Preparing Bulbs To Force Indoors

Two weeks ago, we began to take a look at getting a jump on spring, indoors, in the middle of winter by forcing spring bulbs into bloom. But, as I noted, the time to start this work is now, right now! This week, the steps involved in the potting and chilling of the bulbs, how to do the forcing, and some of my favorite varieties of tulips, hyacinths and daffodils that I’ve had success with.

First a little buying tip. Remember that the flower for the bulb that will emerge next spring has already been formed. There is little you can do now to make that flower bigger, but all these bulbs are graded by size and, for example, you may find one variety of tulip in three different size bulbs. The largest bulbs produce the largest flowers, and the largest bulbs are usually the ones sold singly and not prepackaged. In this case, bigger is indeed better.

Also consider that the different bulbs — and in some cases, even different varieties of the same bulb — can require different cooling periods. For this reason this project becomes much more complicated if you try to mix and match tulips, hyacinths and daffodils in the same pot. It’s not impossible, but it does take some experience. For now, do different pots for different varieties. Still, if you have cooling space to experiment with then you can try mixing them up. But keep the smaller varieties, for example crocus, on the outside of the pot with taller varieties like tulips toward the inside. And keep notes so that in succeeding years you can learn from your mistakes and create some amazing forced pots.

Now comes the part that most people have trouble with: the cooling.

Remember that what you’re trying to do is fool the bulbs into thinking that they have been planted outdoors in cool soil. As the soil temperature drops to the 50s and 40s, root development starts and continues until the soil cools to the 30s when the roots are finished growing. This means that the “forced” pots need to be in a refrigerator, wine cellar, unheated garage or cold frame, or buried in the ground and covered with about 2 inches of soil. Alternatively, put the pots on the ground and mound soil over them (and use rodent-repelling bulb dips or wire cages).

In the refrigerator, the potted bulbs should go into a vegetable crisper where the humidity is higher or inside a loosely sealed plastic container or plastic bags on a shelf. Remember that modern frost-free refrigerators suck the moisture out of the air, thus no frost. But, the same refrigerator will suck the moisture out of your pots (and bulbs) and dry them out. The crisper or a plastic container or a plastic bag with a few “breathing” holes will keep the pots evenly moist, though some water may need to be added in the first six to eight weeks of cooling.

If you have a spare refrigerator you can even start your pots on the top shelf where it will be a bit warmer, and then after a month or so move them down to the lower shelves where it will be several degrees cooler. You might even stuff the refrigerator and once or twice fiddle with the internal thermostat slightly to make it cooler — just don’t freeze the bulbs.

Burying the pots may present a bit of a problem. While the temperatures will be perfect, if the soil is frozen when you want to retrieve the pots — ya got a problem. The soil needs to be kept slightly moist, not wet, until they are frozen and may need watering if there is a thaw of a couple of days or more.

With some luck and cooperation from Ma Nature, by the 1st of February you’ll have 12 weeks of cooling, and your first pots can be brought into a warmer spot for a few days, though the majority of your pots should have a couple of weeks or longer of cooling. Thaw the pots gradually and don’t rush them into a sunny bright room or they’ll force too quickly.

One year, some of our tulips that were potted on October 29 were brought out of the cold frame on February 2 and flowered March 1, but this can vary from variety to variety because another tulip done at the same time bloomed a week earlier. As a rule of thumb, it should take three to four weeks to get blooms from the time cooling is stopped.

As the foliage begins to emerge you may want to insert two to three thin, foot-tall bamboo stakes around the perimeter of the pot to support the emerging leaves and stems that can get a bit floppy. The stakes can be cut to size as the flowers develop, and green garden twine can be used to create a cage around the stakes that will hold the plants upright and rigid. Once the plants fill in and bloom, the stakes and twine should be unnoticeable.

A good sign that a particular pot is ready to be forced or brought in is when you see roots coming out of the drainage hole in the bottom of the pot. But while this works with tulips, it may not work with all bulbs.

Unfortunately, once a bulb is forced it’s usually not planted in the garden. It’s kind of tough planting them in February or March and their internal timing clocks are all screwed up, though some people tell me that they’ve had some success in getting forced daffodils to rebloom in the garden the following year. If you can keep the foliage growing until the ground is workable, tulips may be plantable. But it may be several years before they flower again, so the cutting garden would be a great place for planting them.

Some quick tips: Bulbs should always go into the pots “nose,” or point, up. Tulip bulbs have a flat side which should face the pot rim. Double-nosed daffodil bulbs will ruin the blooming symmetry. A 6-inch pot will hold up to six tulips or three daffodils or more than 15 crocus. Use a deeper pot and you can add layers of bulbs. Fill the pot. Don’t leave spaces between the bulbs.

Here’s a short list of some bulbs that I’ve forced and been very satisfied with, and if you’ve got some favorites of your own please let me know. Tulips (16 weeks) Cassinni, Merry Widow, Palestrina, White Hawk, Apricot Beauty (my favorite), Peerless Pink and Tambour Maitre. Try to avoid the tallest tulips as well as the very shortest varieties. Hyacinths (12 to 16 weeks) Amethyst, Blue Jacket, Jan Bos, L’Innocence, Pink Pearl, Delft Blue and Carnegie. Crocus (10 weeks) Pickwick, Remembrance, Peter Pan, Flower Record, Jean d’Arc, and Purpurea Gradiflora. Daffodils (12 to 16 weeks) Barrrett Browning, Brida Crown, Dutch Master, Ice Follies, Salome, Pink Charm, Tete-aTete, Jenny and Cheerfulness. You’ll find more varieties, charts and more information here: extension2.missouri.edu/g6550. Keep growing.

For those of you who are peepers (as in leaf peepers) it’s time to get out on the road as this weekend may be the peak for colors in New York (Mid Hudson Valley) and lower New England. The drought along with two frosts and a freeze over upstate New York and inland New England had some color showing up two weeks ago. By the time you read this, northern New England will be past its peak while the Catskills and Berkshires will be at slightly past peak this weekend. Take a day — better yet, take two — so you can see one of the few things that we miss on the East End.

And speaking of drought, did you know that this is actually the 11th year of a long-term drought in the Northeast? If you’ve done any planting in the past year or if you plan on planting trees or shrubs this fall, it’s critical to water, then water some more. As long as these plants are growing, and they do grow even though they may drop their leaves, they need water.

If you ordered flower bulbs from a mail-order source, they may be a bit late. Suppliers are so swamped with orders that some wouldn’t take new orders until their existing orders were filled. There’s also a delay in garlic (seed garlic that is) that’s coming from California and Oregon. The fires out there have delayed some harvesting by about two weeks. Not to worry though, as long as you get your garlic planted by the third week in October.

If you had a mulching mower, you wouldn’t have to rake up as many leaves. If your landscaper used a mulching mower, he or she wouldn’t have to take the leaves to be recycled. They’d be recycled right into your lawn with the grass clippings, thus reducing the need for fertilizer by as much as half. And speaking of fertilizer, if you haven’t put it down, do it now. November 1 is the legal deadline, but you still want to do it now when the soil is warm, especially if you are using organics.

Doing a new trial on getting rid of Japanese stiltgrass. When it shows up in patches in my lawn I spray the area with the organic herbicide Burnout. It kills the stiltgrass so it can’t go to seed and while it burns off the tops of perennial grasses it doesn’t kill them and they quickly recover. Stay tuned on this one. Oh, and how does stiltgrass spread? Many times it gets moved around on, of all things, the soles of shoe.