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The basics of naturalizing bulbs.

Given the right conditions, many kinds of spring-blooming 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 10-10-10) into the soil; these are generally better sources of nutrients than bonemeal. Fertilize again at bloom time or just when flowers fade. During the following seasons, broadcast fertilizer over the soil and rake it in when flowers first emerge.


By laying out bulbs on top of the soil before you dig the first one in, you can fine-tune your planting scheme and distribute bulbs evenly. Or, for a natural random effect in a field or large planting area, just toss the bulbs onto the ground and plant them where they land.

In well-prepared or sandy soil, one of the easiest ways to plant is to use a trowel. Hold the trowel as shown below, stab it into the ground, and pull it toward you. Then drop the bulb in and cover it with soil.

For planting depth, the standard guideline is to set a bulb so it's covered with soil three times as deep as the bulb's diameter. But there are exceptions. In hot climates or sandy soil, plant slightly deeper than recommended; in heavy soil, plant slightly shallower. Some types of bulbs should be planted just below the soil surface.

Bulbs can handle a tremendous amount of crowding, but if you want bulbs to naturalize for a few years without having to divide them, don't jam them together.


Water bulbs well at planting time, then water as needed to keep the soil moist (but not saturated) through winter and spring while roots are growing and flowers are blooming. A layer of mulch over the soil will help maintain soil moisture.

Right after petals have faded or fallen off, remove the flower stalks, but let the foliage remain and continue photosynthesizing, so bulbs will store up nutrients for next season's show. Wait for foliage to turn limp and yellow, then cut it back to 4 to 6 inches above the soil; pulling it off too soon can damage the bulb. Or wait until foliage dries up and then pull it off.


Many bulbs can be left undivided for years. But if bulbs aren't blooming well because of overcrowding, then it's time to divide. Daffodils may need dividing every three to five years; divide them by separating one or more healthy noses from the clump as shown above right.

Lift most bulbs in summer after the foliage dies down. Using a spading fork, carefully dig up and separate clumps into individual bulbs; each new bulb should include a piece of basal plate - the area from which new roots grow.


If bulbs decline prematurely, the problem is more likely to be over-watering than disease. To prevent infection, plant where there's plenty of air circulation, keep beds free of debris, and keep the soil dry when bulbs are dormant. Remove and destroy any infected plant parts and rotting bulbs.

Gophers go after most bulbs except daffodils. So do mice, which use mole tunnels to reach bulbs. To ward off these critters, use hardware cloth to surround bulbs or to line an entire bed. You can fashion a protective basket by bending two rectangles of hardware cloth into U shapes and nesting one inside the other so you have wire on all four sides; bury the basket so the edges are at soil level.
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Copyright 1996 Gale, Cengage Learning. All rights reserved.

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Title Annotation:caring for flowering bulbs
Date:Sep 22, 1996
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