By: Mary H. Dyer, Credentialed Garden Writer
Help, my cilantro leaves have spots! What is cilantro leaf spot and how do I get rid of it? The causes of leaf spot on cilantro are mostly beyond our control, which makes cilantro leaf spot control extremely difficult. It’s possible to manage the disease so it doesn’t destroy your prized crop of cilantro, but it requires dedication and persistence. Read on for tips.
Leaf spot on cilantro is a common bacterial disease favored by cool, damp conditions. Cilantro with leaf spots develop yellowish, water-soaked lesions that eventually turn tan or dark brown. The lesions may become larger and grow together and the leaves become dry and papery.
The pathogen responsible for cilantro with leaf spots is Pseudomonas syringae v. coriandricola. Although leaf spot is a common disease that affects many plants, this pathogen affects only cilantro.
Leaf spot on cilantro often begins with infected seeds, but the disease is spread by rainwater and overhead sprinklers, which splash the water from plant to plant. It is also transmitted by contaminated tools, people, and animals.
Since control of the disease is difficult, prevention is normally your best course of action in fighting it. Start by purchasing certified disease-free seed and allow at least 8 inches (20 cm.) between plants to provide ample air circulation. If you’re planting cilantro in rows, allow about 3 feet (1 m.) between each.
Practice a three-year crop rotation to reduce the level of bacteria in the soil, rotating cilantro with members from a completely different plant family. Avoid rotating with any of the following plants:
Remove infected plants and plant debris immediately. Never put infected plant matter in your compost pile. Keep weeds under control, especially related plants such as wild carrots, or queen anne’s lace.
Fertilize carefully, as too much fertilizer appears to enhance cilantro leaf spot. Avoid fertilizer with high nitrogen levels.
Water early in the day so the plants have time to dry before evening. If possible, water at the base of the plant and minimize use of overhead sprinklers. Avoid working in your garden when the soil is wet.
Copper fungicidal sprays may help control the disease if you spray as soon as symptoms appear, but the sprays won’t eradicate leaf spot in cilantro. Experts at your local cooperative extension office can help you select the best fungicide for your situation.
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Read more about Cilantro / Coriander
Picking cilantro works best in the early in the morning when the leaves are crisp and at their peak of flavor. Using sharp, clean scissors, trim the leaf stem 1 to 2 inches above the soil line. To keep your cilantro plants producing, harvest no more than 1/3 of the leaves from each plant. More leaves will grow over the summer as long as you keep the plants cool and the flower heads trimmed back. You can also harvest all the leaves at once. You can then plant more cilantro seeds for another crop of cilantro in a few weeks. When the weather is hot, however, cilantro has a short life cycle, as it tends to bolt, producing white, lacy flowers (which are the basis of the cilantro seeds, or coriander).
Cilantro wilts quickly once it has been harvested so take it inside as soon as possible after you pick it. To keep the stalks fresh until you're ready to use them, stick the cut ends in a glass of cool water. If it will be more than an hour before you use your harvested cilantro, cover the glass and leaves with a plastic bag and store them in the refrigerator.
Cilantro has a fairly high respiration rate, similar to that of other green leafy vegetables. Therefore, in order to maintain optimum post-harvest quality, cilantro should be harvested at the coolest times of the day (either early morning or in the evening), and stored under low-temperature, high humidity conditions. Although aromatic quality decreases before visual quality does, a shelf life of 14 days can be expected if cilantro is stored at temperatures close to 32°F. Because of cilantro's high water content, storage slightly above 32°F is necessary to avoid freezing damage.
A high surface area to volume ratio makes cilantro very susceptible to water loss. Specially designed bags (either those with perforations for ventilation or those constructed of a partially permeable polymer) may be used as packaging however, cool temperatures must be maintained.
A field trial in 1999 found no significant difference in shelf life for cilantro harvested with roots intact compared to root removed. Where refrigeration is not an option, wilting can be delayed by placing harvested cilantro in water and keeping the plants shaded from sunlight (Mangan, et. al., 1999. See references).
The cilantro plants that we planted back in October are now making tall stems and are flowering, and so I have been cutting the tall stalks, trim and save the leaves at the bottom 4", and then put the stems in a plastic water glass that I keep in the kitchen near a window, although lately I have been putting it in the living room in the evening next to one of the orchids for some extra green. I think it makes a nice floral arrangement, and it is convenient to have the stalks at hand when I want to use them, and so I do not have to go outside (often in the dark) to harvest leaves when I want them. I used to let the plants go to seed so that I could harvest the seeds, but I already have two jars full of seeds and do not need any more coriander.
Anyway, I thought this is a nice way to keep cilantro close at hand when the plants are flowering, and it encourages growth of the lower leaves. I've already frozen large quantities of cilantro this winter, and I dried quite a bit also, to see how that will work. If it doesn't work, I have more in the freezer than I can use in a while anyway. If I try to grow cilantro in the summer, I have to keep it in a shady spot, and bromeliads and orchids have taken up the best shady spots already, and I really don't have time in the summer to take care of it - plus it takes a lot of water. It doesn't dry out as fast in the winter because I get a bit of coastal fog in the early morning, although less this year than most.
This isn't the best photo, but I took it this morning and was rushed for time. It's next to a meat slicer and in front of a food processor - not the prettiest spot, but it got light from the window.
This post was edited by publickman on Fri, Feb 21, 14 at 1:18