It’s possible that cleomes’ lack of popularity comes from the fact that they look like weeds when they are young seedlings. Cleomes don’t usually bloom until they are well established in the garden, unlike pretty marigolds or bright New Guinea impatiens. Some gardeners plant seeds in early spring, but most choose to do it in late fall, right in the garden soil.
Cleome is a gorgeous, old-fashioned annual flower that deserves a spot in any summer garden. Its tall spires adorned with spider-like flowers come in shades of pink, purple, white and bi-colors, adding height, drama and irresistible beauty. Hummingbirds, butterflies and bees simply can’t get enough!
The secret to growing cleome successfully is knowing when to sow those tiny seeds. With a little planning and preparation, you’ll be rewarded with months of spectacular blooms.
Before we get into the ideal cleome planting times, let’s take a quick look at this delightful flower.
- Botanical name: Cleome hassleriana
- Common names: Spider flower, spider plant, bee plant
- Hardy annual
- Native to South America
- Grows 3-5 feet tall
- Flowers summer to frost
- Prefers full sun
- Tolerates heat, humidity and some drought
- Attracts pollinators
- Very easy to grow from seed
With its open, airy habit and delicate-looking flowers, cleome brings a touch of grace to the garden It combines beautifully with old-fashioned annuals like zinnias, cosmos, sunflowers and morning glories Or use it as a see-through filler in perennial beds and borders.
When to Start Cleome Seeds Indoors
Cleome can be direct sown outdoors once the soil warms up. But starting seeds indoors will give you a head start on the season with faster germination and healthier more vigorous transplants.
If you want blooms by early summer, sow indoors 6-8 weeks before your last expected spring frost. Cleome needs a consistent 70-75°F soil temperature to germinate so use a seed starting heat mat if your indoor conditions are cooler.
Follow these steps for the best results:
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Fill seed starting trays or pots with a lightweight, sterile seed starting mix. Moisten the mix well before planting.
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Sow seeds on the surface of the mix; don’t cover them. Cleome needs light to germinate.
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Mist gently to water in the seeds without displacing them. Keep the soil evenly moist but not saturated.
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Move pots to a warm, bright location like a sunny windowsill, under grow lights or in a greenhouse.
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Germination takes 10-14 days at optimal temperatures. Thin seedlings to 1 per cell once the first true leaves appear.
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Harden off plants for 7-10 days before transplanting into the garden after danger of frost.
When starting indoors, use individual biodegradable pots so the roots won’t be disturbed at planting time. Aim for stocky, compact transplants without yellowing leaves.
Direct Sowing Cleome Outdoors
One of the easiest ways to grow cleome is by direct sowing the seeds into the garden. There’s no need to start them indoors first.
In most regions, sow cleome seeds outdoors 3-4 weeks after your area’s average last spring frost date when soil temperatures reach at least 60°F.
Follow these simple steps for direct sowing success:
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Prepare the planting bed in full sun with rich, well-drained soil. Turn over and break up clay, amend with compost as needed.
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Sow seeds 1/8 inch deep in rows 18 inches apart. Space seeds 3 inches apart in the row.
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Mist gently to water in the tiny seeds without burying them too deeply.
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Keep the soil moist until germination, which takes 8-14 days. Thin to 18-24 inches apart once plants are 3 inches tall.
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Mulch to retain moisture and control weeds. Stake tall varieties if needed.
You can continue direct sowing cleome every 2-3 weeks until early summer for a continuous supply of flowers over an extended bloom season.
Timing Cleome Succession Plantings
For the longest lasting cleome display, make succession plantings every 2-3 weeks from early spring through early summer.
Stagger your planting dates to ensure new flowers will be ready to replace the old. Follow your regional frost dates as a guide:
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In the Deep South, start sowing in February and continue into June
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In the Lower South, start sowing in March and continue into June
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In the Upper South, Mid-Atlantic and Pacific Northwest, start sowing in April and continue into June
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In cooler northern regions, start sowing in May and continue into early July
Just make sure outdoor soil temperatures are at least 60°F before direct sowing each new batch. This will give you fresh cleome blooms from midsummer through fall frost.
Caring for Cleome Through the Seasons
Once your cleome is up and growing, proper care will keep plants thriving all season:
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Water regularly during dry spells, aiming for 1-2 inches per week. Cleome is quite drought tolerant once established.
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Apply a balanced vegetable fertilizer monthly or as needed to support vigorous growth.
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Pinch off spent flowers to encourage more blooms.
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Stake taller varieties to prevent toppling, especially in windy areas.
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Watch for aphids, spider mites and whiteflies, and treat promptly to avoid spread. Cleome is otherwise pest and disease resistant.
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In areas with high humidity, powdery mildew can be an issue. Improve air circulation and avoid wetting foliage.
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Deadhead before seeds form in fall to control self-sowing for next year. Or let some mature for collecting seed.
With its long bloom period and easy care needs, cleome is one of the best old-fashioned annuals for non-stop color. Time those first spring plantings right and you’ll be enjoying its graceful beauty all season long!
Soil
Cleomes do best in average garden soil or rich, well-drained garden loam.
Water
Once established, cleomes are drought-tolerant, making them a welcome addition to the xeriscape garden. If you cover their planting bed with three inches of organic mulch, they will need even less water.
How to Grow Cleome Spider Plant from Seed Growing Cut Flower Garden Annuals
FAQ
Is cleome hard to grow from seed?
Does cleome come back every year?
How long does it take for cleome seeds to flower?
Will cleome bloom first year?
Do cleomes grow from seed?
Planting cleomes from seed usually results in a vigorous display of the tall, fragrant cleome spider flower. Newer cultivars, some in dwarf varieties of the cleome plant, have no fragrance and do not produce next year’s flowers as the seeds are sterile.
How far apart should Cleome seeds be planted?
Cleome seeds require light to germinate, so be careful not to cover them when planting. Learn more about germination light requirements here. Seeds should be planted 1/8th inch deep and left uncovered. Space 3 inches between seeds, and space 18 inches between rows. Thin to 18 to 24 inches apart when plants are 3 inches tall.
When do Cleome flowers grow?
Cleome flowers grow best in full sun, and shady conditions can make them grow too tall and topple over. If you start with transplants, blossoms will appear from early summer until the first frost. Gardeners who grow cleome from seed usually see the first flowers in mid- to late-June, depending on the climate.
When should I start Cleome seeds?
Start cleome seeds indoors 6-8 weeks before the last expected frost date in your area. Alternatively, you can sow them directly in the garden after the last frost date. Fill seed trays or pots with a high-quality seed starting mix or a well-draining potting soil. Make sure the soil is moist but not waterlogged.