What Is Cleistogamy? Flowers That Self Pollinate Without Opening
Cleistogamy is a plant making flowers that pollinate themselves without ever opening. NC State Extension describes common blue violet doing this in summer, after its showy spring flowers fade.
The short answer
Cleistogamous flowers stay shut, pollinate themselves inside and still set seed. Common blue violet makes showy open flowers in early spring, then closed flowers in summer that develop fruits with fertile seeds. On a patch of violets, look near the soil line under the leaves to find them.
What is cleistogamy?
UMass Extension describes cleistogamous flowers as inconspicuous, close to the ground, self pollinating and closed. NC State Extension explains that pollination moves pollen to the stigma, and in these flowers that happens inside the bud. See cannabis leaf anatomy for plant part names.
Where do you find cleistogamous flowers?
On common blue violet, a rhizomatous perennial native to eastern and central North America. Illinois Extension says it blooms April to June, and NC State says the closed flowers form in summer. UMass notes the seedpods are three sectioned capsules.
Why do plants make flowers that never open?
Extension sources give no reason. They do show the result: the violet sets seed without help from insects, while spring flowers stay open to visitors, as in what roles do bees play in outdoor cannabis. NC State adds that birds and small mammals eat the seeds, and violets can pair with other plants as in companion plants when growing marijuana.
Cleistogamy at a glance
| Item | Detail | Source |
|---|---|---|
| Spring flowers | Showy and open | NC State |
| Summer flowers | Closed | NC State |
| Location | Near the ground | UMass |
| Pods | Three sections | UMass |
| Bloom | April to June | Illinois |
Sources: NC State Extension, UMass Amherst Extension, University of Illinois Extension.
How to: step by step
- Find a patch of violets in summer.
- Part the leaves near the soil.
- Look for small, bud like flowers.
- Watch them over a few weeks.
- Look for seed pods forming.
- Compare with the spring flowers.
Troubleshooting
Can’t find them: hidden low. Check the soil line.
Mistaking buds for flowers: small and closed. Watch for pods.
No pods: wrong season. Check in summer.
Kind Seed Co shares more plant notes on the blog.
Sources
- Viola sororia (common blue violet), NC State Extension Gardener Plant Toolbox
- Viola papilionacea (weed herbarium), UMass Amherst Extension
- Common blue violet (HortAnswers), University of Illinois Extension
- Extension Gardener Handbook, chapter 3: Botany, NC State Extension
FAQ
Do cleistogamous flowers make seeds?
Yes. NC State Extension says the summer flowers of common blue violet never open but develop fruits with fertile seeds.
Which plants are cleistogamous?
Extension sources describe common blue violet and don't list other species.
Why do violets spread so well?
NC State Extension says violets self seed freely and may become weedy, and UMass notes they reproduce by seed and rhizomes.
Are cleistogamous flowers ever open?
No. UMass Extension describes them as inconspicuous flowers near the ground that self pollinate and do not open.
When do violets bloom?
University of Illinois Extension says common blue violet blooms April to June. The closed flowers come in summer, NC State notes.
