Madly Saving from Planet Nong in Western Australia has left a comment this morning asking about our shade arches. I'll pop a few links on here for you and any one else who's garden is in need of some shady help in this terrible heat we've been having this summer.
The aim is to have the plants screened from the midday sun.
For fruiting vegetables it is best to have 50% shade cloth in as light a colour as you can get.
These are best placed at about 1800mm (6ft) high to allow morning and afternoon sun to hit the plants leaves. Most plants require about 6 hours of direct sunlight for proper growth.
Having said that I have been placing extra covers, old curtains, stronger shadecloth (70%), and net curtains (??% sun screen) over plants when the temperature hits over 40C (or a bit over 100F in the old talk). These emergency covers are not permanent though and should be removed in the evening or on a cloudy day after a cool change. I also remove the shade cloth in winter to allow full sun on the garden beds.
These shade covers cut down on the evaporation rates, which at this time of the year are extreme where I live. When combined with a good mulch layer help to conserve water.
The shade structures we have made are based on the poly pipe arch concept found in many permaculture books and articles.
See the following links for detailed instructions for building these structures/arches:
Poly Shade Structure
Pot on, Dudes from Doc's blog (Doc's my hubby) where we used the basic principle to built a small poly tunnel or hot house which has since been converted into a shade house here Hot House Conversion .
By the way these arch structures also come in handy to act as frames for bird netting over fruit trees see here. This is something we intend to do a lot more of this winter because the birds are eating too much of our fruit.
While I've said that 50% shade cloth is ideal for most vegetables this seems to be true for the southern states of Australia. In Queensland growers seem to prefer 30% cloth. Also for growing green leafy veg and salad greens 70% seems to prevent scorching on these extreme heat wave days. Again trial and error comes into it as it does with a lot of gardening in these ever changing climatic conditions we are experiencing lately.
While it isn't a problem at the moment (as we have no rain in sight) I do like to pull these covers back if we have light showery rain forecast but find they can remain in situ if heavy rain is forecast as the shade cloth helps to break up the force of the rain (and can also help prevent some hail damage).
See our latest shade building fun here on Doc's blog.