Plant Doctor Archive

Rosemary hedge

My wife and I have a two-year-old rosemary hedge grown from cuttings from the one bush. The hedge is now about 0.5 to 1 metre high and is a shelter for our vege garden; it is planted in the vege garden up against a low brick and concrete wall. For several months about 25% of the rosemary plants have turned brown and died. Despite the Nelson drought, I managed to keep the vege garden going. Why is the rosemary dying?

Your rosemary may have mites. The leaves will be matted together in a web, and before the leaves go brown they will look mottled. Tiny spider-like insects will be visible on the foliage.

To control mites, spray with Conqueror Oil or Mavrik. Cut back the damaged foliage and your rosemary should come away.

If it isn't mites, have you cultivated too closely to the roots of your rosemary hedge? They have a superficial fibrous root system.

Rosemary is a Mediterranean plant and likes a warm, sunny, free-draining position. They don't like being overwatered, excessive amounts of fertiliser or hard frosts.

Advice by Dr Dan Blanchon from Unitec's Diploma in Sustainable Horticulture and Bachelor of Resource Management.

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