Starting fall seeds in summer heat can be challenging because many vegetable seeds struggle to germinate in hot soil. However, with the right timing and techniques, you can successfully grow a productive fall garden even during the hottest months of the year.
The seeds of different vegetables have optimum temperatures for germination, but right now most of them will not like this heat.
Vegetables That Germinate in Hot Weather
Vegetables That Struggle in Summer Heat
Best Soil Temperatures for Seed Germination
| Vegetable | Ideal Germination Temp | Heat Tolerance |
|---|---|---|
| Lettuce | ~65°F | Low |
| Spinach | ~70°F | Low |
| Beets | 50–85°F | High |
| Carrots | 55–85°F | Moderate |
| Cabbage | Up to 90°F | High |
| Broccoli | ~75°F | Moderate |
| Cauliflower | ~80°F | Low |
How to Start Seeds in Hot Weather (Proven Tips)
To increase your chances of success with starting seeds in midsummer, there are a few tricks you can employ:
- Since soil heats up fast and dries out quickly in the sun, spread a light layer of straw over the seedbed to give it a bit of shade and to help trap in moisture.
- Plant seeds a little deeper than usual. The soil will be a touch cooler and wetter farther down. Just don’t plant them too deep or they may never come up!
- Plant extra seeds just in case germination is poor. Just remember to thin them out once the plants are up and growing.
- Plant them in the shade of taller crops. I usually do my summer planting of radishes in the cooler shade of the pea vines. The peas are fading by the time the radishes are up and growing and need more sunlight.
- Water daily (in the morning) or even twice a day if it is especially hot and sunny.
- Use row covers, screening, or shade cloth to provide shade to the bed and protect the tender emerging seedlings from hot sun and drying winds.
- If all else fails, start the seeds inside where you have more control over the conditions. Transplant the new seedlings to the garden when they have gotten strong enough and the weather has cooled down a bit.
Frequently Asked Questions
When should I start fall seeds?
Most fall seeds are started in mid to late summer depending on your growing zone.
Can seeds germinate in hot soil?
Yes, but only heat-tolerant crops like beets, carrots, cabbage, and kale perform well.
How do I keep seed beds cool in summer?
Use mulch, shade cloth, and frequent watering to reduce soil temperature.
What vegetables grow best for a fall garden?
Cool-season crops like lettuce, kale, carrots, spinach, and broccoli thrive in fall.
Should I start seeds indoors for a fall garden?
Yes, starting seeds indoors can improve germination success during hot weather.
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