Extension Master GardenerSM Volunteers of Buncombe County

Weeds

Weeds Overwhelming? How to Cope!

Warm, wet weather equals a wealth of weeds. Despite many of us being home more of the time this summer, we can’t seem to keep up with the weeds! Fortunately, there are weed scientists who can help!

 

 

Weeds compete with your vegetable garden crops


Why care about weeds?
Maybe you are hoping to just peacefully coexist with your weeds, but according to Kira Sims, a Ph. D. candidate and graduate teaching and research assistant in the North Carolina State University Horticultural Science program, weeds:

  • Compete for resources—such, as nutrients, space and sunlight—with more desirable plants.
  • Can reduce crop yields.
  • Adversely affect human health—some weeds such as ragweed and poison ivy can cause allergic reactions.
  • Alter ecosystems—weeds can crowd out native plants or even make soil less hospitable to natives through altering pH, for example.

What can you do about weeds? IWM!
Integrated Weed Management is “Science-based, socially acceptable, environmentally responsible and economically practical crop protection against pests” says Sims, using all of the tools in your toolbox!

What’s in the toolbox?
Sims advocates the PAMS approach:

  • Prevention tools include:
    • Using clean (weed-free) compost, mulch, seeds, topsoil, transplants.
    • Don’t let weeds reproduce—by setting seed, suckering and so on.
    • Water desirable plants not weeds.
    • Clean equipment that might transport weeds
    • Remember you and your pets can transport weed seeds!
  • Avoidance tools include:
    • Clearly define where you want to exclude weeds
    • Help your desirable plants outcompete the weeds by:
    • Choosing appropriate plants
    • Plant at the correct time
    • Fertilize appropriately
    • Rotate crops
  • Monitoring tools:
    • Scout for weeds regularly
    • Keep records of crops and the weeds that cause problems
    • Test soil to determine appropriate fertilization
  • Suppression tools for when you can’t prevent or avoid all weeds:
    • Reduce tilling—which brings up weed seeds
    • Use narrow row spacing to shade out weeds
    • Use cover crops and/or mulch over bare soil
    • Manage irrigation

                                    

                                          Article by Buncombe County Extension Master GardenerSM Volunteers

For more information:

Weed publications from NCSU, including specific links on managing crabgrass, Japanese stiltgrass, and ragweed:

https://content.ces.ncsu.edu/catalog/?keywords=weed-management

 

 

 

 

 

OUCH! “Thorny” Weeds

You know when you touch a thorny weed because it hurts! But technically, botanists identify those “thorns” on weeds as spines or prickles. They not only give gardeners pause, but also help protect plants from animal damage. Thorns, spines, and prickles appear on different plant parts and can help with identification.

Honey locust tree_Gleditsia triacanthos_Dane Larsen_CC BY-NC 2.0_Flickr
Thorns on honey locust tree
  • Spines are modified leaves, leaflets, petioles, or stipules. Think cactus or thistles.
  • Prickles are modified epidural (outer) cells found on blackberry, raspberry, and rose stems.
  • True thorns are modified stems or branches—like those on honey locust trees (Gleditsia triacanthos)—that are long, wicked-looking things, capable of serious damage.

To gardeners who get their fingers stuck while weeding, it matters not if that weed has spines, prickles, or thorns.  It still hurts!

Weeds that stick and prick
Common cocklebur (Xanthium strumarium) is a native summer annual. It has alternate, triangular leaves and the stems have spots ranging from maroon to black. The oval shaped fruit (bur) is covered with spines. Burs start out green and turn brown in the fall. Each bur has two seeds—one growing the first year, with the second seed growing the next year. Cockleburs are spread by the burs hitching rides on animals and humans. They can be found in fields, roadsides, and wasteland.

Burrweed or spurweed (Soliva sessilis) is an annual winter weed found in lawns, mostly along the coast and in Piedmont N.C. It has low ferny foliage and sharp, spiny seed pods that ripen in spring and hurt your feet if you step on them barefoot. It is an early source of food for honey bees and other pollinators.

Spiny sowthistle (Sonchus asper) is a summer annual weed with deeply notched and wavy leaves with sharp spines on leaf margins. The young plant is a basal rosette (leaves radiating from the base of the stem and usually close to the ground). Older plants have an upright flowering stem (yellow flowers). It flowers in late spring into summer. It has alternately arranged oval leaves. Crushed leaves or stems produce a milky white latex. It is found in lawns, waste areas, and roadsides.

Perennial catbrier or greenbrier vines (Smilax) include some of the “ouchiest” of weeds you may face here in Western North Carolina. These are native vines that are desirable wildlife food—rabbits eat the new shoot, deer browse the leaves, and birds eat the fruits—but may not be welcome in your garden.

Thistles (Cirsium) are members of the Asteraceae (aster) family and are native to North America, Europe, and Western Asia. The European invasive bull thistle (Cirsium vulgare) is found throughout the United States and Canada. 

