PROPAGATING MINIATURE BULBS INDOORS
Whether they’re to be exhibited in competition at a flower show, or displayed for close-up enjoyment in the living room, uniform perfection is the objective. First, then, buy the finest-quality bulbs available—the most plump, firm, healthy bulbs you can find. If the catalogue listing includes “recommended for forcing” or “specially treated for forcing,” so much the better.
Time for potting, and length of time required for rooting, vary with the varieties. We’re usually potting up bulbs for forcing through most of October, occasionally into the first week of November. Our favorites are potted at two-week intervals, so we’ll have a continuous show of flowers in winter and early spring.
We prefer clay pots because of their porosity, and shallow pots because most miniature bulbs are shallow-rooted. A generous layer of pebbles or broken crocks goes in the bottom of every pot. The potting soil is a house-plant mixture with a teaspoon of lime mixed in for a six-inch bulb pot. Bulbs are set so their tips are barely covered with soil; then pots are set in water up to the rims to make sure both soil and pots are thoroughly moist.
Before they can be forced into flower, bulbs need time to grow sound root systems. They need to be stored cool, and in the dark so that premature top growth won’t be encouraged.
Our potted bulbs are pre-rooted in the cold frame, the pots sunk in the soil, each pot covered by another pot turned upside down over it. Soil is added to cover the top pots; and after severe weather sets in, we top with at least six inches of salt hay.
In lieu of a cold frame, a fairly deep trench, with a layer of pebbles or sand for drainage, can be used in the same way, with twice as much salt hay on top or even more. Some growers set the pots on shelves in cool, dark corners of the basement, but our cellars have always been much too warm. Soil should be kept moist, but not wet, during the rooting period.
When the pot is completely filled with roots, and a few stick out the drainage hole in the bottom, the potted bulbs are moved to a cool, shady spot in the house or greenhouse for just a few days. Then they are brought into the sun for growth and flowering. For the best and most lasting flowers, try to provide temperatures between 55 and 60 degrees by day, five degrees or more cooler by night.
The window of an unheated bedroom or attic, or an enclosed porch, may be the only place where temperatures are low enough for healthiest growth. These are good places to grow the plants until they open their flowers, then they can be brought into warmer quarters for a flowering display.
If you are trying to force bulbs into flower at some specific time, and if the buds aren’t swelling as fast as they should, warmer temperatures and a booster feeding of liquid manure should speed up the process. Cooler temperatures will help retard flowering.
Keep the soil always moist before, during, and after flowering. When the leaves begin to yellow, gradually hold back on watering and keep it barely moist until time to set the bulbs out in the garden. Forcing bulbs two years in succession is not usually successful.