Plant of the week

Mazus reptans is a low growing ground cover only 1 to 3 inches high. (JB Johnny, Baltimore Sun / July 2, 2012)

My roses are denuding. Some leaves are spotted, some yellow, but they are disappearing fast. Help!

The fungal disease called black spot causes 1/16- to 1/2-inch spots on leaves, leaf yellowing, and leaf drop. In severe cases the entire shrub defoliates. Some steps to combat black spot include:

•Never using overhead watering methods

•Removing all infected leaves from the plant and from the ground

•Pruning to open the center of the bush to allow sunlight and air

•Mulching underneath to prevent soil from splashing spores back onto the leaves

•Keeping rose plants watered when needed to prevent them from becoming stressed

Fungicide sprays prevent infection, they can't cure. Use copper or other fungicide recommended for roses, such as Immunox. Alternate fungicides that have different modes of action. Susceptible roses need to be sprayed on a regular basis throughout the growing season.

Next year, watch for the first black spot on a leaf at the beginning of the summer, remove the leaf, and spray. Many folks opt to avoid black spot altogether by only selecting highly resistant rose varieties.

The leaves on some of my tomato plants are curling. Otherwise the plants look okay so far. Are they starting to get a disease?

Tomato leaves will curl because of several reasons (usually high heat), but the fact that only some of your tomato plant exhibit curling leaves suggests that it is a varietal characteristic.

You can look at the handy diagnostic chart in our tomato publication, "IPM Series: Tomatoes", for a list of reasons why tomato leaves may curl. It is online or can be requested by calling us at the Home and Garden Information Center's 800 number.

University of Maryland Extension's Home and Garden Information Center offers free gardening and pest information. Call 800-342-2507 or send a question to the website at hgic.umd.edu.



Plant of the week



Mazus



Mazus reptans

Mazus reptans is a low growing ground cover only 1 to 3 inches high, suitable for filling small areas, such as between stepping stones or in rock gardens. Its bright green foliage persists into the fall, staying semi-evergreen in the winter. An added bonus is its purplish-blue or white flowers appearing in June and July. Mazus grows in full sun to partial shade and prefers moist conditions. Being an herbaceous perennial, it can spread fast by its creeping stems which root at the nodes forming a thick mat. Mazus will take some foot traffic, has no disease or insect problems, and is deer resistant. –Bob Orazi