forcing bulbs – Lee Reich

It could be spring. Now. Indoors, with the sweet fragrance from a flowerpot of pastel colored hyacinths and other spring-flowering bulbs. All it takes is a little bit of trickery. The bulbs don’t have to wait till spring. Forced tulip bulbs

Knowing what a bulb is helps understand the trickery. But first: All that we commonly call a “bulb” is not, in fact, a bulb botanically speaking. To conjure up an image of a true bulb, picture a stem that’s been telescoped down from a couple of feet or more long to a fraction of an inch. All the leaves on that bulb also move down and closer together. The leaves, except the innermost ones, are thick and juicy, the better to store both moisture and food reserves. Near the center of the bulb is a sleeping flower bud.

Hyacinths, daffodils, and tulips are true bulbs.

Though often called a bulb, crocus is an example of a “corm.” A corm is also a short stem, in this case a short fat stem which provides storage for food reserves for winter and to fuel early spring growth.

Forcing a bulb, real or not, to flower early, indoors is, in many ways, just like forcing a cut branch of dogwood or plum to flower early, indoors. Daffodil, hyacinth, tulip, crocus, dogwood, and plum stems all enter winter with flower buds sleeping within.

All these stems of cold-climate plants are savvy enough not to start growing in the dead of winter, even after a freak warm spell. They do this by marking time, counting hours and days when temperatures are between about 30 and 45 degrees Fahrenheit, that is, cool but not frigid. Once sufficient hours have accumulated, their chilling “bank” has been filled, warmth can awaken a stem, whether its a dogwood branch or a daffodil bulb.

The first step in forcing a bulb is to get it to grow roots by planting it in a pot of soil or stones, or to suspend the bulb above water with only its base in the drink. A bulb’s roots, like the roots of other plants, grow whenever soil temperatures are above 40°F., so they can be in place and ready to support leaves and flowers when spring comes.

In time, typically 6 to 8 weeks, which varies with the type and variety of bulb, roots will grow and the the winter chilling requirement will be satisfied. Once the chilling “bank” has been filled, growth can begin. A well-grown, spring-flowering bulb comes packed with a flowerbud-in-waiting . . . waiting, that is, for a chilling period to break its dormancy and then sufficient warmth to allow growth. The larger the bulb, the more flowers-in-waiting.

Keeping a potted bulb cool at this point is useful for staggering flowering for multiple pots of bulbs or delaying flowering for a specific date, such as someone’s birthday.

When ready to enjoy the flowers, don’t just bring the pot into a hot room. They would blast open and collapse. The plants, at this point, need gradually increasing warmth, and enough light to draw out a sturdy flower stalk. Forcing bulbs to blossom out of season demands a certain amount of artistry in addition to science.

If you want flowers and want them now, and haven’t prepared bulbs ahead of time, you still have some options. Purchasing pre-chilled bulbs is one option.

The other option is to bypass the whole chilling rigamarole and force Paperwhite narcissi. These bulbs hail from perennially warm climes and will bloom without any prior chilling. All that’s needed is to pot them up and wait as long as it takes for the fragrant, white blossoms to unfold. To stagger their blooms, pot them up sequentially; lack of water keeps them dormant.

When the flower on a forced bulb has wilted and the show is over, the usual next home for the bulb is the compost pile. If the plant has been planted in soil, and if the emerging leaves can be kept growing in very bright light for many weeks, sufficient energy can be garnered keep the bulb alive through the following dormant season. Then plant the bulb outdoors this autumn and it should flower again — in a few springs hence, once it garners enough energy to also make flower buds.

My kitchen isn’t filled with the fragrance and beauty of blooming daffodils, and I have no one to blame but — no, not myself, but — the local store where I bought the bulb last autumn. How could I have resisted? Sitting right by the checkout counter of the store was a bucket full of bulbs, each bulb only one dollar and having the makings of fragrance and beauty already locked within.

