Testing the rules is one way to expand your gardening knowledge.When you see the reasons behind the rules clearly, you understand betterhow far you can bend them to suit your own circumstances and desires. How deep should you plant a daffodil bulb? Should you chill thebulb before you plant it? To find out, we tested early and late kinds to daffodils in each ofthe West’s four major climate zones. Photographs at left and onpage 261 show the results in Southern California; beds in the Northwestand the desert are pictured on page 262. Results were clear and consistent for all three daffodil varietieswe planted. Shoots in each section emerged and bloomed all atonce–chilled bulbs bloomed one to three weeks before unchilled onesplanted at the same depth; shallow ones bloomed a week or more beforethose at the next depth. Only in Seattle was this staggering of bloomless pronounced.
Know the rules before you break them Chilling daffodils is not essential and only recently has beenrecommended for mild-winter climates. The traditional planting depth istwo to three times the diameter of the bulb–froughly 6 to 9 inches deepfor daffodils as large as these. This is no doubt the safest all-around depth–deep enough toprotect bulbs from frost and summer heat, but shallow enough to avoidminor soil or drainage problems.
But our tests show that there are conditions where other depths maybe preferable. And chilling the bulbs definitely yields earlier bloomand an extra margin of safety in mild-winter climates. Putting testresults 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 ofa variety proved the strongest influence on bloom sequence. You canfind the bloom season from nursery labels or bulb catalogs. Chill half the bulbs.
In mid-winter climates, refrigerate half thebulbs of each variety for six to eight weeks before planting. Store themin paper bags so air can circulate. Plant at different depths. For the same variety, a 3-inch increasein planting depth meant a five- to eight-day difference in bloom time inboth areas or California and in the desert. For maximum impact at each sequence of bloom, be precise inplanting all bulbs in the same group at the same depth. Plant thedeepest or latest-blooming bulbs in front to mask the decline ofearlier-blooming ones in back. To delay bloom on early varieties (some bloom by Thanksgiving inCalifornia), try planting deeper than usual.
In climates where soil freezes in winter or bakes in summer, stayclose to the traditional depth if you leave bulbs in the ground allyear. 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 anddrainage might cause bulbs planted deeper to fail. Choose multiflowered varieties. Single daffodil flowers all lastedabout the same number of days.
Since ‘Thalia’ and’Geranium’ have many flowers per stem, their beds performedfour days to 1-1/2 weeks longer than ‘King Alfred’ in theNorthwest and California. After primary bloom, they also produced manysecondary stalks–too short to be showy in the garden, but useful forcutting. To give an example of the advantage these techniques can yield: inMenlo Park, one test square of ‘Thalia’ performed for 2-1/2weeks. Together, the three planting depths spread bloom over 4-1/2weeks. Chilling half the bulbs at each depth extended the color to 5weeks. In comparison.
‘King Alfred’ bloomed for 1-1/2 weeks,and up to 4 weeks by planting at three depths or by chilling half thebulbs. The results, zone by zone As a guide to how much you can stretch the rules, refer to resultsin 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. Even12-inch-deep bulbs caught up with shallower-planted ones within a fewdays, perhaps because soil stayed more evenly cold at all depths.Because bulbs in cold-winter climates normally get ample chilling, wedidn’t test chilling here. In the San Francisco Bay Area, every bulb bloomed and leafed outwell, but unchilled ones a foot deep had to struggle to surface.
Bothchilling the bulbs and varying their planting depth staggered bloom overseveral weeks. In Southern California, chilling made the difference betweensuccess and failure for bulbs stressed by depth or heat. All chilledbulbs bloomed, but unchilled later-blooming kinds planted a foot deepdidn’t emerge fast enough to bloom. Desert heat allows less leeway with these bulbs. Plant earlierthan late December, choose early-blooming varieties, and chill bulbs ifat all possible. If you must plant late, plant shallowly; otherwise, 6to 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 experimentsyou make with depth or chilling. Send a plot plan and copies of yourrecords, with photographs if possible, to Bulb Editor, Sunset Magazine,Menlo Park, Calif. 94025.