Saturday, April 29, 2017

Saffron grown on roof in wet temperate climate

Saffron flowering on a rooftop in Wellington, New Zealand.

I tried growing Saffron (Crocus sativus) on my roof after attempts to grow it in the ground and on a window sill failed (it grew fine but did not flower as is normal in areas with "poor summers" (1)). I thought putting it on the corrugated iron roof might work because the plant likes hot, dry conditions.

There would be a limit to how many heat loving plants one could put on a roof as they would prevent the corrugated iron roof from heating up by shading it, but exactly what that limit would be I don't know at this stage.


Water Chestnut (Eleocharis dulcis) is another heat-loving crop that has grown on a corrugated iron roof here in temperate Wellington. So far it has failed even in black plastic tubs in full sun on the ground. 

It may be coincidence but so far only plants with significant underground storage parts seem to have benefited significantly from being on the roof. Perhaps these plants require high soil temperature and get this from being on a roof while plants requiring high air temperature don't. 

I'm also trying to find out if putting things on a corrugated iron roof is a good idea in terms of roof longevity. Rust due to constant trapped moisture seems like a risk. So far there has been no sign of this after three years. Debris does accumulate under the pots and "mats" they sit on, potentially causing water to drain slowly, making leaks at "joins" possible. 

Presumably it would be possible to grow heat loving crops in this way with iron sheets laying on the ground, if you have lots of space.

Ref 1. Encyclopedia of Herbs & Their Uses. Deni Bown 1995

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