Outdoors or indoors, they‘re blooming lovely.
We here in Atlantic Canada are often blessed—or cursed, depending on whether you’re a gardener or a winter-sports enthusiast—with long, mild autumns. Parts of the region don’t get killing frosts until well into autumn, and often the ground doesn’t freeze for the season until December or even January. Oh, we may have cold days, but we also have untimely periods of thaw, limited or no snowfall, mild rainy days…and these can work in a gardener’s favour, especially if, like me, you purchased spring-flowering bulbs early in autumn and forgot, or were too busy, to plant them out in your garden before November or December.
The good news: don’t panic. Normally, I get most of the bulbs planted at some point in October or early November but sometimes life conspires against us.
The other good news: in the event of a freak early winter with heaps of snow, frozen ground and unplanted bulbs, all is not lost. Plant them in containers, subject them to a period of cool temperatures, then grow them indoors in winter for a welcome anodyne to the blahs of February, March and April. This technique is called “forcing”, but I prefer to call it “coaxing.”
There are actually five different types of plant structures we refer to as bulbs:
- True bulbs are mostly rounded/oval in shape, with a pointed tip at the top and a flat area at the bottom called a basal plate, from which the roots emerge. Cut a bulb in half, and you see distinctive rings of storage tissue inside (think of the rings of an onion). Many have a papery protective covering, to help keep them from drying out before they are planted. They multiply by producing little bulbs, called offsets or daughter bulbs. True bulbs include alliums of all sorts (including garlic and true onions), amaryllis, hyacinths, daffodils, tulips, and true lilies.
- Corms are a modified stem structure and don’t show rings of tissue when cut in half. Like bulbs, they have a definite top and bottom to them, with a growing tip and a basal plate. Types of corms include gladiolus, crocosmia, crocus, and autumn crocus.
- Tubers are modified stem tissues and don’t have the basal plate of true bulbs and corms. They tend to be fleshy, with growth points called eyes or buds scattered over the tuber surface. New growth—shoots and roots—emerge from those points. The most common tuber is the humble potato, although we obviously don’t grow them for their flowering characteristics. Flowering tubers include anemones, oxalis (sometimes called shamrock or sorrel) caladiums, and cyclamen.
- Tuberous roots are larger, fleshy roots that grow in clusters and hold food and nourish the plant during its growing cycle. Their main role is to feed the plant—buds for new growth are located at the very top of the roots or at the base of the main stem. Plants that grow from tuberous roots include sweet potatoes, tuberous begonias and dahlias. No one will scold you if you lump tubers and tuberous roots together in a discussion, though.
- Rhizomes are specialized, horizontally growing stems that grow just under or at the soil surface. They are jointed and branch out, allowing the plant to spread. Irises, fibrous begonias, lily of the valley and cannas all reproduce from rhizomes.
Get coaxing (aka forcing)
With all that botany out of the way, it’s time to gather our supplies and get planting, but first, a few words on cold treatments. To successfully grow bulbs indoors, we have to subject them to a cold period once we’ve planted them: this period of cool temperatures triggers them to break dormancy, sprout and bloom. There are a few bulbs that have been pretreated so you simply plant them in the appropriate growing medium, and wait for them to do their thing. Pretreated bulbs include Christmas paperwhites and narcissus, some hyacinths, and of course amaryllis bulbs. The pretreated paperwhites and hyacinths cost a little more than other related varieties due to that extra treatment they received before being shipped to nurseries.
There’s a bit of flexibility in chilling temperatures for bulbs, which will respond and grow after they’ve been held for a number of weeks at maximum temperatures of between 2-10°C (35-50°F). It’s better to chill them for a little too long than not long enough: the only result that will come from a longer chilling period is that flowering will be delayed, but if bulbs aren’t cooled long enough they are unlikely to grow or flower well.
Some of the best bulbs for forcing are: hyacinths, narcissus/daffodils, tulips, crocus, dwarf iris, fritillaria, grape hyacinth (Muscari) and snowdrops. Whatever you choose, make sure to select large, firm bulbs with no signs of bruising, mould, or drying out. Forced bulbs in a pot look best if they are a bit crowded: an eight-inch diameter pot can hold 5-7 tulips or daffs, 8-10 crocus or iris and a dozen or more muscari or snowdrops. You can also mix and match bulbs—group each type together in the pot for a stronger effect—and chill the pot for the number of weeks required by the largest bulb in order to make sure they’re all awake when you put them in your living area.
If you want to have one type of bulb, such as tulips, producing blooms indoors over a period of weeks, you can plant new bulbs weekly, label the date of planting, and put them in your chilling area for their cold period. The important thing to remember here is bulbs should be stored in a cool, dark, dry place before planting, to help them stay fresh and alive. Don’t put them in a refrigerator, cold cellar or other storage area where you have fresh fruit, however, or you’ll end up with no flowers. Ripening fruit produces ethylene gas, which kills the embryonic flowers of bulbs. If you have a dedicated beverage fridge in your basement, garage or man-cave, this is a good place to protect bulbs until you’re ready to plant.
What you plant your bulbs in depends on your tastes and what you’re planting; just make sure your containers have drainage holes in the bottom, for excess water to drain. If you have fancy pottery or metal planters you want to use to display your flowering bulbs but that lack drainage holes, plant the bulbs in a lightweight plastic pot that fits inside the showier container.
Bulbs planted in containers do best in a porous, light soil. Don’t dig up garden soil, especially if it is heavy with clay—it will compact down too much in containers, won’t drain well and can lead to bulb rot. Garden soil may also carry weed seeds and soil pathogens, and while these aren’t usually life threatening to the bulbs, they can make for heavy, messy containers. For the best performance from your bulbs, purchase a peat-based potting mixture at local nurseries or department stores. Percentages of ingredients may vary according to brand, but most houseplant mixtures are made with peat moss, sterilized compost, perlite for additional drainage, and sometimes, sharp sand for even more drainage. Water the potting medium thoroughly before planting bulbs, allowing it to drain so it is moist but not soggy.
Some bulbs can be forced using only water and stones, glass beads, or marbles. Fill a wide container about half to two-thirds full of stones or marbles, add water to cover, and then wedge bulbs into the container with just their bases in the water but deep enough so they won’t fall over once they sprout leaves and flower stems. Hyacinth glasses are hourglass-shaped vases that you fill with water. The bulb sits in the top of the glass with only its base in the water—the pinched neck of the vase prevents it from falling into the water and rotting.
Once you’ve set up your untreated bulbs, put them in that chilling area, write on your calendar when you planted them, and wait. It takes some weeks of cool temperatures to trick the bulbs into thinking it’s spring—as little as 10 weeks for some small bulbs like crocus, as much as 16 weeks for larger bulbs like tulips.
It’s not necessary to fertilize indoor flowering bulbs—the nutrients they require for sprouting, producing leaves, stems, and blooms, are contained in that compact package. With the exception of amaryllis, many of the bulbs that force well aren’t going to be perennial indoor bloomers, so you can compost them without guilt once the flowers have faded. Or, if you have the space in your house, and the inclination, keep the potted bulbs indoors until spring and then plant them out in your garden; they won’t flower again this season, of course, but they may settle in, rest and grow and flower next year outdoors.