Tag Archive | weeds

Trick Your Weeds

by Sharon Morrisey, Consumer Horticulture Agent in Milwaukee County

sow-thistle-weedIn fall, weeds’ natural biology changes gears from growth mode to storage mode and they start moving carbohydrates into their roots for winter. By applying herbicides to weeds at this time, you trick them into doing some of the dirty work for you. They will carry the chemicals into their roots along with their carbohydrates where these products kill the plants, roots and all. Shorter days and a string of several evenings with temperatures in the 30s are the signals for plants to shirt to storage mode and for you to get out your sprayer.

Choose your weed killer carefully. Although some products can tell a dandelion from a blade of grass, they do not distinguish between that dandelion and your prized dahlia. That is why it is so difficult to use broadleaf herbicides in mixed flower and vegetable beds where the weeds and your precious plants are all broadleaves. Other herbicides kill everything green and living, dandelions, dahlias, and your lawn alike. Making this mistake for spot treating your lawn leaves dozens of little round dead spots where you sprayed.

The Battle Against Weeds

1452647202156The battle against weeds is relentless. In every square yard of soil it is estimated that there may be as many as 100,000 weed seeds. Why are they such a bad thing? The simple answer is that they compete. They drink water and absorb nutrients from the soil. They crowd yours crops for space, hogging the light and putting them in the shade. And they play host to all kinds of pests and diseases.

Perennial weeds

  • Bindweed – one of the most difficult of all weeds to eradicate. Dig up and destroy every piece of root, or spray leaves with systemic weedkiller.
  • Bramble – vigorous and invasive, with painfully sharp thorns. Roots are deep and must be dug out completely.
  • Creeping buttercup – a low, spreading weed that throws out horizontal runners, producing new plants at each node. Uproot the whole lot.
  • Dock – dig up the long taproots without letting them snap or they will regenerate.
  • Stinging nettle – dig out the roots of stinging nettles in order to eradicate completely. But be careful, the sting really hurts!
  • Creeping thistle – its root system is so tenacious that a systemic weedkiller may be the only solution to the problem.
  • Dandelion – remove dandelion flower heads before they fade and release their tiny, parachute-like seeds — and dig out the entire tap root.dandelion-flower-02
  • Ground elder – dig up carefully — this determined weed with regrow from any stray bits of root left in the soil.

Annual and biennial weeds

  • Goosegrass – also known as ‘cleavers,’ the plants have tiny, hooked hairs that cling to supports. Dig up by the roots.
  • Plaintain – uproot the whole plant — including its tap root — before it flowers and produces seed.
  • Annual meadowgrass – hoe regularly to prevent the grass from flowering and spreading across your plot.
  • Ragwort – remove and compost before the yellow flowers turn to seed.
  • Groundsel – dig up and remove before the fluffy, dandelion-like seed heads form.
  • Common chickweed – a low-growing weed that spreads vigorously but has shallow roots which are fairly easy to pull up.
  • Shepherd’s purse – easy to uproot when still young. Compost only if the heart-shaped seed pods have not yet formed.
  • Hairy bittercress – pull up when young, before the long, cylindrical seed pods appear.

verve_shutterstock_lifestyle_2016_151Weeding tips

  • Hoe regularly so that you catch weeds when they are young and while their roots are still shallow.
  • Don’t let weeds flower, or they will generate a new crop of seeds.
  • Hoe when it’s dry so that severed and uprooted weeds die quickly.
  • If the soil is damp, collect up and dispose of any remains to ensure that they don’t regrow.
  • Loosen soil thoroughly so that when you dig up roots you leave nothing behind.
  • Don’t put perennial weeds on your compost heap; they may live to fight another day.
  • Use lightproof membrane mulches to kill established weeds.
  • Spread surface mulches to suppress the growth of new weeds.
  • Use chemical systemic weedkillers as a last resort.

