Growing Cleome from Seed: Heirloom Spider Flower Tips for Success

Although cleome has been around for hundreds of years, it’s a fairly new addition to our flower garden. We added it to the outer border of our flower patch because it needs room to grow. It’s been one of my favorite flowers because of how much the pollinators love it. Whenever I’m out in the garden, I can see bees and butterflies buzzing around. 

Cleome is an excellent flower for a large, showy landscape, and it’s also fascinating to watch up close. The tightly rolled petals emerge like fireworks, and then as they grow up the stem, the seed pods dangle on thin branches.

Cleome is easy to grow from seed and can be started indoors or direct sown outdoors once the soil has warmed. Because cleome seeds need light to germinate, they should be sown on the soil surface and gently pressed in rather than covered.

• Start indoors: 6–8 weeks before your last frost date

• Direct sow: After all danger of frost has passed and soil temperatures reach 75–80°F

• Planting depth: 1/16 inch (lightly press seeds into the soil; do not bury)

• Spacing: 12–18 inches apart

• Cleome seeds need light for germination

• Soil temperature should be between 75-80ºF

• Keep soil moist but not soggy

• Germination can be slow and uneven, but with light and warmth, they should germinate in 8-12 days.

If starting indoors, harden seedlings off gradually before transplanting outdoors. Cleome seedlings transplant well when handled carefully. Once established, cleome grows quickly and puts on height early in the season.

Cleome is a tall, branching annual that typically reaches 3–5 feet tall, making it ideal for the back of flower beds, borders, and cottage-style gardens. Plants need adequate spacing to branch freely and develop sturdy stems.

Cleome does not require deadheading. After flowering, long seed pods form along the stem while new flowers continue to open above them. These seed pods can be left to mature for seed saving or removed to prevent self-seeding.

Although tall, cleome generally does not require staking when planted in full sun and given enough space. We haven’t seen a need to stake the plants in our garden. The stems are naturally sturdy, and the plant’s slightly spiny growth habit makes it deer resistant.

Cleome performs best when planted directly in the ground rather than in containers, where its deep roots and height can become difficult to manage.

If you start cleome indoors, harden off the seedlings gradually before transplanting them outdoors. These are warm-weather plants that don’t tolerate frost. 

Start with good soil, and you won’t need to add additional fertilizer. Too much fertilizer can result in leggy plants. We generally add compost to our garden beds before planting, and that is sufficient for healthy plants.

Cleome is generally trouble-free, but occasional insect pressure may occur. We haven’t noticed any pests or diseases, but some gardeners have seen harlequin bugs on their cleome.

• Flea beetles: Minor leaf damage early in the season; plants usually outgrow it

• Cabbage worms: Rare, but possible if planted near brassicas

• Harlequin bugs: Uncommon, but monitor if growing nearby susceptible plants

Overall, cleome’s spiny stems and strong growth habit help deter most pests.

Cleome readily self-seeds in the garden. If you want to prevent volunteer plants next season, remove flower stalks before the seed pods mature.

The plant develops spines along the stem. This keeps deer from eating them.

Heirloom varieties of cleome will self-seed.

The seed pods develop after the flowers bloom, and the stalk continues to grow taller.

To save seed, allow pods to dry on the plant. Harvest when pods turn brown and begin to split. Seeds can be stored in a cool, dry place and replanted the following season. Heirloom cleome varieties will grow true from saved seed.

Cleome is an annual, but because it readily self-seeds, it can return year after year.

Even though it self-seeds, cleome isn't considered invasive because it doesn’t spread.

Yes. Its spiny stems and strong scent make it unattractive to deer.

I love how Cleome is a low-maintenance, high-impact annual that fills large garden spaces with height, texture, and constant pollinator activity. 

With minimal care, strong heat tolerance, and the ability to self-seed, it’s an excellent choice for gardeners who want bold flowers without constant pampering.