TheGardenLady received this question from Diane.
I planted some Gladiolus bulbs in the spring and they were coming up beautifully. Today I noticed the leaves on one of them were turning yellow. I haven’t had any bloom yet but the stalks were very green and hardy. What can I do for this plant? Why would it have turned yellow?
Gladiolus grow best in loamy soil with proper drainage. Glads do not grow well in soil that is too wet. Soggy, compacted soil hampers root growth, diverts moisture and locks up plant food. Glads need plenty of water. Lack of water inhibits spike growth, flower development and corm growth. Watering at planting will help develop a good root system. Provide at least one inch of water each week to ensure good growth, making sure the water soaks 6-8 inches into the soil.
Not having seen your gladiolus, I cannot give the most accurate reason for why your one gladiolus is turning yellow. Gladiolus are very hardy and have few problems. But all living things do HAVE problems.
You may have bought a corm, or what you call a gladiolus bulb, that was deceased. There are a few root rots or corm rots that fit the description of gladiolus getting yellowing leaves.
From the University of Minnesota extension they write,
Stromatinia Corm Dry Rot – This corm disease, caused by the fungus Stromatinia gladioli, is found during periods of cool, wet weather. Leaves produced from infected corms turn yellow prematurely and die. Small, red-brown, sunken lesions develop on the corms. When an infected corm is cut in half, dark streaks can be seen radiating out from the core to the surface of the corm. The fungus produces sclerotia (over-wintering structures) in infected tissue. Often plants are infected in groups as the fungus spreads from the original infected plant. To manage this disease, discard infected corms, plant only healthy corms in well-drained soils and in the fall harvest corms during dry weather. T. Do not replant gladiolus corms in infected soil.
Or another corm rot described in a professional gladioli website is Fusarium oxysporum f. sp.gladioli . During the growing season, leaves turn yellow prematurely and stems collapse. During storage, corms develop a reddish-brown dry rot. Diseased corms produce spindly, weak plants the following year.
Because corms are inexpensive, it would see best to pull up and discard the one plant that looks yellow and hope that if there is a disease, it has not spread to your other gladioli. Never plant another gladioli in the spot where the infected corm was.