Hhmm, difficult - you need to speak to an expert on this one, I reckon, as you want something fast-growing, non-toxic, large spreading branches etc.
Ours are all ancient oaks, planted years ago by somebody or other from the now ruined Abbey I think - ok if you don't mind waiting a few hundred years or have the resources of Capability Brown's clients to transplant fully-grown ones! LOL
Some sort of willow maybe, if you have damp conditions or plane trees, which give good shade I believe & are pretty quick growing?
Not yews or oaks. Some horses chew the bark of willow as it contains aspirin - clever things, horses! Sycamore grows quickly but I don't know if it is poisonous. A field shelter would be quicker...
I have no idea whether they are poinsonus but eucalyptus grows like mad - I put a few in my garden and have to hack about 10 foot off each year in order to keep them managable.
Just looking into this for the same reason - hedges but no shade. Thinking about a walnut - slow growing but fabulous dappled shade and the horses do like to eat it plus all the nuts for us too! Then I have also seen a type of birch with a really white bark and very straight trunk. Thought we might put a small stand of them in and there will be lots of shade in between the trees. Also looking at Rowan (Mountain Ash) and beech - lovely shade.
well, avoid oak they are posiunous but I am sure you know that. Sycamore are great for shade but take a long time,, maybe you should construct a shelter whilst the grow
mountain ash, hazel, rowan and field maple are quick growing. Small -leaved lime, elm, sycamore,ash are slower growing. I am planting some trees this autumn. I am planting the 4 quick growing varieties and some small-leaved lime trees.
We've planted over two thousand trees in our time, and the following grow the best.
European Larch, bright green in summer, rusty gold in winter. (in 14 years ours are now 30 odd feet high!)
Eucalyptus, lovely bark, leaves all year round.
Rowan.
Any of these may be poisonous I really don't know, but we haven't seen the horses eat any of them.
I would always plant holly by choice, it provides shade and shelter in bad weather.
If you need shade quick, try this, buy the massive square bales of straw put them in a Y shape two deep, hense shade and shelter, a non permenant fixture which you can get rid of when ever.