How to sow cleomes?

Cleomes (Cleomes) are often called spider flowers because of their long stamens that resemble spider legs. They catch the eye with their exotic appearance and generous flowering. These plants, with upright flower clusters and finely divided leaves, offer a palette of vibrant colours and attract many pollinators, thereby enriching the biodiversity of your garden. These annual plants in our regions, are easily sown indoors from winter for transplanting in spring into the garden.

Follow this guide to sow these spectacular flowers successfully and bring a touch of elegance and dynamism to your garden.

Cleomes in a nutshell

Cleomes are distinguished by their unique structure and their exuberant flowering, made up of flowers with long stamens, creating a striking visual effect, resembling spider legs (hence their name). Their flowering lasts from summer until the first frosts, ranging from pure white to vibrant pink and delicate mauve depending on the variety.

Among the most appreciated is Cleome spinosa, known for its robustness and ability to thrive in various conditions, with varieties such as 'Violet Queen' and 'Cherry Queen', with intense hues and a majestic habit.

In our regions, Cleome is grown as an annual because it dislikes cold and disappears when temperatures fall below 2 °C.

When to sow Cleomes?

Cleomes need minimum temperatures between 13 °C and 18 °C to germinate.

Ideally, we recommend sowing the seeds indoors 6 to 8 weeks before the planned transplanting outside, that is from February–March, to allow the seedlings to strengthen and ensure a long summer flowering afterwards.

If you choose to sow outdoors, wait until late May or early June, when the soil has warmed up and the risk of night frosts has passed. Ideally, night temperatures should be at least above 10 °C.

How to sow Cleomes?

Sowing in buckets

1- Fill your buckets with a seed compost, light and airy, ideal for promoting germination.

2- Gently place 2 to 3 seeds per bucket at a depth of about 0.5 cm. Cover the seeds with a fine layer of compost and press lightly to ensure good contact with the substrate.

3- Moisten the compost with a spray to avoid dislodging the seeds. Keep the compost moist but not waterlogged to prevent seed rot.

4- Place the buckets in a warm spot (around 20 °C) and well lit, but out of direct sunlight.

5- Cleome seeds generally take between 10 and 30 days to germinate. Once seedlings appear, continue to keep them in a bright environment at a stable temperature.

6- Transplant them into open ground, into rich, well-drained, loosened soil, as soon as the risk of frost has passed and night temperatures are above 10 °C. You can also grow them in pots on a terrace or balcony.

Sowing outdoors

1- Choose a sunny location. Ensure the soil is enriched by adding compost or well-rotted manure and is well drained by adding sand or gravel.

2- Work the soil to a depth of 15 to 20 cm (ideally with a broadfork to avoid disturbing soil life).

3- Sow the seeds in groups of 4 or 5, spacing them 30 to 40 cm apart to allow good plant development. Bury the seeds to a depth of about 1 cm and cover them gently with soil.

4- Water the sowing area carefully to moisten the soil without displacing the seeds. Keep the soil consistently moist until germination (10 to 30 days), avoiding excess water.

5- If nights are still cool, consider protecting the sowings with a cloche or fleece to maintain a more stable temperature and promote good germination.

Tips for abundant flowering

• Thinning: When seedlings have a few leaves, thin them out by keeping only the most vigorous. This will allow optimal development.
• Pruning: Pinch the tops of young plants to encourage a bushier habit and denser flowering. Regularly remove spent flowers to stimulate new blooms.
• Staking: Depending on the variety, Cleomes can reach up to 1.50 metres in height. Use stakes or supports to keep stems upright and prevent them breaking under the weight of the flowers, especially in windy areas.
• Watering: Continue to water moderately, ensuring the soil drains well. Excess water can affect flowering.
• Fertilisation: Apply a phosphorus-rich fertiliser mid-season to encourage flowering. Avoid fertilisers too high in nitrogen, which would favour foliage at the expense of flowers.
• Mulching: When your plants reach 30 cm high, add mulch to the soil to retain moisture and prevent it drying out too quickly.

For more information, read our full sheet: Cleome, spider flower: sowing, planting, cultivation.