How deep to plant daffodil bulbs? Chill then or not? We put them to the test.
How deep should you plant a daffodil bulb? Should you chill the bulb before you plant it?
To find out, we tested early and late kinds to daffodils in each of the West's four major climate zones. Photographs at left and on page 261 show the results in Southern California; beds in the Northwest and the desert are pictured on page 262.
Results were clear and consistent for all three daffodil varieties we planted. Shoots in each section emerged and bloomed all at once--chilled bulbs bloomed one to three weeks before unchilled ones planted at the same depth; shallow ones bloomed a week or more before those at the next depth. Only in Seattle was this staggering of bloom less pronounced. Know the rules before you break them
Chilling daffodils is not essential and only recently has been recommended for mild-winter climates. The traditional planting depth is two to three times the diameter of the bulb--froughly 6 to 9 inches deep for daffodils as large as these.
This is no doubt the safest all-around depth--deep enough to protect bulbs from frost and summer heat, but shallow enough to avoid minor soil or drainage problems.
But our tests show that there are conditions where other depths may be preferable. And chilling the bulbs definitely yields earlier bloom and an extra margin of safety in mild-winter climates. Putting test results to use
You can spread bloom over a longer period by the following methods. For more predictable results, experiment with either depth or chilling, but not both in the same bed.
Choose early, midseason, and late varieties. The natural timing of a variety proved the strongest influence on bloom sequence. You can find the bloom season from nursery labels or bulb catalogs.
Chill half the bulbs. In mid-winter climates, refrigerate half the bulbs of each variety for six to eight weeks before planting. Store them in paper bags so air can circulate.
Plant at different depths. For the same variety, a 3-inch increase in planting depth meant a five- to eight-day difference in bloom time in both areas or California and in the desert.
For maximum impact at each sequence of bloom, be precise in planting all bulbs in the same group at the same depth. Plant the deepest or latest-blooming bulbs in front to mask the decline of earlier-blooming ones in back.
To delay bloom on early varieties (some bloom by Thanksgiving in California), try planting deeper than usual.
In climates where soil freezes in winter or bakes in summer, stay close to the traditional depth if you leave bulbs in the ground all year. This still gives you a 3-inch range.
In all zones, be cautious about planting any deeper than 9 inches. Even in cool climates, small bulb size or less-than-optimum soil and drainage might cause bulbs planted deeper to fail.
Choose multiflowered varieties. Single daffodil flowers all lasted about the same number of days. Since 'Thalia' and 'Geranium' have many flowers per stem, their beds performed four days to 1-1/2 weeks longer than 'King Alfred' in the Northwest and California. After primary bloom, they also produced many secondary stalks--too short to be showy in the garden, but useful for cutting.
To give an example of the advantage these techniques can yield: in Menlo Park, one test square of 'Thalia' performed for 2-1/2 weeks. Together, the three planting depths spread bloom over 4-1/2 weeks. Chilling half the bulbs at each depth extended the color to 5 weeks. In comparison. 'King Alfred' bloomed for 1-1/2 weeks, and up to 4 weeks by planting at three depths or by chilling half the bulbs. The results, zone by zone
As a guide to how much you can stretch the rules, refer to results in the climate most like your own.
The Northwest is ideal daffodil country. We planted late, shallow, and deep with no ill effects--but also with little gain. Even 12-inch-deep bulbs caught up with shallower-planted ones within a few days, perhaps because soil stayed more evenly cold at all depths. Because bulbs in cold-winter climates normally get ample chilling, we didn't test chilling here.
In the San Francisco Bay Area, every bulb bloomed and leafed out well, but unchilled ones a foot deep had to struggle to surface. Both chilling the bulbs and varying their planting depth staggered bloom over several weeks.
In Southern California, chilling made the difference between success and failure for bulbs stressed by depth or heat. All chilled bulbs bloomed, but unchilled later-blooming kinds planted a foot deep didn't emerge fast enough to bloom.
Desert heat allows less leeway with these bulbs. Plant earlier than late December, choose early-blooming varieties, and chill bulbs if at all possible. If you must plant late, plant shallowly; otherwise, 6 to 8 inches is probably best. Partial shade also helps to prolong bloom. Help us continue our experiment
A single yearhs experiment is not proof. To advance horticultural knowledge further, we'd like to know the results of any experiments you make with depth or chilling. Send a plot plan and copies of your records, with photographs if possible, to Bulb Editor, Sunset Magazine, Menlo Park, Calif. 94025.
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|Date:||Nov 1, 1984|
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