The Farmer’s Almanac is claiming an accurate prediction for last winter. While exact storm dates may not have been spot on, the overall predictions were. Whether you believe in the accuracy of these annual predictions or not, I think we are safe in making some general predictions of garden problems that may pop up in 2019.
Late in the fall of this year, we began to see the inevitable effects of a wet year. Many conifers showed more dead than could be explained by usual fall shedding. Closer inspection led to early signs of root rot. If I was able to convince gardeners to go out during a rain event and watch where water was running, they were often surprised to learn that the run-off patterns mirrored the dieback patterns.
It is not unusual to see healthy plants very close to affected plants. Plants that remain just outside the run-off may have just good enough drainage to escape disease. While dodging a bullet during warm weather, you may not be so lucky when you add in the very cold winter temperatures that are predicted. Root rot can affect deciduous plants as well as evergreens. Sometimes the damage is not evident until spring.
When plants are already pushed to the brink of their tolerance rotting in the cold is common. Once soil-borne diseases establish it can take a long time for them to go dormant again. Like so many things in life, these things come in cycles.
It is very difficult to suppress root rot once it gets a foot-hold. A better option may be to consider replacement with a different variety. Keep telling yourself diversity in the landscape is good. Next time we have a dry year the plant varieties that are suffering now may be the ones that fare better.
A challenge will be in winter watering of fall-planted plants. It is true that there is little lateral movement of water between the native and nursery soils. Until the plant roots escape into native earth, they will need attention to water throughout winter. Winter winds desiccate the plant at a time it is unable to replenish moisture because the roots are frozen.
Water only when you feel the soil is above freezing and able to percolate well. Don’t confuse surface runoff with percolation. Don’t kill your plant with kindness, but do address its need to replenish what is lost to wind and cold. We get several opportunities if you pay attention to weather patterns.
The up side to this wet year is spider mites were unusually low on summer samples I saw. Other insects may prey on stressed plants, however. In early spring, before bud break, horticultural oils may be used to suppress insects you observe carrying over, like scale. Be on the lookout for early signs of foliar diseases if conditions favor outbreaks from reproductive structures.
Barbara Leach, Horticulture Technician, VCE Roanoke