Spider flower: sowing, winter hardiness & toxicity of cleome
The spider flower is a unique summer bloomer that is wonderful for cottage gardens. Planted in tubs, it also embellishes balconies and terraces with its extraordinary flowers.
The spider flower (Cleome spinosa) is cultivated in Central Europe as an ornamental annual, but is impressive for its long flowering period and impressive floral display. We reveal whether the spider flower is hardy and which location is optimal for successful planting.
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Spider flower: Origin and characteristics
The Cleome spinosa, which we cultivate as an annual, belongs to the spider family (Cleomaceae) and comes from subtropical Central and South America. The taxonomy of the beautiful spider flower has not yet been clearly defined, which is why you can also come across names such as Cleome hassleriana and Tarenaya hassleriana when looking for the summer flower. It is often called spiny spider flower or bee plant. The long stamens of the flowers give this special ornamental plant its name. Together with the petals, the appearance is reminiscent of a spider with long legs. This is why it’s known as the “spiny spider flower”. The long and narrow pod fruits are formed during the flowering period from July to October. Depending on the variety, the spider flower shines with pink, purple, red or white flowerheads and grows between 90 and 160cm tall.
The leaves are alternate and palmately divided. The stem is also slightly spiny. The spider flower secretes a sticky substance to protect it from insect damage, which can be felt when touching the leaves and stem. Overall, the plant is robust against diseases and pests, although vine weevils (Otiorhynchus) can be dangerous to the spider plant. The larvae of the pest living in the root area are able to eat root hairs and later even damage woody parts of the root.
Is the spider flower bee-friendly? Yes, the spider flower attracts bees and other insects with abundant nectar. The pollen supply, on the other hand, is somewhat less abundant.
The most beautiful varieties
- ‘Helen Campbell’ is distinguished by its pretty white flowerheads. The variety usually does not grow taller than 130cm.
- ‘Senorita Blanca’ grows up to 150cm tall. It enriches the garden with bright, almost white, fragrant flowers.
- ‘Senorita Rosalita’ grows to a manageable height of 60cm and bears intense pink flowers. A remarkable feature of this variety is its long flowering period, which begins as early as May and lasts until October.
- ‘Cherry Queen’ exhibits showy flowers in cherry-red to carmine-pink colour. It grows to a height of about 150 cm.
- ‘Sparkler F1 Lavender’ flowers from July to October in a beautiful purple and grows between 70 and 90cm tall. As it is a hybrid and therefore not seed resistant, this variety cannot be propagated by its seeds.
Tip: in the trade, colour mixtures with different varieties and thus flower colours from violet to pink to white are often offered.
Planting spider flower: Sowing, location and more
Choose a warm, sunny and wind-protected location for the spider flower. It also grows in partial shade, although the flowers are somewhat less abundant. The soil should always be moist to fresh, but well-drained, as the spider flower does not tolerate waterlogging. If the soil has a high nitrogen content, the spider flower tends to be less stable. If a suitable site has been found, Cleome spinosa can be planted in the garden in May after the last late frosts. Ideally, lay a drainage layer of gravel or chippings to ensure good water drainage. If several specimens are planted, a planting distance of 50 to 60cm should be maintained. Then plant the spider flower deep enough so that the lowest leaves are above the soil. Then press the soil well and water the freshly planted spider flower moderately.
Tip: the spider flower looks beautiful planted individually as well as in larger groups. Their unique flowers integrate easily into an existing arrangement of summer flowering plants, such as coneflower (Rudbeckia), Phlox, or aster species.
Seeds of the spider flower can be grown on the windowsill from March onwards:
- Take seed pots or trays and fill them with a suitable substrate.
- For such a sowing, we recommend using a special growing soil, as this is lower in nutrients and thus promotes the root formation of the seedlings.
- Our Plantura Organic Herb & Seedling Compost, for example, is characterised by its peat-free nature in addition to its optimal nutrient composition.
- As the spider flower is a so-called light germinator, the seeds are simply pressed lightly onto the substrate at a distance of at least 2cm and watered a little.
