Planting flower bulbs that return year after year

Bulbs return each year when they are planted at the right depth, set in soil that drains well and given time to rebuild their energy after flowering. Most spring-flowering bulbs go into the ground in autumn, when cool soil lets roots form before winter. The bulb then blooms the following spring, using energy it stored during the previous growing season.

Whether a bulb comes back depends on the type of bulb and on the climate. Daffodils and many species tulips are generally more reliable perennials than the large hybrid tulips that many gardeners treat as one-season plants. Choosing varieties that suit your region and the conditions in your bed is the most important decision before you dig.

Choose the right time and bulbs

Plant spring-flowering bulbs in autumn, typically about six weeks before the ground freezes in cold climates. That interval gives roots time to establish before winter arrives. In milder regions, planting in late autumn or early winter usually works well, though local guidance on timing is worth checking. Many spring bulbs need a period of cold to flower well, which is one reason they are grown in temperate climates.

Select bulbs that are firm and free of soft spots, mold or cracked skins. A bulb that feels light for its size or looks shriveled may have dried out in storage and will be less likely to produce a strong flower. Plant the varieties with a reputation for coming back, such as daffodils, grape hyacinths, crocus, snowdrops, alliums and species tulips. Daffodils and alliums are also less attractive to deer and rodents than many other bulbs, which can make a difference in gardens where animals are a problem.

Not every bulb comes back in every climate. In cold-winter areas, many summer-flowering bulbs, corms and tubers, such as dahlias, gladiolus and cannas, are tender and will not survive the ground freezing. They return only if you lift them after frost has blackened the foliage, dry them and store them in a cool place that stays frost-free over winter, then replant them in spring. In warm-winter regions the problem is reversed for spring bulbs. Tulips and hyacinths need a period of cold before they flower, and in mild winters they often bloom poorly the following year, so many gardeners treat them as one-season plants there. Pre-chilling tulip and hyacinth bulbs in a refrigerator is possible, but the bulbs must be kept away from ripening fruit, which releases ethylene that can damage flower buds.

Set the depth, spacing and soil

A common rule is to plant bulbs at a depth about two to three times their height. In practice, small bulbs such as crocus and grape hyacinth go about three inches deep, while large bulbs such as daffodils and tulips often go six to eight inches deep. Set each bulb with the pointed end facing up. If you cannot tell which end is which, plant the bulb on its side. Most bulbs will still find their way up, although the flowers may emerge a little later.

Space bulbs roughly two to three bulb widths apart. That spacing gives each bulb room to multiply without becoming crowded, and it allows the planting to look full the first spring. Plant in groups rather than in a single straight row, since clusters look more natural and tend to produce a stronger display. Drifts of one kind of bulb, or a mix of early and mid-season types, make the bed look intentional.

Mark the planting area with a label or a sketch of the layout, so that you do not dig into the bulbs when you plant something nearby later. Bulbs in containers need more care than bulbs in the ground. Their roots are more exposed to freezing in cold climates, so pots should be sited against a sheltered wall or moved into a protected, unheated space over winter, and every pot needs drainage holes.

Soil drainage is the factor most likely to decide whether bulbs survive. Bulbs rot in waterlogged soil, so choose a site where water does not pool after rain. Loosen the soil to about a foot deep and mix in compost. In heavy clay, adding organic matter and planting on a slightly raised area can improve drainage. Water the bed after planting to settle the soil around the bulbs, and apply a bulb fertilizer or a balanced granular fertilizer at planting time, following the label. Keep high-nitrogen lawn fertilizer away from the bulb bed, since too much nitrogen encourages leaves at the expense of flowers.

Let the foliage die back

After bloom, the leaves keep working. They gather light and send energy back into the bulb, which is what allows it to flower again next year. Leave the foliage in place until it has turned yellow and died back naturally, which usually takes about six weeks after flowering. Cutting leaves early, tying them in knots or braiding them can reduce the energy the bulb stores and weaken the following year's bloom.

Hiding the fading foliage is easier than it sounds. Plant perennials that emerge later in the season among the bulbs, so their fresh growth covers the yellowing leaves. Removing the spent flower heads, if you prefer, keeps the plant from putting energy into seed. Feeding timing matters here. Apply a bulb fertilizer at planting, then feed again in spring as the shoots emerge or just after flowering, while the leaves are still green. Once the foliage yellows, the bulb is already withdrawing its reserves and takes up little, so feeding then does little for next year's bloom.

Bulbs need patience. The first season after planting often gives the strongest show, and the following seasons depend on the variety, the soil and how crowded the bulbs have become. When a clump begins to flower less or to produce smaller flowers, lift it after the foliage has died back, separate the bulbs and replant them at the correct depth and spacing. Dividing a crowded clump every few years is part of keeping a bulb planting going for many seasons. Keep a short note of which bulbs flowered well and which did not, since that record makes it easier to choose replacements or additions the following autumn.