It’s hot! We have a couple of months before we get much of a break from it, too. Plants feel the heat and the stress it causes is almost unbearable at times. This is an important time of year to keep close watch over your plants, if you’re concerned about their health and vigor. Many problems that your plants may be experiencing can be accentuated by hot weather and the hot weather can be the cause of other problems. If you can develop a sensitivity to your plants’ needs this time of year, they will greatly appreciate the attention.

You’re thinking that the biggest problem plants have to deal with in the heat is a need for additional water. Even the least experienced gardener knows that things dry out faster when it’s hot and dry. However, the need for additional water isn’t based only on the fact that the ground dries out faster. Plants use much more water in the heat because water evaporates from the leaves much faster. This process is called transpiration. In the heat we perspire, plants transpire. Since plants transpire more, the ones with good, healthy root systems will be happier than those with shallow, underdeveloped root systems. This isn’t the first nor will it be the last time I suggest that infrequent, deep watering is the best way to develop good, healthy root systems. You won’t have healthy plants nor will you get deep root development by watering daily or every other day. Roots must be induced to grow deeply and, if the soil is constantly moist near the surface, there is no need to.

Since plants are working harder and transpiring more, they not only use more water, they will take up nutrients faster. Fertilization is important for many plants this time of year because of that. As plants are being watered deeper or more frequently, many nutrients move out of their root zones with the water as it penetrates deep into the soil, which is another reason to fertilize. However, if you have conditioned your plants to produce deep, healthy roots, they will have more nutrients available to them longer and won’t need fertilization as frequently. Using fertilizers regularly on bedding areas will improve the looks of your annual and perennial flowers and the performance of most vegetables.

Chlorosis is characterized by yellowing leaves and is generally caused by nutrient deficiencies. It will be more prevalent during the heat of summer if there is a lack of fertility in your garden. The most common cause of chlorosis in older leaves toward the bottom or the inside of plants is due to a lack of Nitrogen, one of the most important nutrients plants need. Nitrogen doesn’t adhere to soil particles and leaches deeper into the soil with every watering. Soon the soil around the roots is depleted of Nitrogen and you see the resulting chlorosis in the leaves. This can be prevented or corrected by regular fertilization, as recommended, because most fertilizers contain nitrogen (which is indicated by the first of the three numbers listed on fertilizer packaging). Chlorosis can be caused by deficiencies of a whole slew of major and minor elements needed for plant vigor. The major nutrients are called macronutrients examples of which are Nitrogen, Phosphorus and Potassium. The three numbers on a container of fertilizer refers to the amount or percentage of these nutrients in the product. Micronutrients, such as Iron, Zinc, Manganese, etc are important to plant health as well and are listed separately in an analysis of ingredients on fertilizer labels. Plant scientists and pathologists are trained in recognizing the symptoms of specific nutrient deficiencies or toxicities. (You’re familiar with toxicities if you’ve ever over-fertilized and witnessed the resulting yellowing or scorching.) We’ll leave the soil chemistry and diagnosis to the scientists who can help when all good practices and measures have been taken and chlorosis persists. However, let’s cover some good fertilization and nutrition basics.

There are lots of fertilizers out there, chemical and organic. When purchasing fertilizers, look for one that has a good amount of micronutrients listed on the label. Water soluble fertilizers can be sprayed on and around plants. The nutrients from these fertilizers can be absorbed through a plant’s leaves as well as its roots. Some nutrients can be unavailable in the soil depending on its chemistry. When these elements are tied up in the soil, foliar feeding can be beneficial. This method can be a quick fix but it doesn’t last long so you should apply water soluble fertilizers weekly. Granular fertilizers can be applied monthly or even less frequently if the fertilizer is time-released. If you must apply a fertilizer in the heat of summer, make sure you make your application early in the morning when it’s cool. If applying a granular fertilizer, lightly water it in after the application. This will wash the granules off the foliage and prevent scorching.

Maybe you’ve heard about better chances for the survival of the fittest. It is true for plants. The healthier they are, the better they can resist or cope with problems. That includes the stresses brought on by the summer heat.