Tips and Tricks
This is a relatively random assortment of things I've learned and would like to pass on to others. Some of those things are links, but others are just bits that I come across.
Walnut trees really do have an impact on your garden. Time after time I hear from people whose tomatoes wilt in the middle of summer, for no apparent reason; I can count three specific instances in which walnut trees were the culprit. The roots and leaves put out a toxin that kills members of the nightshade family and a few others; the toxin can persist in compost for up to two years.
I'm planning a small study to figure out what veggies are more tolerant of juglone. For now, I just plant my tomatoes, peppers, potatoes, and such plants on the other end of the garden from the walnuts here, and I haven't had a problem yet.
When saving seed, dry it down thoroughly (with a dehydrator if necessary) and stick it in the freezer for two days before storing. The freezer will kill any pests that may have taken up residence in the seeds outside, but won't harm properly dry seed.
Let parsley, carrots, celery, dill, and other plants in the same family go to seed in your garden. Not only will you continue to have the plants year after year, the flowers themselves attract trichogramma wasps and hoverflies, both great predators of garden pests. They may be tiny insects, but they have a huge impact.