As the seasons grow on long hot days soaring to Fahrenheit in the 90s, your vegetable garden is a bit visible… The risk of frost has been passing for a long time, and you can ultimately grow your favorite warm weather crop, but the summer heat is also challenging.
So, what’s going on here?
The answer may surprise you: high temperature.
All of these crops require the sun and warmth, but very hot weather can make everything a creaking stop. Here are seven common problems in the summer, why they occur, and what you can do:
1. The plants are green and healthy, but do not produce fruit.
Certain vegetables, such as peppers and squash, are very sensitive to excess nitrogen. Applying high-nitrogen fertilizer in the middle of summer can actually delay flowering (producing many lush growth).
I usually recommend adding compost, worm casting, and/or slow release granular fertilizer at the beginning of the season (when planting) and using liquid fertilizer to boost the plant if necessary. If the temperature exceeds 90°F, stop fertilization. Most plants are unable to utilize the nutrients you provide them, and fertilizing in the peak summer often increases their heat stress.
Disclosure: If you shop from my articles or purchase through any of my links, you may receive a fee for some of the products I recommend.
2. Despite proper fertilization, the plant appears to be stunted.
Does your plant stop growing and appear to remain the same size for several weeks?
During periods of drought and extreme heat, many plants either focus on survival rather than production, slowing growth completely or stopping growth completely. It is a stress response similar to dormancy, and it is a way for plants to save energy. Once the temperature returns to normal or cools a little, growth resumes.
When you see long-term heat spells in your prediction, you can hang a shaded cloth over your garden bed to give the plants daytime relief. Mulching also helps keep the soil cool and retain more moisture so that the roots don’t dry out.
3. There is not much bee activity in the garden.
Many people worry about a lack of bees in their garden. Also, if you are growing many vinning crops that rely on pollinators (such as squash, melons, certain types of cucumbers, etc.), this means little or no fruit.
A lack of bees does not necessarily mean that you need more flowers to draw bees (though it’s a good place to start). Just as people prefer to take it easily and rest in the shade on hot days, so do many species of honeybees.
The ideal temperature range for pollination is between 60°F and 90°F (warm temperatures promote more pollination). When the temperature exceeds 90°F, many bees slow down. Pollination can still occur, but not too often, and this can reduce pollination outcomes.
One way that can help friendly neighbours bees is to create a small “watering station” where they can stop and drink. They need hydration just like us, and especially love shallow, stagnant water. Place a large saucer (or another shallow dish, like a shaved or baking pan) with some pebbles protruding from the water. These provide a safe place for honeybees to land and drink without being owned.
4. Vegetables suddenly turn brown, rotting, incorrectly or unusually small.
Remember when I mentioned the results of poor pollination in the above few paragraphs?
This is what your zucchini and pumpkin look like they’re forming, but suddenly breaking down and moldy. If there is no sufficient bee activity, sufficient pollen will not be transferred from males to female flowers to properly pollinate.
Incomplete pollination can also lead to deformed fruits, which can lead to uneven development and odd shapes of cucumbers.
However, bees aren’t the only reason why it looks strange. Very hot climates can reduce pollen quality. Or, with beans, there is less pollen (and less pollen means fewer bean pods).
5. Squash plants have many male flowers, but few female flowers.
As I have written previously about how squash pollination works, high temperatures can significantly affect the male to female flower ratios of squash plants. Male flowers tend to appear when the weather is warm, while female flowers prefer cooler temperatures. If it exceeds 90°F during the day or at night, it can cause the plant to develop more male flowers.
This means that summer or winter squash plants may have lots of flowers in the summer, but they are mostly male flowers that do not produce fruit.
What can you do about this? If you have a persistent heat spell, hang a shaded cloth over the plants to help keep it cold a few degrees.
Hot climates need to start squash plants early in spring to encourage more female flowers to develop to beat the heat, or even in the middle of summer, as temperatures begin to taper. (It’s a great option for midsummer planting, as you can find many summer squash varieties that will mature in just 40 days.)
Some plants may retain their flowers, but if they are not pollinated within two days, the flowers will shrink and fall off. Especially on hot nights, pollen can be made sticky and unfeasible, and rounds of tomato flowers can be dropped without pollination.
But flower drops are not just a tomato problem. Pepper, beans and squash are also very sensitive to hot weather, and can abort flowers if the temperature exceeds 95°F.
One of the easiest ways to make sure your tomato plant survives the hot summer is to choose the right variety in the first place, such as an early girl, a stupid or yellow pear. These heat-resistant varieties can form fruit even when temperatures rise in July and August.
If you cannot find heat set tomatoes in your area, you can plant short-season tomato varieties that will mature within 70 days before serious heat arrives. Tomato types are also a good option. Because they tend to set fruit in shorter windows early in the season.
Tomatoes (and other crops that are prone to flower) appreciate some shade to keep the hottest parts of the day (which can be made with shady cloths, old bed sheets, or strategic planting in the garden), knocking down flower drops (and preventing other problems like cracked fruits), and to keep mulch even.
7. Tomatoes will ripen forever.
Yes, excessive heat can affect tomato aging! The optimum temperature range for fruits to mature is between 68°F and 77°F, and lycopene, the pigment that gives the tomatoes a red color, is not produced above 85°F.
This means that tomatoes remain green until you experience a cool night that gives you time to ripen between the ideal temperature windows. They ripen more slowly in this way, but they get there.
Related: 3 other reasons why your tomatoes aren’t red
However, there is no need to wait for the tomatoes to ripen the vine. In fact, it is recommended to pick the tomato before it turns red and ripens indoors. (This method also allows you to get high-quality tomatoes.)
