Winter hazel is sick

Asked March 13, 2013, 5:10 PM EDT

My winterhazel is not doing well. Half of the shrub has dead looking branches (facing house) and other half (facing sidewalk) produced limp flowers. Suggestions? Thanks!

Multnomah County Oregon

1 Response

I'm thinking root rot described below
Some of the best evidence indicating a Phytophthora disease are symptoms shown by the plant itself. Knowledge of the plant’s susceptibility is also helpful (see the table Plants Susceptible to Phytophthora Diseases, below).
It is necessary to thoroughly examine above- and belowground parts of the plant. Aboveground symptoms are useful but not completely diagnostic. Many different problems can result in the same aboveground symptoms as Phytophthora root rots. Anything that girdles or cuts off water and nutrients to the top of a plant results in wilting, leaf chlorosis (yellowing), leaf necrosis (browning), and premature leaf fall and plant death. Causes include feeding by root weevil larvae, winter injury, mechanical injury, wire or plastic used to keep trees straight after planting, nursery tags, lack of water, and other fungal root rots as well as Phytophthora root rot. In Oregon, many plants with Phytophthora root rot do not show aboveground symptoms until summer. As hot, dry weather sets in, the plant does not have enough functional roots left to keep up with transpiration. Plants frequently wilt and collapse within a week. Because of the wilting, many people water plants even more than usual, flooding their roots, encouraging the pathogen, and potentially spreading the disease even more. Belowground symptoms of Phytophthora root rot include the plant’s having few if any feeder roots while the remaining roots are dark and in some stage of decay. Symptoms will be most severe at the root tips and least severe near the root crown. Decaying roots are generally due to other microorganisms’ feeding on the roots after being killed by Phytophthora. There are some exceptions, which will be discussed shortly. Near the advancing margin of a Phytophthora-infected root, the roots generally are firm. Use a pocket knife on larger roots (fingernails are okay on smaller roots) to expose the vascular cambium. The area between the bark (phloem) and inner wood (xylem) is highly discolored where the Phytophthora organism has been actively colonizing the root or root crown. Many times the cambium has a dull red to reddish brown color. Above this area, the cambium will be the normal color for the plant, generally some shade of white to light green. The transition between the discolored area and the healthy area may be sharp, with a distinctive margin.