they're outdoors, right? in the ground too...? if so, spraying daily with plain water will drive them off of the plants and over a couple weeks should solve your problem. they usually don't thrive in the outdoors as they have plenty of predators outside that keep down their populations. they're not usually a problem for outdoor gardeners...
i'd use soapy water 2nd, AFTER trying a couple weeks of straight water and a soft setting on your spray nozzle. move any smaller spiders you find around the house/yard too (but not on the plants you'll be spraying of course)...make your garden welcome to the right bugs and hell on the pests...naturally.