For healthy growth, all plants require heat, light, humidity, proper soil conditions, food, and water in varying amounts, according to the type and the year’s season.
The absence or overabundance of one of these essentials is always the limiting factor to best plant growth.
The window gardener will soon discover the one affecting their plant collection and take prompt measures to correct the situation.
Proper Amount Of Sunlight
The amount of sunlight is usually the limiting factor in the fall and the winter.
Since sunshine is essential for manufacturing plant food, plants grow less during winter’s short, dark days.
The other basic requirements will not compensate for this loss, even in abundant supply. Plants naturally respond to the diminishing amount and strength of sunlight.
Unless flower buds are already set and ready to open by early autumn, plants will make little progress until the days begin to lengthen again in January.
After house plants are brought back indoors in September, they should be held back for several weeks.
In fact, it is unwise to force them into growth by exposing them to warm temperatures, excessive feeding, and overwatering during this season.
A cold room or sun porch can be turned into a conservatory during the dark months by providing heavy curtains which can be pulled across the windows at night.
An electric radiator will keep the temperature above freezing.
Much Needed Rest Period
Many house plants, including cacti and other succulents, have a rest period during the early winter.
By the time the sun climbs higher in January, they can be moved to warmer quarters in a much happier state than if left there for the whole season.
However, all house plants, especially foliage plants, do not need to be rested at this time.
Likewise, plants object to sudden changes in the environment.
For example, they do not want to be too wet for a day or two, followed by a period of becoming bone dry.
All changes should be gradual, and it is important to find ways to make them so.
Providing friendly conditions for successfully growing house plants is sometimes a challenge, even to those who garden skillfully outdoors.
Rooms are usually too hot, day and night, while the air is too dry.
Storm windows that conserve heat allow comparatively little fresh air to reach the plants.
When it does, it may blow as a cold draft directly on them, and a few tender plants can survive such treatment. Yet another deterrent to sturdy growth is insufficient light.
Illuminating gas, used for heating or cooking, often proves the last straw.
Many a specimen that might otherwise hold its own against unequal odds is compelled to languish for the rest of its days.
Many communities are now converting to natural gas, which will remove the biggest single obstacle.
It is possible to overcome, at least in part, some of the difficulties in growing house plants if a little forethought is given to the matter.
Favorable Temperature Conditions
Conditions made more favorable for plants are also better for people, to their mutual advantage.
With modern thermostatically controlled heating systems, it is possible to regulate the temperature so that it never runs higher than desired at any time, day or night.
A maximum of 70° degrees Fahrenheit by day and around 60° degrees Fahrenheit by night is ideal for most plants.
High temperatures furnished by the sun do not harm plants as much as those provided by artificial heat.
Some plants will not grow if the night temperature, in particular, is unfavorable.
In cases where the night temperature should be low, it helps to draw curtains to shut off the plant window from the rest of the room.
Thin, plain shower curtains, used for this purpose, are equally valuable when dead plants are being syringed.
On freezing nights, do not draw the curtains; instead, place pieces of stiff cardboard cut to fit the windows between the plants and the glass.
These are more efficient than floppy newspapers.
Humidity Is Important
Efficient humidifiers are available to correct the dry winter atmosphere in houses.
An electric vaporizer can be purchased for about $5, evaporating a quart of water in 3 hours.
If the vaporizer is used for an hour or two in the morning and again in the afternoon, it would approximate a country kitchen where house plants are supposed to succeed so well.
A steaming tea kettle evaporates a quart of water in about 4 hours.
Every possible means should be employed to keep the atmosphere moist.
Set pans of water on radiators, or plants may be placed on pebbles on shallow trays filled with water.
If a tray to fit the window is not feasible, set each pot on a large saucer filled with pebbles and water, though the pot must not actually stand in the water.
Pots can also be set in larger pots, filling the space between them with wet sphagnum.
The plants themselves can be sprayed with a line mist from an atomizer.
Supply Artificial Light
If windows receive poor light, artificial light can be supplied by 150-watt incandescent light bulbs or 40-watt fluorescent tubes with reflectors, placed about 3’ feet above the plants and turned on for 3 or 4 hours late the day.
The tubes can be put nearer the plants than the light bulbs because they give off a cold light.
A 3500° daylight white tube is recommended. If attached to pulleys, the tubes can be pulled up out of the way when not in use.
Plants can be brought from other parts of the house if made stationary over a table for their light treatment.
Some plants bloom better if elevated above surrounding plants.
The ardent house plant fancier might eventually consider a sun-heated pit or conventional greenhouse, which makes window gardening yet easier.
