Answer: Clay soil can require an amazing quantity of organic matter on an ongoing basis. This means you can till in a twelve inch deep layer when you prepare the soil and continue every year with topdressing with compost as well as using a year round layer of organic mulch several inches deep. In heavy clay you can sometims also add an inch or two of coarse sand such as builders use (not play sand, that is too fine) or fine grit. The organic matter you use should be fairly rough in texture, rotted chopped leaves, partially finished compost, old spoiled straw, well rotted stable manure and bedding, that type of material. You can also used milled spagnum peat moss; do not use peat humus as this is already too decomposed.
Using a slightly raised bed helps, as does gardening on a slight slope.
Most important you need to select plants that tolerate a heavier soil or at least those that do not require perfect drainage. (Lavender for instance would not be a good choice.)
Then remember that watering is done only as needed to supplement rain. Clay soil holds moisture for a long time, but once it dries out it requires a careful, very slow watering to seep back down deep. A sprinkler will tend to compact it, so a drip system or leaky hose, for example, running very slowly is better. This has the added benefit of keeping the foliage dry and losing less to evaporation.
Your goal is to keep the soil evenly moist, not saturated or sopping wet. An occasional slow deep watering that soaks down in and encourages deeper rooting is better than a daily light sprinkling. (You want the roots down where the soil naturally stays moister longer.) After you water, wait a few hours and then dig down to see how far the water went, sometimes it can be surprising.
How often to water depends on the soil and on the weather each year. There is no set schedule for watering. To know if you need to water, dig into the soil with your finger. If it is still damp, don't water yet. In your area in a typical year you might not really need to water until the heat of summer when a dry spell occurs. (An exception of course would be newly planted plants.)
As far as the spiders go, your local birds and other creatures will take care of them naturally. I would not recommend doing anything about them. You can go around the garden in the morning with a stick in your hand to break up any webs that happen to be in your way. Otherwise, just let them be. They are beautiful covered with dew in the sunshine.
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