You really know summer is here when the brightly colored spires of gladioli appear. Gladiolus plants are tender corms which produce sword-like foliage and spectacular blooms arrayed on a tall, slender stalk. Yellowing leaves on glad plants may be an early sign of disease or can be the normal cycle of the plant as it gets ready for winter dormancy. It can also have cultural basis or even be the result of insect infestation. Learn why gladioli has yellow foliage and how to treat or prevent this condition.
Why Gladioli Has Yellow Foliage
Gladioli produce best in well draining loamy soil. They require full sun for abundant colorful blooms and need additional nutrients in the form of bulb food or worked in organic material. If your gladiolus turns yellow in the leaf area, several conditions may be the cause. Prevention starts with choosing healthy corms with no blemishes and a firm texture and good color. Often bacterial, fungal or viral diseases hitchhike into your garden on unhealthy corms which develop into sick plants. The most common reason for gladiolus leaves turning yellow is Fusarium rot. This fungus affects the corm, which will become dark at the core and may exhibit black to brown spots on the surface as well. Unhealthy corms can produce foliage but it is yellowish and the stems grow with a pronounced arch. Any flowers that begin to develop will wither and fall off. The only treatment is to remove the infected corms. Do not replant gladioli corms in the same location until you have treated the soil with methyl bromide-chloropicrin or solarized the area to kill any pathogen.
Other Causes of Yellowing Leaves on Glad Plants
Another fungal disease, Stromatinia corm dry rot, produces yellowing leaves on glad plants. Reddish brown lesions on the corm and streaking on the interior can help identify the problem. The fungus overwinters and spreads to neighboring corms from which growing gladiolus turns yellow. Gladiolus with yellow leaves can also stem from viral diseases such as cucumber mosaic virus or tomato or tobacco ringspot. These will result in yellowed streaking and mottling of healthy leaves which will eventually fade and yellow entirely. A gladiolus with yellow leaves may also be the result of a bacterial infection called scab. It results in gladiolus leaves turning yellow but it initiates in the corm, where water soaked lesions turn yellow and sunken. Occasionally, you may notice yellowing leaves due to chemical herbicides carried via wind or from accidental spraying.
Prevention and Treatment of Gladiolus with Yellow Leaves
The bad news is that once you have gladiolus leaves turning yellow, there is little to be done. The infected corm should be removed and destroyed and no other bulbs or corms can be planted in the soil unless you sterilize it. Many rot diseases of corms can be prevented by pulling up the corms in fall and storing them indoors for winter. Dig up the corms and check for any diseased material, which should be discarded. Presoak the corms for two days and discard any that float. Dip corms in water heated to 131 F. (55 C.) for 30 minutes and then immediately cool in clean, cold water. Cure the corms in a warm area for at least a week until they are dried completely. Dust them with fungicide before placing them in mesh bags in a dry area of the home to overwinter. In spring, check corms for any damage and discard any that aren't clean and perfect.
Gardening tips, videos, info and more delivered right to your inbox!
Sign up for the Gardening Know How newsletter today and receive a free download of our most popular eBook "How to Grow Delicious Tomatoes."
Bonnie Grant is a professional landscaper with a Certification in Urban Gardening. She has been gardening and writing for 15 years. A former professional chef, she has a passion for edible landscaping.
8 Ideas For Decorating With Poinsettias This Holiday Season
When you’re decorating with poinsettias, consider experimenting with different varieties and fun holiday ideas.
By Mary Ellen Ellis Published
How To Pick A Perfectly Ripe Watermelon
Pick the the ripe watermelon from the bunch every time.
By Amy Grant Published
Gladiolus Plants With Scab – Controlling Gladiolus Scab On Corms
If you are growing gladioli, you’ll want to know about gladiolus scab. For more information and tips on prevention and control, click here.
By Teo Spengler Last updated
Gladioli Mosaic Virus – Managing Symptoms Of Gladiolus Mosaic
Gladiolus blooms are featured in many cutting gardens for mid-summer bouquets. When issues like mosaic occur, this can naturally be alarming. Good cultural control can help prevent mosaic virus in gladiolus. Learn more in this article.
By Susan Albert Last updated
Botrytis On Gladiolus Plants: How To Control Gladiolus Botrytis Blight
Gladiolus botrytis diseases are not uncommon, so knowing the signs and how to manage them is important. Learn about gladiolus blight here.
By Mary Ellen Ellis Last updated
Treating Glads With Fusarium: How To Control Gladiolus Fusarium Rot
If the corms of your unplanted glads appear discolored and unhealthy, they may be infected with gladiolus fusarium rot. Learn more about fusarium wilt and rot on gladiolus plants in this article to see if your corms can be saved.
By Becca Badgett Last updated
Gladiolus Leaf Diseases: What Causes Leaf Spots On Gladiolus Plants
When kept healthy and disease free, gladiolus plants will return year after year. Issues like gladiolus leaf spot, however, may cause decline of your plants. Becoming familiar with the signs of gladiolus leaf diseases is important in preventing spread. Learn more here.
By Tonya Barnett Last updated
Is Your Gladiolus Falling Over – How To Stake Glads In The Garden
Growing glads is so simple, but sometimes the tall gladiolus falling over in the garden can be troublesome, if not unattractive. Luckily, with a little added support, this can be easily remedied. Click this article for additional information.
By Mary H. Dyer Last updated
Gladiolus Are Falling Over – Learn About Staking Gladiolus Plants
Prolific bloomers they are, but gladiolus plants falling over is not uncommon. Staking gladiolus plants will keep their brightly colored heads from dipping or breaking, and there are any number of items that can be used as gladiolus plant stakes. Learn more here.
By Amy Grant Last updated
Companion Planting With Gladiolus: Plants That Grow Well With Gladiolus
As well as bouquets, gladiolus looks amazing in flower beds and along garden borders. But what are some good companion plants for gladiolus? Click this article to learn more about plants that grow well with gladiolus.
By Liz Baessler Last updated