Those who grow potted, greenhouse, or indoor basil quickly notice when the leaves become translucent or transparent. Why does this happen?
When basil leaves lose their green color and turn translucent or transparent, it may be caused by:
- lack of sunlight and chlorophyll production
- insects sucking out the juice
- cold drafts causing plant stress
- infection by a fungus or a bacteria, or
- a nutrition deficiency
The value of basil plants in our lives makes it important for us to keep them healthy. Here’s a quick review of how basil contributes to human civilization, promotes health, and increases enjoyment.
Since the dawn of history, various civilizations have benefited from basil plants in cuisine, food preparation, and medical treatment.
Today, many enjoy growing basil indoors. The green of basil leaves exudes a soft, glowing sheen that comforts many indoor atmospheres.
And that’s not all.
Basil is a natural antibacterial. For instance, a paste of basil leaves can help prevent acne. Making tea from basil leaves can fight depression. Essential oils from the basil plant can treat upset stomachs and lower blood sugar in diabetics.
In addition, research indicates that essential basil oil extracts work as antitumors, antioxidants, antibacterial, and anti-aging agents. These extracts are sold in capsule form such as this one on Amazon, and also in liquid form such as this one, also on Amazon.
At the same time, basil provides us with a natural source of Vitamin A for clarity of sight, magnesium for healthy blood, and eugenol – a natural anti-swelling alternative to ibuprofen or aspirin. All free in a little pot by the window.
Chlorosis is the loss of the natural green color of leaves. It can indicate a serious problem such as nutrient deficiencies, high alkalinity in the soil, compacted or damaged roots, poor drainage, and so on.
When basil leaves become translucent or transparent, the questions border on panic: Is my basil sick? Is it dying? What’s wrong with my basil? What can I do?
No worries, the answers are here. Read on.
1. No Chlorophyll? Expose to Sunlight
The epidermis is the outermost layer of the leaf. This layer is colorless, that’s why we can see the green layer of chlorophyll below.
The issue: Chlorophyll forms only when there is sunlight. With lack of sunlight, leaves lose and change their green color (chlorosis). Leaves become light yellow or pale cream. Finally, the leaves can totally lose all color and become translucent.
Suggested solution: To restore chlorophyll production, gradually expose the plant to sunlight. Be gentle and give the plant enough time to recover slowly.
- Initial intervention: At first, a few hours of indirect sunlight will do. Position the plant near a window that admits early morning or late afternoon sunlight.
- Gradual exposure: As the leaves recover, expose the plant to longer hours of indirect sunlight.
- Recovery: Finally, expose the plant to regular sunlight. Keep in mind that basil thrives in at least 6 hours of sunlight each day.
- Non-recovery: If the damage is too severe, the translucent leaves may drop off. This is fine as long as the other leaves are green and healthy.
Alternative solutions: If you think that your basil leaves are losing color due to lack of sunlight or they’re not getting enough natural sunlight indoors, try out a full-spectrum growing lamp.
Any plant-feeding insect with a proboscis, (a needle-like mouth) can pierce the leaf epidermis and suck the green chlorophyll out of the leaf. This leaves behind tiny, transparent spots that can spread and do further damage.
The issue: Insects such as whiteflies, spider mites, or aphids suck out juice from basil plants. In some cases, this leaves very tiny, colorless spots on leaves (you’ll need a magnifying glass). In most cases, the damage causes leaf stress that shows as curling, turning brown, and dropping off.
Suggested solutions: There are several suggested methods to control the most common insects that feed on basil leaves.
- Spider mites: Spider mites feed on plant sap and tissues on basil. You can use miticides such as this one on Amazon, an organic neem oil repellent such as this one from Amazon.
- Whiteflies: Whiteflies are plant suckers that can destroy basil leaves. Insecticides for soft-bodied insects are suggested. Examples include malathion such as this one on Amazon. Be careful, though. Leaves sprayed with these chemicals can contain chemical traces that are poisonous.
- Aphids: Aphids suck the sap out of basil leaves, stems, and buds. Organic solutions include nicotine sulfate and neem oil such as this one from Amazon.