Yes, “already locked within.” Spring bulbs’ flowers are initiated in the growing season before the flowers appear. The key to unlocking the pleasures lurking within most spring bulbs is cold temperatures. A period of cold weather lets these bulbs know that winter is over and it’s all right to awaken and blossom. Exposure to cold happens naturally outdoors, with the flowers appearing in spring.

When “forcing” bulbs for early bloom, you trick the bulbs into thinking that winter is over by exposing them to the requisite amount of cold, which varies for different kinds of bulbs. Brought indoors in winter to warmer temperatures, they can then blossom out of season.

The bulb that I bought was a “paperwhite” daffodil, a species (Narcissus tazzeta) that originated in warmer regions of the western Asia. In those warm regions, paperwhites evolved to flower without needing to experience winter cold. So buy one of these bulbs in autumn, pot it up or put its base in water, and bingo, flowers soon appear.

Except for the paperwhite that I purchased. That bulb just kept growing leaves, an indication that last year’s growing conditions were not good enough — insufficient light, fertility, or water perhaps — for the bulb to divert energy into making a flower bud.

The present bulb is the second one I got from the same bin this past autumn. After the first one showed no sign of flowers, I went back to the store, explained why, as long as the bulb grows, it should make a flower, and received a second one free of charge.

I figured the first bad bulb was an aberration. It wasn’t. I’ve been watching leaf after leaf unfurl on the second dud for weeks and weeks.

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In an effort to make my farmdening even more sustainable, I’m swearing off peat moss, or hoping to. Peat moss is the partially decomposed remains of plants, mostly sphagnum species. In the garden or farmden, peat moss is very useful for improving soil aeration, and water and nutrient retention. Mostly, these benefits are put to use in potting soils to help roots in their rather limited growing space. My home-made potting mix, which I’ve made for over 30 years, is 1/4 by volume peat moss (the other 1/4s comprised of garden soil, perlite, and compost, and a bit of soybean meal and kelp meal for added nutrients).

Use of peat is unsustainable because its mining outstrips its rate of formation. Peat accumulation can occur at a snail’s pace: an inch or so per thousand years. Peat develops under boggy conditions and to mine it, the bog must be first drained. Air replaces the water and the result is that some of the carbon stored in peat is oxidized to carbon dioxide. And we all know what that does. As a final blow to sustainability, draining and mining peat bogs upsets its unique ecological habitats.

So must gardening and farmdening, both potentially sustainable practices for providing local food that can to be grown with minimal environmental disruption, be wedded to the use of peat moss? Not necessarily.

Other organic materials, such as compost and leaf mold, can fulfill the same functions as peat moss in potting mixes. They have the further advantages of being local and richer in plant food than peat moss. They have the disadvantages that you have to make the stuff, that planning is needed because you have to gather the materials and wait for them to “cook,” and that the final product may not always be consistently the same.

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A consistent, commercial peat substitute coming down the pike is coir, a renewable byproduct of coconut processing with characteristics very similar to peat moss. I’ve experimented occasionally with coir over the years and it seemed to work well enough. However, seedlings planted in a recent batch containing coir aren’t thriving.

Anytime a component of a potting mix is changed, changes might also be needed in watering regime or fertilization. My guess is that watering is the problem since my potting mix has plenty of nutrients from the compost and soybean meal, and the symptoms — poor growth and leaves wrinkly but not off-color — don’t indicate any nutrient deficiency. The symptoms seem more like those due to poor root growth, possibly from excessive moisture. Or perhaps the soil or compost had some weak root pathogen that’s getting the upper hand.

I need to sleuth out this problem soon because I’m about to make a large sowing of cabbage and its kin as well as peppers and eggplants. On the plus side, all this is some of what makes gardening so interesting.

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Any gardening questions? Email them to me at garden@leereich.com and I’ll try answering them directly or in this column. Come visit my garden at www.leereich.blogspot.com.

Posts

An Early Spring

Coir, A Substitute for Peat