Are Your Zinnias Dying? (Here’s Why & How to Fix It!)

Zinnias die mainly due to Alternaria leaf spot disease and bacterial leaf spot disease. Powdery mildew also can kill your Zinnias. Zinnias could also die due to overwatering/prolonged waterlogged conditions.

Zinnias are grown for their beautiful blossoms that come in different colors. They are grown with passion in the United States.

It is easy to grow Zinnias in the garden. Sometimes the plants do run into some issues. Let’s see what the issues are and how to fix them.

Zinnia leaves turning brown and crispy?

Zinnia leaves turn brown and crispy when the plant is affected by leaf spot diseases. Leaf spots are caused by a variety of fungal pathogens.

Alternaria leaf spot

Alternaria leaf spot disease also affects Tomatoes, Sunflowers, and Lettuce. So, it can spread from such plants to your Zinnias.

Reddish-brown spots appear on the surface of the leaves. These reddish-brown spots expand and the centers turn greyish white.

Don’t water your Zinnias in the afternoon/evening. When you do water your Zinnias, don’t let the leaves get wet.

Make sure your Zinnias are planted at a good distance from each other. Proper air circulation can prevent such fungal infections.

Bacterial leaf spot

Bacterial leaf spots start as dull gray spots. They appear like water-soaked blotches. Eventually the foliage is filled with yellow spots.

The foliage turns brown after a few days. This browning confuses the gardener because the spots are quite similar to Alternaria leaf spots in appearance.

Identify infections early on and get rid of the fallen leaves. Dispose of the infected plants from your garden as soon as possible.

When watering make sure you don’t splash water on the neighbouring plants. 

How to treat leaf spots on Zinnias

Below are few instructions to control Alternaria leaf blight in Zinnias. 

  • Follow hygienic cultural practises to avoid Alternaria fungal infections in your Zinnias. 
  • Don’t wet the foliage when watering your Zinnias. Wet foliage are an invitation to a variety of fungal pathogens.
  • Spray suitable insecticides on Zinnia foliage. Fontelis and Amistar can be sprayed to control leaf spot in Zinnias.
  • Organic gardeners spray Captan or Copper-based fungicides on the victim plants. But, trust me, it’s quite hard to control the fungus this way. This might work if you identify the disease early on.

Tip: Respond as soon as you see small, brown spots on the foliage.

Best fungicide for Zinnias

Amistar and Fontelis work efficiently to eliminate Alternaria fungus from your Zinnia plants. Organic gardeners often try their luck with Captan/Copper-based fungicides.

Wear proper protective equipment when spraying fungicides on your Zinnia. Don’t spray these fungicides if there’s a prediction of rain that day.

Powdery mildew on Zinnias

Powdery mildew starts as small, powdery-white spots on Zinnia foliage. These white spots spread to form a layer of white, powdery cover on the leaves.

The infection starts as few, white spots on the lower leaves. If you don’t treat the plant at this stage, it spreads to the shoots and buds.

Powdery mildew can even kill your Zinnia. This is a common disease in Zinnias and begins usually in the mid-summer. 

What causes Powdery Mildew on Zinnias?

Powdery mildew is caused by fungal pathogens. The infection of a species of plant doesn’t spread to the other.

Powdery mildew infects your Zinnia if it doesn’t get enough sunlight. Powdery mildew is also seen in plants where the air circulation is poor.

High humidity promotes the growth of these fungal pathogens. So, don’t overwater your Zinnia. Try not to wet the Zinnia foliage to avoid this infection.

How do you get rid of Powdery Mildew on Zinnias?

  • Trim the affected leaves using a pair of pruning shears. Disinfect the pruning shears after using on an infected plant. Dispose of the affected leaves carefully, away from your plants.
  • Spray sulfur-containing organic fungicides to treat Powdery mildew on your Zinnias.
  • Neem oil also works as a natural fungicide. Use it according to the instructions on the label.

How to prevent Powdery mildew on Zinnias

  • You can prevent powdery mildew on Zinnias by spraying sulfur-containing organic fungicides on the plants. Do this prior to summer.
  • Do not wet the leaves of your Zinnia when watering it.
  • Keep the area around your Zinnias clean. Do not let the dead leaves pile up. Water your Zinnias adequately to prevent such infections.
  • Plant your Zinnias in full-sun. Space your Zinnias/other plants generously to avoid such fungal infections.
  • Get Zinnia cultivars that are resistant to Powdery Mildew.

Can you overwater Zinnias?

No, Zinnias can’t take a lot of water. Zinnia becomes easily prone to fungal infections if it’s exposed to waterlogged conditions for too long.

Water your Zinnias only when the soil has gone completely dry. Check the soil with your bare fingers if needed. Getting a soil moisture meter is worth it if you ask me.

Check the soil as soon as you see limp/drooping leaves on your Zinnia. Leaves become droopy when the plant sits in waterlogged conditions for too long.

Droopy leaves turn yellow eventually. Zinnia leaves turn brown after yellowing. The brown leaves are usually seen when the roots get rotten.

How do you fix Overwatered Zinnias?

  • If you diagnose waterlogged conditions, stop watering your Zinnias immediately.
  • Uproot the affected Zinnia and take a good look at the roots. Are they brown and mushy? If yes, the roots got rotten. If most of the roots are still white, the plant can be revived.
  • If some of the roots are rotten, clean the roots in diluted Hydrogen Peroxide. Re-plant your Zinnia in a different pot with fresh soil.
  • Make sure the soil drains efficiently to prevent future fungal infections in the roots.

Deformed Zinnia flowers

Zinnia flowers deform when the plant is infected by Aster yellows. Infected plant’s leaves get distorted, discolored, and eventually turn yellow.

The infected Zinnia plant gets stunted. This disease is common in Zinnias and other related plants. The disease is spread by Aster Leafhopper insects.

Aster yellows disease can’t be controlled by chemical means. Get rid of the infected plants as soon as you identify them to prevent a large-scale infection.

Hang yellow, sticky cards around your Zinnias to know of their presence early on. Spray Neem oil or Horticulture oil to control the insect’s populations.

Zinnia leaves curling

Zinnia leaves curl when the plant gets infected by the leaf curl virus. Zinnia leaves may also curl due to aphid infestations.

Infected Zinnia’s leaves get curled and the plant gives out fewer blossoms. The flowers also become smaller.

Whiteflies are usually seen on the plant that’s infected by the leaf curl virus. There is no chemical treatment for the leaf curl disease.

I advise you to control the disease by following certain cultural practices.

Aphids/Spider mites munch on Zinnia leaves. Such feeding also distorts the foliage of this beautiful plant. The leaves turn yellow due to such infestations.

How do you fix leggy Zinnias?

Zinnias grow leggy when the external conditions are too suitable for the plant’s growth. The plant thrives in such conditions and shoots/leaves grow vigorously.

Below are few instructions to fix leggy Zinnias.

  • Prune half the shoots to 2/3rds of their length with a sterile pair of pruning shears. Let these shoots blossom. This usually takes around two weeks.
  • After the shoots blossom, prune off the other half of the shoots. Your Zinnias won’t be leggy anymore.

Happy Gardening 🙂