What to Plant in August in Zone 4

Garlic bed prep starts, but the summer garden is not finished yet

Garlic is new to this month's list, and prepping its bed means clearing space without rushing to shut down crops still producing well. Cucumbers, summer squash, and sweet corn planted in May often have another 3 to 5 weeks of real output left here, since a late September frost gives back weeks a colder zone already spent.

Work compost into any bed that has genuinely finished, 2 to 3 inches spread and turned in, and let it sit uncovered for 2 to 3 weeks so it is ready well ahead of an October clove planting.

Set up protection now for crops that will run into fall

Any fall brassica or lettuce started back in June or July benefits from a low tunnel frame built this month, even before you cover it. A simple hoop frame with wire set every 3 feet takes under an hour to assemble, and having it ready means you can throw cover on with a single evening's warning once the first cool snap arrives.

Check soil moisture on everything twice a week through late summer. This is often the driest stretch of the whole season here, and a fall crop stressed by drought now rarely fully recovers even once September rain returns.

Hold the actual garlic planting off until October regardless of how ready the bed looks. Cloves set too early into warm soil sprout top growth before winter arrives, and that early green growth gets damaged by the first hard freeze, weakening the bulb that forms next summer.