Bull thistle_Cirsium vulgare_Suzanne Caldwell_CC BY-NC 2.0
Bull thistle

What to do?
While these weeds mostly show up in pastures, agricultural fields, and roadsides, they can invade the garden. When dealing with any of these “ouchy” plants, it is best to wear thick gloves and approach with caution. Control vines by digging the tubers or rhizomes. Repeated cutting back and applying a drop of herbicide to the cut stem are also effective. Maintain a layer of mulch in the garden to retard weed growth. Scout for and manually pull weeds when they are small and especially when the ground is soft after a rain.

Article written by Kay Green, Extension Master GardenerSM Volunteer.

Goldenrod in the Garden: Dispelling the Allergy Myth

If late summer and autumn allergies—known as “hay fever”—affect you, you are not alone! Millions of Americans suffer from seasonal runny nose and itchy, watery eyes. Much of this allergic reaction is blamed on goldenrod and ragweed, when, in fact, only ragweed spreads irritating pollen—goldenrod does not! Goldenrods (Solidago spp.) and ragweed (Ambrosia spp.) mature in late summer; but the showier goldenrod is insect-pollinated, not wind-pollinated and that’s what makes the difference.

Goldenrod meadow_by BLeonard_BCEMGV
Fall meadow dressed in goldenrod

Ragweeds are the villains!
Ragweeds are annual native weeds found in cultivated areas, as well as along roadsides and meadows in heavy soils. In early spring, common ragweed’s (A. artemisiifolia) first leaves are opposite but become more deeply dissected and arranged alternately as the plant matures. It can grow to 4 feet tall. It produces only inconspicuous flowers of nondescript color, but in early autumn, breezes distribute clouds of allergy-causing pollen as we seek to enjoy the late summer and early autumn. If you learn to recognize its leaves, it is easy pull any time before it flowers, and mowing will keep it under control—you will be shearing off any flower stalks before they bloom. Note that we also have giant ragweed (A. trifida) in our area that also produces irritating pollen. It is much taller—up to 16 feet!—and has opposite leaves with 3 to 5 large lobes and flowers much like common ragweed.

Welcome goldenrod to your garden!
Goldenrod is a native herbaceous perennial in the aster or Asteraceae family that presents dazzling displays of brilliant yellow flowers in open meadows and roadsides. These bright yellow flowers hold sticky pollen that attract bees, butterflies, and other insects until early frost. As the floral display matures, birds flock onto upright stems to enjoy the seeds.

Although sometimes viewed as weeds, these wildflowers represent a very diverse collection of many species:

  • They range in size from little more than 12 inches to 6 feet tall.
  • Some spread aggressively, while others form well-behaved clumps.
  • In addition to soft plumes, goldenrods’ yellow flowers can be spiky or even zig-zagged!
  • There are species adapted to many habitats, from salt marshes, to swamps, prairies and woodlands.
Goldenrod (Solidago)_Leonora (Ellie) Enking_CC BY-SA 2.0_Flickr
Goldenrod in the garden

Those found in our mountains are a welcome addition to perennial gardens, combining well with Echinacea, ironweeds (Vernonia spp.), Joe Pye weeds (Eutrochium spp.), Rudbeckias, taller sedums, and ornamental grasses to add vivid color to the late summer garden. They are also lovely additions to floral arrangements. Some local natives include:

  • Early goldenrod (Solidago juncea) starts blooming in July and is drought-tolerant.
  • Sweet goldenrod (Solidago odora) has anise-scented shiny leaves, reaches only about 2 to 3 feet tall and has a well-behaved clumping habit.
  • Common goldenrod (Solidago altissima altissima also known as Solidago canadensis var. scabra) is a tall (up to 6 feet) plant that spreads aggressively by underground rhizomes, which can be an advantage in controlling erosion, even on steep slopes.

Goldenrods are subject to very few diseases, and although you may see some galls, spider mites and lace bugs, deer typically ignore them.

So, as September arrives, bringing the first falling leaves, hints of coolness in the air, and breezes carrying pollen, don’t be concerned about goldenrod. It’s a harmless beauty!

What to do about allergies?
Donna Teasley, Extension Agent, recommends ways allergy sufferers can keep symptoms to a minimum:

  • Avoid hanging laundry to dry outside.
  • Hire someone to mow the lawn during late summer.
  • Keep bedroom windows closed at night.
  • Keep car windows rolled up while driving.
  • Stay indoors on windy days and at peak pollen hours—early morning and late afternoon.

While these suggestions can certainly help allergy sufferers cope, one final thing we can do to lift our spirits as we gaze outdoors or ride along is to take time to enjoy the goldenrods!

Article written by Mary Alice Ramsey, Extension Master GardenerSM Volunteer.

More information
Read about different types of goldenrod, from the wildflower to cultivars for the garden.
NC State Extension publications

Common Ragweed
by Charles Peacock, Professor and Extension Turfgrass Specialist
NC State Extension

Giant Ragweed
by Dr. John Hilty, Illinois Wildflowers

Allergy Sufferers Alert
by Donna Teasley, Extension Agent, Burke County, NC
NC Cooperative Extension

Contact Us

Buncombe County Extension Office
49 Mount Carmel Road
Asheville, NC 28806
Helpline 828-255-5522

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