Forcing Indoor Bulbs

When February blizzards roar, a preview of April arrives in my window garden. [Learn how I build my window garden.] This is when a lengthy parade of bulbs begins to bloom indoors.

I prepare my bulbs for a February bloom date in the fall. October is the time to plant a few of these bright harbingers of spring as most bulbs require dark, cold rooting periods.

In this slide show, I'll teach you a trick to stunt the height of fragrant paperwhites, as well as covering the basics of some common methods for forcing spring bulbs.

Are you forcing any bulbs this year?

Kevin Lee Jacobs blogs at A Garden for the House. He was introduced to gardening when he was no taller than a delphinium. Today, his home in upstate New York features formal rose gardens outdoors and lavish window gardens indoors.

If you need flowers in a hurry, by all means obtain a few Narcissus paperwhite bulbs. These take less than 21 days to bloom.

Use caution when selecting varieties; ‘Ziva’ and ‘Ariel’ each have a strong, musky scent, which is loved by some and loathed by others. I usually plant the less musky ‘Inball,’ pictured here. A variety called ‘Winter Sun’ offers no fragrance at all.

Paperwhites will thrive in any planting medium.  I grow mine in a 4"-deep china bowl filled with pebbles and water. The only downside to the pebbles is that it prevents the staking of the flowering stalks.

Paperwhites can quickly attain 18" or more in height, and then collapse in a miserable heap just as the flowers open. The cure for such exuberance? A bottle of gin.

After the bulbs have grown in a sunny window for one week, pour the water off, and replace it with this solution: one part gin to five parts water. If you don’t have gin, use any spirit which is 40-proof, such as rum or tequila. As evaporation occurs, top off with the same cocktail. So inebriated, the plants grow to only half their normal size, but with flowers just as large and fragrant as usual.

It's also easy to force the small Dutch bulb Muscari armeniacum in a bowl of pebbles and water.  I can’t imagine a winter without this so-called “grape hyacinth” in one of my windows.  The scented sky-blue clusters, as sweet as May sunshine, make the snow outside seem like a mirage.

A small container, a handful of pebbles, and watering twice weekly are all that muscari require for early bloom indoors. A bowl that is 6"-wide  and 3"-deep will easily accommodate ten bulbs. Fill the bowl halfway with pebbles (aquarium gravel is attractive), and arrange the bulbs on the surface, pointed tips up.

Add enough water to reach the base of the bulbs. Spread more gravel around and between the bulbs to anchor them in place. Set the bowl somewhere dim and cool while roots and foliage develop. This usually takes about eight weeks. Then bring the bowl to full sunshine and warmth (no more than 65°F). Generally, October-planted bulbs will bloom during the first week in February.

Then there is the tiny Dutch Gallanthus nivalis.

You might know this common snowdrop from your outdoor garden, but I think that its icy-white, green-brushed petals are best viewed indoors, at close range. Nivalis’s beauty is easily achieved: Plant five bulbs in a 4" pot of ordinary potting soil.  Then set the bulbs in a cold and dark spot (35° to 45°F) for eight weeks. They will bloom for you three weeks later in a cool, but sunny, window.

Perhaps some other time I will tell you about the gold-licked, Persian-blue Iris reticulatas, the lemon yellow species tulips, and the violet anemones I’ve successfully forced in the exact same manner as Gallanthus. But for now, let’s move on to a beauty that demands neither darkness nor cold to brighten our winter windows.

Who can resist the pastel flowers and intoxicating fragrance of Freesia lacteal? Not me!

I plant my freesia bulbs in October for February bloom.

You can’t go wrong this tropical treasure. But don't neglect to arrange for staking at planting time. Freesia’s long, grassy foliage, which appears well before the flowers emerge, will look messy unless it is kept upright.

To plant freesia, fill a clay pot half-full with a well-draining potting mix. A 6" “azalea” pot will comfortably hold five bulbs. Arrange the bulbs with their sprouting tips pointing up. Then plunge a 2'-long bamboo stick next to each bulb, as show. Tap down the soil around each stick to hold it in place. Add more mix to barely cover the bulbs, and gently tap it down. Be sure to leave a 1" of empty space between the top of the pot and the top of the soil as a water reservoir. 

Soak the pot well, and thereafter, provide just enough water to maintain even moisture. Never let the soil dry out, nor become so saturated that it invites rot.

Full sun and cool temperatures (60°F is better than 70°F) produce the best growth. When foliage exceeds 12" and begins to flop over the pot, loosely tie it, with string or floral wire, to a bamboo stick.  You can tie the flowering stems, too, if you wish, or let them dangle gracefully. You can rely on three to five flowering stems per bulb. Mercifully, these do not emerge all at once, but in a long, luxurious, scented sequence that lasts for weeks.

Everyone loves the legendary perfume of Dutch hyacinths (Hyacinthus orientalis).  You can force the bulbs in soil, in pebbles and water, or in special little vases designed just for hyacinths. I happen to prefer the vases because they allow a cheerful, deep-blue display on the narrow latch ledge of my parlor window.  If blue isn’t your color, there are luscious pink, white, and red varieties to be had.

 
To force a hyacinth in a bulb-vase, simply fill the vase with water in early autumn. When the bulb is in place (pointed tip up), the water should just touch the bulb’s flat underside, or basal plate. Like all Dutch bulbs, hyacinths need to make their roots in a cold, dark place (35° to 45°F). If you have an unheated cellar, set the bulbs there.

I find that a shelf in my refrigerator works well as a cool, dark place for my bulbs, as long as fresh fruit is kept out. Ripening fruit gives off ethylene gas, which can sterilize bulbs.

Top off the hyacinth vases with more water as roots grow. After 12 weeks in cold storage, bring the bulb to a sunny, but cool, window (55° to 65°F if you can manage it). Give the vase a quarter-turn each day to encourage strong, upright growth.

To get the biggest bang for my bulb buck, I continue to care for the bulbs even after their flowers have faded.

The dead flowers are cut off, but the plants are allowed to remain in an east or west window. I keep them watered and fed until their yellowed foliage signals dormancy. At this time, the bulbs are removed from their pots, and saved in paper bags filled with sawdust. There they stay until the fall, when I give them a permanent position in the outdoor garden. In two year's time they will bloom again, as if they had never known the inside of my house.