Even though Basil plants are fairly easy to maintain, there are certain factors that may cause this herb to lose its beautiful green color.
The most common reasons for Basil Leaves turning white are nutrient deficiency and fungal diseases. In addition to these factors, overwatering, pest infestation or too much sun can cause Basil leaves whitening. To fix the problem it is important to identify the cause and then take necessary actions.
In this article, you will find out why your Basil leaves are turning white, and solutions to the problem.
Basil needs warm temperatures for proper growth and very sensitive to cold weather. It cannot tolerate temperatures lower than 50°F (10°C). It is recommended to keep it in temperatures ranging from 68 to 80°F (20 to 27 °C).
If your basil is exposed to too high temperature, physiological activities will be altered. This can manifest as:
- Yellowing/whitening of leaves
- Distorted growth
- Don’t plant your basil seeds until any danger of frost is gone.
- If possible, adjust the temperature settings of your home or the room where you keep your plant.
- Provide a stable temperature, ideally in the range of 72°–82°F (24°–28°C),
for the Basil plant. Temperature fluctuation can shock the plant and stunt its growth.
Downy mildew is a common Basil plant disease caused by Peronospora belbahrii fungus. These are the symptoms of downy mildew:
- Yellowing or whitening of the leaves (chlorosis)
- Intense yellowing around the middle vein on the leaf
- Fuzzy gray growth on the underside of the leaves
- Basil leaves eventually curl, wilt and turn brown
- If you think your plant has downy mildew, it would be best not to try any home remedies.
- The only way to fight off downy mildew for sure is to buy a fungicide which is labeled for downy mildew.
Fusarium wilt is a very common basil disease caused by a soil-born Fusarium oxysporum f. sp. basilicum fungus.
In its early stages, fusarium wilt can manifest itself as chlorosis, which means yellowing and whitening of the leaves.
As the disease progresses, the plant turns brown, wilts, and eventually dies.
- There is no cure for the Fusarium wilt of Basil. The only remedy is removing the infected plant and disinfecting the pot.
Aphids are small insects that suck on the juices of basil leaves and deprive the plant of water and nutrients. They are usually a pale green color or a brown color. The first sign of aphid infestation is the yellowing and drying of the leaves due to the lack of water and nutrients.
- Small numbers of aphids on Basil can be crushed by hand or removed by pruning as they are found.
- Insecticidal soaps are very effective against aphids.
- Coca-Cola in a spray bottle works very well against them because they suffocate in the sugary liquid.
Nematodes are microscopic worms that damage Basil’s roots and compromise the plant’s ability to take up water and nutrients from the soil.
Infected plants can show symptoms similar to nutrient deficiency – yellowing of leaves and wilting. Due to lack of nutrients leaves will lose its green color and turn pale green.
- In healthy soil small number of nematodes is not a problem. The effective solution is using a resistant variety.
These are tiny flying insects on the leaves. It may seem like some kind of white stuff on your basil leaves but are flying insects. These insects also damage the leaves sucking the juices out and leaving them a pale green color.
Excess salt dehydrates your Basil plant. Salt build-up causes the plant to retain water, so this can manifest as dry or white leaves. The reason for this might be water quality and overfertilizing.
- Put your plant in a pot with drainage holes. The excess water will flush out, reducing the risk of salt-build up.
- Use rainwater, filtered water, or distilled water. Tap water usually has chemicals that can cause salt build-up.
- Don’t overfertilize your plant. Too much fertilizer may cause salt build-up.
- Nitrogen deficiency results in uniform yellowing of old leaves.
- Potassium deficiency manifests as large yellow regions along leaf edges and also scattered yellow spots between leaf veins.
- Magnesium deficiency presents itself as yellowing between leaf veins.
- Sulfur deficiency exhibits uniform chlorosis across the entire leaf, affecting the whole plant.
- Iron deficiency results in interveinal yellowing of younger leaves.
- Apply a smaller dose of water-soluble, balanced liquid fertilizer every two weeks during the growing season (Spring-Autumn).
- Put fertilizer into the soil before planting or repotting your Basil.
Basil prefers full sun, preferably 6 to 8 hours of sun per day.
All plants need light in order to produce chlorophyll (the green pigment), which is crucial for making their own food. Without light and without chlorophyll, the plant loses its color and this can lead to leaves appearing lighter or yellow.
- Place your Basil plant in a spot with direct sunlight 6 to 8 hours a day.
- Keep your Basil plant 6 to 12 inches from two 40 watts, cool white fluorescent bulbs for 14 to 16 hours.
Too Much Sun Exposure
Even though Basil thrives under direct sunlight, too much of it at the wrong time can actually harm the plant.
Too much direct light might cause your plant to dry out and lose water and nutrients, which can manifest as dry white leaves.
- Don’t keep your plant in direct, midday sunlight during really hot days (typically during summer months).
- Instead, keep your plant in direct sunlight during the morning, and move it into the partial shade around noon.
Overwatering and excess moisture can cause root rot, which damages the root system and prevents them from transporting food and water to the rest of the plant.
Overwatering (root rot) can manifest as whitening/yellowing of the leaves because they aren’t getting enough water and nutrients from the soil.
- Take your plant out of its container and check if there are any rotten roots.
- If root rot has set in, remove the affected parts. They will look brown and mushy.
- Move the plant to a new, sterile container with fresh new soil mix
- Trim off the rotten roots with a disinfected scissor.
- Place it in a pot with drainage holes so there is no excess water or moisture in the soil.
Underwatering your plant will deprive it of its ability to produce its own food and receive hydration and nutrients from the soil.
Similar to overwatering, your Basil simply isn’t getting enough water in its tissue and this can cause whitening and dryness of the leaves.
- If your basil is underwatered, give it a deep watering and it should perk up within the next few days.
- Water your basil when the top 1-2 inches of soil feels dry.
Helpful tip: When watering basil, water at the base of the plant to ensure the foliage stays dry.
This way, you’re reducing the risk of fungal and bacterial infections.
Wrong Soil Type
Basil thrives in well-drained soil which allows air circulation and oxygen availability.
Basil grows well in soils with a pH ranging from 5.5 – 6.5. Inappropriate pH can make some of the essential nutrients unavailable for your basil.
It would also be good for the Basil to add some type of organic matter into the soil. This can help prevent nutrient deficiency and help produce rich, healthy plants.
If there’s something wrong with your soil, Basil leaves will start yellowing or whitening. This can be because of a few reasons:
- The soil isn’t allowing air circulation and drainage, so excess moisture is trapped, making the roots more susceptible to root rot.
- Your basil is experiencing a nutrient deficiency.
- Mix organic matter, such as compost, into the soil before planting or repotting.
- Add recommended dose of a balanced fertilizer to the soil each month.
- Basil likes fertilizers that are high in nitrogen, but be careful not to overfertilize and cause salt build-up.
Close to a Heat Source
Basil is generally not that sensitive to heat, but keeping it near a heat source for a prolonged time can have consequences. For example, an electric heater or radiator can actually cause the leaves to dry out and put on a yellow/white color.
When your plant is exposed to too much heat, this can increase transpiration. If transpiration is increased, your plant will lose more water than it should.
Without water, the leaf tissue will lose its chlorophyll pigments and start whitening.
- First of all, water your plant thoroughly if you suspect that it has gone through heat damage.
- Keep your Basil plant at least away from any heat source.
- Don’t keep the plant outside if temperatures rise above 85°F (29°C).