Magazine article Sunset

The Basics of Naturalizing Bulbs

Magazine article Sunset

The Basics of Naturalizing Bulbs

Article excerpt

Bulb sizes of 'King Alfred'-type daffodils are graded, from left to right, DN 3 (one flower per bulb), DN 2 (one or two flowers), DN 1 (two or three flowers), and jumbo (three or four flowers).

Given the right conditions, many kinds of springblooming bulbs become so well established in the garden that they naturalize: they keep coming back year after year, and some even multiply. Among the best bets for naturalizing are daffodils, Dutch irises, freesias, and species tulips. But to get maximum flower production from naturalized bulbs, it helps to stack the odds in your favor. Success depends on a number of factors-from the size of the bulbs you buy to how you plant and maintain the beds.


Like eggs, bulbs are graded by size. Generally, the bigger the circumference, the more flowers you get. The most common sizes of daffodils range from DN 1 down to DN 3. The largest `King Alfred' types are called jumbos. Daffodils smaller than DN 1 may be labeled in centimeters (typically 14 centimeters and smaller).

Dutch irises are graded in centimeters. They range in size from 6 to 12 centimeters or larger; 8 to 9 centimeters is typical.

Sizes vary according to variety, too. For instance, large-cupped and trumpet daffodils produce larger bulbs than species and miniatures, and blue Dutch iris bulbs are larger than the purple and yellow kinds.

Look for a note in catalogs that indicates the size and quality of bulbs; it may simply say top-size bulbs. When shopping locally, buy early in the season and choose firm bulbs that aren't sprouting. Generally, they should still have their outer skins intact, although sometimes pieces fall off in the box.


Good soil drainage is the key to long bulb life. Where the soil drains poorly, plant your bulbs on a slope or in raised beds.

Before planting, add organic amendments if your soil is clayey, sandy, rocky, or low in nutrients. Your best bets are leaf mold, redwood soil conditioner, compost, or similar products; unless it's well aged, manure can burn bulbs. If the soil is low in organic matter, spread about 3 inches over the planting area and dig it in; use only an inch or so if the soil is already fairly loose and loamy. In acid soil in the Pacific Northwest, you may need to add lime to neutralize the soil.

At planting time, mix a bulb food or a balanced fertilizer (such as 1010-10) into the soil; these are generally better sources of nutrients than bonemeal. Fertilize again at bloom time or just when flowers fade. …

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