How to grow bulbs

Monday, May 21, 2012
Mitre 10 MEGA
How to Grow Bulbs  (Thinkstock)

Follow our gardening how-to guide for advice on when to plant and how to grow bulbs.

Autumn is the time to start planting your spring flowering bulbs. Their colourful flowers emerge as a welcome signal to the end of winter. Bulbs are also great for picking and can be grown in patio pots. Best of all, bulbs are easy to grow.

When to plant bulbs

Plant popular spring flowering bulbs such as anemones, hyacinths, tulips, irises and daffodils in autumn through to early winter. In New Zealand we start planting in March and April.

Summer flowering bulbs such as nerines, dahlias, begonias and lilies are planted in winter through to early spring.

How to grow bulbs

Most bulbs thrive in well drained soils. There are only a few bulbs (such as the Japanese iris and arum lily) that will tolerate damp soils.

Bulbs are best planted in full sun, although they will tolerate light shade. Some spring flowering bulbs such as lily of the valley, snowflakes and bluebells flower happily in shade.

Before planting bulbs, dig in plenty of compost or well-rotted organic material. In heavy clay soils where drainage is poor, or where roots from surrounding trees and shrubs are a problem, plant bulbs in raised beds. Adding sand to the planting hole improves drainage.

The general guideline for planting is to plant the bulb to a depth equal to twice the bulb's diameter. For example, if a daffodil bulb is 5cm in diameter, the planting depth is 10cm. (See the diagram below as a guideline to the common planting depth for various bulbs.)

Lifting and storing bulbs

As your bulbs finish flowering, we recommend that you fertilise them with bulb food. The bulb will store this food and use it to feed the bulb for next season's growth.

After flowering, leave the bulbs to die down completely. It is tempting to cut off the straggly foliage, but don't! The leaves contain the bulbs' food supply for the following season. Tie the foliage in a knot or fold the foliage over and secure with a rubber band to tidy them up.

Bulbs can be lifted when the foliage starts to die down. If you know you are going to lift your bulbs, plant them in bulb baskets. This makes lifting easy and the bulbs easy to find.

Leave the foliage attached until it dries off naturally. After the foliage has dried, remove it. Store the bulbs in a net bag or seed tray in a cool, dry, airy place. A dusting of Mite and Mildew powder will protect the bulbs during storage.

Not all bulbs need lifting. Usually bulbs can be left in the ground for 2-3 years until they become overcrowded. At this time they can be dug up, divided, replanted or stored.

Feeding

When bulbs push through the soil surface it is a good time to apply a specially blended bulb fertiliser. Do this again when they have finished flowering. This ensures plenty of flowers the following season.

See Mitre 10 MEGA's Seeds & Bulbs for suitable feeding products for bulbs.

Watering

With spring flowering bulbs nature takes care of the watering — giving us rain. Summer and autumn flowering bulbs may need additional water during their growing season depending on the weather.

Pests and diseases

Bulbs are relatively pest and disease free. Slugs and snails can be a problem when new shoots emerge through the soil. Apply Slug & Snail Pellets, Baysol or Blitzem.

See Mitre 10 MEGA's Plant Health and Pest Control products for more on stopping slugs and snails.

Bulbs for bowls

Bulbs look great planted in patio pots, tubs and bowls. The best spring flowering bulbs for bowls are daffodils, tulips, freesias, hyacinths, grape hyacinths, bluebells and crocus. Summer flowering bulbs suitable for containers are begonias, calla lilies, dahlias and lilies.

Use a quality potting mix such as Container Mix. Plant bulbs close to each other, even touching, in layers.

Bulbs grown in containers are best planted into the garden when they have finished flowering.

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