Recognizing Baby Weeds
By Bethany Abrahamson, with special guest, Dr. Leslie Beck!
Photo by Marisa Thompson
It's important to pull weeds while they're young, but how can I identify weeds as seedlings?
--Sandoval County
Many weeds are most easily controlled by physically removing them before they have a chance to become established. But staying ahead of these undesirables is no small task in any garden: just when you think you've removed them all, monsoons germinate a whole new crop of weed seeds that were just lying in wait. Weed seeds can germinate well into the end of the year if temperatures are warm. And if you are starting garden from direct seeding, such as a native pollinator garden or meadow, it may be difficult to tell the "goodies" from the "baddies". Weed identification can be difficult and may take practice, as well as the use of field guides or your local Cooperative Extension office. Identifying baby weeds is also complicated by the fact that not all 'small' plants are 'baby' plants: some common weeds of New Mexico, like London rocket, can reach maturity and start flowering when they are only a few inches high. Recognizing the weed's life stage is important especially when applying herbicides for control. Physical removal is more effective when plants are young, because the plants lack many of features that help them entrench themselves in a landscape, such as seeds and deep roots.
Once you know what to look for, identifying the common weeds in your areas as soon as they emerge can greatly reduce your time and effort spent weeding (so you can spend more time on other garden chores, of course!)
Here are some baby weeds you might find in your neighborhood.
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Bermudagrass (Cynodon dactylon)
Bermudagrass resilience is what makes it such a great choice for heavily trodden turf, and a difficult-to-control weed when it breaks containment. Look for flat or folded blades of grass with lots of branching stems above ground (stolons) that may be rooted deeply into the ground at several points. If you look closely, you will see hairs growing around each leaf base, and new leaves all rolled up. Bermuda grass just needs a fragment of root to sprout again, and can spread through water, manure, the fur of animals, and hay.
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Kochia (Kochia scoparia L.)
Photos by Bethany Abrahamson (top) and Marisa Thompson (bottom).
This non-native weed can be hard to identify due to the fact that its leaf shape can be affected by the amount of water it receives. See if you can find the fuzzy hairs on the leaves that help this plant resist herbicides. Other notable characteristics include the way that the leaves are attached to the main stem with no leaf stalk, and flat leaves compared to the rounded ones of Russian thistle. As an adult it can look a lot like a Russian thistle, and can also form tumbleweeds. Unlike some of the other weeds listed here, kochia can contain levels of certain chemicals that can result in the poisoning of livestock that feed on it, especially older, drought-stressed plants. The taproot can be pulled easily at a young age.
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London rocket (Sisybrium irio)
London rocket is a very common winter annual mustard weed in the state of New Mexico. Although it is a winter annual weed (and usually germinated in the fall months) it can also germinate in the spring as well. Young plants resemble dandelion plants since they grow in a basal rosette; however, they do not have sharp teeth that are pointed downwards in their leaves like dandelion does. The easiest way to determine a dandelion from a mustard weed (e.g. flix weed, tansy mustard, London rocket, etc.) is to break the leaves/stems and check for the lack of a milky sap which is characteristic of a dandelion or other similar looking Asteraceae plants. As they mature, London rocket (and most other mustards) send up a vertical stem in a process called ‘bolting’. Once these plants reach the bolting stage, it is unlikely that herbicide will help with maintenance since they are too mature.
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Pigweed (Amaranthus spp.)
Look for oval, football-shaped leaves with a smooth leaf edge, straight and evenly spaced leaf veins, and a little notch at the tip of each leaf. Some may have a purplish tint to the stems and undersides of the leaves. As the plant gets bigger, the leaf stems will often become longer than the leaves. While there are many non-native pigweeds in New Mexico, many are native and some can be grown as crops. Some pigweeds are resistant to herbicides.
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Puncturevine (Tribulus terrestris)
The dreaded goat head! Pick it early to avoid a painful misstep later! Little helpers known as the puncturevine weevils were introduced into the Southwest in the 1960s to help reduce puncturevine seed production and reduce plant vigor (learn more about these fascinating critters here!). This weed might be confused for spurge, another weed (pictured on the right, puncturevine is one the left). While they both grow flat on the ground, spurge leaves are hairless (glabrous) compared to the often-hairy puncturevine leaves. Spurge also secretes a milky sap, and does not have puncturevine's yellow flowers.
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Russian thistle (Salsola tragus)
Photos by Marisa Thompson (top) and Bethany Abrahamson (bottom).
Photo by Mary Ellen (Mel) Harte, Bugwood.org, CC BY-NC 3.0 US.
As seedlings, Russian thistle has long round spikes for leaves that grow in a round bunch, almost looking like a succulent at this early stage. If you look close you might also see a little extra spike at the end of each leaf (bottom image). This weed can be controlled by sheep and goat grazing. Since it is an annual plant that can only grow from seed, pull while the plant is young, so it doesn’t have a chance to become established or form a tumbleweed.
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Siberian elm (Ulmus pumila)
Photo by Bethany Abrahamson.
This is another weed that goats and sheep love to eat, and thankfully these seedlings are very recognizable even at a small size. Look for oval leaves with a pointed tip and a serrated edge, with alternate branching. Physical removal is very easy and effective when they are when they are just a few inches tall, since this weed does not put down rhizomes or grow from fragments like some other weeds. Trying to pull them after they have become established can prove quite difficult. Diligence all year long is your friend when removing Siberian elm!
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Tree-of-heaven (Ailanthus altissima)
When scouting for this seedling, keep an eye out for the distinctive three-part leaf shape that starts emerging right after the first two seed leaves of the seedling. Leaves can be almost lime-green or yellow like the ones shown on the left, or darker like the one on the right, and you may see a bit of rusty color toward the middle and stem area. This weed tolerates anything from shade to pollution to bad soil. The root crown, tap root, and creeping lateral roots must be removed for effective control, and sections like to break off as soon as you try to pull them up. Pull carefully when the soil is moist for best results.
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NMSU's Noxious Troublesome Weeds of New Mexico, by Leslie Beck and James Wanstall, is available for quick reference online here!
Have a weed you need to identify? Contact your local Cooperative Extension Office.
Here are other sources about some of the weeds mentioned here:
"Bermuda grass" by CornellCALS.
Bermuda grass, by F. Sholedice and M. Renz, O&T Guide W-2, New Mexico State University Cooperative Extension Service (2006).
"How to identify pigweeds" by CornellCALS (2025).
Identification and Management of Kochia and Russian thistle. Fact Sheet No. 6.314, Colorado State University Cooperative Extension, by S. Bokan, K. Crumbaker, and G. Beck. (2012).
Kochia, by F. Sholedice and M. Renz, O&T Guide W-10, New Mexico State University Cooperative Extension Service (2006).
Puncturevine, by F. Sholedice and M. Renz, O&T Guide W-13, New Mexico State University Cooperative Extension Service (2006).
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