“…a deliciously scented hyacinth bursts into bloom in your office on a cold February day”
Shortened days and colder winds signify the coming of winter, a season that can strike fear into a gardener’s heart. Whatever are we supposed to do for the next few months until spring remembers where Atlantic Canada is?
The answer, of course, is that we garden indoors. We grow a range of houseplants from exotic orchids to eccentric succulents, sigh over seed catalogues, and plan our planting activities for next year.
One way to give ourselves a much needed midwinter lift is to plant spring-flowering bulbs in containers for use indoors. When a deliciously scented hyacinth bursts into bloom in your office on a cold February day, or a pot of flamboyant orange tulips acts as a delightful centrepiece to your dining room table, you take heart in knowing that spring will come again.
Forcing bulbs for indoor winter cheer
The following chart gives a rough estimate for the length of time that bulbs should be chilled before they will be ready to break dormancy, grow and bloom, and an estimated time for them to bloom once brought into your living room. If you’ve forgotten to mark down when you planted the bulbs, carefully check one bulb to see if it has developed a good root system. This is easiest to do with bulbs being water cultured, but you can carefully push soil away from a bulb in a standard planting to see if it has put out a good root system. Another sign to look for is green growth emerging from the tops of your bulbs; this indicates that they are ready to be brought into warmth and light.
Now is the time to plant bulbs for “forcing”—or as I prefer to call it, “coaxing” into bloom indoors throughout the winter. Perhaps, like me, you’re always a little bit late getting your spring-flowering bulbs planted outdoors, and you find yourself with a good selection still to plant. Why not try a few of them indoors instead of waiting for the next late-autumn thaw? Or if you’re the efficient type who has already planted all your bulbs out of doors, don’t worry; you can often find healthy bulbs still available at nurseries and garden-supply stores throughout November and December. Mail-order nurseries that specialize in bulbs such as Botanus or GardenImport will also still have some varieties available, although for best selection next year remember to order early.
In order for bulbs to bloom, they must be subjected to a cold treatment of between 35-48°F for up to 15 weeks, which forces (or coaxes) them to break dormancy. There are a few exceptions to this need for a cold treatment (see sidebar on no-chill bulbs).
If you have a cool basement or unheated attic, a garage that doesn’t freeze, or a “beer fridge” that has some space and isn’t used to store fruit, any of these can work as a place to store your containers of bulbs for their chilling period. In milder climates, gardeners sometimes leave their containers of bulbs outdoors in a cold frame, covered with a protective mulch such as straw, woodchips or leaves. I personally have never tried this because the vagaries of an Atlantic Canadian winter mean we might have no snow one day and snowdrifts four feet deep the next.
One of the most important things to know about forcing bulbs is not to store their containers anywhere near fruit such as apples, plums and pears. Ripening fruit give off ethylene gas, which is harmless to us but which will damage flower embryos inside your bulbs, so that they never flower correctly. This gas can also shorten the life of cut flowers of many types, (not only flowering bulbs), so this is something to bear in mind if you have cut flowers in your kitchen and have fresh fruit in a bowl or basket in the same room.
To coax a little spring into your winter, you will need good potting medium, containers of your choice, and a variety of bulbs. For the best effect, plant bulbs of all one colour or species in one pot, rather than having a polka-dot effect of different colours in one container. Pots should have drainage holes in the bottom; if you have fancy containers that lack such holes, plant your bulbs in standard green or brown plastic pots and give them their cold treatment. When the bulbs have had their chilling period, put these pots into your decorative containers.
To prepare bulbs for forcing:
- Partially fill the pot with growing medium. You want a minimum of two inches of soil underneath the bulb’s base, to provide space for roots to develop.
- If desired, you may add a few grains of bulb fertilizer or bone meal to the container, but it really isn’t essential. All the food the bulb needs to produce its flowers and foliage is already stored within the bulb.
- Gently set bulbs into the soil so that they aren’t touching one another, with pointed ends facing the top of the pot.
- Carefully add more potting mixture, not tamping it down, and only filling the container to the point where the “neck” of each bulb is still exposed to light.
- Water each container thoroughly, allowing excess water to drain away.
- Cover each container with plastic wrap, or set them into large plastic bags that have had breathing holes cut into them.
- Label each pot with the type of bulbs and the date planted.
- Place in cool situation for the appropriate number of weeks (see chart).
At the end of the chilling period, bring the containers into a cool, sunny room, but avoid placing them in direct sunlight. It’s important that the room not be overly warm (under 68°F) so that the bulbs gradually adjust to their new conditions and realize that it is time to begin growing. For longer-lasting blooms, don’t place your blooming bulbs in direct sunlight or in too warm a room, and the flowers should keep looking fresh for several weeks.
For a different look, try forcing amaryllis, hyacinth and paperwhites in water rather than in soil. While this is a lovely decorative option for anyone to try when forcing bulbs, “water culturing,” as this method is called, is also a great demonstration or experiment for teachers introducing their students to the mysteries of growing plants. There are dedicated hyacinth glasses that work well, but you can use any clear vase, jar, or other see-through container. You simply place a couple of inches of decorative stones, marbles, mermaids tears (sea glass) or aquarium gravel into the bottom of your container, and set the bulbs into the vase so they are supported by the stones. Pour enough water into the vase to cover the base of the bulbs, but do not fill the container or submerge the bulbs, or they will rot.
When your forced bulbs are finished flowering, if you’re a fan of foliage you can leave these plants growing until the leaves start to yellow, but don’t expect them to flower again next year. If you can stand having them around until spring, you can plant them somewhere outdoors and see if they will come back in subsequent years. (I have had tulips return for a year or two after having been forced, but suspect it was the fact that they were species tulips rather than a fancy variety, so were hardier.)
In most cases it’s easiest to simply compost spent bulbs once flowers have faded. I used to resist doing this, then it occurred to me I enjoy annuals throughout the summer but compost them without a moment’s regret after frost, and these bulbs are no different. Besides, I always figure I’m stimulating the economy when buying more plants, bulbs, or other gardening supplies.