“It looks like this purple coneflower is growing babies out of the seedpod. What is going on?” writes Birds & Blooms reader Tom Nealon of Tillsonburg, Ohio.

Horticultural expert Melinda Myers says aster yellows caused this bizarre growth. The disease leads to distorted growth and discoloration of flower petals.

The aster leafhopper spreads aster yellows disease. When this insect feeds on an infected plant, it ingests the disease organism, then injects it into the next plant it feeds on. Your plants will survive but will serve as a source of infection for other nearby plants. Remove infected plants as soon as you find them to reduce the spread.

Did you know? Aster leafhoppers are thin, wedge-shaped and dull light green. Look for six white spots on the top of the head.

Aster Yellows and Brown-Eyed Susans

“There’s something growing out of the tops of my brown-eyed Susans. What could it be?” writes Stephen Ziring of Willow Grove, Pennsylvania.

Myers: Aster yellows, again. This disease attacks more than 300 species of plants, including rudbeckias, coneflowers, marigolds, carrots and potatoes.

To treat, first remove any infected materials. Controlling leafhoppers is difficult as they’re continually on the move, and spraying insecticides can harm beneficial insects that manage pests.

“Why did an additional row of green petals grow around this bloom? Another flower on the same stem was normal,” write John and Judy Haynicz of Monroeville, New Jersey.

Myers: Aster yellows likely caused this bizarre growth. The aster yellow leafhopper carries the phytoplasma disease organism from infected plants to healthy specimens. Remove infected plants as soon as you find them.

More Coneflower Growing Problems

“I’ve been having difficulty growing coneflowers and zinnias. Any advice you can give me on how to make them thrive in my garden?” writes Sierra Conine of El Dorado, Kansas.

Myers: Start by reviewing your growing conditions. Both these plants prefer full sun and will tolerate dry soils once established. If you find your conditions are appropriate, the problem could be disease.

Both plants are susceptible to aster yellows. The disease can stunt the plants and distort and discolor the flowers. Remove infected plants as soon as you see them to prevent the disease from spreading to healthy plants.

Read More