Seed-Starting Schedule By Zone

Here’s a seed-starting schedule by USDA Hardiness Zone for September—perfect if you’re planning fall veggies, herbs, or flowers. This helps you know what to direct sow, what to start indoors, and what to transplant.

🌎 September Seed-Starting Schedule by Zone

🟦 Zone 3–4 (Very Cold Winters)

Avg. first frost: Late Sept–Early Oct

🟢 Start Indoors:

• Lettuce

• Spinach

• Arugula

🌱 Direct Sow:

• Radishes

• Mustard greens

• Turnips (early Sept only)

✅ Tips:

• Use row covers for frost protection

• Most outdoor planting ends early this month

🟩 Zone 5–6 (Cold Winters)

Avg. first frost: Mid-Oct

🟢 Start Indoors (early Sept):

• Kale

• Chard

• Lettuce

• Arugula

🌱 Direct Sow:

• Spinach

• Turnips

• Radish

• Mache

• Mustard greens

✅ Tips:

• Last month to divide or plant perennials

• Garlic can be planted in late Sept or early Oct

🟨 Zone 7–8 (Mild Winters)

Avg. first frost: Late Oct–Mid Nov

🟢 Start Indoors:

• Cabbage

• Broccoli

• Cauliflower

🌱 Direct Sow:

• Kale

• Lettuce

• Spinach

• Radish

• Carrots

• Beets

• Green onions

• Collards

✅ Tips:

• Perfect time to plant fall herbs: cilantro, parsley, dill

• Start cover crops mid-month (like clover or rye)

🟥 Zone 9–10 (Warm Winters – e.g. Arizona, SoCal, South Texas, Florida)

Avg. first frost: Dec–Never

🌱 Direct Sow All Month:

• Lettuce, kale, mustard greens, arugula

• Radish, beets, carrots, turnips

• Green onions, bunching onions

• Cilantro, parsley, dill

🟢 Start Indoors (early Sept if temps still >90°F):

• Broccoli

• Cabbage

• Cauliflower

✅ Tips:

• Start fall veggie garden now (great time in the desert!)

• Transplant tomatoes/peppers for winter harvest if growing under cover

• Start second season of basil & summer squash in southern AZ/SoCal

🌸 BONUS: Flower Starts for Fall Planting

• Zones 5–10: Start pansies, violas, calendula, snapdragons

• Zones 7–10: Sow wildflowers (late Sept) for spring blooms

• Zones 3–6: Prep spring bulb beds, but wait until October to plant

Phoenix Specific!

Here’s a September seed-starting and planting schedule specifically for Zone 9b in Phoenix, Arizona, where the climate is desert-like—hot, dry days and mild winters.

This is one of the best months to start your fall garden in the low desert!

🌿 September Gardening Schedule – Zone 9b (Phoenix, AZ)

🌡️ Average Temps:

• Highs: 95–102°F early in the month, cooling to mid-80s

• Lows: 70s, dropping to 60s later

• First frost: Usually very late December (if at all)

🥬 Vegetables to Direct Sow in September

You can plant these directly in your garden anytime this month:

🧑‍🌾 Start Indoors or Transplant

🌼 Fall Flowers to Start or Transplant

💧 Watering Tips

• Water seeds daily until germinated, then reduce

• Use mulch to retain moisture and reduce soil temp

• Shade cloth or frost cloth helps cool soil for germination

✅ Key Tips for September in Phoenix

• Early Sept: Use shade cloth to protect seedlings from high temps

• Late Sept: Great time to plant citrus trees and perennials

• Avoid planting cool-season crops too early (wait until highs drop below 100°F for best results)

• Keep an eye out for aphids and whiteflies as temps cool