Tomato Plants Need Well-Draining Soil

Tomato plants need well-draining soil, especially when they’re in containers. Use a quality potting mix that’s rich in organic material and add compost or other amendments to the planting hole.

Tomato stems are covered with fine hairs (trichomes) that reduce water loss and facilitate nutrient absorption. They can produce adventitious roots, particularly at nodes and internodes.

Light

Tomato plants grow and flower quickly when bathed in far-red light, but the benefits of this illumination don’t stop there. This same boost in growth and flowering speed also makes tomatoes more attractive to bumblebees, which then help with pollination and yields.

Researchers used a greenhouse to study the effects of far-red spectrum lighting on tomato plant morphology, water use efficiency (WUE) and photosynthesis. They also measured stomatal conductance and the concentration of intracellular carbon dioxide. They found that stomatal conductance reached a maximum at a PPFD of 240 mmol m-2 s-1, which is very close to the peak value that was seen under normal sunlight.

Normally, a tomato plant’s leaves absorb green light and reflect red light. Tomatoes with high-red-to-green ratios tend to be more bushy and sprawling, while those with low-to-medium red-to-green ratios are shorter and compact. This variation in morphology is caused by the interaction between light and hormones, specifically the auxin hormone, which can promote or inhibit growth.

As tomato plants mature, they may elongate along their stems. This is usually a good thing, as it means they are able to absorb more sun and wind, but can be problematic for grafted plants. Tomatoes that have long, elongated stems are also more susceptible to the rot that often occurs around grafts.

Tomatoes are a thirsty crop, and their thirst only increases as they set fruit. The best way to keep them healthy is to water deeply, and infrequently. This helps prevent scalding the roots, and will ensure that the plant’s water supply is always readily available.

Tomatoes can be infected with a number of viruses, including tobacco mosaic virus, which causes mottling of older leaves and can stunt growth. Other viruses include potato virus Y and bacterial leaf spot, which cause symptoms such as dark green spots or shoestring-like leaves. Infected plants have reduced production rates and lower quality. Affected plants can be treated with fungicides to help suppress disease. However, this treatment is not a guarantee that the plants will recover. The virus may persist in the soil, so the plant will likely remain susceptible to future infections.

Water

Tomato plants need water for both root growth and to transport nutrients up to the leaves. Water is also used to cool the plant and help it maintain a stable internal temperature. Tomato plants become stressed and damaged when the roots or soil are overwatered. This causes the plant to pull its energy into water uptake and away from photosynthesis, resulting in a reduction of production and lower quality fruit.

The amount of water a tomato plant needs is determined by evaporation from the soil and transpiration from the leaves. This process is called evapotranspiration (ET). ET is determined by the amount of sunshine, wind speed, humidity and the temperature of the environment. The higher the ET, the greater the yield of the crop. A study done at the University of Guelph showed that a season with 88 mm of ET produced the highest marketable yield of processing tomatoes on Fox sandy loam.

As the weather turns warmer, a tomato plant’s need for water increases. The optimum temperature for growing tomatoes is 75 to 85 degrees Fahrenheit. During these temperatures, the plants’ water needs are met by ET of about 300 to 400 ml/ha.

It’s best to use rainwater rather than tap water when watering a tomato plant. Tap water contains chlorine that can kill the plant, especially when it’s poured on the soil near the roots. Also, stagnant water breeds bacteria that can prevent the plant from soaking up its nutrients. If you must use tap water, allow the water to sit for an hour or two before using it on a tomato plant.

If you’re growing your tomato plants in containers, be sure they have plenty of drainage holes. It’s also a good idea to set up a regular watering schedule, and the container should be allowed to dry slightly between each watering session. Too much water suffocates the roots and slows down growth, but too little water may reduce fruit production.

When it comes to fertilizing your tomatoes, a balanced NPK fertilizer is essential. This can be purchased at your local garden center. Look for a fertilizer that has three numbers on the label, such as 10:5:10 or 2:2:2. The first number represents nitrogen (N), which is important to promote leaf and stem growth; the second is phosphorus (P) and the third is potassium (K). For healthy tomatoes, you should apply this fertilizer every two weeks throughout the growing season.

Temperature

Tomato plants are generally very sensitive to temperature extremes during reproductive stages, and this is a primary reason for low fruit numbers during heat waves. A rise in the air temperature during daytime can interrupt or disrupt the plant’s normal circadian rhythm, and it also interferes with photosynthesis. The model results indicate that when temperatures become too high, the tomato plant shifts a larger share of its resources toward maintaining itself during daylight hours rather than directing those resources to reproductive functions. This results in fewer pollen grains produced and, in turn, reduced fruit set at maturity.

During hot weather, it’s a good idea to check your plants frequently, and keep the soil moist. In hot climates like California, the Southwest or Florida, you may need to water tomatoes daily or even twice a day. This prevents fruits from cracking, and it defeats blossom drop, a common problem that causes the plant to stop producing flowers and, ultimately, fruit.

As the heat lingers, another common issue that affects tomato production is fruit with irregular coloration or no color at all. This is due to heat stress that makes the tomato plant produce a green pigment instead of red, which prevents the fruit from ripening. This is why it’s important to keep your tomato plants well-watered and shaded when temperatures are consistently warm, even in the early part of the growing season.

High humidity can also thwart pollination by inhibiting the release of pollen from the stigma. This is a big reason why dreaded blossom drop occurs on tomato plants, because when the weather is so hot and humid for extended periods, the pollen never gets the chance to make it to the stigma.

Gardeners can also help with pollination by using an inexpensive tool called a VegiBee, which vibrates at the tip and sends out a fine spray of pollen. When used correctly, this tool can greatly increase the number of ripe fruits per tomato plant. For best results, place it at the base of each blossom, or on the stem between each cluster of flowers.

Humidity

Tomato plants have a delicate dance with humidity. Too high, and they’re swimming in fungal disease; too low, and they might as well be crawling through the desert. Getting it right is like walking a tightrope, with each step potentially threatening to sabotage your entire crop. To maintain a rich, lush harvest you need to make sure your tomato plants are in the Goldilocks zone of 60-85% relative humidity.

Humidity is the amount of water vapor in the air. When it’s too high, it prevents the plant from evaporating enough water to perform its most basic functions, and this can lead to a host of problems, including foliar diseases, blossom-end rot, cracking, and lower yields. Conversely, too little moisture in the air can cause your tomatoes to suck it up faster than they can evaporate it, resulting in a dry and thirsty existence that impedes nutrient uptake and hinders growth.

As temperatures rise, so does the plant’s water needs. When temperatures get above 25-27 °C, it becomes difficult for the roots to spread and feed, which in turn reduces plant development. A run of hot weather will also scald green and ripening fruit, and inhibit pollination and fruit set.

To counteract this, you should try to keep your greenhouse or shadehouse at the right temperature, and monitor the humidity levels using a hygrometer. The ideal RH level for tomatoes is between 65% and 85%, and a hygrometer will help you dial this in throughout the day to boost growth and improve fruit quality.

Tomatoes are a lot more tolerant of moisture stress in the early part of the season than some other crops, and they can adjust their physiological processes to conserve water and maintain their vitality. However, long periods of water stress can eventually result in irreversible damage to the plant, reducing both yield and fruit quality.

Another factor that affects moisture in the air is nitrogen. Research has shown that high nitrogen concentrations in the growing medium can lead to excess vegetative growth and reduce flower and fruit set, so you should keep the nutrient level under control.