- Place the seed pots in a light and warm place, for example on a windowsill with a temperature of 18 to 20 °C.
- The cultivation should always be kept moist, but not wet.
- If sowing is successful, the cotyledons will show after a few days – if you see the first true leaves, the young plants are pricked out into individual pots with nutrient-rich potting soil.
- When the last frosts are over, the spider flowers can slowly be planted outdoors.
Tip: the spider flower should be acclimatised slowly to the temperatures and sunlight outdoors. For example, place the plant for the first few days in partial shade on the balcony and close to the house wall — where the temperatures are still a little milder.
Alternatively, the spider flower can be placed in a tub on the terrace or balcony. Purchased spider flowers in pots should definitely be repotted into a larger container. Choose a container that offers a distance of about 15cm from the ornamental plant to the edge and has a water drainage hole. In addition, a drainage layer of expanded clay, for example, should be created. A high-quality, nutrient-rich potting soil such as our Plantura Organic Flower Compost, which contains, among other things, crushed expanded clay, is suitable as a substrate. This not only leads to an optimal structure of the substrate, but also to a lower total weight of the container and reduces the risk of waterlogging. In addition, our substrate is peat-free and produced using less CO2.
- Perfect for all flowering plants in garden beds & pots
- For beautiful blossoms & healthy plant growth
- Peat-free & organic soil: CO2-saving composition
Plant care
If there is no rain, the spider flower should be watered regularly, but in moderation, so that the soil is always moist. The morning or evening hours are suitable for this. Nevertheless, keep in mind that short dry phases are better tolerated than waterlogging. In order to enjoy decorative flowers for a long time, additional fertiliser is needed. For this purpose, we recommend a slow-release fertiliser for outdoors, such as our Plantura Flower Food. This only needs to be applied once in spring for planting and once in summer. The phosphorus it contains promotes flower formation and ensures numerous flower spikes. For plants in tubs, liquid fertilisers such as our Plantura Liquid Flower Food are suitable. This can be conveniently applied to the irrigation water about every 3 weeks and, like all of our fertilisers, is harmless to your pets. Pruning of the spider flower is not necessary as the ornamental plant dies in autumn and is removed from the bed.
- Perfect for all flowers & balcony plants
- Liquid fertiliser for a lush blossom throughout the season
- Quick & easy application - child & pet friendly
Tip: leave some wilted flowers at the end of the flowering period to allow seed formation. The seeds can be harvested for propagation and also serve to naturally seed the spider flower.
Spider flower getting yellow leaves: yellow leaves on the spider flower are usually a reaction to nitrogen deficiency or waterlogging. If possible, the drainage layer should be checked here – if the water drainage hole is blocked with substrate, for example, a piece of clay can be placed on top. Adjust your watering as well. However, the substrate should never be wet.
Is the spider flower hardy?
The spider flower is not hardy in our area, as it dies at temperatures below 15 to 10 °C. Unlike the mother plant, however, the spider flower seeds are frost-hardy. If the ornamental plant sows itself, it will germinate all by itself in the bed next spring.
Propagating spider flowers
Amateur gardeners who have a specimen in the garden or on the balcony and terrace can propagate the spider flower by its seeds. Wear gloves when doing this, as the spider flower is poisonous. This applies in particular to the spider flower seeds.
- After flowering, the small pods form together with the seeds.
- The pods can be harvested whole in autumn when they turn brown and dried in a cool and shady place.
- Once the pods are well dried, open them carefully and take out the seeds.
- Until sowing, the seeds should then be stored in a dry, cool and dark place.
- In the spring, proceed as described for sowing.
Is the spider flower poisonous?
Yes, spider flowers contain toxic substances in all parts of the plant. A particularly high concentration can be found in the seeds. If small children or pets are around in the garden, you should refrain from planting the spider flower or choose an inaccessible location. Eating the seeds can cause severe stomach discomfort, and touching them can possibly cause inflammation and irritation of the skin.
Unlike the spider flower, the gracefully flowering pincushion flower (Scabiosa) is non-toxic and can be planted beautifully in herbaceous borders and wild gardens.
