Cross-pollination is only a bad thing if you are trying to save pure seed of a particular variety (such as a family heirloom), or if you intend to share seed with others.

For your own use, there is no need to prevent crossing. The results will be unpredictable, but can be fun as well. Many heirlooms were originally created this way, by intentionally crossing varieties with good characteristics, and selecting from the best plants each year.

You may - or may not - get crossing with tomatoes, even if you do nothing. Some varieties are more likely to cross than others:
- potato leaf
- currant
- double blossoms
- some older heirlooms
Paste tomatoes, in my experience, seem the least prone to crossing.

Even if you do get a cross with tomatoes, the result should still be edible. If snap beans cross with other beans, however, the result might be stringier than you would like. You can get some VERY strange crosses with squash.

I am in a situation where cross-pollination could be a disaster. I am growing a Coyote Gourd or Cucurbitia Foetidissima (sp?) in a community garden. many of the other gardeners have plots with some form of domesticated edible cucurbit - squash - pumpkin - cucumber and the like. My native or wild plant is extremely bitter and in-edible. If pollen from my plant gets into their plots their produce could be ruined. I will remove every male flower unless I use it to pollinate a female. Then the male gets destroyed. The female flowers get bagged until they drop off of the growing gourd.

The unpredictability is what people fear. If I grow a specific variety I like and want to grow it again, then the seeds must be pure and the plant should never be allowed to cross pollinate. However, if you never save seed then it doesn't really matter unless you're growing vegetables that are effected by the cross in the current year (i.e. you're eating the seeds primarily) like corn. Then taste can be affected right away. Tomatoes, peppers, etc. doesn't matter.

Another problem if a wild or ancestral variety of your domestic edible is growing within pollination range. If they can cross-breed you may get seeds producing unpalatable to inedible produce.

The only reason for "pure seed" is to keep a plant as is, like a clone only from seeds.

If you do not care if your seeds are a clone of the plant that produced it, no worries.

All seeds that are in the garden today are hybrids of some kind, man has been selective growing for thousands of year & hybridizing for over four hundred years.

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