What to plant after harvesting potatoes and garlic?

If I am doing my calculations correctly and remembering last year, I should be harvesting potatoes and garlic around June or July. What would be good to put in the ground right after I harvest them? I was thinking brassicas (I really want to try brussel sprouts) but I know they hate hot weather. I may also try spinach, but once again - I'm not sure how they will hold up to the MD heat.

I have mostly gardened in climates with a longer growing season than MD (GA and CA), but I've successfully done late zucchini, corn, and okra after potatoes, onions, and garlic. This year I plan to try sweet potatoes that way, possibly by setting the little plants among the garlic before it's pulled up, since they stay small for several weeks and can be spot-watered while the garlic (or onions) dry down. A little later in the summer, rutabagas are a good bet, too....

beans and peas?
maybe some additional plantings of short lived crops (which you might already have) like summer-lettuces (maybe take a board to shade them a bit) and radishes. maybe start some flowers to mix into like sunflower, calendula and tagetes. maybe some basil.

maybe it would make sense to make a polycultural seed mix and work it in while harvesting the potatoes.

Cabbage kale and broccoli

You could plan for two stages. Buckwheat is super fast growing. You could plant groats from the store (dirt cheap), chop and drop it after a few weeks, wait a bit, then plant your brussels sprouts etc. when things cool off a bit.