Not vouching for any company, but here are some sources for heirloom and open pollinated seeds.
The advantages of these varieties is, they are not genetically engineered, they are not patented, they often have better taste, compared to new varieties. They have long histories, sometimes hundreds of years. They grow true from seed - assuming you are not growing them near other varieties of the same species.
The disadvantage is that some hybrids may grow faster or better, and hybrids are more widely adapted. Some hybrids are developed for their shipping qualities, or purely for appearance, so are not as tasty. But some hybrids are excellent. Examples, Sungold Tomato, and Lemon Boy Tomato.
I grow both. I want to save more of my own seeds, and by using open pollinated varieties, that can be done. It can not be done with hybrids.
I've bought from SeedSaver's Exchange and Territorial Seed Company, and was happy with both.
There are others - here listed on Treehugger.com
Comments / additions / discussion welcome.
I googled: "problem, tomatoes, split" and found this:
I agree with everything the author wrote.
To get green leaves, you need high proportion of nitrogen, such as comes from manure. If your plant produces all leaves and no fruit or vegetable, you need less nitrogen.
I googled "Problem: watermelon cultivation" and found this:
It is for Oklahoma and so is not exactly what you need. If you call, email or write your county, Idaho, Extension Agent and they will have answers for you. I find my County Extension agents are friendly, very informative, and want me to succeed. They often give me follow-up calls.
Here is a better article, and it is from Ohio Extension. I don't use black plastic, but many experienced gardeners do; I just learned on the farm and I just can't get the farm out of the city girl.
You have much friendlier temperatures than I for cucs and melons. Spokane Valley grows these beautifully, but I live at a high elevation. When I lived in central Texas, at Fort Hood, I grew both successfully, so I know it is not just me. Home grown is so much superior than supermarket! Be sure to check your pH and you can do that with a cheap meter or get instructions from your Extension Agent for how to test your soil.
Remember, I keep parts of my garden acidic, another part alkaline and another part neutral.
My uncles used to have contests to see who would have the largest melons for the county fair. Other families didn't even have a chance. They used trucks and cattle hoists to get from the field to the fair grounds.
My grandfather was a trap and skeet shooter and we always had Thanksgiving turkey from his winning the prize.
Home grown watermelon would be wonderful! I suspect my summer is too cool and short for it. Might try. Moon and stars looks very interesting!
Spud, how about this one, developed in Idaho:
'Bred by SSE member Glenn Drowns in the 1970s when he lived in northern Idaho, where summer nights average 43°F. Gorgeous green-black round fruits weigh 6-12 pounds. Deep scarlet flesh is super sweet, juicy, and crunchy. Perfect for short season areas; also does well in hot humid climates. 65-75 days."
I'm liking this one but ripening time is a little longer:
Cream Saskatchewan 80-85 days