Tomatoes are one of the few garden vegetables that can land their caretakers in a world of despair when problems erupt -- for all their trouble, it's a wonder anyone grows them. When tomatoes develop yellow leaves, it's unlikely to be caused by too much fertilizer, but could be due to other environmental problems or diseases.
Fertilizer is a useful product for plants such as tomatoes. The plants use the fertilizer as food to grow large and healthy. But, any gardener who has ever thought, "if a little bit is good, a lot will be better" in regards to fertilizer, soon finds out the hard way that the opposite is true. Too much fertilizer can burn the roots of plants, and can cause wilting, yellowing and even death.
Fertilizing tomatoes
A home soil test kit will give you valuable information about your tomato patch. Tomatoes thrive with medium fertility and show problems when fertility is too high or too low. Usually, they don't require any feeding at planting time, unlike many vegetables. Successful tomato producers may wait to feed tomato plants until fruits are about the size of table tennis balls. At this point, side-dress tomatoes with a small amount of nitrogen fertilizer every four to six weeks until the final harvest.
Signs of too much fertilizer
Over-fertilizing tomatoes early in their lives results in plants that are tall and spindly, with lots of deep green foliage, but few flowers. Tomatoes can't simply use the ideal amount of nitrogen they need to thrive. Instead, excess nitrogen in a tomato plant tells the plant to produce more leaves and stems at the expense of blossoms and fruits. Sometimes, excess nitrogen can be leached from the root area of tomato plants by repeated, deep waterings.
Causes of yellowing leaves
Common causes of yellow leaves on tomatoes include cool soil, age-related death of the lower leaves and a myriad of nutritional deficiencies including nitrogen, boron, potassium, iron and magnesium. Leaves may also yellow when affected by fusarium wilt, bacterial wilt or verticillium wilt. These disease are the result of fungal or bacterial pathogens multiplying rapidly in vascular tissues, causing the plant to die from lack of nutrients. Root knot nematodes can kill plants in a similar fashion, but the roots will bear distinctive swollen knots. Wilts and nematodes are difficult or impossible to treat once plants are severely affected.
Soil solarization
Although the disease and pest causes of yellow leaves on a tomato are difficult to cure once the plant is already showing symptoms, you can use soil solarization to destroy these organisms before you plant your next tomato crop. After the troubled tomatoes have died or are removed, till the garden well and smooth the soil with a rake. Apply a 1 mil clear plastic tarp over the prepared and watered soil and leave it there for six weeks. This heats the soil to high enough temperatures to destroy many nematodes and soil-borne fungi and bacteria before the upcoming growing season.
Fertilizer is a useful product for plants such as tomatoes. The plants use the fertilizer as food to grow large and healthy. But, any gardener who has ever thought, "if a little bit is good, a lot will be better" in regards to fertilizer, soon finds out the hard way that the opposite is true. Too much fertilizer can burn the roots of plants, and can cause wilting, yellowing and even death.
Fertilizing tomatoes
A home soil test kit will give you valuable information about your tomato patch. Tomatoes thrive with medium fertility and show problems when fertility is too high or too low. Usually, they don't require any feeding at planting time, unlike many vegetables. Successful tomato producers may wait to feed tomato plants until fruits are about the size of table tennis balls. At this point, side-dress tomatoes with a small amount of nitrogen fertilizer every four to six weeks until the final harvest.
Signs of too much fertilizer
Over-fertilizing tomatoes early in their lives results in plants that are tall and spindly, with lots of deep green foliage, but few flowers. Tomatoes can't simply use the ideal amount of nitrogen they need to thrive. Instead, excess nitrogen in a tomato plant tells the plant to produce more leaves and stems at the expense of blossoms and fruits. Sometimes, excess nitrogen can be leached from the root area of tomato plants by repeated, deep waterings.
Causes of yellowing leaves
Common causes of yellow leaves on tomatoes include cool soil, age-related death of the lower leaves and a myriad of nutritional deficiencies including nitrogen, boron, potassium, iron and magnesium. Leaves may also yellow when affected by fusarium wilt, bacterial wilt or verticillium wilt. These disease are the result of fungal or bacterial pathogens multiplying rapidly in vascular tissues, causing the plant to die from lack of nutrients. Root knot nematodes can kill plants in a similar fashion, but the roots will bear distinctive swollen knots. Wilts and nematodes are difficult or impossible to treat once plants are severely affected.
Fertilizer burn
The damage done by over fertilizing plants is known as fertilizer burn. This is because plants that are given too much fertilizer have a burned appearance, with foliage that turns brown and crispy. Fertilizer burn occurs when the chemicals in fertilizer draw water out of the plant. As a result, the plant dries out. This process is known as a hygroscopic process. Salt in fertilizers are the frequent cause of the fertilizer burn.
The damage done by over fertilizing plants is known as fertilizer burn. This is because plants that are given too much fertilizer have a burned appearance, with foliage that turns brown and crispy. Fertilizer burn occurs when the chemicals in fertilizer draw water out of the plant. As a result, the plant dries out. This process is known as a hygroscopic process. Salt in fertilizers are the frequent cause of the fertilizer burn.
Symptoms
Over fertilized tomato plants first show signs of damage in their leaves. As water withdraws from the leaves, they appear limp and begin to yellow. As the symptoms progress, the yellow leaves turn brown and become crispy. The best way to check for fertilizer burn around a tomato is to take a sample of the soil from around the plant and submit it for analysis to a soil laboratory. The soil laboratory will inform you if there is a high level of nutrients in the soil.
Problems from lack of fertilizer
Despite the dangers of fertilizer burn, most tomatoes are heavy feeders. Without fertilizer, tomatoes may suffer from blossom end rot, a condition that occurs when there is not enough calcium in the soil. Blossom end rot appears on tomatoes first as a slightly brown, water-soaked lesion on the blossom end of the tomato. The lesion eventually enlarges and turns black and leathery.
Over fertilized tomato plants first show signs of damage in their leaves. As water withdraws from the leaves, they appear limp and begin to yellow. As the symptoms progress, the yellow leaves turn brown and become crispy. The best way to check for fertilizer burn around a tomato is to take a sample of the soil from around the plant and submit it for analysis to a soil laboratory. The soil laboratory will inform you if there is a high level of nutrients in the soil.
Problems from lack of fertilizer
Despite the dangers of fertilizer burn, most tomatoes are heavy feeders. Without fertilizer, tomatoes may suffer from blossom end rot, a condition that occurs when there is not enough calcium in the soil. Blossom end rot appears on tomatoes first as a slightly brown, water-soaked lesion on the blossom end of the tomato. The lesion eventually enlarges and turns black and leathery.
Soil solarization
Although the disease and pest causes of yellow leaves on a tomato are difficult to cure once the plant is already showing symptoms, you can use soil solarization to destroy these organisms before you plant your next tomato crop. After the troubled tomatoes have died or are removed, till the garden well and smooth the soil with a rake. Apply a 1 mil clear plastic tarp over the prepared and watered soil and leave it there for six weeks. This heats the soil to high enough temperatures to destroy many nematodes and soil-borne fungi and bacteria before the upcoming growing season.
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