I think ‘fall bulbs’ is a rather confusing term for many gardeners. It seems to imply that fall bulbs bloom in fall when, in fact, they are just planted in fall so that they will bloom the following spring.
I think "fall bulbs" is a rather confusing term for many gardeners. It seems to imply that fall bulbs bloom in fall when, in fact, they are just planted in fall so that they will bloom the following spring.
But, from a bulb’s perspective at least, they really don’t care about the names we humans give to our seasons. Their goal is to bloom when the weather is good so that they can flower, produce seeds, and populate the planet. If you provide them with a growing environment that meets their needs, they will happily bloom any time of year. In fact, any one of us can manipulate a bulb’s growth cycle, if we so choose. The technique is called ‘forcing’ and it’s not that tough to do. Plus, it offers some fun.
A bit of science
Before you can force a bulb you need to understand a bit about what they are and what makes them tick. The term ‘bulb’ is properly applied to bulbous structures common to plants like tulips and onions. But it has evolved into a generic description for all large, fleshy, subterranean structures that plants produce to endure adverse climatic conditions like drought and cold. Corms, rhizomes and tubers are bulb-like structures but aren’t true bulbs. Still, unless you are writing a botany exam, I think it’s OK to call them all bulbs.
Forcing bulbs to bloom out of season is easier to accomplish if you think of them as ‘biocomputers’ that are continuously undergoing internal chemical changes as they monitor their environment. For example, if you plant a tulip into your garden in the fall, it will generate roots and a very short shoot and then stop growing while it waits for the next round of environmental signals before resuming growth and eventually blooming. For tulips, it’s the accumulation of a minimum number of hours of frosty temperatures that allows the plants to flower, once the warm weather returns. Forcing is little more than placing bulbs in a cold spot like a fridge or unheated garage for several weeks and then warming the bulbs up to force blooming.
For some tulip species, 14 weeks of cold is sufficient to trigger a flowering response come spring. That’s why it’s not all that rare to see tulips poking up near house foundations during an extended warm spell in February. The bulbs have ‘accumulated’ all of the cold that they need and think it’s spring. Apparently, they don’t understand the Canadian prairies very well.
In warmer climates like California gardeners aren’t ‘blessed’ with winter cold, so they must refrigerate bulbs if they want to enjoy their blooms. I’ve talked to a number of garden centre owners in California who sell tulips to gardeners and provide them with instructions on chilling bulbs in refrigerators. Once the bulbs have had sufficient fridge chilling, they bloom just as beautifully as those that are grown outside.
What should you do?
Growing my own plants at home, I’ve forced bulbs — some planned, some unplanned. On the planned side of things, in September I plant tulips into my pots and then leave them there until October before moving them into my unheated garage for the winter. In late March I move them back to my deck for a beautiful floral display when my trees are still leafless and my lawn is completely brown.
But this past winter I forgot that I had left a package of ‘Canada 150’ tulips in my garage. So in April, I just pulled the ‘forced’ tulips out of the garage and planted them in containers on my deck and I had a beautiful display of red and white flowers by early May. I didn’t let on to anyone that this patriotic display wasn’t planned.
Now don’t forget that forcing is also a great technique for growing tulips in a glass jars. No pots, soils or gardens are necessary. You just need some chilled bulbs, a clear vase, some decorative rocks and, of course, some water in the base. If you are a bit of a rebel you could chill the tulips in your fridge and have them blooming in glass vases for Christmas.
Here are a few final tips on forcing. Check the requirements on your bulb species. Some need chilling, some don’t like it, and some already come pre-chilled by the grower. Also, don’t put your bulbs into a freezer because it’s too cold. You’ll need a fridge or a cool (but not extremely cold) garage. And don’t forget that kitchens and living rooms are far too warm for ‘growing out’ the forced bulbs. Cool indoor temperatures are always best to prevent soft, floppy, weak growth once the bulbs are poking through the soil.
Planting bulbs directly into the garden is still a great way to go, but think about saving a few bulb for some forcing. It might just redefine the world of gardening for you.
- Jim Hole