Brutal summer heat won't spare lettuce, but basil, okra, and zinnias still thrive

July can be a tricky month for gardeners. Store shelves may still be full of flowers, but many backyards are already baking in heat waves.

While it may be tempting to plant in midsummer for a fall harvest, that doesn't mean you should.

What's happening?

Traditional planting calendars are becoming less reliable as hotter summers and longer dry spells reshape growing conditions across the country. As Tom's Guide reported, experts say July planting now depends less on the date than on the forecast.

"The most disruptive change that is impacting many gardeners today is the increasing occasions of brutal summer heat and humidity driven by events like El Niño," said John Cho, the founder of the gardening weather app My Cozy Plant.

One of the biggest challenges is transplant shock. When you move a plant from a pot into the ground, it has to establish roots while still supporting its leaves and stems. That process becomes much harder in high heat, when soil dries out faster and foliage loses more moisture.

According to Tom's Guide, Cho recommends delaying planting when temperatures remain above 85 degrees Fahrenheit. In those conditions, crops that do well in cooler weather, like lettuce, spinach, and arugula, are especially likely to struggle. Large-leaved flowering plants like hydrangeas can also have a hard time. 

Starting new sod is risky as well. Keeping it alive in midsummer often requires heavy watering.

Why do planting times matter?

Poor timing can mean wasted money, wasted water, and disappointing harvests. Growing food at home can help households save money on produce while also providing fresher, better-tasting herbs and vegetables than many store-bought options.

And gardening has a whole host of benefits beyond the above. Digging, watering, and weeding can support physical activity. Spending time outside and caring for plants can improve mental health and reduce stress. 

But extreme weather can make those benefits harder to access if plants fail before they ever have a chance to grow.

Kate Schneider, founder and CEO of Ibis Coastal Landscapes, said to Tom's Guide, "Even native plants need time to establish healthy root systems during the milder seasons before they can withstand prolonged heat and drought." 

She added, "Planting in the middle of summer asks them to survive some of the year's harshest conditions before they've had a chance to get established."

The shift is also changing gardening habits. Cho said, "We are starting to see some gardeners planting earlier than normal to ensure plants have established root systems by the time the brutal heat kicks in."

What can I do?

If you are determined to plant in July, the safer bet is to focus on varieties that like the heat. 

Cho highlighted edible crops like peppers, okra, and basil. Flowers like zinnias, cosmos, and marigolds will likely do well as well. Tom's Guide also noted that a second planting of sunflowers can succeed, since many varieties reach maturity in about 60 to 80 days.

Experts recommend getting new plants into the ground early in the day, ideally before 10 a.m., so roots have some time to settle before the worst afternoon heat. They also advise deep watering in the morning and, if needed, again in the evening to support stronger root development.

Helping plants through summer can also come down to what covers the soil. 

Schneider said, "It may seem counterintuitive, but one of the best ways to help new plants survive summer heat is to apply a generous layer of mulch."

Cho added to Tom's Guide, "Fall planting is quickly becoming a popular window for putting new things in the ground."

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