Garlic Leaves Turning Yellow

Garlic leaves turn yellow in reaction to an environmental factor that is causing the plant stress. Identifying the cause of this change in color is important, to know how to properly remedy the problem.

The most common causes of yellowing garlic leaves are cold temperatures, disease, pests, poor plant care, lack of nutrients and soil problems.

In this article, we will discuss the different causes of yellowing garlic leaves and how to remedy each one.

Why are the leaves on my garlic plant turning yellow?

Cold temperatures

The leaves of a young garlic shoot will turn yellow in cold temperatures, especially when there is frost. This can be a problem when the air temperature is below freezing, because often the frost on the ground makes the soil even colder than the air. When you see morning frost, it means there was night frost on the soil, and the tips of the garlic leaves will most likely have turned yellow due to the cold and the frost.

In the winter, protect your garlic beds from frost by mulching them. You can use straw, fine chips, peat and humus to mulch the beds. These organic materials are most ideal since you are also using them to fertilize your vegetable crop. Lay about two inches of mulch to protect the plants from frost.

In order to prepare your garlic for the winter, plant it as early as September. Mulch the beds after planting so that they survive the winter frost.

Disease and pests

Both disease and pests can also cause garlic leaves to turn yellow. It could be due to fungal disease or a host of insects. It is not that hard to determine the cause of yellowing in this case; you simply need to inspect the plant and look for the usual signs. Dig up the plant and look at the bulb. If you find any bugs or larvae, or any mechanical damage to the bloom or root system, then pests are likely to blame for the yellowing leaves.

You can narrow it down to fungal disease if you see the head of the plant begin to rot after the aerial part has dried up.

The most common diseases of garlic plants are fusarium and bacterial rot.

Fusarium causes young garlic to turn yellow. This fungal disease discolors the tops of the leaves first, followed by brown stripes. The leaves and stem will then start to dry out until the entire plant dies. This disease acts very quickly. One of the first signs is a pink coating in the sinuses under the leaves. You will also notice that the bulb with fusarium will have a dead root system and the base will be soft. Unfortunately, there is nothing you can do to save a garlic plant with fusarium; the best you can do is make sure it does not spread to your other plants. Remove all the affected plants and burn them. Make sure you treat the soil of the diseased plant with concentrated copper sulfate solution.

Bacterial rot causes garlic leaves to turn yellow and even to develop brown spots. The disease will start with the plant turning yellow, followed by the stem. As the disease progresses, a more and more noticeable rotten smell will develop from the bulb. The bacteria that cause the rot come from the soil. If there are no signs of mechanical damage to the plant, the disease is unlikely to infect the plant. However, if there is damage due to insects, this provides the bacteria with a route into the plant to destroy it. As with fusarium, there is no treatment for bacterial rot.

One of the most common pests to infest garlic plants is the stem nematode, which may also cause the garlic plant to turn yellow. They feed on the juice of the plant until the plant eventually dies. The tips of the leaves will turn yellow first, and then streaks will appear. The more the disease spreads across the plant, the more the leaves will curl and the plant will wither.

There are no known treatments for stem nematodes. You will have to remove the plants and burn them.

Poor plant care

Improper plant care can also cause the tips of the garlic plant to turn yellow. Insufficient watering as well as overwatering can negatively affect the appearance and condition of the plant. The first leaves to turn yellow are the ones at the bottom, and the yellowing gradually moves upwards.

Make sure you care for your plants properly by watering them twice a week when there is little rain. If there is no rain at all, water the plants four times a week. If there is plenty of rain in the spring, you do not need to water the plants. Garlic plants are more tolerant of excess water than lack thereof. Loosen the soil around the plant the day after watering.

Lack of nutrients

If you have eliminated all other possible causes of yellowing leaves and are still stumped as to what the cause could possibly be, it is most likely a nutrient deficiency. The plant needs magnesium, nitrogen and potassium. You cannot determine alone which elements your plant is lacking, but if you very rarely apply organic fertilizer, it is not a stretch to assume that the plant needs at least one of those elements.

Mineral fertilizers applied in early spring can help with the yellowing effects of nutrient deficiency. Make some furrows between the plant beds and pour the fertilizer into the furrows. Pour the rest of the fertilizer onto the plot and then water it. Make sure the three elements are present in the fertilizer you use.

Soil problems

The type of soil you use can also cause yellowing on the garlic plant’s leaves. This plant does not do well in acidic soil and prefers a neutral pH. If the soil is acidic, the garlic plant will turn yellow after a few weeks.

You can bring the soil back to a neutral pH using wood ash. You will need to cover the entire plot with this; mere handfuls of wood ash will not do the job. You can also use lime to lower the soil’s acidity. Lime works faster and can keep the soil at a neutral pH for up to a decade.

Conclusion

Yellowing garlic leaves are indicative of an environmental factor that is causing the plant stress. Being able to correctly identify the cause is the first step in remedying the situation.

The most common causes of yellowing garlic leaves are cold temperatures, disease, pests, poor plant care, lack of nutrients and soil problems.

Image: istockphoto.com / YuriyS