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weed with puple seed head

What's that purple weed?

I’ve received a few questions asking what the purple weed is that is appearing in the landscape. It is probably either purple deadnettle (Lamium purpureum) or henbit (Lamium amplexicaule).
These weeds often get confused because they look similar. They both belong to the mint family, have square stems, have an ascending growth habit, opposite leaves, purple/pink flowers, and are winter annuals. When trying to identify if you have purple deadnettle or henbit, key ID traits to tell them apart are listed below.

Purple deadnettle that was found in Van Buren County this spring (2016).
Photo taken by Nancy Carr

Key ID traits for purple deadnettle:

  • Purple-tinged leaves on upper stem triangular with pointed tips
  • Upper leaves with petioles, not directly attached to stem

Henbit may look similar to purple deadnettle, but there are some key ID traits to look for to tell these weeds apart.

Key ID traits for henbit:

  • Leaves rounded with deep lobes and venation on upper stem
  • Upper leaves directly attached to stem with no petioles
  • Densely pubescent (hairy) leaves

Since both are winter annual, preventing seed production is key to management. Tillage and herbicides are effective management options for these weeds. Both species are flowering now and management with herbicides will not likely result in full control. Fall or early spring herbicide applications will be most effective at managing problem infestations. Contact your local Iowa State University Extension & Outreach field agronomist for resources regarding control of these weeds.
Another weed that belongs to the mint family and is making lawns appear purple right now is ground ivy (Creeping Charlie, Glechoma hederacea). Unlike henbit and purple deadnettle that are winter annuals, ground ivy is a perennial weed, and also generally stays confined to lawns.

Weed with puple seed head

Weed Control
Maintenance

It’s time now to prepare your lawn for the grass weeds to come this year. Weed identification can be the hardest part of the process but essential. Once you know what it is, you know how to best treat it. But more importantly, prevent grass weeds by keeping your lawn healthy.

Wintergrass

Wintergrass grows in tufts of light to dark green leaves. It emerges from autumn to spring but can infest lawns year-round in the shade. It’s seed heads produce plenty of seeds soon after germination which are easily spread through the wind, water and traffic.

Capeweed

Capeweed is a winter annual that forms in a rosette shape. The deeply lobed leaves have a white underside. Small flowers stand above the leaves with a black centre and creamy-white petals.

Crowsfoot Grass

Crowsfoot Grass appears yearly around summer. It has flat, dark green stems and the leaves sprout from white sheaths. This weed tends to seed from late spring, throughout summer and into autumn. It’s seed heads have between 2 and 10 spikelets on a long stem.

A node is a point of the plant that leaves or bud sprout.

A biennial plant grows over two years. The first year it produces leaves, stems and roots. Then, in the second year, it sprouts flowers.

Nutgrass

Nutgrass is a rapidly spreading perennial sedge. With flat leaves and stems, Nutgrass has small yellow-brown seeds that are produced in narrow spikelets during summer. Nutgrass is difficult to remove due to its underground tubers that can regrow.

Dandelion

A perennial weed, the dandelion is well known for its white, puffy seed heads. It produces yellow flowers in spring and summer from long, hollow, purple stems. As well as the parachuting white seeds, Dandelions can spread through fragments of its taproot.

A sedge plant is similar looking to grass that typically grows in wet ground. They have triangular stems and inconspicuous flowers.

A perennial is a plant that lives for more than two years.

Summergrass

A summer annual, Summergrass crawls across the ground with roots growing for the nodes. Broad, glossy leaves sprout from often purple sheaths with seed heads appearing from late summer to autumn. The seeds are black and sticky, spreading easily through passing traffic.

Cudweed

Cudweed is a winter biennial, forming in a basal rosette. With waxy green leaves, oblong in shape, the underside is a silvery white. Cudweed will typically flower in early summer or autumn and the flowers can be brown, purple or pink. This weed produces an abundance of seeds, so it is best to get rid of the seeds before it can spread.

Mullumbimby Couch

A perennial sedge, Mullumbimby Couch grows in mats and has a similar appearance to grass. It can grow up to 15 cm high with dark green, glossy leaves. It produces a single, compact seed head that has three short leaves emerging from its base. Mullumbimby Couch flowers in warmer months and spreads through its seeds and rhizome fragments.

Bindii

The bindii is recognised by most Australian children by its hard, spiky seeds. It is a low-growing perennial with roots growing from the nodes. With carrot-like leaves, the seeds appear in spring and are soft until the plant starts to die when they create sharp burrs.

White Clover

The White Clover weed is another well-known weed. Its leaves form in heart shapes, usually in sets of three but at times, if you are lucky, you will find a set of four. Paperwhite flowers appear during spring and autumn and commonly attract bees.

So now that is done, all that is left is to treat it. Most weeds can be hand removed, as long as you remove the entire root system, or they can be removed with a herbicide. It is always best to remove the grass weed before they seed, otherwise, you end up with a bigger problem than just weed identification.

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‘Tis the Season of Thistles

Hey everyone, ’tis the season for knocking back patches of thistle!

Following tips from Teton County Weed and Pest District and Bridger-Teton National Forest, Teton Conservation District staff members Emily Smith and Morgan Graham recently removed over 125 lbs. of thistle seed heads in the vicinity of the Munger Mountain and Game Creek trailheads! We intend to revisit these sites in future years to track our mechanical control progress.

Thistles are tricky and can come back even after being sprayed or pulled. If a thistle looks dead or drooped, but you still see a purple seed head, the thistle has succeeded in expanding its footprint.

If you want to get out there and be a native habitat hero, here are a few tips on treating thistles:

Pop and BAG the seed heads/flowers. Sometimes thistles will trick you and put out seeds after they’ve been sprayed or pulled (check out our IG stories). Make sure to bag the flowers/seed heads and put them in the trash, not on the ground.

Rip out the plant and let it compost in the field. You don’t have to bag the whole plant – just the seed head.

When treating thistles or other weeds with herbicide, check with Teton County Weed and Pest about the appropriate herbicide and correct concentration. Over-application of herbicide can negatively impact native vegetation. It is not uncommon to observe “scorched earth” where the incorrect amount or concentration of herbicide has been sprayed. These bare patches of ground can inadvertently provide a clean slate for rapidly establishing invasives like musk thistle and houndstongue to reseed and prosper without competition from slower growing native vegetation.

Also, shout out to Chris Owen with Friends of Pathways for helping us truck out all the seed heads we collected! Thank you!

Top photo by Penny Mayes / Musk thistle (Carduus nutans) / CC BY-SA 2.0