Air roots

Update on propagator with 100% humidity. 100% failure with white Centranthus after 18 days. The plants were still growing well in the propagator, but had totally failed to make any root. Seed is the normal method for Centranthus - but I wanted white plants, and I have red and white planted next to each other. I will try seeds next.

100% (4 out of 4) success with Verbena Homestead Purple after 18 days. But I was intrigued with the aerial root, which you can just see in the picture. There are loads of normal roots as well below the surface. I can imagine an aerial root surviving in 100% humidity, but any less humidity and I would have thought it would have dried out. Do many plants aerial root naturally?

 

I've seen lots of cutting produce aerial roots in the propagator Peter, but they usually die once the cuttings are hardened off.

I pesume its a similar process to air layering, if the area around the stem is damp enough long enough, roots will form.

 

Yes, you are right Pete. After making the post I removed all my other cuttings and I saw Diascia had lots of roots on the surface of the soil as well.

I suppose it is back to basics. Plants need heat, light, air (at leaves and roots), water, and nutrients. And if they get them they can grow foliage and roots. They don't need soil - its just a convenient way of supplying water and nutrients.

But as you say once they are removed from the propagator, the aerial roots will dry out and die, unless they are covered by soil to retain the moisture.