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How to naturalize spring-flowering bulbs

Bulb flowers that have been naturalized will come back every spring if planted in the right location.

By Sally FergusonNetherlands Flower Bulb Information Center / October 29, 2009

Once you've grown alliums, it's hard to imagine life without them. Their lollipop flowers add an element of elegant whimsy to garden and landscape settings. Alliums naturalize beautifully and are pest-resistant.

Photo courtesy of Netherlands Flower Bulb Information Center.

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Gardeners know that fall is prime time for planting. The cooler temperatures and frequent rains of autumn make conditions perfect for establishing the flower bulbs, perennials, trees, shrubs, and lawns that add to a home’s appeal.

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Of these, only spring-blooming bulbs absolutely must be planted in fall. This “now or never” push makes fall bulb planting an annual tradition in many households, where spending an hour or two each fall can reap colorful spring time benefits for years.

Not surprisingly, it’s many bulbs’ ability to naturalize and come back to bloom year after year that attracts people.

This come-back benefit makes bulbs a smart investment, both financially and emotionally. When naturalized spring bulb flowers come up and bloom each spring, you begin to think of them as more than seasonal markers. You wait for them. They come back as "friends."

Spring-blooming bulb flowers – including daffodils, species tulips, grape hyacinths, crocus, scilla, and more – can be planted to naturalize in beds, ground covers, even the lawn where you can tuck the bulbs right under the grass.The secret to planting naturalized bulbs is that you don’t have to do it all at once. Pace yourself. Each year treat yourself to something new or something more.

What does naturalizing mean?

Many spring-blooming bulbs will thrive in a wide variety of garden conditions. Some, including many tulip varieties and hyacinths, are best treated as annuals. Others will “perennialize” or do well for three to four years before diminishing.

Others will make themselves right at home and “naturalize” into the landscape. Technically, naturalizing bulbs are those that accommodate themselves fully to their new sites, feeling so at home that they multiply naturally, on their own, increasing in numbers year after year.

Why will some bulbs naturalize and others won't? Actually, most bulbs are, by definition, perennials. But, in reality, not all bulbs will adapt to diverse growing conditions so readily.

A lot depends on the particular type of bulb and the particular planting site. Soil, climate, water, and other conditions all play a part in determining which types of bulbs will be the best repeat performers in any given environment.

A further critical factor is that, to naturalize, the bulb plant must be left undisturbed after bloom, with leaves left intact for six weeks or more to die back naturally. It's during this post-bloom period that the green leaves take on the task of recharging the bulb with stored food starches for next year’s bloom via the process of photosynthesis.

Look for bulbs marked “good for naturalizing” or “good for perennializing” on packaging, in mail-order website listings, or at www.bulb.com (see Spring Bulbs).

What about squirrels, deer and other pests? Good old Mother Nature is a step ahead of you here, having programmed flower bulbs as mini-subterranean survival units.

Many (though not all) of the bulbs that naturalize best are also among the most pest-resistant! If animal pests are a problem in your area, check out the lists of pest-resistant bulbs on www.bulb.com (Spring Bulbs, pest prevention tips).

Plant in soil that drains well. Soggy soil rots bulbs. Avoid planting where water collects such as the base of hills, near downspouts, or in landscape depressions.

In garden beds, work organic matter such as compost, well-aged cow manure, or peat into the soil, mixing it in deep enough to provide drainage at root level.

Consider the sunlight. Most bulb plants prefer full sun. But don’t let fall planting conditions fool you. What’s dark and shady in fall may be bright and sunny next spring before the trees’ new leaves come out.

For early and mid-season spring bloomers, most deciduous trees will not yet have leafed out. For late-season bloomers, shade may be an issue.

Which sites are best? When naturalizing, think long term. You want to choose sites where your colorful spring bulb flowers can become a part of the landscape, multiplying and spreading over time.

Flower beds are great, of course. So are sunny or partly sunny lawns, ground cover beds, forest edges, roadside edges. These are all places where flamboyant spring bloomers thrive.

Even shady woodlands areas can be enlivened with permanent naturalized bulb plantings of shade-loving species such as Allium ursinum (ransom), Anemone nemorosa (wood anemone), Corydalis, Arum italicum, Fritillaria meleagris (snakeshead fritillaria), Galanthus nivalis (snowdrop), Hyacinthoides non-scripta (bluebell), and Ornithogalum umbellatum (star of Bethlehem).