I recently started Echinacea angustifolia from seeds indoors, and I noticed an incredible speed and reliability of germination achieved just by covering the seed tray with transparent plastic sheet (the seedlings appeared in just 5 days, germination rate 70%-80%). The cover was removed after 5 days, when seedlings appeared en masse.

Can a similar method be applied if the seeds are sown outdoors, directly in the garden? I mean, covering the area where the seeds are sown with some transparent cover for few days, or until germination? Or perhaps I don't see some bad side effects of doing that?

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    For your deleted question: do you think gardener know about bird biology? I think that you should get better answer in biology.SE. Apr 2, 2018 at 17:48
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    I sewed my carrots that way. Covered the seeds with an opaque weed mat until they sprouted, and then removed it. Worked a treat. Apr 3, 2018 at 6:59
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    Further to Graham’s comments, you might be interested in this YouTube video by Conor Crickmore of Neversink Farm. People use many different materials to cover seed in many different ways to promote consistent germination. It is important (perhaps obviously) to remove the cover at the appropriate time to ensure seedling growth is not stunted. Apr 3, 2018 at 8:36

2 Answers 2


I'm not sure. On seedling pots, the plastic will increase the humidity (and constant humidity), so seeds germinate earlier.

Outdoor, the principle it is the same, but you have much more soil, so water could go down. The soil is also more "lively", so you can have more damages from animals (because it is wet) and more fungi.

But I think it depends on soil. Try and test the method.


For sure it will help the seeds not be be eaten by birds. Plastic is also used in later phases, to keep soil more moist (less evaporation). Personally, I think it will have some effect, but not as large as in seedling bed/pots.


You are talking about what is essentially a Cold Frame; a temporary structure that keeps the plants inside warm and moist. In the past they were used to start small-scale commercial crops earlier without having to worry about frost, rain, insects, etc...

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    The cover warms the soil. The downside is it traps moisture and fungus can start very quickly. Apr 3, 2018 at 14:43
  • Watch out for 90° (F or C) days if you do this. You can cook your seedlings. Apr 3, 2018 at 15:06

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