While I typically sow and grow radishes in the spring, give fall a try too! Keep in mind that sowing and growing summer or winter radishes is similar. If you need a refresher on radish types such a spring and winter radishes, just click on the link.
Outdoor Sowing Tips:  1) While radish seeds will germinate in soil temperature between 45 and 80°F, they love the cooler weather for growing. 2) Before sowing, loosen or fluff the soil. 3) Radish seeds should be sowed about 1/2″ deep. 4) Most spring radish seeds should be 2 to 3″ apart or 16 per square foot and winter radishes should be 4 to 5″ apart or 9 per square foot.
I typically start sowing spring radish seeds in early spring outside under cover. Radishes are great candidates for succession crops and for interplanting.
Indoor Sowing Tips:  1) Since fast growing root crops don’t like their roots disturbed, I would NOT start radishes them indoors to move them outside.  2) However, you can grow them inside under grow lights. You just need to make sure your pot is deep enough so the radishes don’t dry out. I think a good rule of thumb is to have double the soil depth for however long you expect the radish to get. 3) and 4) – see above.
Growing Tips: 5)  Start thinning when the radishes form two true leaves. When thinning, do not pull the other seedlings out, just cut them at the soil line to stop them from growing. Don’t forget the seedlings that you snip are great microgreens! 6) Radishes love consistent moisture. 7) Overall , I typically don’t give radishes any plant food. If I did , it would be used coffee grinds or some bone meal which are good for root growth.  8) If you put radishes under cover or add leaf mulch, you can achieve a longer growing period and protect the roots from any drastic temperature changes.
While I have not had any bug issues with the root of the radish, I have had flea beetles nibble on the leaves. I usually don’t notice the flea beetles flying around, but I do notice the bites which are tiny holes in the leaves.  Don’t forget radishes are in the brassica family.
