Silvering

Silvering can be a symptom of disease, environmental stress, insect feeding, or mineral deficiencies, similar to bronzing.

Silvering on eggplant leaf (Scot Nelson) Public Domain

Healthy blueberry leaf next to unhealthy bronzed leaf (OPENi) CC BY 3.0

Chlorosis on outer leaves of squash plant

Silvering is not the same thing as chlorosis. Chlorosis refers to leaves becoming a paler green over time, usually due to insufficient nitrogen, eventually turning yellow. Chlorosis can ultimately lead to silvering, but silvering generally describes how some leaves become white rather than yellow. There are several causes for silvering.

Diseases that cause silvering

Silvering may occur in mosaics, a collection of viral diseases. Leaf silvering is also a symptom of, wait for it, silver leaf. Silver leaf is a fungal disease of apple, cherry, and pear. Fruit silvering refers to whitened areas under the skin of peppers or tomatoes. The Phytophthora oomycete causes fruit silvering, avocado root rot, buckeye rot, and potato blight.

Fruit silvering of bell pepper (Elizabeth Bush, VPISU, Bugwood.org) CC BY 3.0

Environmental stresses that cause silvering

Drought and temperature extremes can cause silvering. Chemical overspray and pollution can also cause leaves to turn silver, especially among tomatoes and peppers. Also known as chimera or head silvering, environmental stress can turn leaves grayish-green and small. You may also see blisters on the leaves and pale streaks on the stems. When this occurs, flowers are usually sterile. Any fruit that grows will have grayish-green streaking and be less flavorful. If you see white patches on fruit, it is probably sunscald.

Drought damage to corn (R.L. Croissant, Bugwood.org) CC BY 3.0

Silvering due to insect feeding

Sap-sucking insects can cause leaf silvering. The most common causes of leaf stippling or silvering include feeding by:

Thrips feeding damage to pole bean leaves (Scot Nelson) Public Domain

• Lace bugs
• Leaf miners
• Leafhoppers
• Mites

• Scale insects
• Spider mites
• Thrips
• Whiteflies​

Silvering due to nutrient deficiency

​Potassium deficiencies can cause leaf silvering. In this case, you will see upward leaf curling. Manganese deficiencies can cause leaf silvering, premature leaf drop, smaller-than-normal leaves and seeds, and weak roots and stems. An inexpensive lab-based soil test can help determine if this is the problem.

Potassium deficiency of tobacco (R.J. Reynolds Tobacco Company, Bugwood.org) CC BY 3.0

Silver plants

Silver in the garden isn’t always a bad thing. Silver plants can add a nice color contrast to potted plants and landscapes. These plants usually prefer full sun. They often get their silver appearance from a coating of white trichomes that look like fur. Most white and silver plants are ornamentals, but there are some edible silver plants:

• Cardoon (Cynara cardunculus)
• Kiwifruit ‘silver vine’ (Actinidia polygama)
• Lavender (Lavandula x intermedia – Dutch group)
• Olive trees (Olea europaea)
• Pineapple guava (Acca sellowiana or Feijoa)
• Sage (Salvia officinalis)

Lamb's ears (David J. Stang) CC BY-SA 4.0

Common sage growing at the Missouri Botanical Garden (Kate Russell)

​Many of these plants make lovely additions to butterfly gardens and pollinator gardens. May all the silver in your garden be the good sort.