Repotted rosemary - Ask Extension
I bought these two fairly large rosemarys at Home Depot, repotted both of them in the yard to give them a larger pot. Loosened the root ball and cut ...
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Repotted rosemary #646959
Asked June 06, 2020, 12:48 PM EDT
I bought these two fairly large rosemarys at Home Depot, repotted both of them in the yard to give them a larger pot. Loosened the root ball and cut it down, their roots looked great not rot or bugs. Now they both started to yellow and looks like they are taking a turn for the worst. I potted them in a mixture of cactus soil/ succulent mix, potting soil, perilite, vercil, peat moss, also put some fertilizer (blood meal) to help the ph levels. The last photo is the wood pot they are both in separate ones. I drilled extra holes so they can properly drain. I’m nervous about over watering. I stuck my finger in the soil it isn’t dry somewhat moist. Was cutting down the root system and losing it up the change in color?
El Paso County Colorado
Expert Response
Thank you for your question and pictures.
There are just a few basic rules for growing herbs in containers. First, is to make sure to plant in a soil that drains well and second, plant in a pot with a hole in the bottom to allow for adequate drainage. Only apply enough water to drain out the bottom for preventing salt build-up.
Healthy roots should be white. In your rosemary there looks like signs of Phytophthora root rot. There is wilting, decline and eventual plant death. Dark colored, unhealthy roots on this rosemary plant could be Phytophthora like Pythium is a a lower fungus favored by excess moisture and excess nitrogen fertility. Unlike Pythium, species of Phytophthora are more aggressive, more likely to be host specific, and less frequently found in greenhouses. The most likely source of origin is infected plants or in plant debris. This fungus - like organism can form swimming spores (zoospore) that move in water, so infections can be severe with prolonged irrigation or if plants re sitting in puddles of water. Disease spores are dispersed via overhead irrigation or when water moves from infected plants to one nearby.
There are just a few basic rules for growing herbs in containers. First, is to make sure to plant in a soil that drains well and second, plant in a pot with a hole in the bottom to allow for adequate drainage. Only apply enough water to drain out the bottom for preventing salt build-up.
Healthy roots should be white. In your rosemary there looks like signs of Phytophthora root rot. There is wilting, decline and eventual plant death. Dark colored, unhealthy roots on this rosemary plant could be Phytophthora like Pythium is a a lower fungus favored by excess moisture and excess nitrogen fertility. Unlike Pythium, species of Phytophthora are more aggressive, more likely to be host specific, and less frequently found in greenhouses. The most likely source of origin is infected plants or in plant debris. This fungus - like organism can form swimming spores (zoospore) that move in water, so infections can be severe with prolonged irrigation or if plants re sitting in puddles of water. Disease spores are dispersed via overhead irrigation or when water moves from infected plants to one nearby.
Phytophthora is very difficult to control because it produces several different types of spores that can cause disease. This walled zoospores can survive between crops on plant containers, benches, floors and in potting media.
Sorry for the bad news. On the bright side, it wasn't your fault. Next time be sure to pull the plant out of the pot and confirm that there are white roots.
P.S.
There are very few fungicides labeled for herbs, therefore it is very important to prevent disease. Start with soilless growing media and avoid contaminating media with soiled hands, tools, or containers. Promptly remove diseased plants, avoid splashing water when irrigating and keep hose ends off the floor.
There are very few fungicides labeled for herbs, therefore it is very important to prevent disease. Start with soilless growing media and avoid contaminating media with soiled hands, tools, or containers. Promptly remove diseased plants, avoid splashing water when irrigating and keep hose ends off the floor.
Hi there Kerry!
Thank you so much for that detailed response. Its great information for the future with buying rosemary, or any herb! Rosemary is one of my favorite herbs and I never could win with one. Its good to know about the white roots, also never knew that transferring of sickness with water, or tools that came in contact with those plants. I really appreciate the information, and time. Ill be careful in my garden from now on. Hope all is well.
Warm Regards
Christina
Thank you so much for that detailed response. Its great information for the future with buying rosemary, or any herb! Rosemary is one of my favorite herbs and I never could win with one. Its good to know about the white roots, also never knew that transferring of sickness with water, or tools that came in contact with those plants. I really appreciate the information, and time. Ill be careful in my garden from now on. Hope all is well.
Warm Regards
Christina
