275

Forcing Bulbs



Thanksgiving’s come and gone. The frost is on the pumpkin, the fodder’s in the shock and all that stuff…. but in many households there are still spring flowering bulbs not yet planted outside in the garden.

Although tulips can be put out as long as one can dig in the ground, for most bulbs it’s too late, and it’s also too cold to enjoy fumbling around outside in freezing soil.

But don’t fret. The left over bulbs needn’t be wasted. Instead just plant them in pots in good soil. Water with a little soluble fertilizer (but don’t get them too soggy). Then put them someplace cold (not frozen) for between 2 1/2 and 4 months depending on variety. When you bring them in, spring will come a little early to your house.

How To Pot Left Over – There are lots of detailed instructions about how to pot bulbs for forcing, with many nuances and opinions about soil mix, fertilizer, shape of pots and such. While all of these can improve the spring show, most bulbs will flower even without any sophisticated horticultural perfection. The reason is that when bulbs reach blooming size, they already have enough stored carbohydrate to grow in spring and a fully formed flower bud in the center. They just need a chilling period to trigger them into blooming. (Ready-to-flower bulbs purchased from mail order catalogues have already been chilled by the growers.)

How Long To Chill Potted Bulbs Before Bringing Them In – Different species require different lengths of chilling time. The Dutch have made a compulsive science out of this and their detailed advice is as follows.

Chilling Times with temperature around 40°:

  • Hyacinths — 10 weeks


  • Crocus — 14 weeks


  • Daffodils And Narcissus — 15-17 weeks. Short narcissi such as Tete a Tete, Little Beauty, Little Gem and Topolino take 14 weeks.


  • Tulips — 10 to 12 weeks at 41o or 14 to 16 weeks at 48°. Bloom in 5 weeks. There is a special variety of red tulip called ‘Brilliant Star’ or ‘Christmas Tulip’ which takes only 10 weeks at 48°, then blooms in 3 weeks.


  • Muscari (Grape Hyacinths) — 15 weeks


The Dutch Manual for Forcing suggests that if bulbs are well watered at planting time, and are in a humid place, they will stay moist through the chilling period. An unheated crawl space or back hall is perfect. A brown paper bag over the top helps preserve moisture. If the temperature is higher than 48°:, add extra chilling time. Too short a cold period causes they flowers to dry up too quickly when they bloom. So does low humidity at flowering time, or a too hot house. If the flower stems are too short, the cold period may have been too short. If the plant topples over, it means the cold period was too long. (Sometimes you just can’t win.)

But not in the refrigerator. Most refrigerators are between 37°: and 42°: but are very drying. Also ethelyene gas, released by ripening fruits, ruins the flower bud on certain varieties, especially tulips. Dry, desiccated roots are subject to botrytis fungus, while too wet soil fosters pythium rot.

In other words, forced bulbs are touchy to bring into perfect bloom. But with left over bulbs, better to stick them in a pot and try than to let them freeze or desiccate over the winter and never bloom at all. It’s old Yankee frugality, plus it’s a fun project for children.

How To Plant Them – Under duress, at this busy season, I stuff them into pots with bulbs barely touching each other. Impatiently, I have planted them in a double layer (though making sure that the pointed tops from the bottom layer have a clear space to grow between the bulbs on the top layer). It’s also possible to plant more than one variety in the same pot as long as the chilling times are the same. It used to be recommended that forced bulbs be thrown out because they wouldn’t bloom well again if planted out in the garden. However, if put into a nursery bed and fertilized heavily for a year or two, many will recover and bloom again. The Dutch fertilize their bulbs heavily, with a 12-10-18 mix , twice a year, spring and fall. We traditionally add only bone meal. Perhaps there’s something to be learned from them which can be applied to reinvigorating forced bulbs.

Of Course If All This Seems Too Daunting, it’s easy to buy pre-chilled bulbs ready for planting which will bloom in 5 or 6 weeks. Great for gifts with no work.

© Mother’s Garden by Ruth S. Foster

all rights reserved

May not be reprinted without permission

Credit: Mother’s Garden