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Indoor Gardening

Forcing Bulbs Indoors

Forcing bulbs: is the process of stimulating bulbs to bloom out of season. Amaryllis, paper-whites and hyacinths are the most common bulbs forced indoors. However there are many others that can be forced for an early display indoors.

Storing Bulbs:

  • Bare bulbs can be stored for several weeks in your refrigerator prior to potting.
  • The best way to store bulbs is in a mesh bag or a paper bag with holes that permit ventilation. Check periodically to make sure the bulbs are not molding or drying out.
  • Pot your bulbs right away if you have an appropriate location immediately available - an old (functioning) fridge, a root cellar or cool basement . Can use vegetable crisper drawers but don’t store bulbs in the same drawer you keep ripening fruit or vegetables which give off ethylene gas which can harm the bulbs. (Also some bulbs are poisonous, so this method of storage in not recommended for households with young children)

Potting Bulbs for Cooling / Rooting:

  1. Use clean pots with drainage holes (depth will depend on the bulbs being grown). Allow for 2" of soil below the bulb and the top of the bulb should be even with the rim of the pot when placed on the soil.
  2. Place 2" of soil in the pot, place (don’t push) bulbs into position. Add enough soil to fill the pot, firming the soil gently around the bulbs being careful not to bruise them. Water well in order to settle the soil around the bulbs. Bulbs can be planted close together—even touching—this gives the best show when in bloom.
  3. Different types of bulbs require different periods of time to root well. Therefore, it is not advisable to combine different types of bulbs together. Label each pot so you know what variety you planted and when it should come out of storage.
  4. It takes bulbs approximately 3-4 weeks to flower after they are brought out into warmer temperatures. Allow for 15 weeks from time of planting to flowering - 12 weeks for rooting (cold storage**) and 3 weeks in warmer temperatures to flower.
** Cold storage - 41-48°F - functioning fridge, root cellar or a cool basement

Timetable for planting:

January flowering, plant in September or early October. For February flowering, plant early to mid October. For March flowering or later, plant in late October to early November

* Amaryllis and paperwhites are exceptions!

Forcing Bulbs:

  • The forcing stage begins when you remove the bulbs from cold storage and move them into warmth and light. This triggers the growth of leaves and flowers. Sunlight and temperature are the most important factors in promoting successful flowering. It takes 3-4 weeks from the time the bulbs are removed from cold storage to bloom.
  • After rooting period (cold storage) , place pots in a spot that receives indirect sun about 60°F for 1-2 weeks.
  • When the shoots (stems) are 4-6" tall, move the pots to a bright sunny window to stimulate blooming. Temperature around 68°F and direct sun will give the best results. When buds take on colour, move plants back to indirect light which will make blooms last longer. Keep soil moist at all times.
  • If flowers are developing too quickly, you can stall them by placing them in a cooler location out of direct sun. Acclimatize them to sunlight and warmer temperatures when you want then to resume growing.
  • After blooming, hardy bulbs (hyacinths, tulips…) cannot be forced again and should be thrown away. Or you can plant them outdoors where they may rebloom within 1-2 years.

Amaryllis:
  • Amaryllis are warm climate plants that are ready to grow and unlike most other bulbs will bloom again and again provided they are properly cared for.
  • Choose a pot that has a 6-8" diameter with drainage. Fill pot one third full of good quality potting soil. Place bulb in pot spreading roots out gently. Fill the pot up the rest of the way with soil, leaving the neck of the bulb exposed. Water thoroughly one time, then water sparingly until the bulb starts to grow. Do not over water. Place pot in a warm sunny spot.
  • Each amaryllis bulb seems to have its own schedule but generally flowers will be open in 6-8 weeks. 
  • After the bulb finishes blooming, cut off the flower stock close to the base. Keep the plant moist and add house plant fertilizer regularly. Stop watering and feeding in August/September, and allow the plant to dry out completely in the sun. In early fall, remove and clean the bulbs of old scales and dead foliage. Roots should be fleshy and not damaged.
  • Re-pot in a clean pot with the neck of the bulb above the soil, water and place in a cool, sunny spot. Water sparingly until the first sprout appears, then keep moist.

Paperwhites:
  • Paperwhites are warm climate bulbs that are ready to grow. They do not require a 12-week rooting period. They are easy to start and can give you indoor blooms from November through March, if planted successively.
  • Paperwhites are most often potted in shallow containers of gravel. Place bulbs on a layer of gravel and carefully fill in enough gravel to hold bulbs but not cover them.
  • Add water to the container. It should go just to the base of the bulbs, but not touching the bulbs. Place container in a sunny spot. Roots should appear in a day or so and in 3-5 weeks you’ll have flowers.

Easiest Bulbs for Forcing:

Paperwhites - popular, grow in soil or gravel.Amaryllis - popular Christmas plant (plant bulb in early November no chilling required).Large-flowering Crocus - requires 12-14 weeks of chilling, can be potted in soil, gravel or water.
Hyacinth - fragrant favorite, requires 12 week chilling, can be forced in special vases with water.
Colchicum - easy for forcing, can even grow on a window sill without soil or water, blooms in about 2 weeks.
Muscari (Grape Hyacinth) - requires 16 weeks chilling. Iris (Iris reticulata) - easy but need excellent drainage, 15 week chilling. Tall varieties are less suited for forcing.

 

Bulb Forcing Timetable:

Bulb

Weeks of Cold

Week to Bloom

Amaryllis

none

6-8

Chinodoxa

15

2-3

Crocus

15

2-3

Eranthus

15

2

Frittilaria

15

3

Galanthus (snowdrop)

15

2

Hyacinth

11-14

2-3

Iris

15

2-3

Muscari

13-15

2-3

Narcissus

15-17

2-3

Paperwhites

none

3-5

Scilla

12-15

2-3

Tulipa

14-20

2-3

 

Other bulbs for forcing:

Tulips - do not do as well as garden planted tulips because they require a long chilling period with non-fluctuating temperatures to be successful - at least 15 weeks
Daffodils - require very bright sun (greenhouse) to flower well. Only miniature hybrid varieties are recommended. They require 12-14 week chilling. Once removed from chilling, place in a location that receives full sun - sun room or under a skylight.