Forcing Bulbs

At this time of the year many gardeners are just plain burned out. The hot and dry summer, the bugs, the weeds … they all take a toll and it’s hard to look ahead and try to plan new projects, let alone contemplate next year’s garden.But well before next year’s annuals are planted and the bare-root perennials arrive on the doorstep, in the dead of the winter of 2017, wouldn’t you like to look out at the snow-covered landscape as you sit indoors smelling the hyacinths, daffodils and tulips blooming away on the dining room table or kitchen windowsill, with their wondrous colors and promise of spring? It’s going to be a long and cold winter. Here’s a chance to get some spring indoors while the snow and ice melt.

If you’ve ever wanted to force spring-flowering bulbs and have them bloom on demand next winter, then now is the time to take action. Bulbs for forcing need to be potted up now or arrangements need to be made with your garden center so that the bulbs are either shipped to you or available for pickup in the next few weeks. If you wait longer then you’ll be disappointed at the selection available and you’ll run out of “cooling” time. However, by getting the work done now you have the choice of colors, sizes and varieties … and bulb forcing is much simpler than you’d think.

In previous years we’ve ordered our bulbs by late August and received them in early- to mid-October, but other arrangements can usually be made with suppliers or garden centers. Close to perfect timing is important since most bulbs that are forced (and not all can be) need from 12 to 16 weeks of cool temperatures to get them blooming from February through April. So, bulbs potted up in mid-October can be timed to bloom from late January right through late March.

There are plenty of intimidating articles and even books and precise growing guides on how to pot the bulbs, cool them to one temperature and then another and yet another, then cover them with sand and finally a regime of raising temperature exposures that will result in blooms when you want them. Well, if you want to have your tulips blooming precisely on Valentine’s Day you can follow those prescriptions, but if you want blooms around the middle of February or sometime in March … it’s real easy.

Pot up your bulbs no later than the end of October. Use clay pots unless you can restrain yourself when watering, since plastic pots can retain too much moisture and encourage rot. The preferable pots are the kind called “bulb pans” that are available from 8 to 12 inches in diameter and 4 to 6 inches deep, or pots which are very shallow (the depth about half their diameter). Standard pots can work, but the increased depth can allow too much moisture in the root zone, so shallow is better. If you are using old pots, wash them well to eliminate any possibility of mold or algae buildup.

No special soil is needed, but soil from the outdoor garden should be avoided, and we’ve had no problems with Pro-Mix right out of the bag so long as you DON’T get it dripping wet and keep it that way all winter. Any peat-lite potting mix will do, but try to find one that doesn’t have any fertilizer in it, or water-retaining crystals. The bulbs are planted so that the nose or tip of the bulb is just a quarter to a half inch below the top of the soil, and it takes a little practice to get the right amount of soil under the bulbs, around them and on top of them. After a pot or two you’ll catch on real quick. It doesn’t cost anything to practice, and since the whole process starts out dry you can just empty the pot, refill it and place the bulbs until you have it right.

Take a dry run using a pot and some dry soil and the appropriate number of bulbs before you moisten the soil. Add or subtract bulbs and rearrange them as needed. This practice will allow you to space the bulbs, get them to the right level and fill in the voids with the soil. The pot should be somewhat crowded with bulbs to result in a “full” presentation when they bloom. Then, once you’ve got it right, use lukewarm water to moisten the soil and “set” the bulbs in their beds. Bulbs can also be layered in larger, deeper pots and this results in graduated heights of blooms when flowering takes place.

With tulips you’ll notice that the bulb has a flat side and rounded side. The flat side should face outward, but with hyacinths and others it doesn’t matter. A 10-inch pot is probably the most popular and as a rule of thumb for tulips and daffodils, try to get in one bulb for each inch of pot diameter and space them evenly around the pot. So an 8-inch diameter pot can have eight or so bulbs, but if the pot is deeper you can layer the bulbs and get nearly twice that number in. Hyacinths are spaced at about half this rate, so we try to squeeze five into a 10-inch pot, while you can get a dozen Scilla, Muscari or Iris reticulata into the same size pot.

For now, get your pots together, and you can start collecting your bulbs, keeping them in a cool dark place until you’re ready for potting. Think about where and how you’ll cool your pots. They can go in an unheated garage or shed, an uncovered cold frame or even a backyard pit. It’s probably a good idea to cage your pots or dip your bulbs in rodent repellent to keep the mice and voles at bay.

Using modern refrigerators to cool the bulbs presents a challenge because the frost-free functions suck all the moisture out of the bulbs—but you can work around this by keeping your pots on the dry side, putting them in plastic bags and sealing them inside the fridge. And you don’t need to do all your bulbs at once. If you have the fridge space, do a few pots (or more) every week for a month to stagger when they’ll bloom, or you can pot them all at once and just stagger when you pull them out.

The whole object of the cooling period is to stimulate the bulbs to develop roots. These roots will then supply moisture to the developing foliage and flowers once you begin the actual forcing next year. It’s the same process that the bulbs go through when planted outside in the garden. They develop their roots in the cool fall soil, then go dormant until the soil warms and shoot development and flowering take place.

Next week, the steps to take and how to do the chilling process, the forcing and some varieties that I’ve had good success with. But if you want to jump right in take a look here: tinyurl.com/gnv3qtb. Check back next week for more—and keep growing.