Selecting and Planting Flower Bulbs

From the purchase to maintaining them throughout the season, this simple guide to bulbs will help ensure garden success.
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Alliums Planted in Fall and Flower in Early Summer

Alliums Planted in Fall and Flower in Early Summer

Known as flowering onions, Allium are exotic, unique and extend flowering season with dramatic color and unusual, show stopping shapes and forms. They produce dense globes of starry flowers that are planted in the fall and bloom in early summer.

©2011, Dorling Kindersley Limited

2011, Dorling Kindersley Limited

Known as flowering onions, Allium are exotic, unique and extend flowering season with dramatic color and unusual, show stopping shapes and forms. They produce dense globes of starry flowers that are planted in the fall and bloom in early summer.

Bulbs are very easy to grow; simply plant them a few months before they are due to bloom. Most prefer full sun and free-draining soil, but some will thrive in shady sites beneath deciduous trees.

This diverse group of plants offers interest almost all year round, from snowdrops at the end of the winter to colchicums and nerines in the fall, with a vast array of bulbs in bloom in between. For a year-round display, start with colorful spring bulbs, such as tulips and daffodils, and mix in some alliums, which will flower on the cusp of the new season, their pom-pom blooms providing dramatic accents in beds and borders. Lilies are the stars of summer, with their large, fragrant blooms in shades from cool white to deep maroon stealing the show. From midsummer, spice up your garden with tender dahlias, gladioli, cannas, and long-flowering Peruvian lilies (Alstroemeria), and end the year with a display of delicate nerines, if you have a sunny, sheltered garden to suit them, or cyclamen and colchicums in colder spots.

What Is a Bulb?

It can be confusing when you discover that the word “bulb” is often used as a blanket term for any plant that has an underground food-storage organ. As well as true bulbs, there are three other forms: corms, rhizomes, and tubers. Each type of bulb has evolved to cope with a variety of growing conditions and allows the plants to survive when dormant and during adverse conditions, such as during prolonged periods of drought. Learn more below about the bulbs that will best suit your garden space: 

  • True bulbs: Daffodils, tulips, and Eucomis are all true bulbs. The bulbs are made of leaves layered like an onion, covered with a protective papery skin or tunic. Lily bulbs are looser in form and lack a skin—plant them on their sides to prevent water from seeping in and rotting them.
  • Rhizomes: The most common rhizomatous plants are bearded irises, although Dutch and reticulata irises are bulbs. Rhizomes have a swollen root that grows horizontally near the soil surface and produces several buds along it, which then develop into leaves and flower stems.
  • Corms: Gladiolus and crocus are typical corms. These are formed by the swollen bases of the plants’ stems and are more rounded in shape than true bulbs. They produce one or two buds at the top, and tiny cormlets grow around the base.
  • Tubers: Tubers fall into two categories: root tubers, such as dahlias, which are basically enlarged roots, and stem tubers, like begonias, which are swollen underground stems similar to rhizomes. Tubers produce buds or eyes along their length, and each can form a new plant.

Unusual Varieties

Create a talking point by growing a range of unusual bulbs in borders or containers for a striking mix of foliage and flower forms. Seek out specialty suppliers for the widest choice, and ensure that your site and soil are suitable; growing bulbs in containers will allow you to control the growing conditions more easily.

In spring, try the elegant maroon or cream bells of the stately bulb Fritillaria persica. Unlike its diminutive cousin the snake’s head fritillary (F. meleagris), this large plant grows up to 5 feet (1.5 m) in height, creating a dramatic statement in a border. Triteleia hyacinthina is smaller but equally impressive, producing umbels of starry white flowers on slim stems.

For summer color, try Dichelostemma with its tubular bell-like blooms in reds, pinks, and purples, and the elegant corn lily, Ixia viridiflora, which produces dainty star-shaped blooms. Also add a few brightly colored Sparaxis hybrids, which come in an assortment of fiery shades, and in pots, beds, or borders are guaranteed to turn heads throughout the summer months. 

When to Plant

  • Spring flowers: Plant spring-flowering bulbs, such as daffodils, tulips, grape hyacinths (Muscari), crocuses, and other hardy types in the fall to overwinter and then flower the following year. Most can be planted early in the season, but leave tulips until late fall to minimize the risk of the plants developing the disease tulip fire.
  • Summer flowers: Alliums, which flower in early summer, are best planted in the fall, but the majority of other summer bulbs should be started off in the spring. Plant tender types, such as dahlia tubers and gladioli corms, in pots indoors to be moved out later, or plant outside when the soil has warmed up and the worst frost has passed.
  • Fall and winter flowers: Plant nerine bulbs in a warm, sheltered, free-draining site or in a container in the fall to flower the following year. Cyclamen and colchicums are also planted in the fall. Snowdrops are an exception: plant them after they have flowered when still in leaf, known as “in the green.”

Planting Depths and Layering

For bulbs to flower successfully, you need to plant them at the optimum depth. Most, including daffodils, grape hyacinths, and alliums, should be planted at about three times their own depth.

However, there are exceptions. Tulips prefer deeper planting, at four times their own depth, while cyclamen species should be planted with the top of the tuber at or just below the soil surface.

Bulbs make beautiful container plants, and by layering two or three different types in one large pot you can either produce a sequential display or, with careful planning, one that will flower simultaneously for a big burst of color.

To create a long-lasting display, place a layer of compost or bulb fiber at the bottom of a pot. Lay some tulip bulbs on it, then add more compost on top and set small crocus bulbs on this. Finish off by adding the final layer of compost. Store the pot in a sheltered spot and move into the sun in spring.  

After Flowering

After spring bulbs have bloomed, remove the flowerheads to prevent them from setting seed, and apply a bulb fertilizer. Allow the foliage to die down naturally before cutting it off. Many bulbs will bulk up year after year to produce large clumps, but tulips may stop flowering if they are not lifted every year after the leaves have died down. Dig them up carefully with a fork, and remove any diseased bulbs. Clean the compost from the healthy bulbs, and store them in paper bags or boxes in a cool dry place for the winter. Replant them in late fall. If large swathes of snowdrops have developed, you can lift and divide them in spring after they have flowered. Lift tender bulbs, such as dahlias, begonias, and gladioli before it frosts.

Naturalizing Bulbs

Decorate your lawn with a sprinkling of colorful bulbs. Arrange them in random groups or swathes, or opt for ordered stripes across the lawn. You could also plant them in rings around the base of large trees or shrubs. Choose robust types, such as snowdrops, daffodils, or crocuses, which can compete successfully with the grass and spread over time, creating a colorful carpet of blooms.

Before planting in fall, remove perennial weeds, such as dandelions, and mow the grass. If you are planting bulbs over a wide area, scatter them across the lawn and plant each individually—a bulb planter will make this job easier.

Plant smaller areas by lifting a section of sod. Use a sharp spade to cut an “H” shape into the grass. Holding the spade horizontally, slice under the sod, and carefully roll it back to reveal the soil. Add a small amount of fertilizer, and space the bulbs out on the soil; you may need to dig deeper to accommodate larger bulbs like daffodils. Gently replace the flaps of sod, firm down gently, and water well.

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