The summers just seem to be getting hotter. If you live in an area with hot summers, you might be wondering what you can grow successfully during these months. I have certainly planted a lovely patch of leafy greens and herbs just to have them bolt and rush into flowering before I could get my harvest. We hope that you can avoid our past mistakes by choosing the right plants for your climate.

Cool vs. Warm Season Growing

Plants are like people in that they thrive in a variety of temperatures and climates. The key to growing a successful garden is knowing what and when to plant. To figure out what is best for your growing location, observe the natural weather patterns. At what time of the year do you avoid going outside because it is too hot? When do you turn the furnace on? When does it rain or snow? Does it stay cold long enough for the ground to freeze? Each of these factors can help you understand what your growing season looks like as plants tend to be most comfortable in the same type of weather as people often do.

As a general rule, plants grow between 50-85 degrees Fahrenheit. Below 50 and your vegetable seeds will likely not germinate. Above 85 and your plants will most likely stop growing new foliage and instead “bolt” or start prioritizing seed development to preserve the next generation. At freezing temperatures of 32F, many plants start experiencing damage. At 28F (hard freeze), your plants may die completely. Knowing your average first and last frost dates can help you avoid running into problems with freezing plants. But what about when it is too hot?

Not all plants can endure the warm summers experienced across North America. This is where it becomes important to understand cool vs. warm season plants. Cool-season plants typically can germinate and grow well in the cool spring and fall soils. They are mostly made up of leafy greens, root vegetables, and brassicas. Sudden rises in temperature above 75-80F will trigger these plants to flower and develop seeds. When this happens, the foliage can become very bitter tasting and undesirable. At this point, you might as well pull these plants and replace them with heat lovers. Focus on growing cool-season vegetables when the temperatures are between 50F and 75F in the spring and fall.

Cool-Season Vegetables:

• Peas
• Carrots
• Lettuce
• Spinach
• Cabbage
• Pak choi
• Beets
• Broccoli
• Cauliflower
• Kale
• Mustard
• Turnips
• Radish

Most heat-loving plants require more time to grow and bear fruit. This is why it can be important to start plants like tomatoes and peppers ahead of time if your growing season is not long enough. Your growing season is the time between your average last spring frost and first fall frost. Regions that experience less than 120 days. If you find yourself in need of vegetable varieties that can mature quickly, check out our Short Season Vegetable Gardening article. Starting Seeds Indoors is a great way to grow plants as annuals that would not normally occur in your region. This is how most people are able to grow diverse vegetable gardens regardless of what their local climate is like.

Warm-Season Vegetables:

• Tomatoes
• Peppers
• Eggplant
• Winter Squash
• Cucumber
• Okra
• Onions
• Summer Squash
• Carrots
• Beans
• Corn
• Potatoes

When Can I Plant Warm-Season Vegetables?

Heat-loving plants can usually be planted outside when temperatures are reliably 65-80F. The closer you get to 80+, the more heat stress your seedlings will experience. This leads to another important factor of growth…water. Will your plants get enough water from natural events like rain? Does your growing location experience hot and dry summers? Or are they hot and humid? If you fall somewhere in the middle, you are quite lucky. Water availability can be an important factor to think about when selecting the right plants for your garden. Most warm-season vegetables are naturally heat tolerant to some degree. But without enough water, your plants may become scorched, wither, and become more susceptible to pest damage. When growing in hot and dry climates, you must utilize irrigation systems, or hand water with a hose daily.

Drought and Heat Tolerant Vegetable Varieties:

***While these cool-season vegetable varieties can handle heat and drought stress much better than other varieties, they should be carefully monitored during summer heat and drought conditions. Best grown in areas with afternoon shade (during the summer months) to help prevent bolting and reduce water loss. Rather than considering these drought and heat tolerant, I prefer to think of them as bolt resistant. Keep in mind most plants that are drought tolerant still require frequent watering until they become well established.

• Pea - Wando (Shelling)
• Carrot - Danvers 126 (Heat Tolerant, Somewhat Drought Tolerant)
• Lettuce - Webbs Wonderful
• Spinach - Malabar Spinach
• Cabbage - Charleston Wakefield
• Pak Choi/Bok Choy - Hotau Hybrid
• Beet - Red Ace Hybrid
• Kale - Black Tuscan
• Mustard - Tendergreen
• Turnips - Purple Top
• Radish - Daikon

Warm-season vegetables will handle bouts of extreme heat and drought conditions more easily than cool-season vegetables. These varieties are known to peform well under stressful conditions.

• Tomato - Early Girl Hybrid (Indeterminate) and Marglobe (Determinate)
• Peppers - Sweet Banana, Pablano, and Jalapeno
• Eggplant - Florida Market, and Millionaire Purple Hybrid
• Winter Squash - Waltham Butternut and Table Queen Acorn
• Cucumber - Marketer and Arkansas Little Leaf
• Okra - Clemson Spineless 80
• Summer Squash - Black Beauty Zucchini
• Beans - Kentucky Blue and California Black-Eye (Cowpeas) - While most bush and snap beans are drought tolerant, they may delay pod production beacause of excessive heat.
• Corn - Corn generally grows well in hot and dry climates, especially "Indian Corn" or Flint-types. True drought tolerant sweet corn is a current topic in plant research. Until more development occurs it is best to make sure your watering needs are met for desired yields.