Plant diseases

No Pity for Green Flowers!

Yes, there are a few plants with green flowers: green roses, green zinnias, green glads, green echinaceas, etc. These plants are hybrids developed for their unusual color. But if a plant you choose for flowers of another color suddenly starts producing green flowers, the chances are pretty good it is suffering from a disease: aster yellows.

It’s a Virus! It’s a Bacteria! No…it’s a Phytoplasma!

Aster yellows is a very common in the wild, found especially in goldenrods, asters and other wildflowers, and is caused by a phytoplasma (formerly it was called a mycoplasma), a bizarre entity closely related to bacteria, but behaving like a virus. Notably, once a plant is infested, no treatment can cure it.

Leafhoppers

Aster yellows is transmitted by leafhoppers: by piercing plant tissues, they inject the phytoplasma which then extends gradually throughout the plant, affecting its growth and gradually weakening it, but the first symptom is usually the greening of the flowers. This is called phyllody, the abnormal development of floral parts into leafy structures. In the case of echinaceas, a kind of green growth starts to form on the cone in the flower’s center . Over time, the cone produces small satellite flowers that are completely green. Weird… and really not too wonderful!

Aster leafhopper, Macrosteles quadrilineatus. Photo: Whitney Cranshaw.

No Treatment

The only treatment for aster yellows is to destroy the plant. If left alive, the disease will gradually gain the neighboring plants, including echinaceas, asters, cosmos, strawberries, daisies, marigolds, zinnias and more than 300 other plants.

In agriculture and horticultural production, aster yellows can also have a major impact. For example, a reduction in carrot yield can vary between 25 and 80% when infected.

This is a case where a quick strike solves a ton of future problems: yank the infected plant out at the first sign of symptoms and you can prevent the disease from spreading to your other garden plants.

This text was first published on this blog on September 27, 2014. It has been revised and the layout updated.

Garden writer and blogger, author of 65 gardening books, lecturer and communicator, the Laidback Gardener, Larry Hodgson, passed away in October 2022. Known for his great generosity, his thoroughness and his sense of humor, he reached several generations of amateur and professional gardeners over his 40-year career. Thanks to his son, Mathieu Hodgson, and a team of contributors, laidbackgardener.blog will continue its mission of demystifying gardening and making it more accessible to all.

4 comments on “No Pity for Green Flowers!

  1. This is great information. Thanks

  2. Love my green Zinnias I will have to check some of the others out.

  3. Thomas Hunsdon

    Good advice. Thank you

  4. Special thanks for this bit of advice. I have a lot of coneflowers. Haven’t seen green ones yet, but I’ll keep a look out from now on.

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