Can You Force Spring Flowering Bulbs Outdoors To Flower Early? [YES]

Many gardeners take it for granted that spring flowering bulbs planted in the garden will bloom when it is time and nothing will cause them to bloom earlier.

There are, however, planting practices that will “force” flowering from a few days to three weeks or more. These practices are especially worthwhile for those tired of a flowerless winter garden and can hardly wait for the first spring bloom.

Daffodils, tulips, crocuses, and most other kinds of spring-flowering bulbs come in early, midseason and late varieties.

large group of spring flowering crocus bulbs

Variety Makes Early Blooms Easier

It is easier to enjoy early blooms from an early variety than from midseason or late kinds, but any variety can be forced to bloom ahead of its normal time.

The easiest way to force bloom in the garden is by planting bulbs along the south side of a:

  • House
  • Wall
  • Fence
  • Slope
  • Stone
  • or anything else offering protection on the north side

These bulbs will bloom earlier than other bulbs of the same variety given any other exposure.

A daffodil planted in front of a basement window on the south side of a house will bloom earlier than others in the same row because of the heat reflected from the glass.

Some varieties bloom as much as three weeks early with such planting.

The bulb for which south side planting is most important is probably the crocus because so much of its garden value is its earliness. Crocuses planted on a slope facing south will bloom considerably earlier than the same variety planted in the lawn.

The steeper the slope the earlier the bloom.

Some gardens repeatedly have crocuses planted against the south side of a tree finish blooming before the same variety in the lawn opened its first buds.

Planting Depth Influences Time Of Bloom

The time of bloom is influenced also by the depth of planting. The depth recommended for most bulbs is three times the bulb’s diameter, though the madonna lily (Lilium candidum) and certain other bulbs are exceptions to the rule.

Planting at less than the recommended depth tends to hurry bloom from one to several days in bulbs, much more in the case of some late summer bulbs.

Spring bulbs given very shallow planting are often heaved out of the ground during thawing weather. Strong growing kinds show no apparent injury if they are promptly shoved back into place.

Only strong growing bulbs should be given shallow planting. Bulbs of questionable hardiness should be planted at the recommended depth.

This is particularly true, for example, of tulips in areas of the country where it is an achievement to get them to bloom for more than a single season, or even for one season.

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An important incidental effect of shallow planting is a rapid increase in the number of bulbs. A daffodil bulb planted at half the usual depth will in many locations produce a hundred or more bulbs in a dozen years.

Most of the bulbs will be too small to bloom but can be grown to flowering size in a year or two if the clump is lifted, separated, and the bulbs replanted.

Tulips, hyacinths and other bulbs tend to increase more quickly with shallow planting than at the usual depth but not at anything like the rate of daffodils.

yellow spring blooming Daffodils

Speeding Up Spring-Planted Lilies

Hurrying bloom by shallow planting is particularly worthwhile for spring-planted lilies such as speciosum.

Lilies should, of course, be planted in the fall but it is in spring the garden center stores display a wealth of irresistible looking lily bulbs.

If you select firm, compact bulbs heavy for their size and give them shallow planting they should bloom safely ahead of frost.

If planted in the spring at the recommended depth comparatively few will bloom the first fall. A covering of two inches is usually enough for speciosum lilies planted in the spring.

The shallow planting does the bulb itself no good. On the other hand it does no great harm if the bulbs are lifted their first fall and quickly replanted at the usual depth.

Liquid Fertilizer Feeding

Feeding with liquid fertilizer will hurry the flowering of most bulbs by a few days, providing the feeding is started after flower buds show.

If started too early the feeding may cause the bulb to make extra leaf growth at the expense of bloom.

Any soluble fertilizer can be made into liquid fertilizer by dissolving it in water. Insoluble fertilizers such as manure should be put in a barrel or other coverable container with plenty of water.

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After standing ten days or longer the water will be excellent liquid fertilizer. Dilute to the color of weak tea before application.

Any liquid fertilizer should be applied to the ground around the bulb and avoid touching stem or foliage.

A cupful to the bulb or clump of bulbs is enough.

Make applications at weekly intervals. Results are best if the application is followed by heavy watering.

A quick-acting stimulant is nitrate of soda. It should be used only in solution as too much will kill any plant quickly.

Fortunately only so much – approximately a tablespoonful to a gallon – will dissolve in water no matter how vigorously you may stir.

This strength is safe to use at the rate of a small cupful to the bulb or clump of bulbs, provided it does not touch stem or foliage and is well watered in.

A single application should hurry bloom three or more days.

Ground Heat

Heating the ground will hurry bloom provided it is not overdone. A popular method is using buried low voltage soil heating cables.

It is possible to hurry bloom by this use of electricity almost as much as by the old hotbed.

During sunny weather, the ground heats in the daytime. Any method of holding the heat in the ground after the sun goes down will speed up bloom.

Night covering is another common method. Fabric caps or cloches, wood boxes or baskets, corrugated paper cartons – all have been useful where just a few bulbs are concerned.

A box is large enough to cover a crocus, a bushel basket will cover a sizable clump of daffodils or tulips. The overturned box or basket can be covered by an old rug or quilt.

Make sure the foliage does not touch the covering.

Managed Mulching

Mulching can be managed to influence time of bloom by a couple of days or more. Early removal of mulch will hurry bloom a little.

Often it is safest to remove it in installments rather than to remove all of a heavy mulch at one time.

Bulbs growing in the garden a year or longer will bloom ahead of the same variety given similar planting the previous fall.

Gardeners may, therefore, reasonably expect earlier bloom a year after planting than the first spring after planting.

Summing Up The Forcing Of Spring Flower Bulbs

To sum up…

In general, the earliest bloom can be expected:

  • From an early variety established in the garden for a year or more
  • Planted at a shallow depth on the south side of the house
  • In front of a basement window
  • Given right covering
  • Proper feeding of liquid fertilizer

Enjoy!