I've got 3 or 4 clumps of onion & garlic chives. They are easy to divide, so let 'em spread.
Our target date is 05/15 but I usually wait until 06/01. Kentucky Pole beans, Diva cucumbers, Annie Oakly II okra, Jackpot zucchini get planted right after the tomatoes & peppes go in. I missed the spring pea planting, but will try them in fall.
If you like HOT peppers, about a month before harvesting, mistreat them- little or no water & they'll get hotter & vice versa.