Expert’s Tip: Wild Parsnip — What is it and why should we be concerned about it?

by Ken Schroeder, Portage County UW-Extension Agriculture Agent

Wild Parsnip, Pastinaca sativa, is an invasive member of the carrot family that continues to spread into unmanaged areas throughout Wisconsin. It likes to grow in sunny, grassy areas along roadsides, railroads, and field borders but is not limited to these conditions. Primary means of spread is by seed that can be moved long distances while mowing roadsides after the plant has set seed.

What’s the concern?  The biggest concern isn’t the fact that it is invasive and rapidly spreading but that it will cause burns and blistering of the skin if you come in contact with plant sap in the presence of sunlight. This is known as phytophotodermatitis. Blisters and rashes appear 24 to 48 hours after exposure. Blisters do not spread like poison ivy but are uncomfortable and may leave scars lasting for several months to two years.

Pastinaca_sativa_'wild_parsnip'_2007-06-02_(plant)How do we identify wild parsnip?  The plant is a monocarpic (the plant dies after blooming) perennial and has two growth stages. The first year it produces a non-flowering leafy rosette of pinnately compound leaves with 5 to 15 leaflets.  It looks a lot like celery at this stage.  In the second to third year, it produces a flowering stem four to five feet tall. Stems are grooved, hollow, and have alternately arranged compound leaves with 2 – 5 pairs of opposite, sharply toothed leaflets and petioles that wrap around the stems. Flowers are flat-topped clusters (umbels) of yellow flowers 2 – 6” wide blooming in late spring to mid-summer in Wisconsin. Seed begins to form mid to late July changing from yellow-green to tan as they mature.  Along with the seeds maturing the stems and leaves begin to senesce, turning tan to brown in color.

How do we manage wild parsnip?  Early detection when populations are small allow for pulling or digging.  Be sure to wear gloves, long sleeves, long pants, and safety glasses or face shields to avoid skin contact with the sap.  One can simply cut the taproot with a shovel or spade 1 – 2” below the soil surface.  With larger populations mowing is an option if done after emergence of flower heads, but before seeds enlarge.  Additionally, several chemical options exist.  Be sure to read and follow label directions when using chemicals.  For more detailed management options see the UW-Extension wild parsnip management publication A3924-15 at the Learning Store website https://learningstore.uwex.edu/ .

What can I do as a Master Gardener to help?

  • Know how to identify wild parsnip and report locations at the Wisconsin First Detectors Network website http://fyi.uwex.edu/wifdn/get-involved/report-invasive-species/.  Several options are listed including a downloadable smartphone app.
  • Educate others about the existence and danger of wild parsnip.
  • Carry a sharp shovel or spade with you and when you see only one or a few plants consider cutting off the stems below the soil surface.  As long as they haven’t gone to seed the plants can then be left to die.  Check back the next year to see if additional plants emerge and cut those too.  CAUTION do not do this on private property without getting permission from the property owner.

Additional invasive species information

  • The University of Wisconsin Weed Science website http://fyi.uwex.edu/weedsci/ is a great resource for weed id and management info and has several short YouTube videos to help with identification.

The Wisconsin DNR invasive species website http://dnr.wi.gov/topic/Invasives/ has a wealth of information on not only terrestrial invasive species but aquatic and wetland invasives as well.

Another New Weed!

Gesnouinia_arborea_(Tree_Pellitory)_seedlings.Thanks to OCMGA Master Gardener Mary Learman for discovering this information.

Keep an eye on your garden and your lawn. As though we didn’t have enough weeds and invasives to watch, the University of Illinois Extension warns of Pellitory (Parietaria pensylvanica) appearing in the midwest. Funnily, the leaves remind one of peony plants or, perhaps, dianthus before it blooms. Don’t be fooled, however, as it’s aggressive enough to take on your whole garden and flexible enough to grow out of cracks.

For more information, follow this link to the article published by the University of Illinois Extension.