How to grow and care for cleome
How to grow and care for cleome (spider flower).
The spider flower (Cleome hassleriana) is a tall-growing, frost-tender annual that makes a spectacular and striking display of unusually shaped large flower heads from early to mid-summer until the autumn. The flower heads are made up of many small blooms that are white, pink, or purple-pink, with long, conspicuous stamens that give the flowers their whiskery or ‘spidery’ appearance. Blooms are borne on tall, upright stems up to 1.5m high, the stems are often spiny and are clothed with attractive mid green palmate leaves. Flowers are scented, and attractive to bees and butterflies. This annual makes a splendid ‘dot’ plant to add height to a mixture of summer flowers, or in a border to add colour and height amongst long-lived plants. Cleome also makes a good cut flower. Despite its exotic looks, this sun-loving half-hardy annual is straightforward to grow from seed.
How to grow cleome
Sow cleome seed in warmth in early spring and grow on in a warm well-lit spot under cover before hardening off and planting out after the frosts. Water during dry spells and feed to boost flowering. Plants may need staking to protect against wind.
Where to grow cleome
Grow spider flower in full sun and in fertile, well-drained soil. Site it where plants are sheltered from wind as the tall stems are susceptible to damage. Good sites include the middle to back of a border, mixed with other colourful annuals to create a summer bedding display, or in gaps in borders amongst permanent plants. Due to its tall growth, spider flower isn’t ideal for pots apart from large containers.
How to plant cleome
Harden off plants growing under cover to acclimatise them to the outside for 10-14 days before planting out in early summer once the frosts are past. Water in immediately after planting.
Caring for cleome
After planting out, keep watered for the first few weeks until established and then water regularly during dry spells. Stake or support plants as stems grow tall and flower heads form. Fortnightly throughout summer, apply a liquid fertilizer high in potash to boost flowering. Deadhead faded blooms to encourage more flowers.
How to propagate cleome
Start seeds under cover in February/March, sowing onto moist seed compost and covering with a fine layer of perlite or vermiculite. Keep at a temperature of 20°C for seed to germinate reliably. Once the seedlings are large enough to handle, transplant into individual pots and grow on until sufficiently large to plant out, in early summer.
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Pests and diseases of cleome
Young plants are susceptible to slug and snail damage. Minimise risk of damage by growing plants to a good size in pots before planting out, then using an environmentally friendly barrier protection to combat pests.
As a brassica, cleome foliage may be eaten by the caterpillars of large and small white butterflies. Inspect leaf undersides regularly, hand pick caterpillars, and transfer them to a sacrificial crop of nasturtiums, instead.
Advice on buying cleome
- Buy cleome seed from nurseries, garden centres and mail order suppliers
- Companies that offer a limited range of seeds may only offer cleome as mixed colours in one packet, while seed suppliers offer a wider selection with individual colours/named varieties