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How to prevent disease from attacking garden phlox

Phlox plants1 / 2
Don Kinzler, gardening columnist 2 / 2

Q: I have phlox plants in my back yard and every year about this time the leaves start turning yellow from the bottom up. The tops of the plants are fine and they eventually bloom. What is causing this and what can I do about it? The variety is called Miss Mary. - Walt Meidinger, Fargo.

A: Tall garden phlox (Phlox paniculata) are beautiful perennials that are commonly susceptible to leaf blight diseases, including powdery mildew, caused by fungi. Some phlox varieties are more susceptible than others and because it's a widespread problem newer varieties have been developed with resistance or tolerance, usually indicated on the plant tag.

To prevent less-resistant varieties from succumbing, plants can be sprayed with an all-purpose fungicide for flowers and vegetables. Fungicides are best applied as preventatives while the leaves are still healthy.

Fungi are often soil-borne. Remove and discard diseased tops in fall. Avoid overhead sprinkling that splashes soil and wets foliage. Water in the morning, rather than evening. Many phlox growers have found that thinning out the numerous stems increases airflow, reduces disease and promotes larger flower heads. Mulching around plants with a layer of shredded bark keeps soil cool and moist, which phlox prefer.

Q: How do I get rid of creeping Charlie? I literally hand-pulled a garbage bag full over the weekend. This is the worst I've seen them in 20 years. Any advice would be appreciated. - Verna Metzger, Perham, Minn.

A: Creeping Charlie must be having a good year, based on the mailbag. It's a low-growing weed in the mint family with rounded leaves and little purple flowers. It spreads quickly and vigorously in lawns and perennial flowerbeds. Persistence is the key, because a one-time kill is almost impossible.

Several universities are recommending herbicides having a high percentage of the active ingredient triclopyr as being the most effective. It's a broadleaf weed-killer that won't harm lawn grass. If used in perennial flowerbeds, it must be carefully spot-applied to avoid contact with desired plants. Check product ingredient labels for triclopyr.

Apply the herbicide when creeping Charlie is blooming in spring or early summer. Then apply again in September. The fall application is very important. In severe cases, some homeowners have opted to kill everything and start over.

There's an internet remedy being circulated that's recommending borax for creeping Charlie control. Researchers have tested it, found it to be non-effective long-term, plus it can damage lawn grass and other plants.

Q: How much and how often should you water strawberries now that they're producing berries, or shouldn't you water? My plants are June-bearing, still full of blossoms, and berries are about an inch in size, but not turning red yet. - Jean

A: The recommended moisture amount for strawberries is one inch of water per week, either from rain or by sprinkling, which can be applied in one or two waterings. Adequate moisture is especially important when strawberry plants are bearing. When June-bearing varieties are finished fruiting, moisture is less crucial but still important for overall plant health. Everbearing and day-neutral varieties benefit from consistent watering throughout the season.

If you have a gardening or lawn care question, email Don Kinzler at All questions will be answered, and those with broad appeal may be published, so please include your name, city and state for appropriate advice.