My two year old climbing rose is going pale with green veins. I read this might be chlorosis. It’s in full sun on a south facing fence. I’m on st Clair in a good tomato growing neighbourhood. We do have clayey soil, which I tried to amend before planting. Do you have the impression that this is just a particularly wet year? And I’m wondering if there’s anything I can do now – would you recommend trying iron or rose fertilizer? I have only fed it compost and some manure last year. Thanks!
Thank you for contacting the Toronto Master Gardeners regarding your roses
Botanical Dictionary defines chlorosis as “abnormal reduction or loss of the normal green coloration of leaves of plants, typically caused by iron deficiency in lime-rich soils, or by disease or lack of light.”
According to The University of Illinois Focus on Plant Problems : ” Possible causes of chlorosis include poor drainage, damaged roots, compacted roots, high alkalinity, and nutrient deficiencies in the plant. Nutrient deficiencies may occur because there is an insufficient amount in the soil or because the nutrients are unavailable due to a high pH (alkaline soil). Or the nutrients may not be absorbed due to injured roots or poor root growth.”
What is the cause of your chlorosis is determined by colour of the leaves as well as what foliage turned chlorotic first. If the plant is iron deficient its newest (youngest) leaves are more yellow than the older ones, and the interveinal areas show chlorosis while the veins remain green. If the chlorosis is a result of oxygen deficiency as a result of overwatering or poor drainage, the veins of the leaves will be yellow while the rest of the leaf will be green. Manganese or zinc deficiencies in the plant will also cause chlorosis. Chlorosis due to manganese and zinc deficiencies develop on the inner or the older leaves first and then progress outward to the younger leaves.
From your description it sounds as if you have interveinal chlorosis caused by iron deficiency. According to the Marin Rose Society ” Chlorosis due to a true absence of iron from the soil can be resolved with the application of iron sulfate; this is the cheapest and most widely available type of iron fertilizer. Apply liberally, and scratch into the soil around the plant. Generally, there is plenty of iron in the soil, it ís just not in a form that is available to the plant. If that ís the case, you can add chelated forms of iron available at your local garden centre A chelating agent is a synthetic organic substance that can maintain iron (as well as copper, manganese and zinc) in a nonionized, water-soluble form that is readily absorbed by plants. Scatter dry granules within the plant’s drip line, then water thoroughly so the chelate soaks into soil around roots. Leaves should start to green up in two to three weeks.”
Good Luck with your Roses.