Alternative solutions: If you think that your indoor basil’s leaves are turning translucent because of insect attacks, you can spray the leaves with a mixture of 1 tablespoon soap in a quart of water (or 5 tablespoons of soap in a gallon of water). Some organic farmers recommend a spray of cow urine. Others suggest ants, which are natural predators of soft-bodied insects.
3. Cold Drafts? Control Temperatures
A cold draft is a current of cold air from outdoors. Because the natural environment of basil is tropical, cold drafts can stress out the basil plant and its leaves can turn translucent.
The issue: Cold drafts can stress out indoor tropical plants simply because they naturally thrive in the warm temperatures where they originally came from. Basil came from India, was imported into the Mediterranean, and later to the colder climates of Europe and the USA.
- Basil thrives in warm, humid atmospheres such as in Asia, Africa, and India.
- In colder climates, basil can thrive indoors or in temperatures between 80 and 90 degrees Fahrenheit (or 27 to 32 degrees Celsius).
- When basil is exposed to cold drafts, translucent or transparent spots can appear on its leaves as signs of stress.
Suggested solution: One way of minimizing stress from cold drafts is to enclose your indoor basil with a reusable plastic cloche such as this one from Amazon, or any dome glass cloche you have at home (perhaps for some fancy candles).
- It works indoors: The cloche is a bell jar that acts as a mini-greenhouse, keeps the immediate air temperature stable, and serves as a barrier to cold drafts.
- It works outdoors, too: On porches, gazebos, or decks, cloches can also be used to protect fragile potted plants from frostbite.
Alternative solutions: If you think that your indoor basil’s leaves are turning translucent because of cold drafts, here are some alternative strategies that can restore your plant leaves to their normal color..
- Reposition: Move the basil plant away from doorways, windows, exhaust, vents, louvres, or other possible sources of cold drafts.
- Expose to sunlight: During cold weather, position your basil plants on a windowsill that receives between 6 and 8 hours of direct sunlight each day.
- Move to warm spots: You can also move the basil plants to warmer spots such as in the kitchen, near the back of a refrigerator, or near a heater or heat lamp.
- Use artificial light: When direct sunlight is rare or impossible, use a grow lamp designed to make indoor plants thrive.
Bacterial or fungal diseases can cause leaves of basil plants to turn translucent or transparent, even plants that are grown indoors with care. Bacteria and fungus can develop due to high humidity levels.
The issues: When small translucent spots on leaves begin to grow bigger and show dark edges and the leaf begins to turn brown, yellow, or black, your basil plant may have a bacterial or fungal infection called leaf spot. Here are some solutions:
- Ventilation: Space out the basil plants for better air circulation.
- No backsplash: Water the plants in a way that bacteria is not splashed onto the leaves. Drip irrigation prevents back-splashing.
- Keep dry: Don’t over-water. Always check and ensure that water drains well from the soil around the plant’s roots.
- Choose your seeds: Use basil seeds that are certified to be free of infection.
- Choose your soil: Plant your basil seeds in sterilized soil or growing medium.
- Choose resistant varieties: Cultivate basil varieties that are resistant to infections such as the Genovese-type cultivars (Aroma 1, Aroma 2, Nufar) such as this one on Amazon.
Suggested solution: Spray with fungicides or homemade bacterial sprays such as:
- Sulfur spray: IN 1 gallon of water, dilute and mix 3 tablespoons of sulfur such as this one from Amazon.
- Copper spray: Dissolve 100 grams of hydrated lime such as this one from Amazon, or copper sulphate in half a bucket of water.
- Baking soda spray: Dissolve one teaspoon of baking soda in 1 quart of water.
Alternative solutions: Gardeners who’ve fought similar infections before prepare themselves with copper fungicides such as this one on Amazon or organic insecticides such as this one, also from Amazon.
You can also uproot and burn or disinfect plants to avoid spreading the infection to other plants. At the same time, closely inspect nearby plants for similar signs of infection.
PRO TIP: For vigorous growth, basil needs about 1½ inches of water a week, but this depends on the type of soil and the air temperature.
Iron Chlorosis? Acidify The Soil
Basil is a tropical and subtropical plant. In colder climates, they are particularly susceptible to iron deficiency. This nutrient issue can stress out basil plants and leaves can lose color and turn pale to the point of being translucent.
