A Boxwood in My Garden Looks Unhealthy. How Can I Determine What Is Wrong With It and Is There Something I Can Do to Help It?

Are the leaves on your Boxwood blistered and browned?

Are the leaves on your Boxwood curled and cupped around stem tips?

Are the leaves on your Boxwood stippled with yellow flecks and the foliage is webbed?

Are the leaves on your Boxwood completely yellow and covered by small bumps?

Are the leaves on your Boxwood yellow, sparse, distorted with brown edges, branches are dead or dying, growth is stunted?

Are the leaves on your Boxwood brown and the twigs had died back?

Blisters and browned leaves on Boxwood are caused by Boxwood leafminers. These tiny, orange larvae tunnel trough and feed within leaves. After some time larvae change to adult form, tiny, orange mosquito-like flies. You should monitor your Boxwood for the emergence of adults, which is usually somewhere around late April or early May and spray the plant with insecticidal oil.

Cause for leaf curling on Boxwood are Boxwood psyllids. The eggs and larvae of this tiny green insect overwinter on buds and infest new leaves in spring. At the first sign of damage, spray your plant with insecticidal soap, or pyrethrin for serious infestations.

Yellow flecks on leaves and webbed foliage is caused by spider mites. These tiny, spider-like pests feed by sucking sap from the underside of the plants leaves causing yellow flecking on the upper leaf surfaces. You can control spider mites by spraying plants thoroughly with water 2-3 times a day for several days. For severe infestations, spray plants with insecticidal soap, or pyrethrin as a last resort.

Yellow leaves covered by small bumps are caused by scales. These tiny, shelled insects often feed on the undersides of the leaves, causing an unhealthy appearance with yellowish blotches on the upper leaf surfaces. Scrape off minor infestations with your fingernail. Prune out badly infested growth, or use a soft brush and soapy water to gently scrub the scales off the stems. Control scales by spraying insecticidal oil during the growing season.

Yellow, sparse and distorted leaves, dead or dying branches and stunted growth are the signs of plant decline. Plant decline does not refer to a particular disease but rather to a general loss of plant vigor usually caused by several stresses acting on a plant over the years. It may have been caused by bad soil compaction, improper pruning, root damage, repeated insect attacks or any other factor. If you can identify and eliminate the source of the problem, your plant might recover.

Brown leaves and die back twigs are caused by winter damage. Cold and dry winter winds can injure tender growth on Boxwood seriously. You can try to protect your plant by mulching in the fall. Water your plant well before the land freezes and fertilize only early in the spring. You should cut off any plant parts that have been affected by freeze damage.

If the whole plant looks stunted and lacking vigor the cause might be nematodes. Nematodes are microscopic, wormlike creatures that attack the roots of the plants. A clear sign of the nematodes infestation is knotlike galls on the roots which can be seen if you dig up the plant. To prevent nematodes, mulch regularly with compost to ensure that soil organic matter levels remain high. Heavily infested plants can only be removed and replaced with some other plant species.