Although the atmosphere in which house plants grow is important to their health, it is not always possible to change it radically when the plants are unhappy.
Therefore, it is especially desirable to pay particular attention to the factors which can be controlled, such as soils and methods of potting.
Use Fibrous Loam
Good fibrous foam is the basis of all potting mixtures.
This is best obtained from rotted sods stacked in layers upside down, alternating with layers of manure 2” inches thick.
- Peat, leaf mold, and well-rotted or dried manure are invaluable soil conditioners and should be added to the basic soil as directed.
- Coarse sand is also a requirement. If these materials are unavailable, buy potting soil ready mixed from a florist.
- Peat or leaf mold is usually added to potting compost in the ratio of one part to three of the soil.
- Some authorities prefer a ratio of one to two or equal amounts of soil and organic matter.
One reason for this disagreement is probably the difference in texture and structure of the basic soils used.
Three Basic Elements
Three elements, in particular, are essential for plants’ growth; suitable amounts must be incorporated into the potting soils and fed to the plants during their periods of active growth.
These are the:
- Nitrogen
- Phosphorus
- Potassium
Calcium must also be provided except for plants of the heath family that despise it.
Nitrogen assures healthy vegetative growth, and phosphorus stimulates root growth and flower and seed production.
In addition, potassium is necessary to manufacture sugars and starches and helps plants resist adverse conditions.
Calcium affects both the plant and the soil and makes the three elements mentioned above more available to plants. It is usually applied as ground limestone.
These elements can be obtained in various mixtures, the analyses of which the gardener should note well before using.
The most common source is a complete, inorganic, commercial fertilizer such as 5-10-5.
The three figures stand for the percentages of nitrogen (N), phosphorus (P), and potassium (K) in a given amount, always in this order.
The higher the analysis, the lower the cost of a pound of plant food to the purchaser.
Three Basic Potting Mixtures
Three basic potting mixtures used by American authorities are listed here to demonstrate the disparity in their recommendations. All are excellent.
- 2 parts good loam, 1 part peat moss, 1 part clean, sharp sand. Add 2 quarts of Driconure well mixed with 1-quart bonemeal per bushel.
- 4 parts loam, 2 parts leaf mold, 2 parts sand, 1 ½ part dried manure. Add 2 cups bonemeal per bushel.
- 3 parts loam, 1 part manure, 1 part leaf mold, 1 part sand. Add a 3-inch pot of Electra per bushel.
The greatest disparity is in the kinds and amounts of fertilizers suggested.
More sand and peat are added for plants wanting sandy loam and humusy soil, respectively.
Acid-loving plants and cacti and succulents require special mixtures, as do orchids.
John Innes Potting Compost
The John lnnes Horticultural Institution, Merlon, England, has worked out a mixture suitable for practically all requirements in place of many variations familiar to old gardeners.
No manure is required, and their use is strongly recommended.
The ingredients are:
- 7 parts medium loam
- 3 parts peat moss
- 2 parts coarse sand
Here’s what you need to do:
- Mix by weight 2 parts hoofs and horns meal, 2 parts 16% percent superphosphate (1 1/2 parts 20% percent), 1 part sulfate or muriate of potash.
- Add 1/2 lb. of mixture plus 1 oz. (1 level tbs.) ground limestone to a bushel of compost.
This mixture of meal, phosphorus, and potash is known as John Innes Base.
The amount of Base can be doubled or trebled for plants making vigorous growth, and the amount of limestone also be doubled and trebled.
The amateur gardener cannot go wrong if he sticks to this formula. If the loam is not good and fibrous, the proportion of peat should be increased.
The window gardener may not need a bushel of compost.
If only a peck is desired, add two tablespoons of J. I. Base plus a scant one-fourth teaspoon of ground limestone.
A variation on the standard compost is recommended for African violets, begonias, gloxinias, ferns, foliage plants, and a few others.
To a given amount by the bulk of regular mixture, add from 25% to 50% more by the bulk of organic matter (leaf mold, peat, and very old manure), depending on the quality of the loam in the mixture.
When a potting compost contains much organic matter, charcoal broken into small pieces should be incorporated in small amounts to keep the soil sweet.
Azalea Potting Mixture
Equal parts of loam, peat, leaf mold, and sand plus one part of old manure if rich compost is desired.
Cacti and Succulents Mixture (John Innes Formula)
Equal parts heavy loam with, but little organic matter, coarse sand, and broken bricks or flower pots pounded into tiny pieces.
Add a little granulated charcoal and the same amount of crushed clean eggshells.
44659 by Kathryn S. Taylor