Bulbs can be forced into bloom indoors long before flowers appear outside. Both hardy bulbs and tender bulbs can be brought into flower if they are given proper treatment.
Hardy bulbs include tulips, hyacinths, narcissuses, daffodils, irises, snowdrops, grape hyacinths, the glory-of-the-snot, and scillas. All of these and corms of crocuses are given the same treatment.
Tender bulbs include the amaryllis and paper white narcissus. These bulbs require special treatment.
Bulbs That are Good for
Indoor Flowering
Crocuses
Grape Hyacinths
Large-, medium-, and short-cupped daffodils
Early tulips
Hyacinths
Triumph tulips
Darwin tulips
Bulbs not Generally Good
for Indoor Flowering
Species tulips (including Fosteriana, Red Emperor)
Scilla hispanica
May flowering cottage tulips
Parrot tulips
Use Flowering Size Bulbs
For indoor blooming, purchase only flowering size bulbs. Bargains in bulbs should
be avoided; such bargains often prove to be bulbs not large enough to flower.
You will be more sure of success with tulip bulbs over one and a half inches
in diameter than with smaller bulbs.
Some Varieties for Forcing
Daffodils
Carlton - yellow
Cheerfulness - white
Golden Harvest - yellow
King Alfred - yellow
Thalia - white
Twink - primrose and orange
Hyacinths
Bismarck - light blue
City of Haarlem - yellow
Edelweiss - white
LaVictoire - rose
L'Innocence - white
Pink Pearl - pink
Tulips
Bartigon - red
City of Haarlem - scarlet
Prince of Austria - orange-red
White Sail - white
William Pitts - red
Plant hardy bulbs in late October in regular flower pots or in bulb pots. (Bulb pots are shorter than regular flower pots.) Leave them in a cool (40oF. to 50oF.) dark place for at least six weeks. Then bring them gradually into warmer, lighter conditions.
I. Potting the Bulbs
Step 1. Mix equal amounts (by volume) of sand (the size used for
concrete work is very good), garden soil, and peat moss. Bulbs grow satisfactorily
in this well-drained mixture. No fertilizer is needed.
Step 2. Put a one-inch layer of chips, little pebbles, or gravel in the bottom of the pot. This material provides good drainage.
Step 3. Add the mixture of sand, garden soil and peat moss to the pot. Put in enough for the bulb to be set properly (see step 4.)
Step 4. Place the bulbs in the pot. Plant them in the following ways:
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Tulips: Set three bulbs in a five inch pot. (A five inch pot has a five inch inside diameter at the rim.) Place the bulbs so that their tops will show above the soil line (figure 1). Deep the flat side of the tulip bulb toward the wall of the pot. The lower leaf grows from this side of the bulb. Hyacinths: Put three or four bulbs in a seven inch pot, or plant one bulb in a four inch flower pot. Allow only the tops of the bulbs to show above the soil line. Hyacinths also can be grown in water in a hyacinth glass (figure 2). This is a container devised to hold the bulb so that only the base of the bulb is in the water. Keep bulbs to be grown in glasses in a cool, dry place. Put them in the glasses in early December. No soil is needed for such a container. Daffodils and narcissuses: Plant three or four bulbs in a seven inch pot with one-half of the bulb showing above the top of the soil. Crocuses, snowdrops, grape hyacinths, and other small bulbs: Place several of these in a pot, leaving some space between them. Set them so they will be one inch below the soil surface. Step 5. Firm the soil around the bulbs. Make sure there is no soil within a half inch of the top of the pot. This will prevent overflow when you water the bulbs. Step 6. Water the soil until some water flows through the hole in the bottom of the pot. II. Cold Storage |
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Instead of putting the bulbs in cold storage outside, you may store them in a dark basement or room (such as a vegetable cellar) if the temperature does not go over 50oF. To prevent tops from growing too much during storage, keep bulbs at 40oF. rather than 50oF.
Success with forcing hardy bulbs depends upon their developing roots during
the cold storage period. Leave the pots of bulbs in cold storage at least until
the first week in January. Then bring pots of bulbs indoors as desired.
III. Indoor Treatment for
Blooming
Once you remove bulbs from cold storage, put them in a partly shaded location
with a cool, spring-like growing temperature of 60oF. to 64oF.
Since most homes are not kept this cool, put the pots in a room where the temperature
is as close of 60oF. as possible. Do not put them in a hot living
room, or near a radiator or register. Leave them in this location until the
shoots begin to show green color. Gradually move them to more and more light
until they receive high light intensity. Good locations for growing the bulbs
to flowering stage are a sun porch or bedroom window.
Good light, a cool temperature, and regular watering allow the flowers to develop slowly and fully.
How to Get a Series of Bloom
To have flowers over a period of time, remove hardy bulbs from cold storage
at two week intervals. New bulbs will come into flower when others are past
their prime. To do this, you must keep bulbs at about 40oF. in cold
storage. Tops do not grow actively at this temperature.
Tender bulbs do not require cold storage treatment.
Paper-white narcissus is good for only one blooming period. Grow them in any medium (sand, gravel, pebbles, or soil) that will hold the bulbs upright. Place them in bowls or low pots, and set them immediately in a well lighted location at 60oF. Temperatures of 75oF. or more are undesirable for they encourage weak growth and loss of flower.
Amaryllis is potted in the winter time. Put one bulb in a pot, allowing an inch of space around the bulb. Leave the upper half of the bulb showing above the soil line. Give these plants good light, a good supply of water, and temperatures above 60oF. They will flower within six to eight weeks. Once they have flowered, keep watering the plants. Amaryllis does better if the foliage is left on the plant and the plant kept growing the year around.
New York State College of Agriculture, a Statutory College of the State University, at Cornell University. Extension Bulletin 1021
For more information contact: Tom Kowalsick, Extension Educator - Horticulture, CCE - Suffolk County
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