Forcing Bulbs Isn’t Hard. So Why Don’t More People Try It?

Before Page Dickey and Francis Bosco Schell spent a single night in their house in northwestern Connecticut, clay pots of flower bulbs slumbered there, setting down roots in a space of their own.

The species tulips, miniature daffodils and dwarf irises that would grace the windowsills and dining table in late winter and early spring — after the couple’s yearlong renovation was complete and the December 2015 move-in day had arrived — were all present and accounted for.

Ms. Dickey, a garden writer and designer and a founder of the Garden Conservancy Open Days program, and Mr. Schell, a retired book editor and lifelong gardener, knew there would be no parade of homegrown flowers in the leanest months if the bulbs didn’t get their needed chill period. That meant starting around October, so they could root and otherwise get ready. With that in mind, they had placed the pressing matter of building at least one cold frame (Ms. Dickey’s preferred bulb-forcing spot) near the top of their to-do list.

The tradition of having homegrown flowers all year-round was one she wasn’t ready to give up or even interrupt, despite the limits of her Northeastern location. And forced bulbs fill the toughest slot in the calendar, when the garden may not offer much more than a pussy willow branch.

So, in that late summer of 2015, Ms. Dickey scanned the bulb catalogs for the fine print, as she had every year for decades. She is doing that again right now, carefully noting any varieties whose descriptions hint at their adaptability to forcing — or being coaxed into extra-early bloom.

“I read the catalogs like you’d read a cookbook,” she said, “marking the ones to try.”

There are some bulbs that she orders every year, including species Crocus and glory-of-the-snow (Chionodoxa), hyacinths and some unusual grape hyacinths, too — not the basic blue Muscari, but “ones you wouldn’t see for sale in the supermarket,” she said.

She won’t be without reliable little Narcissus like Minnow and Hawera — “so pretty in pots” — and some of the cyclamineus types of Narcissus, like February Gold and Jack Snipe, with their distinctive, flared-back petals. And she isn’t likely to forget the Siberian squill (white-flowered Scilla siberica Alba is especially nice) or striped squill (Puschkinia libanotica), either.

That October, when they were still a couple of months away from taking up residence at the former 1793 Methodist meeting house they call Church House, she planted some decorative clay pots with bulbs and tucked them in for their winter’s nap.

She’ll be doing that again next month, too.

Emulating the Seasons

To many of today’s gardeners, forcing bulbs may seem old-fashioned — the stuff of late-winter flower shows in botanical-garden conservatories, or century-old English garden books from a time when it seemed as if everyone was familiar with this technique.

Admittedly, it’s easier to bloom an Amaryllis, hyacinth or paperwhite Narcissus bulb that has been prepared in cold storage by the supplier. Ms. Dickey uses these, too, to provide flowers in the toughest months, December and January.

But in areas where a real winter can provide the needed chill, the forcing process offers a much wider palette of possibilities, she said, and it isn’t that tricky. And the payoff — witnessing a little potted garden of checkered lily (Fritillaria meleagris) emerge, develop and blossom up close — feels like hitting the jackpot.

“Sometimes when I go to the cold frames to pull something out, and I have half-forgotten what’s in there, it’s like pulling a surprise out of a grab bag,” she said.

The process of forcing isn’t so much about fooling Mother Nature as emulating her — and nudging her to hurry, please, just a little. The nudge: When the bulbs are starting to show the first signs of life, each variety in its own time, we create the illusion that spring has come earlier by bringing the pots out of cold storage into indoor light and warmth.

There is much specific advice to be had in books, online articles and some bulb catalogs, with charts of how many weeks’ chill each species requires (from eight to more than 16) and prescribed temperature ranges for that period.

Ms. Dickey has learned some of what she knows by researching, but most of it by trial and error, she said, and she finds that most varieties want about 12 to 14 weeks’ chill.

Some of this is common sense, her insights from growing bulbs in the garden. The earliest in-ground bloomers will need fewer weeks of cold when forced, before they are ready to start flowering — meaning, a crocus blooms faster than a daffodil. And because the bulbs would normally be underground, where no light reaches them, we chill our pots in darkness.

