Testing the rules is one way to expand your gardening knowledge.
When you see the reasons behind the rules clearly, you understand better
how far you can bend them to suit your own circumstances and desires.
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
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
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.