In many locations, it is better to plant winter-flowering bulbs, earlier rather than later in autumn.
In cooler places though, it may be better to plant them later.
It is important to remember that most bulbs don't like to be in hot soil. Try to choose plant types which come from a climate similar to where you live.
In some warmer places you may need to wait until the hotter weather has passed completely before planting. Generally speaking, plant bulbs later in hotter climates than recommendations for temperate regions.
Early autumn is also the best time for planting those spring-flowering bulbs with softer, fleshier bodies because they are more prone to rot if removed from the ground for too long. Some other bulbs may be planted in early autumn to provide earlier spring flowers.
- Spring-flowering bulbs to plant early autumn: muscari (grape hyacinth), scilla (bluebells), erythronium, fritillaria, anemone, crocus and eranthis.
- Spring-flowering bulbs to plant mid-late autumn: daffodils, jonquils, freesias, sparaxis, ranunculus, anemones, tulip, hyacinth, iris, ixia, tritonia
How to Plant Bulbs
As a general rule of thumb, most bulbs are planted at twice the depth of the size of the bulb (so, a 2cm bulb is planted 4cm deep). The same applies to space between bulbs, although you can plant further apart if you intend to naturalise bulbs over time (this gives them more space to multiply before you need to lift and replant them because of overcrowding).
Some bulbs such as tulips for example, need a chilling period to initiate flowering. Buy these early and store them in the fridge (not the freezer) for a few weeks before planting out in the garden.
Bulbs can be planted using a trowel to dig a hole which is deep enough and wide enough to accommodate the bulb. The bulb is placed in the hole with the basal plate (i.e. the bottom of the bulb) resting on the bottom of the hole. The hole is then backfilled with soil and gently firmed down. Cover the soil with a thin layer of mulch (pea straw, manure or fine bark are ideal) to conserve moisture.
Fertilising Bulbs
Bulbs thrive in rich, free-draining soil which has been prepared by adding rotted organic matter. They will not grow well in heavy soils with low nutrients. If you do have heavy soils, plant them in raised beds or pots.
Bulbs usually have sufficient nutrients stored within them to produce flowers and don't need additional feeding at planting, however growth will be stronger with good soil fertility.
If you do need to fertilise, a slow-release fertiliser is more appropriate for bulbs. Use this if you have particularly sandy soils. Avoid applying strong fertilisers directly onto tender tissues (young leaves, new roots) or dormant bulbs.
Organic fertilisers are mostly slow-release, as are pelletised fertilisers or anything that does not dissolve readily and thoroughly in water.
Why Lift Bulbs after Flowering?
For many bulbs, the foliage dies down after flowering, leaving only the dormant bulb in the soil. While in this dormant state, some bulbs are susceptible to rotting, attack by pests, or damage by fertilisers, chemicals in the soil or soil-borne diseases. These bulbs may be lifted and dried in a cold, dry place before wrapping in cloth such as hessian and stored ready for planting the following autumn. It is essential that the bulbs are dry before storage otherwise they are prone to moulds. Always allow the foliage to die back naturally before lifting otherwise the bulb may not have stored sufficient quantities of food. In most cases though this is not needed in our Australian climate.
SOME BULBS TO GROW
Liliums
Lilies do well in cooler areas and are just as well suited to mass plantings and garden beds as they are to woodland gardens.
- Good drainage is essential. They will grow in heavy soils but only where they are well-drained. Sandy soils built up with lots of compost are better if you have the choice.
- A high organic content in the soil is preferred.
- Requirements can vary from one species to the next, so don't over-generalise on growing requirements.
- All types should be protected from strong winds and excessive heat or cold.
- Weed control is important.
Bulbs are lifted after flowering, in mid to late autumn, and stored under cool conditions before replanting in spring.
Daffodils
These do well in most climates, with the exception of tropical areas.
- Soil should be well-drained and fertile and so it is as well to enrich the soil with organic matter before planting.
- Plant in full sun or part shade.
- Planting should be done in early to mid autumn.
- Plant bulbs at 10-15cm depth and 10-25cm apart, depending on the effect you wish to create. Although they are most usually recognised as spring-flowering bulbs, flowering time varies according to the variety and is also very dependent on the location (the earliest varieties appear in early winter whilst the latest varieties flower in late spring).
- After flowering, leave the leaves to die naturally as these will provide the food store for the next year’s flowers. Increase bulbs by lifting and dividing offsets every 3-4 years. The new bulbs will separate quite easily from the larger parent bulb (they may also be grown from seeds sown in the summer but may take between 3 and 7 years to produce flowers).
Tulips
Tulips grow well in most regions but many usually only flower well in the first year.
- They prefer an alkaline, well-drained, fertile soil.
- Most should be planted at a depth of around 10-20cm (15cm on average).
- They may be planted deeper in light soils but not in heavy soils i.e. plant deeper in sandy soils or warmer localities, and shallower in heavy soils or colder areas.
- In heavy soils, grow in raised beds.
- Plant in full sun - if grown in shade, the bulbs will deteriorate over several seasons.
- Bulbs will grow well in pots or tubs (plant about 15cm deep in pots).
- Smaller types grow well in rockeries.
- Dig in manure or blood and bone some time before planting.
- Water regularly but not heavily. The soil must remain moist but not saturated.
- In pots, only water in the morning.
- In warmer climates, plant when ground temperatures are at, or lower than, 14°C.
- Plant in late autumn in snow-prone areas.
- Plant in winter in milder areas (earlier flowering varieties have a better chance of performing well in milder climates).
- If growing as a garden plant, remove faded flowers as rotting stems can spread infections to other parts of the plant.
- In mild areas, it is best for bulbs to be lifted annually after flowering when foliage is dying back.
- In snow prone, cold climates, they can be left in the ground for several seasons provided drainage is reasonable.
- Species tulips normally only need lifting every two to three seasons. After lifting, clean the bulbs (and possibly dust with a fungicide) before storing in a cool, dry, well-ventilated place. Bulbs should be kept at a temperature no higher than 20°C over summer.
- Select large, firm, healthy bulbs for planting, and only buy bulbs from a reputable nursery.
Sparaxis
These come from South Africa and do well in most parts of Australia, England and similar climates.
- They prefer a well-drained but rich organic soil.
- Plant is sheltered sites in cool temperate regions.
- Plant corms in the winter.
- Plant to 5cm deep and 12cm apart.
- In cool climates, lift the corms after leaves and flowers have died back and store dry. Replant the following winter.
- In warmer climates, the corms may be planted in late summer to autumn.
- Lift and divide offsets in winter and replant straight away. These should flower after a couple of years.
- Alternatively, plant seeds in autumn or spring and grow in the greenhouse in cooler regions for several years before planting out permanently. Plant out in the autumn when dormant.
Alliums
Alliums include lots of edible plants (onions, shallots, some types of garlic), plus others only grown for flowers. All are treated similarly.
- Good drainage is important; moist but never overly wet soil.
- A dry and fertile, friable soil is ideal.
- Grow in full sun.
- Plant deeper than other bulbs (3-4 times their depth).
- Larger species may need staking if exposed to winds.
- Deadhead spent flowers so food passes from stems back into bulbs.
- Separate large clumps after several years.
- They are susceptible to rots, particularly white rot of the bulb.
- Slugs are fond of them.
Interested in learning more about bulbs, plants and gardening in general?
