A forcer jar is a specialized piece of glassware used in indoor horticulture to grow flowering bulbs hydroponically. This technique, known as “forcing,” tricks the bulb into blooming early, typically during the winter months, allowing gardeners to enjoy spring flowers out of season. The jar provides a controlled environment that encourages root development and flowering using only water and the bulb’s own stored energy. The method is popular for its simplicity and for the aesthetically pleasing view of the developing root system through the clear glass.
Defining the Forcer Jar and Its Design
The design of a forcer jar, often called a bulb glass, is functional and specific to water culture. These containers are typically made of clear glass so the root growth can be easily observed. The structure consists of two main parts: a wide lower reservoir and a narrow upper neck or cup.
The wide base holds the water reservoir. The narrow neck is the defining feature, perfectly shaped to cradle the base of a single bulb, such as a hyacinth or narcissus. This design suspends the bulb just above the water line, allowing emerging roots to dip into the water while keeping the fleshy bulb tissue dry.
The Mechanism of Water Forcing
Forcing a bulb to bloom involves simulating the natural cycle of seasons. A bulb is essentially a compact storage unit containing the embryonic flower, leaves, and a supply of carbohydrates. This stored food fuels the initial growth and flowering process, eliminating the need for external nutrients from soil.
The biological trigger for blooming in many spring bulbs is vernalization, the required exposure to a prolonged cold period to break dormancy. Once the bulb has experienced this cold period, the return to warmer temperatures signals the plant to begin rapid growth and flower development. The jar’s water serves only as a source of hydration for the newly formed roots, which draw moisture up without causing the bulb itself to rot.
Step-by-Step Guide to Using a Forcer Jar
Water forcing requires selecting large, healthy bulbs that are free from blemishes or soft spots, as these contain the maximum amount of stored food. The first step involves initiating the necessary cold period, which mimics winter and is required for most hardy bulbs like hyacinths. Place the bulb in the empty jar, then put the entire apparatus in a cool, dark location, such as a refrigerator or unheated garage, where temperatures remain consistently between 35 and 45 degrees Fahrenheit.
This chilling period must last between 8 and 15 weeks, depending on the bulb variety, allowing the roots to develop and the flower bud to mature internally. Once chilling is complete and the bulb shows significant root growth and a shoot of about one to two inches, add water to the reservoir. The water level must be carefully maintained so it sits just a millimeter below the basal plate where the roots emerge, preventing the bulb from sitting directly in the water. Finally, move the jar to a location with warmer temperatures, ideally 50 to 65 degrees Fahrenheit, and bright, indirect light to stimulate flowering.