Xtremehorticulture

Rosemary Dying Usually Soil Problem

Q. Can you tell me what is killing our rosemary hedge, by inches?  The plant is 15 years old.  Other rosemarys of the same age on the property are still thriving.  Any help would be appreciated.  Picture attached. Thank you A. There are a few insects such as spittle bugs that get on rosemary but there are not that many diseases that affected except some of the soil borne fungal diseases. In other words, these are disease organisms that are already present in the soil but they need opportunity in order to take advantage of rosemary. When soils remain wet, this stresses rosemary and makes it susceptible to these types of diseases. The usual advantage these diseases get is because soils are from plant stress because soils are kept too wet from frequent irrigations or the soils do not drain water fast enough before the next irrigation. Rosemary dying is usually a soil or irrigation and drainage problem. These diseases attack the roots of the plant and cause dieback of the top similar to what appears to be drought. It appears to be drought because the roots are dying and they can no longer take up water to the tops so, in fact, it is drought but drought caused by too much water present around the roots. Like many Mediterranean plants, rosemary does not like wet soils in the summertime. They can tolerate wet soils as long as there is drainage and the soil has enough time to dry out between irrigations. These types of diseases frequently start at low spots in the irrigated area where water collects or puddles. Usually plants growing where the water has drained to low spots remain healthy. Plants that have extensive root rot from soil disease organisms frequently will pull from the soil fairly easily or are loose in the soil when they are pulled from side to side. The solution? The usual solutions are to water less often or improve the drainage in the soils or both. Rock mulches around rosemary will cause the soil to become more compacted and not drain water well. Organic wood chip mulches help to keep the soil “fluffy” and improve drainage. Organic wood chip mulches help to keep soils more moist so the frequency of irrigation typically has to be less.  If this problem was caused from soil disease organisms it will be difficult to reap plant rosemary in that soil again. You might have to remove the soil from that spot and replace it with an amended soil before you replant another rosemary in that same location.

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Rosemary likes infrequent Waterings Or There Will Be Problems

Q. My Rosemarys are dying.  I planted quite a few thinking that I won’t have a problem with them.  I lost two already that were planted about five years ago.  I just planted six more this last spring. What is going on? They get enough water and fertilizer.  I am afraid that I’ll lose them all. The Rosemarys that died were planted on the east side about two yards away from the house.  They got a hole about 1, 1/2 feet deep and wide with mixed soil. They get sun in the morning and afternoon sun from the west.  The sprinklers go on only four days a week for 10 minutes in the summer, but in the winter I set the clock to go on only twice a week. It could be that there is bad drainage so close to the house. What else should I plant?  I noticed one Rosemary in the front of the house which is the west side, getting dry shoots, which I cut off. Healthy Rosemary on top picture. Rosemary with problems on the bottom two pictures. The middle picture is most likely a water or drainage problem or possibly salinity. A. It is possible that it is due to poor drainage but I still think your watering too often in the summer. They should be able to last longer between irrigations. Posthole digger Usually the soil surrounding the foundation is compacted for the slab’s stability. You could take a posthole digger and go down two or more feet and backfill this hole with amended soil and replant again. I would dig a hole 3 to 5 times the diameter of the container you are planting anything in our soil. Three times a week in midsummer might be too often for rosemary unless you have really good drainage. It is not a desert plant but it does not like wet soil. The soil amendments I am suggesting is really good for any plant, including desert adapted plants so you should be doing this anyway. It is hard for me to recommend something without knowing your needs, the site better and what is available. The most common reason for Rosemary to die is because the soil stays too wet. You definitely do not want to water this plant daily unless the soil it’s growing in drains water exceedingly well. The principal reason for the soil staying too wet is a lack of drainage. Typically if soils growing Rosemary stay too wet the roots will develop a disease called root rot and they die and collapse. Shortly after that you begin to see the top die. Often times you’ll see one or two shoots dying and then typically in the heat of the summer the whole plant suddenly dies. Once the soil gets contaminated with this disease organism other plants susceptible to that disease and placed in that soil might also become affected. Replanting Rosemary in the same soil where it died is not a good idea. It will like a place in the yard in full sun and hot. It will not like shady areas very much. The next time you plant Rosemary make sure the soil is thoroughly mixed with compost to a depth of at least 12 inches. Rosemary originates from Mediterranean climates. Mediterranean climates are characterized by hot and dry summers and cool and wet winters. Rosemary does very well in the heat and can tolerate the cold.

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