What’s most important: identifying (or creating) the right spot for the bulb-filled pots to spend their months preparing to show off.

The Forcer’s Best Friend: A Cold Frame

The goal is to put the pots in a protected place where they won’t freeze, but will stay very cold — above 32 degrees, but below 50. Somewhere from 40 to 45 degrees is probably ideal.

At her previous house, Ms. Dickey sometimes called the space beneath the bulkhead doors to the cellar into bulb-forcing service. A cold, but not freezing, garage or cellar would work, she said, as would a spare refrigerator. For a little extra protection in a slightly too-cold space, you could pack the pots in a Styrofoam cooler.

But she would not be without a cold frame (or several).

Cold-frame envy: That’s what I felt the first time I saw a photo of Ms. Dickey’s three tidy wood boxes with their Plexiglas lids in her 2020 book, “Uprooted: A Gardener Reflects on Beginning Again,” about leaving her longtime garden in Westchester County, N.Y.

These aren’t your average cold frames. Generally, a prefabricated model will be about 18 inches tall on the highest side, its lid slanting downward to a foot or lower. As good as those boxes are for growing salad greens to extend the season or the winter sowing of perennial seeds, they don’t offer enough headroom for the pots and some insulation material, unless you erect the frame above a trench excavated into the ground.

Ms. Dickey’s are three feet wide and three feet high at the back, where the lid hinges, sloping down to a foot tall in front. To keep water from seeping in and rotting the dormant bulbs — when snow is melting, for example — the lids overlap the edges of the frames slightly.

Whatever the dimensions of your cold frame, there’s one caveat: Never leave the lid all the way open when pots are inside, or a storm could soak them.

Also, position the frames where they can get good sun. Ideally the low end should face south or west.

Each of Ms. Dickey’s bottomless boxes sits on the ground. She layers two inches of pea gravel on top of the dirt, to ensure good drainage. On top of that, she puts a few inches of insulating material, like dry leaves or her preferred medium, wood shavings, which are sold as animal bedding. Once the planted pots are set in place, she covers them with about six inches of shavings, creating the required darkness.

The only other issue is rodent control, but Ms. Dickey hasn’t had a problem since the days when she used her bulkhead cellar space and had to cover the pots with screening material.

Step-by-Step on an October Day

Come mid to late October, Ms. Dickey will gather her pots, many of them just six inches in diameter. She’ll set up a table near the frames, positioning a wheelbarrow full of fast-draining potting soil alongside it.

Then she’ll fill each pot about three-quarters full to allow for ample rooting space, and she’ll water it well, letting the water drain through.

The bulbs will go in next, “as closely as I can place them, snug right next to each other,” she said. They will be covered with more medium — “just enough so that you actually don’t see the bulbs” — and watered again.

Into the frame the pots will go, the smaller ones near the front and the larger at the back (never stacked on top of each other). Her advice: Use 12-inch wooden labels that will poke out from the contents, instead of the smaller ones, for an easy-to-read map of what’s where.

Other than propping the lid open slightly with a brick or a stick to vent on extra-warm days, that’s it. “You just leave it alone,” she said.

Crocus and Iris reticulata will be the first pots she pulls out, in late January or so, transitioning them gradually to increasingly warmer spots indoors. A few weeks later, they’ll be the first to bloom. Eventually, the latest-blooming forced pots will overlap with the start of the main bulb displays out in the garden.

The frustrating thing is that some of the forced bulbs won’t bloom until April — “and by then I’ve got daffodils outside, and snowdrops,” she said. “So there’s always sort of a jam up at the end, where I want everything to hurry up and bloom inside.”

After their big reveal, the potted bulbs won’t be tossed. Instead, they’ll continue to grow in an out-of-the-way spot, before being transplanted to the garden in the fall. Ms. Dickey credits this recycling ethic to her husband, who tries never to throw a plant away.

Some of those bulbs may skip a year of bloom, she said, but most will recover. Bulbs are pretty tough. Most are willing to give a little something extra, if we know how to ask.

Margaret Roach is the creator of the website and podcast A Way to Garden, and a book of the same name.

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