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Appearance: This garden weed has light green leaves that look like clover and cup-shape yellow flowers in summer and fall.

Size: 12 inches tall, 6 – 16 inches wide

Control: Mulch garden areas in spring to prevent weeds. Pull oxalis weeds by hand or spray weeds with a postemergence herbicide in spring or fall.

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Size: To 20 inches tall

Where It Grows: Lawns and gardens in sun or shade

Lawn Weed Control Tip: Mulch to prevent dandelions in gardens. Pull dandelion weeds by hand or use a postemergence herbicide (designed for using on weeds after they appear) in lawns.

Don’t let these pesky plants crash your garden party!

Species like Dog-Strangling Vine (Vincetoxicum rossicum and Vincetoxicum nigrum), Garlic mustard (Alliaria petiolata), Buckthorn (Rhamnus cathartica), and Japanese Knotweed (Reynoutria japonica) threaten biodiversity and have adverse effects on the environment. Species like European Water Chestnut (Trapa natans), Water Soldier (Stratiotes aloides) and Common Reed (Phragmites australis) have adverse effects on recreational activities like swimming, boating and fishing and on reproductive strategies of fish, turtles and birds. Species like Giant Hogweed (Heracleum mantegazzianum), Poison hemlock (Conium maculatum) and Poison ivy (Toxicodendron radicans) can be detrimental to human health with exposure causing allergic reactions and dermatitis.

What weed-killing options can you recommend?

JP: Weeds can be detrimental in the garden in a number of ways. Some are aggressive and choke out expensive garden plants. Some are allelopathic which means they produce biochemical(s) that influence the germination of seeds and hamper the growth, survival and reproduction of other plant species, which gives them the advantage over more desirable plants. Others, such as Giant Hogweed (Heracleum mantegazzianum), an invasive species which can grow over 12 feet tall, are extremely dangerous in that they cause burns, blisters and even scarring on the skin when touched. And some, such as Water hemlock, Cicuta species are toxic and deadly when ingested.

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