Get unlimited digital access to baltimoresun.com. $0.99 for 4 weeks.
Lifestyle Home & Garden

On knockout roses, plus a daisy as plant of the week

My Knockout roses are not doing well. First I had to treat them for rose slugs eating the leaves. Now the leaves of two trunks are fading to a pale green. Are they dying? How is that possible with a Knockout?

Knockout roses are highly resistant to black spot, but that doesn't mean they're immune to everything. We get calls primarily about rose slugs, rose rosette disease, and stem cankers. Japanese beetles were heavy this year, too. Some Knockout colors are more prone to problems than others. Check the stems of your rose for cankers (darkened areas) and prune them off below the canker. Contact us if you see other symptoms.

Crabgrass is terrible this year. It grows sideways and roots wherever it touches, so one plant becomes huge. What can I do?

Crabgrass is ubiquitous in Maryland lawns. This annual grassy weed is generally managed by applying pre-emergent herbicide granules in early spring, so that the seeds cannot develop. Some pre-emergent herbicides have limited ability to help after the weeds have grown. There are post-emergent herbicides, too, but they can only kill young crabgrass plants. Since your plants are full-grown, you can hand-pull or dig it out or keep it cut to limit seed formation. It will die at the end of summer. To help prevent crabgrass next summer, reseed and thicken up your lawn in the fall, maintain mowing height of at least 3 inches high (crabgrass need sunlight to germinate), and fertilize in the fall.

For better season-long crabgrass control, consider applying your pre-emergent twice, but make sure the product you choose does not contain fertilizer. Apply first in early spring then again about six weeks later. Also see our crabgrass control publication, "TT43: Herbicides for Crabgrass and Goosegrass Control in Turf"on the HGIC website under "Publications" in the lawn category.

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 extension.umd.edu/hgic.

Plant of the Week

Shasta Daisy 'Becky'

Leucanthemum x superbum 'Becky'

It's easy to see why Shasta daisy cultivar 'Becky' earned the 2003 "Perennial Plant of the Year" award. Showy and reliable, this clump-forming perennial is a summer must-have. The large, clear, white flowers have strong stems requiring no staking. Unbothered by Maryland's heat and humidity, they bloom from July to September if deadheaded. Drought-tolerant once established, they attract butterflies while resisting deer and rabbits. They're a favorite in borders, beds, and containers. Try shastas in cuttings gardens, too, since the flowers have a long vase life. About 3 feet tall and wide, plants thrive in full sun in a moist, well-drained soil. Divide every two to three years and share this beauty with friends. — Marian Hengemihle

Copyright © 2015, The Baltimore Sun
Related Content
  • Garden Q&A Archive
    Garden Q&A Archive

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

  • Seeds of summer bring joy to winter
    Seeds of summer bring joy to winter

    Steve Bender remembers Januaries in his University of Maryland horticulture classes when all the students could be seen carrying garden catalogs for the new season.

  • New plants for 2015: There's a lot for gardeners to love
    New plants for 2015: There's a lot for gardeners to love

    What's that rosy glow in the distance? It's the dawn of a new gardening year! The long trudge of winter may seem to go on forever, but the days are getting longer and it's time to start dreaming and planning.

  • Most expensive homes in the Baltimore region in 2014
    Most expensive homes in the Baltimore region in 2014

    A 10-bedroom Severna Park estate that sold for $6.75 million was the most expensive Baltimore-area home sale in 2014. Anne Arundel County dominated the market for high-end properties with 13 of the 20 most expensive homes. (Source: Data provided by MRIS)

  • Fallston man captures details of his home in model form
    Fallston man captures details of his home in model form

    Fallston resident Bill Tamburrino, 94, has spent more than 30 years building a model of his home in painstaking detail, down to replicas of kitchen cabinets and bathroom fixtures.

  • A splitting tree trunk can have many causes
    A splitting tree trunk can have many causes

    Can you tell me why the trunk of our weeping mulberry is splitting? It is 14 years old and has been moved twice. We treated it for fungus last summer. We are in zone 7a [on the U.S. Department of Agriculture map] and haven't had any big swings in temperature this season.

  • When hanging a hammock, avoid harming trees
    When hanging a hammock, avoid harming trees

    Our hammock has always been attached to an eye bolt screwed into a tree. When we took down the hammock this fall, we discovered the eye bolt has been completely engulfed by bark. Just swallowed up! We barely got the hammock off. How do we cut (drill?) out the eye bolt?

  • Agate objects are design rock stars
    Agate objects are design rock stars

    The allure of gemstones and minerals long has inspired designers captivated with their natural beauty. Slices of agate are particularly rocking home decor because of their mesmerizing crystal quality, swirling bands and range of subtle to brilliant hues. Aerin Lauder likes them; she has...

Comments
Loading