Forest Girl Farm

The best month to plant your fall garden in zone 9 is the month your summer garden looks its absolute best. That’s the cruel joke of it — August is when the tomatoes finally deliver and nobody wants to think about broccoli. But if you wait until the weather feels like fall, you’ve already missed it, and you’ll spend October watching seedlings sit there doing nothing.

Why Start Fall Seeds in the Heat of August?

Cool-season crops don’t stop growing because it gets cold — they stop because the days get short. Once we drop below roughly 10 hours of daylight, which happens here in late November, plant growth nearly stalls out no matter how mild the temperature is. Anything you want to harvest in winter has to reach most of its size before that door closes.

Broccoli needs about 85 days from seed. Count backward from late November and you land squarely in the second half of August. Plant it in October like it’s a spring crop, and you’ll get a little green rosette that sits frozen in place until March.

What Should I Start Right Now?

These go in as seeds this month, most of them in trays in a shaded spot rather than direct-sown into hot soil:

• Broccoli and cauliflower — start in trays now, transplant out in 4 weeks. ‘Di Cicco’ broccoli is forgiving and gives side shoots for months.
• Brussels sprouts — the longest season of the bunch at 100+ days. If you only start one thing this week, start these.
• Kale and chard — ‘Lacinato’ kale sown now will feed you straight through to spring. Chard is the closest thing to a year-round crop we have here.
• Leeks and bunching onions — slow, undramatic, and wonderful in January soup.
• Cilantro and parsley — cilantro finally stops bolting once nights cool. Fall is its real season, not spring.

Hold off on lettuce, spinach, arugula, and root crops until early September. Lettuce seed goes dormant above about 80°F, so an August sowing often just doesn’t come up.

How Do You Get Seeds to Germinate in August Heat?

• Start in trays in bright shade, not full afternoon sun. Under a redwood’s north side is nearly perfect.
• Water lightly twice a day — a seed tray can dry out completely in an afternoon and a dry seed is a dead seed.
• Lay a board or damp burlap over direct-sown beds until the first sprouts show, then pull it immediately.
• Sow a little deeper than the packet says. A quarter inch instead of an eighth keeps seed in cooler, damper soil.

If you want the whole year laid out rather than just this month, I put the sowing and transplanting windows for thirty-eight vegetables onto a free printable planting calendar — sheet 1 and 2 cover the vegetables, and sheet 4 is the month-by-month list I actually keep taped inside a cupboard door.

You don’t have to tear out the summer garden to do this. Tuck trays wherever there’s shade, and by the time the tomatoes give up in October, you’ll have real transplants ready to go into the space they leave behind.

Are you starting fall seeds yet, or still deep in tomato season?