Weeds, Not Wildflowers: Part 3

The battle against invasive weeds never ends. Here are species that should be controlled in your natural area.

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Poison Hemlock (Conium maculatum)

Poison Hemlock, a biennial, is blooming with clusters of flat white flowers atop tall purple-blotched stems. A member of the parsley family, it has lacy compound leaves. A single plant may form upwards of 38,000 seeds. This plant is poisonous if ingested and was the hemlock used to poison Socrates.




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Teasel, Dipsacus sylvestris and D. laciniatus

Both biennials, Teasel is sending up flower stalks now along roadsides and fields from its deep taproots. Its leaves are large, coarse and spiny; clasping the stem to form a cup where water collects. Prickly flower heads appear in summer above needle-like bracts. The flowers then dry into a cone-like seedhead and form up to 34,000 seeds per plant. It will readily reseed if mowed in the fall and can form dense colonies.

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Birdsfoot Trefoil, Lotus corniculatus

This low growing legume plant is blooming now with brilliant yellow pea-like flowers above three-lobed leaves. It thrives in disturbed areas forming a deep root mass and dense mats of foliage that crowd out native species. It also spreads by seed, generating about 5,000 seeds per plant. Fire increases its germination, making it particularly tough to control.


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Purple Loosestrife, Lythrum salicaria

Purple Loosestrife is commonly found invading wetlands, retention ponds, roadside swales, and ditches and can get up to six feet high. It has a flower spike of pinkish purple blossoms and will aggressively form colonies, crowding out native plants. A single mature flower stalk can produce up to 300,000 seeds. Purple Loosestrife spreads readily by seed and can regenerate from root fragments. It was brought to the U.S. as an ornamental garden plant by Europeans. There are some loosestrife-eating insects available, but they cannot completely control the plant.


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Wild Parsnip, Pastinaca sativa

Wild Parsnip is blooming now in natural areas, disturbed sites, and roadsides. Its tall stalks are blooming with bright yellow flat flower clusters. Wild Parsnip typically is biennial with a rosette of ferny leaves the first year and a four foot high hollow grooved flower stalk the second. Flat oval seeds follow the clusters of blossoms. It resembles a yellow version of Queen Anne’s Lace. Be careful when dealing with Wild Parsnip. Its juice in contact with skin in the presence of sunlight may cause a rash or burn.


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Red Clover, Trifolium pratense

The round pink flower heads of Red Clover are blooming above bushy foliage composed of three-part leaflets marked with a pale green V shape. It has a fibrous root system and stems will root at the nodes when in contact with soil, allowing it to fill an area quickly. Commonly found in fields and meadows but readily invades natural areas and native landscapes. Red Clover tends to be between 8 and 20 inches high.


Are these weeds on your property? Contact us about developing a weed management plan today!


Written by Pizzo Group

The Pizzo Group is a family of four companies that restores ecosystems and provides sustainable landscape solutions that are both beautiful and functional. We do this at any job site, any size project and within any ecosystem. Our processes are collaborative and range from design through implementation.