What to Plant in August in Zone 9

Starting fall crops in real heat

August is when the fall garden technically opens, even though daytime highs are still routinely above 90 degrees. Cabbage, broccoli, cauliflower, and Brussels sprouts transplants started indoors in July go into the ground now, and they need afternoon shade for their first 10 to 14 days to keep leaf tissue from scorching before roots establish enough to pull up water fast.

Direct seeding is riskier this month than transplanting, since soil surface temperatures run well hotter than the air in full August sun. Press a bare palm to bare dirt at midday: if you can't hold it there through a slow count of five, that soil will cook seed before it ever germinates. Water a seeded row lightly twice a day for the first week rather than once heavily, keeping the top half inch of soil consistently damp until sprouts appear.

Keep a shade cloth panel handy for the first two weeks after transplanting brassicas, and pull it during the coolest morning hours so seedlings still get 3 to 4 hours of direct light daily rather than sitting in full shade all day, which weakens stems more than the heat itself does.

Potato gets its only fall slot

Fall potato planting has just this one month as a window, since seed potatoes set later run out of cool enough weather to size up tubers before frost, and set earlier rot in soil that is still too warm and wet from summer storms. Cut seed pieces with at least one eye each and set them somewhere warm and airy rather than in the ground right away; the cut face is ready once it looks dry and leathery instead of pale and wet, and skipping that step is what turns a good seed piece into a rotten one.

Leek, celeriac, parsnip, and salsify also start now, and all four are slow growers that need the full stretch of fall and winter to bulk up, so treat any delay past the middle of the month as a real cost to final root size rather than a minor scheduling slip.