Cleome ‘Spider Flowers’: Try Growing These Plants In Ornamental Borders
Elizabeth is a Permaculture Garden Designer, Sustainability Consultant and Professional Writer, working as an advocate for positive change. She graduated from the University of St. Andrews with an MA in English and Philosophy and obtained a Diploma in Applied Permaculture Design from the Permaculture Association.
Reviewed By ROY NICOL
Roy is a Professional Gardener and Horticultural Consultant, specialising in large garden year-round maintenance and garden development. He is an RHS Master of Horticulture and uses his research in the application of no-dig methods in ornamental garden settings. Roy has been a Professional Gardener for more than six years and is a member of the Chartered Institute of Horticulture, Professional Gardener's Guild and Association of Professional Landscapers (Professional Gardener).
IN THIS GUIDE
‘Spider Flowers’ are popular annuals to grow in ornamental borders to add height and colour over the summer months.
Cleome is an annual that grows tall with unique, distinctive flower heads made up of small individual flowers that look like spiders or whiskers.
These plants are native to parts of South America.1Susan.Mahr. (n.d.). Spider flower. Wisconsin Horticulture. Retrieved June 9, 2023, from https://hort.extension.wisc.edu/articles/spider-flower-cleome-hassleriana/
Overview
| Botanical Name | Cleome hassleriana |
| Common Name(s) | Spider flower, pink queen, grandfather’s whiskers |
| Plant Type | Annual |
| Native Area | South America |
| Hardiness Rating | H2 |
| Foliage | Deciduous |
| Flowers | Racemes of flowers with 4 petals and conspicuous stamens in purple, pink or white |
| When To Plant Out | May to June |
Sunlight
Preferred
Full sun
Exposure
Sheltered
Size
Height
1 – 1.5M
Spread
0.1 – 0.5M
Bloom Time
July to September
Soil
Preferred
Loam, sand, clay
Moisture
Moist but well-drained
pH
Any
This plant tends to grow tall, around 1.5m in height, and its flowers come in purples, pinks and white.
A half-hardy annual in temperate climes, spider flowers are used to fill gaps in warm and sunny summer borders, but will not typically survive colder conditions.
Common Varieties
There are several different well-known varieties of Cleome to consider for gardens in the UK.
There is a well-known series known as the ‘Queen’ series with cultivars in different colours, such as ‘Violet Queen’, ‘Rose Queen’ and ‘White Queen’.
I’d also recommend a cultivar named ‘Helen Campbell’, which has white blooms and is another that is highly regarded, having been awarded an Award of Garden Merit from the RHS.
How To Grow Spider Flowers
Cleome is relatively easy to grow as long as it is provided with the conditions that it requires to grow well.
One of the key things to remember is that this is a half-hardy annual that cannot cope with colder conditions and it is therefore a plant which will be in your garden only over the warmest part of the year.
You also need to make sure that spider flowers get plenty of sun and, as tall plants, they should be placed in a sheltered position so that they do not get blown over.
“They fit well into a cottage garden planting scheme towards the back of a border, with lower-growing plants such as Dianthus (Pinks), Aquilegia and Geranium in front and perhaps in between Digitalis (Foxglove) of a similar height,” shares Master Horticulturist Roy Nicol.
Hardiness
Cleome are half-hardy, so cannot cope with colder conditions.
They will do fine outside in a UK garden over the summer months, but they will not cope with freezing conditions and won’t overwinter in a garden.
As annuals, they will be removed after flowering and won’t live for a second year.
Soil Requirements
Cleome likes moist but free-draining or free-draining soil.
It will grow best in free-draining sandy soil or another medium that drains well, but is unfussy when it comes to pH levels.
Growing From Seed
Cleome hassleriana seeds can be sown indoors in March for planting out in May or June once the weather where you live has warmed reliably.
Sow the seeds in a heated propagator or with bottom heat on a bright windowsill indoors for the best germination rates.
Prick out seedlings into individual pots or soil blocks once they are large enough to handle and grow on indoors or under cover until the weather is warm enough to plant outside in the garden.
Remember to harden off your indoor sown plants before you place them out into their final growing positions.
Cold Stratification
Whether or not Cleome seeds need a period of cold before germination is a matter of some debate.
Some simply sow the seeds without giving them a period of cold stratification.
However, some experienced growers argue that it is best to place the seeds in the fridge for a week before you sow them.
Germination can be tricky, so to give the seeds the best chance of germinating, it is important to provide the ideal conditions for them.
This means sowing indoors, where you can give reliably warm temperatures.
It also means sowing on the surface or covering only lightly, so the seeds get the light they need to germinate too.
Another tip that gardeners have come up with is to create fluctuating temperatures by either placing them in a greenhouse for cold nights and warm days or by placing them on a windowsill indoors, then placing them out in the cold for a few nights.
One other thing to note when growing Cleome from seed is that you should not give up on them too early.
I have known it to take 5-6 weeks before the seeds germinate successfully.
Cleome Plant Care
When it comes to caring for Cleome, choosing the right growing position is a big part of the puzzle.
As long as you have positioned these plants correctly, you should generally find them relatively easy to grow.
The simple tasks of watering, deadheading and feeding are really the main jobs to think about when growing spider flowers in your garden.
Watering
Cleome should be watered in well upon planting it out and kept well-watered during establishment, especially for the first couple of weeks.
Thereafter, it will usually only need to be watered during dry spells, when it should be watered regularly.
Pruning
The only pruning or cutting that you have to think about when growing Cleome is deadheading.
Cutting off spent flower heads will encourage the plant to focus on producing further blooms, which can prolong the flowering period.
If you deadhead, you may be able to enjoy Cleome blooms from July through to September.
After flowering, the whole plant will be removed as this is an annual which will complete its lifecycle in a single year.
Fertilising
It is best to encourage blooming by feeding Cleomes with a liquid organic plant feed that is high in potassium every couple of weeks throughout the summer months, while the plant is in bloom.
A feed that is homemade, like comfrey tea, can be ideal for the purpose.
Common Problems
Look out for slugs and snails when the plants are young.
Encourage biodiversity in your garden so the population of these pests does not get out of control and use physical barriers to protect young plants where necessary.
Cleomes may also have a problem with cabbage white butterflies in summer, just like brassica crops, to which they are related.
Nasturtiums can be a useful trap crop for these garden pests and can help to keep your Cleomes safe.
Self-Seeding
Cleome can self-seed in some climates, even to the point of becoming invasive. However, this does not typically happen here in the UK.
Germination rates can be poor without warm conditions, so it is best not to rely on self-seeding if you want to grow this plant again the following year.
I’d argue it’s also best to deadhead rather than letting these plants set seed because if you deadhead, the plants can focus on further flowering and you will have blooms into early autumn and – in more southern areas – even right up until the first frost.
