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Planting Bulbs in the Right Season
Planting Seasons and Blooming Seasons Differ
It’s important to plant bulbs in their proper planting season, but that’s a much different time from when they grow and bloom.
We plant most garden plants from seed a few weeks or months before they mature, but bulbs are different.
You should be familiar with the major groups of bulbs: Spring-blooming, summer-blooming, autumn-blooming, and tropical or evergreens [for a refresher, see: Bulbs and Seasons of Bloom].
Unlike other landscape plants, bulbs use their specialized roots and dormancy habits as storehouses the call on only when it’s the right time to grow.
They instinctively react to the presence of warmth and moisture to break dormancy, rapidly shoot up and flower. Then, they divide or reproduce and store energy before returning to their dormant state.
If we wait to plant bulbs until a few weeks before we want them to bloom, the garden conditions fail to trigger a growth cycle and they stay dormant. We can fool bulbs once through the trick of forcing, but then they go back to their regular cycles [see: Forcing Bulbs].
Take a few minutes to look at the Bloom Season of Common Bulbs [see: Bulbs and Seasons of Bloom].
Most confusing as a group are the spring bulbs—early spring, spring, and late-spring blooming species. You’ll want to consult the Bulb Planting Regions map to choose the best times to plant bulbs in this group depending on where you live and garden [see: Bulb Basics].
Summer- and autumn-blooming bulbs are much simpler. They follow the general gardening rule of planting in the spring to enjoy summer and autumn flowers. Late-autumn and winter-blooming bulbs are planted in late summer, after the heat has broken.
For your convenience, you’ll also find the proper planting times for every popular bulb species in the bulbs guide [see: Bulbs].
When to Plant Summer and Autumn Bulbs
Warm weather’s arrival in spring signals planting time for summer- and autumn-blooming bulbs.
Wait to plant these species until your garden’s soil has warmed thoroughly. That usually lags behind the first weeks of warm days, and avoids surprising cold snaps or cool evenings. The nighttime air temperature is another guide.
The air temperature should be consistently above 60°F (16°C) for at least 10 days before you plant summer and autumn bulbs.
Lilies: An Exception
An exception are lilies, a group of bulbs that are quite hardy. Plant them as soon as the soil can be worked in spring, if possible. Lily bulbs also are susceptible to drying out. Buy them early in the season and plant them immediately.
(If you must store lily bulbs for a time, place them in slightly moist peat moss and keep them in a dark area at about 40°F (4°C) [see: Curing and Storing Bulbs].
Tender Bulbs
The remaining, tender bulbs—tuberous begonia, caladium, calla lily, canna, dahlia, and gladiolus—sometimes sprout early growth before planting conditions are right. This is normal.
When early growth takes place, go ahead and plant them. Protecting them with a floating row cover if frosts occur. In milder climates, apply an insulating mulch over the planting to insulate the soil.
Remember to thoroughly water new summer bulb plantings shortly after planting [see: Post-Planting Bulb Care]. Irrigation helps restore moisture, compacts the soil around the bulbs, and triggers the end of dormancy.
Also apply mulch to the planting area [see: Mulching Landscape Bulb Plantings]. It adds more than a neat appearance to your beds. Mulch retains moisture, insulates the soil, and blocks competing weeds from sprouting.