The issues: Iron deficiency is often caused by high pH levels in soil when calcium carbonate accumulates. As a result, iron is not soluble enough for plants to absorb. Over-watering and cold winters can add to this problem of iron chlorosis.
Suggested solution: Use an all-purpose soluble fertilizer that is designed to acidify the soil, such as this one from Amazon.
Alternative solutions: If you are unsure that the loss of color on your basil leaves is caused by iron deficiency, these steps are suggested:
- Test the soil: Soil pH should be above 6.0. Soil testing with an instrument can measure the pH and calcium carbonate levels in the soil. Lab analysis can tell you how much iron in the soil is available to your plants.
- Increase soil acidity: Add elemental sulfur such as this one from Amazon. The amount depends on the soil texture and how much calcium carbonate is in the soil.
- Apply iron fertilizer: Use a chelated iron fertilizer. Do not use non-chelated iron fertilizers such as ferrous sulfate on soil with high pH. It won’t help your plants.
PRO TIP: Mixing organic matter such as animal manure increases natural chelates in soil, which makes iron more available to plants.
- Apply iron directly to leaves: When a quick fix is needed, spray leaves with 1 gallon of water mixed with 2 ounces of soluble ferrous sulfate powder such as this one on Amazon. Spray the leaves during cool weather to prevent leaf burn. If you must spray in hot weather, do so in the evening.
- Avoid iron deficiency: It’s easier to avoid iron deficiencies than to correct them. Add sulfur when preparing the soil and make sure that the soil has proper drainage.
PRO TIP: Leaf tissue is very thin and easily damaged. Before spraying the entire plant with these suggested solutions, spray a small leaf and wait a day to see if the leaf is damaged.
Since the dawn of history, basil has been a part of human cultures and traditions. Today, basil contributes much to cuisine, wellness, agriculture, trade, commerce, and science. Thus, preserving the wellness of basil plants is essential.
When basil leaves lose their green color and turn pale, translucent, or transparent, at least five possible causes can be addressed.
- If the lack of chlorophyll is caused by a lack of sunlight, position the plant to at least 6 hours of sun every day. Alternatively, use a full-spectrum heat lamp no more than 8 hours a day.
- If discoloration is caused by insects sucking out juice from basil leaves, use a miticide or insecticide, preferably organic sprays.
- If there is chlorosis caused by stress from cold drafts, move the plant to a warmer place or use cloches to keep the plant warm and humid.
- If a bacterial or fungus infection causes pale spots on basil leaves, use sanitary procedures, adequate ventilation, proper watering, disinfected seeds, and resistant basil varieties.
- If you verify that leaves lose color due to iron chlorosis, increase soil acidity. For faster effect, spray the right mix directly on the leaves.
There are no basil varieties with naturally translucent or transparent spots on leaves. Any loss of color is a sign of stress and indicates one or more of these issues. Now that you know the 5 possible causes, you can give your basil plants better care.
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“In-vivo study for anti-hyperglycemic potential of aqueous extract of Basil seeds (Ocimum basilicum Linn) and its influence on biochemical parameters, serum electrolytes and haematological indices” by S. Chaudhary, et al in Biomedicine & Pharmacotherapy
“Common Pests and Diseases of Basil” from J. Seeds
“Basil: A Source of Essential Oils” by J. E. Simon, et al in Advances In New Crops
“Ocimum sp.(basil): Botany, Cultivation, Pharmaceutical Properties, and Biotechnology” by O. Makri & S. Kintzios in Journal of Herbs, Spices & Medicinal Plants”
“Basil: A Source of Aroma Compounds and a Popular Culinary and Ornamental Herb” by J. E. Simon, et al in Perspectives on New Crops And New Uses
“Chemical Characterization of Basil (Ocimum spp.) Based on Volatile Oils” by R. F. Vieira & J. E. Simon in Flavour and Fragrance Journal
“Basil in the Garden” by L. Pearson & D. Drost, Utah State University Extension
“Recognizing and Treating Iron Deficiency in the Home Yard” by J. Walworth, University of Arizona College of Agriculture