Answer: Squash and melons will cross-pollinate unless they're planted a great distance apart. The cross-pollination will not affect the fruits of the plants, but will affect the seeds contained within them. If you saved, then planted the seeds, you'd end up with something other than the parent plant. If your cukes and cantaloupes tasted funny after being grown near one another, I'd suspect the cultural conditions were not quite what the plants required. Sometimes rapid growth in hot weather will make melons taste bland. Irregular soil moisture can make cukes taste bitter.
Squash, melons, etc. don't especially like being transplanted, so while you can start seeds indoors, you'll have better success sowing them directly in the garden.
Other seeds have different germination requirements. Let us know what kinds of seeds you're starting and we'll provide details for each.
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