One of the best benefits of a greenhouse is bringing bulbs to bloom at the time when you most need them—décor, a celebration, or just for cheer in the darkest winter days. This month I’m talking with Brent Heath, the eponymous head of the family-owned mail order business, Brent and Becky’s. After an amazing number of years educating gardeners in how to get the most from all kinds of bulbs, Brent is happy to share some of his best tips for success. “Many bulbs are easy to force,” he tells me.
Tip #1—Pay attention to temperature. The trick with forcing bulbs is to consider vernalization —the process of exposing them to cold which convinces them to bloom ahead of their own schedule. “Most bulbs,” says Brent, “need to vernalize in pots at around thirty-five degrees.” That’s refrigerator temperature. But you take your chances if you tuck them into your regular fridge, because vegetables give off ethylene gas, which can hinder bulb development. Brent says, “A beer fridge is ideal.”
Tip #2—Plan your timing. “With spring bulbs, the earlier they bloom naturally, the shorter the period of vernalization,” Brent says. For the best success, he advises, “Stick to early bloomers.” On average, bulbs vernalize in ten to sixteen weeks, with ones like crocus and Leucojum at the shorter end and tulips at the longest. Brent suggests setting a calendar notice, so you don’t forget to take them out of the cold. Or you can by-pass vernalization altogether by ordering pre-cooled bulbs. When you receive them, pot them up in the same well-draining planting mix you would use for any bulbs, but these you can place on a greenhouse bench immediately.
Tip #3—Consider more light, less heat. Either way, when you shift them from the cold, it takes four to five weeks until bloom time. The flowers will last longest in a cool (50-60 degrees) greenhouse with strong light. If your lighting conditions are not bright, Brent recommends LED lights placed a foot above the emerging foliage to keep stems short and sturdy. Bring the blooming containers into your warmer home to use as décor and then replace them in the cooler greenhouse to extend their winter beauty.
Some of Brent’s recommendations—
Narcissus Abba – Easy to force and fragrant with five or six white flowers.
- Erlicheer – Double sweetly scented white flowers.
Scented Narcissus ‘Earlicheer’ is a great candidate for forcing. (Courtesy Brent & Becky’s) - Kiss Me – Yellow hybrid trumpet matures to white.
Narcissus ‘Kiss Me’ will brighten any space with cheerful gold. (courtesy Brent & Becky’s)
Tulipa Fox Trot – Double early in various shades of rose.
Bonus— no chilling required—Brent suggests these clovers for indoor containers—
Oxalis regnellii var. triangularis – Purple-leafed, white flowers
- tetraphylla ‘Iron Cross’ – Dramatic dark markings, pink flowers
No-chill Oxalis tetraphylla ‘Iron Cross’ is a lucky clover to brighten midwinter decor. (Courtesy Brent & Becky’s)
O. t. – Pink flowers, fine burgundy outline on green foliage