As Evie said, keep debris (rubbish, dead leaves etc.) clear so the spiders have as few hidding places as possible.
There are some old wives tales that some people say do work. I have never tried them, so I can't comment. They are supposed to keep spiders out of the house, so even if they do work, you might find their effect reduced used outside.
1) Conkers (Fruit of the Horse Chestnut) Spiders are supposed to dislike the odour, but I think you need a lot of them to make a barrier which they will not cross.
2) Osage orange (AKA mock orange, wild orange, hedge-apple, horse-apple, hedge ball) Cut into sections and use as with conkers.
3) Lemon juice. Even household cleaners containing lemon can be diluted and sprayed.
4) Strong essential oils (Do the same as above)
5) Pipe or chewing tobacco, put a 200gram pack in 4 ltrs of boiling water and allow to cool. Strain the liquid and mix at a ratio of 2 parts to one with lemon washing liquid to the amount required and spray. The remainder of the tobacco liquid can be saved until next required.
If the conkers or lemon work, perhaps you should invest in a few trees, trouble is, come the autumn, they will make a lot of leaf debris which will give spiders nice hidey holes!
So far as I am aware, there is no plant which deters spiders. Their natural enemies are frogs, toads, lizards, birds and some wasps.
There was a report some years ago of a man & his wife staying in a Sth American hotel. Upon waking in the morning he saw a large Tarantula in the room. He took out his hand gun and shot at the spider. He missed. The spider ran off scott free. The bullet ricochet'ed off the concrete floor, then the wall, then the ceiling, then the opposite wall and lodged in the mans back. He died from this wound.