fertilizer, drainage, and light

and shade factors. Even then we might not be able

to solve his problem entirely, because the kinds

of plants grown also play a part in the overall

picture. So, briefly, let’s start at the beginning.


plants can flower they must make satisfactory

leaf growth. This is because the leaves are the

manufacturing agents. They absorb oxygen and carbon

dioxide from the air; then, in the presence of

adequate sunlight and the green coloring matter

in the leaves, they convert these materials; when

combined with water from the soil, into such foods

as sugars and starches. These are translocated

to other parts of the plant and, when combined

with nitrogen, phosphorus, potassium, etc., they

produce compounds which are responsible for cell

division and’ growth.


be able to produce such growth, most plants have

to be grown in a well aerated, properly drained

soil, with adequate supplies of moisture and fertilizers

at specific times of the year. These facts, of

course, are generalities and do not answer the

particular question, “Why don’t my plants flower?”

But they do give us some leads.


produce flowers we have to have good root action,

and for the great majority of garden plants this

presupposes a well drained, porous soil. It also

means that such elements in the soil as phosphorous,

potassium, calcium and magnesium must be present

in adequate amounts. An application of manure

and complete fertilizer to the soil usually takes

care of this, ‘and such mulches as ground corncobs,

cotton seed hulls or chopped straw are of considerable



may note that nitrogen in whatever form is not

mentioned in connection with root formation-not

that it is not needed, but because it is needed

in smaller quantities. That’s the secret of

good flowering. Too much nitrogen will produce

a lot of foliage at the expense of flowers. This

is particularly true of plants which naturally

flower better in soils of low fertility.


example,, let’s take such familiar -annuals as

celosia, cleome, convolvulus, calliopsis, esehscholtzia,

small flowered .petunia, .phlox or portulaca.

Give these full sunlight so that sugars and starches

are manufactured properly in the leaves,; grow

them in sandy, well drained soil with comparatively

little nitrogen (this means that one application

of a complete fertilizer may be enough in the

spring) ; apply water only when absolutely necessary

(just before wilting)and you’ll have short-grown

plants full of flower, with perhaps small leaves

of light green. What you have done, actually,

is to balance the carbohydrates (the sugars and

starches), which are responsible for initiation

of flower buds, with the nitrogen in such a way

as to have the former predominate. That

is why in sandy, sunny, hot regions such plants

as mentioned above are a riot of color. Give them

a lot of water and much nitrogen and away they

go into marvelous foliage specimens but with few



same situation may be observed in such herbaceous

perennials as anthemis, Asclepias tuberosa, asters,

Euphorbia corollata, gaillardia, gypsophila, hemerocallis,

liatris, limonium and yucca. In this connection

it is well to note that the light factor cannot

be overlooked. In shady or partially shady locations

less flowering may be expected, based on the fact

that with less sunlight there is less food manufacture,

hence larger and more profuse foliage with fewer

flowers. Yet there is a good deal of selectivity

among plants and we find many herbaceous perennials

which do well in partial shade aconitum, ajuga,

anemone, aquilegia, aruncus, asperula, begonia,

chelidonium, cimicifuga, convallaria, dicentra,

dictamnus, digitalis, echinacea, eupatorium, helleborus,

hesperis, hosta, lysimachia, mertensia, monarda,

myosotis, oenothera, polemonium, primula, pulmonaria,

ranunculus, thalictrum, trillium, trollius, veronica,

viola. These plants should not be fertilized too

heavily with nitrogenous materials, when grown

in partial shade, or else they will become too



a question has not already arisen in your mind,

we would like to forestall it. Sounds like a contradiction,

doesn’t it, when we talk about the need of sunlight

fur food manufacture, and in the next breath give

you a whole list of plants which flower well in

the shade or partial shade. But the fact is that

most of these plants flower fairly early in the

season-and that applies to early flowering bulbs

too-and the flower buds are initiated in the spring

before the foliage on trees or other plants which

do the shading has appeared.


this reason, then, there should be a distinction

in the type of shade provided. If it is a permanent

building or structure or a dense evergreen tree,

so that the plants are shaded the year around,

poorer growth and less flowering may be expected

on the shade-tolerant plants. Further, because

of the reduction of light, the perennials and

bulbs grown in partial shade should have greater

amounts of phosphorus, potassium and calcium in

the soil. Such applications should be made yearly

and if possible worked into the soil. Mulches

of corn cobs, straw and even manure will tend

to increase the amounts of these elements in the

soil, so don’t overlook the mulch. It has greater

functions than the mere reduction of evaporation

of water from the soil.


apparent contradiction also needs to be cleared

up. You no doubt have heard of cloth houses being

used to grow many plants commercially, in particular

chrysanthemums, asters, snapdragons, and occasionally

roses. Such a cloth reduces the light intensity

by 30 to 40 per cent and this would seem to contradict

the statement that full sunlight is needed. However,

we know that in midsummer there is really too

much light for economical use by plants, so its

total average reduction is actually desirable.

This is quite different from exclusion of sun

daily for several hours. Thus we find roses, for

example, outdoing themselves in the summer when

grown under cloth, and the same is true of other

flowering plants despite the overall light reduction.


summarize and specifically answer our original

question: First you must know the light, moisture,

and fertilizer requirements of the plants you

are growing; secondly you must provide these conditions

as closely as possible in the light of the explanations

given above.


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