Right on the broccoli rabe and arugula, and the spinach.

On the squashes, you could grow zucchini, butternut squash, and Hubbard squash without them crossing, since they are of different species.

BUT... you can have several squash of the same species (like zucchini, delicata and spaghetti squash) and keep the seed of each pure by pollinating by hand.

Check your squash plants late in the afternoon and mark (with surveyor's tape) the flowers that look like they will be opening the next morning. The female flowers have a small bulb at the base of the flower, which will be the fruit; the male has a long slender stem with no bulb at the base. On some (maybe all) of the cucurbits, the main stem from the root tends to produce male flowers, and the side branches off the main stem tend to produce female flowers, if that makes your search any easier. Tape all the flowers closed, male and female. You will need 'virgin' flowers that haven't been contaminated by pollen-carrying insects tomorrow morning.

Very early the next morning, run outside with a roll of masking tape, and find your marked flowers. If an insect has already found the flower, remove the marker and don't pollinate that flower. That insect-pollinated fruit will be an eating fruit, not a seed-saving fruit. Otherwise, rip off a male flower, remove its petals and touch the moist yellow pollen to the stigma in the center of the female flower. Then immediately close the female flower and tape it closed SECURELY. If an insect can crawl inside, all your work is for nothing, so do one flower at a time. Make sure that flower is securely marked on the STEM, as the flower will fall off soon, leaving just the little growing bulb. Tell your family NOT to harvest any fruit marked with surveyor's tape.

Here is a website with some good photos of the male and female flowers, how the flowers are taped, pollinated and retaped: http://forums.gardenweb.com/forums/load/gourds/msg0611545713356.html

Be sure to do your pollinating early in the season so your fruits will be mature enough to produce viable seed.

One thing you need to realize is that you can't just save a couple fruits from one plant and call it good for that variety. If you do that, the quality of the crop starts to dwindle, no matter what else you do. Every plant of the same kind is going have minute differences from each other. With just a tiny stock of genes, the same thing happens if immediate family keeps interbreeding over several generations. So, try to collect a fruit or two from each plant. If you are growing zucchini and a couple of your neighbors are, also, explain what you're doing and ask if you could come into their yard early on one or two mornings and mark and pollinate a few flowers. They can save the seeds or you could save the seeds. You could co-mingle your seeds and each take half. You could both trade with other people.

Genetic diversity is incredibly important. It gives species the ability to adapt to changing environments, new pests, new diseases and new climatic conditions. The different genes provide the components for breeding new varieties. New varieties can be bred to produce earlier or later, store longer, resist pests, withstand more cold or heat, etc. One well-known lesson of what happens when a population gets to depend upon one variety of one plant was the Great Potato Famine of Ireland in the 1800s, when a potato blight fungus spread through the country and 20% of the people died of starvation.

Besides, you might find it fun!

Sue