dwarf iris ( Iris reticulata )
Courtesy of The New York Botanical Garden

Pictured here: dwarf iris (Iris reticulata)

hyacinth 10 Easy Tips for Forcing Bulbs

Before you even choose a container, check out these pointers from experts at The New York Botanical Garden to successfully force bulbs this fall. » Read It

Forcing is a technique that imitates the environmental conditions that bulbs encounter outdoors, thereby tricking them into flowering earlier. Most bulbs need a chilling or cold-treatment period to flower successfully and put on their best show. Different types of bulbs require different chilling periods, generally between 12 and 16 weeks. Bulbs will perform well as long as they have had the minimum time they need.

Basic Requirements
For chilling, the basic requirement is a cold, dark space where the temperature is below 50° F and above 32° F -- generally between 40° and 45° F is best. An unheated garage or a cellar is usually an ideal spot. Cold frames and window wells are also suitable (cover over the containers with dry leaves or several inches of straw and lay pine boughs on top to help insulate the bulbs). The vegetable compartment of your refrigerator is a good option as well. Store the pot in a plastic bag with air holes punched into it, and do not store with fruit that emits an ethylene gas (such as apples), which is harmful to their growth.

Growing Phase
After the appropriate period of chilling time, the pots will start to show top growth, and roots should be visible through the drainage holes. Bring the pots into a well-lit, unheated room of your house (approximately 50° to 65° F) for about a week. If your basement is the right temperature but not bright enough, fluorescent lights will do the trick.

During this phase, you do not need direct sunlight, bright light is best (you are simply mimicking the arrival of spring with increased temperature and light). If light is coming from one direction, rotate pots every other day to keep flower stems straight. After this adjustment period, you can bring them into a warmer area of the home, but temperatures in the 60s are best for the first three weeks until they are ready to flower.

Exposing bulbs to high heat too soon will cause the stems to elongate and then flop, and the flowers may not open. In general, do not place bulb pots close to heating sources -- the cooler the location, the longer the bloom.

Buried Treasures: Finding and Growing the World’s Choicest Bulbs
Available at NYBG Shop

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Sonia Uyterhoeven, garden expert, The New York Botanical Garden

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