Weed ID | University of Maryland Extension

Updated: May 25, 2023

Weed Identification Photos in Maryland

Identify common Maryland weeds using our extensive collection of photos.

Updated: May 30, 2023

Know Your Foxtails (FS-2023-0658)

Yellow, green, and giant foxtail are the three most common weedy foxtail species in Maryland. Knowing the differences between foxtail species and look-alike grassy weeds can assist with identification, and the selection of effective weed management strategies. Title: Know Your Foxtails (FS-2023-0658); Authors: Dwayne D. Joseph, and Leo Kerner

Updated: December 14, 2022

Poison Hemlock Identification and Management

Poison Hemlock (Conium maculatum, Fig. 1), is a member of the plant family Apiaceae, which contains a few important crops such as carrots, celery, and parsnips. This weed is a tall, invasive, and highly poisonous weed that is sometimes mistaken for one of its crop relatives. It is also commonly mistaken for Queen Anne's Lace (Daucus carota).

Figure 1. Poison hemlock (Conium maculatum) inflorescence.

Updated: September 26, 2022

Japanese Stiltgrass Identification and Management

Now is the time to scout pasture and hay fields for Japanese stiltgrass and take note of its locations. This invasive grass is typically seen in wooded areas, but unfortunately has been creeping into fields. Once the seed heads start to form in another month or two, you’ll want to have the mower ready.

Updated: May 2, 2022

Palmer Amaranth in Maryland

Palmer amaranth, Amaranthus palmeri, is a new invasive weed in the pigweed family that has become a major challenge for farmers across the U.S. for much of the last decade. Native to the Sonora Desert of Arizona and Northern Mexico, Palmer amaranth is well adapted to the hot Maryland summers. It was first discovered in Maryland during the mid-twentieth century, but the presence of herbicide resistant Palmer amaranth was not confirmed until 2014. Since then it has spread to most regions of the state including Eastern, Southern, and Western Maryland. The spread of Palmer amaranth has been hastened by the movement of contaminated equipment, feed, and seed from infested areas.

Updated: May 2, 2022

Managing Herbicide Resistant Common Ragweed

Common Ragweed (Ambrosia artemisiifolia) is a native summer annual weed of many cropping systems in the mid-Atlantic. It is often encountered as weed in agronomic crops as well as vegetable, orchards, roadsides, and abandoned fields. Common ragweed can thrive in lower fertility soils and is often more severe in reduced or no-tillage situations. In Maryland, populations of glyphosate resistant common ragweed were first confirmed in 2014. Resistance to ALS herbicides was also confirmed the same year. In most areas of Maryland, common ragweed has two-way resistance to both glyphosate and ALS chemistry. In 2017, pockets of three way resistant common ragweed plants were confirmed in parts of Delaware and the Eastern Shore of Maryland to PPO, ALS and glyphosate. Herbicide resistant common ragweed can be very difficult to control in agronomic crops, particularly soybeans.

Updated: January 21, 2022

Common Groundsel: Identification and Management in Nursery and Landscape Settings

Updated: September 3, 2021

Time to Pull Palmer Amaranth

Lately, I have seen several fields with Palmer amaranth flowers (Figure 1). It is imperative that these plants be managed before harvest (Palmer amaranth is listed as a noxious weed in Maryland and Delaware). At this point, mowing or herbicides will not improve yield nor prevent Palmer from germinating next year. Plants need to be physically removed from fields. Palmer amaranth has both male and female flowers on separate plants (Figure 2), and focus should be placed on removing the seed-producing females first. A single female can produce approximately 600,000 seeds per plant, and these seeds can remain viable for six years. Palmer seed matures within 2 weeks of flowering and if left unchecked, a single plant can infest an entire field within a few years (Figure 3).

Figure 1. Palmer amaranth emerging through a soybean canopy. Image: k. Vollmer, University of Maryland

Updated: August 6, 2021

Japanese Stiltgrass Identification and Management

Japanese stiltgrass is an invasive grass that is typically seen in wooded areas. It likes shaded, wet areas and can easily take over the forest understory. Unfortunately, it can also creep into pastures and hay fields. The leaves of Japanese stiltgrass are wider and shorter than most of our common pasture grasses. There is also a distinctive silvery midvein that is slightly off-center from the middle of the leaf (Figure 1).

Figure 1. Japanese stiltgrass. Image: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

Updated: July 6, 2021

Agronomy News-July 2021

Agronomy News is a statewide newsletter for farmers, consultants, researchers, and educators interested in grain and row crop forage production systems. The topic for this edition is Double Crop Beans, Not So Fast, Herbicide Field Day, July IPM Insect Scouting Tips, Hemp Twilight Tour, Corn Disease Update, 4R Field Day, Poison Hemlock Identification and Management, Tar Spot: New Disease of Corn, Soybean Board Field Day, 2021-2022 Cover Crop Sign-Up, LEAD Maryland Fellowship Applications, Maryland Commodity Classic, MDA Pesticide Exams, MDA Pesticide Disposal Program, Weather Outlook, and Regional Crop Reports.