The heat of summer is here and most of us aren’t really thinking about next spring. But if you want to add to your spring bulb display, now is the time to begin the search. Spring bulb catalogs are starting to arrive and now is the time to start planning. Ideally, bulbs should be planted no later than Thanksgiving, and probably by Columbus Day. In order to get the best selection, I recommend doing research now and placing orders by early September (which isn’t far away).
If you’re an avid gardener, you may want to try forcing bulbs in containers. By planting them in pots, you can have spring bulbs in flower in your home in February and March, a real treat. And it’s not really all that tricky to do. I’ve planted and grown Narcissus and tulips in containers many times, (usually) with good success.
The key to success is knowing the cold requirements for the species (and cultivar) that you’re working with. Bulbs that flower in the spring in our latitude require anywhere from 12 to 15 weeks of temperatures of 35 to 45 degrees Fahrenheit. This can be a challenge, but it’s not impossible. An unheated garage or, better yet, a coldframe are good spaces to achieve the required treatments.
Start by doing some research and choose early flowering cultivars for better success. There are lots of resources online that give flowering dates of various bulbs. You can use this information to select bulbs to force. And don’t stick to only daffodils or tulips. Try some of the less well-known species; Snowdrops (Galanthus nivalis) or Squill (Scilla spp) work well and are a nice alternative. They can sometimes be easier than tulips, which can be a bit finicky.
Potting should be done when you can give the bulbs cool temperatures, around 50 to 60 degrees. Pot them in clay containers using a well-drained commercial soil mix and don’t be afraid to plant the bulbs so they're touching each other. You want a full display when they flower. Also, if you’re planting tulips, place the bulbs so the ‘flat’ side is facing the outer edge of the pot. The first leaf to emerge from a tulip develops on the flat side and folds down. This is a trick I learned while working at Longwood Gardens, and it produces a nicer display. The top of the bulbs should be at soil surface level. Place the potted bulbs in a cool place, 50 to 60 degrees, for several weeks to allow for rooting.
Now you can move the pots to their winter resting place, where they can get the vernalization period they need. This will take anywhere from 12 to 15 weeks and should be 35 to 45 degrees. The best place to do this is a spare refrigerator. A coldframe or an unheated garage works well, too. The bulbs should be kept dark. DO NOT place the bulbs in a refrigerator with fruit or vegetables, as they give off ethylene gas that is really bad for bulbs.
Bring the bulbs to a sunny location in your home after you’ve met the dormancy and, in a week to 10 days, you should have beautiful flowering bulbs!