Tall Weed With Black Seeds

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Do you have prostrate weeds with small yellow, clover-like flowers in your garden beds or lawn? This leguminous plant from Europe and temperate Asia, commonly called black medic, is also called yellow trefoil, black clover and hop medic. Read more about this annual weed and how to deal with it in this article… WeedAlert.com features detailed color photos of over 100 weeds allowing turf professionals to search and identify weeds by name, appearance or region. Detailed information about each weed includes description, non-chemical cultural practices in how to control the weed, geographic coverage maps of where they grow and when they are prevalent in the various growing zones, as well as herbicide use and recommended control products. Control of bahia grass is important in lawns to minimize competition. The grass seeds prolifically and spreads into turf areas. Find out more about bahia grass and its control in the article that follows.

Black Medic, Medicago lupulina

A dense infestation of black medic.
Black medic, Medicago lupulina, is a common, prostrate broadleaf weed that is found throughout the US and Southern Canada. Native to Europe and temperate Asia, this member of the legume family (Fabaceae) has a few other common names including yellow trefoil, black clover and hop medic. Its is most often found as a weed in in dry, sunny areas in turf and waste ground, such as along roadsides and railroads, but it can be a nuisance in gardens and fields as well. Black medic can be an indication of low soil nitrogen in lawns as it outcompetes weak grass. Black medic and white clover grow in similar sites and are often found growing together in turf. Although it is classified as a cool season summer annual, in mild winters some plants may survive to act as a perennial. It spreads easily by seed and will form large colonies if left undisturbed.
A young black medic plant.
Black medic produces a long taproot that grows deeply into most soils. Several trailing, slightly hairy stems grow out from the base. The plant grows close to the ground, spreading up to 2 feet, but does not root along the stems. Like other members of the legume family, black medic has a symbiotic relationship with Rhizobium bacteria that form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby.
A black medic seedling (L) and trifoliate leaf (R).
The tiny seedlings resemble other clovers, with elongate, dark green cotyledons and rounded first leaf. All other leaves are trifoliate. The plant’s dark green leaves are similar to clover leaves, with three oval leaftlets. Each ½-¾” long leaflet has a small spur or tooth at the tip, toothed margins, and prominent, parallel veins. The center leaflet protrudes slightly on an extended petiole. This characteristic, along with the small projecting tip at the leaflet apex and toothed margins, help to distinguish black medic from other trifoliate legumes. The leaves are produced alternately along the stems. There is a pair of stipules (small, leaflike appendages) where each petiole joins the main stem.
Black medic flower.
The small, bright yellow flowers are produced from the leaf axils. Each inflorescence is a compact, rounded to slightly elongated cluster of 10-50 tiny flowers. Flowers can be found throughout the growing season, although individual plants stop blooming once seeds are set. Honeybees and other bees visit the flowers. The fruits that form after pollination look like small kidneys arranged in clusters. The coiled seed pods turn black when ripe. Each seed pod contains a single gold or brown seed.
In lawns, black medic can be managed through good turf management practices that encourage a dense stand of turf (high mowing, proper fertilization and irrigation), making it difficult for black medic to persist. As black medic often grows where some soil compaction has occurred, such as along curbs and sidewalks, reducing compaction will also help.
Black medic fruits (L) and ripe seed pods (R).
Black medic produces viable seed under normal mowing conditions which can persist in the soil for years, so it is important to control this weed before flowering and seed set. Individual plants can be hand pulled. Even larger plants are easy to pull out, particularly after rain has softened the soil. However, for large areas or dense infestations, a broadleaf herbicide can be applied to actively growing plants during the seedling to flower growth stage. Chemical controls are best applied from late spring through early summer and again from early through mid-autumn. Read and follow label directions carefully.
– Susan Mahr, University of Wisconsin – Madison

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Tall Weed With Black Seeds

Bahiagrass, a coarse-textured warm-season perennial (C-4) which does not form a tight knitted turf. Bahiagrass has a rolled vernation, ligules which are membranous in nature with short hairs on the back of the ligule. Auricles are absent and the sheath is flattened. The leaf blades are coarse, light green in color, pointed at the tip and sometimes have hairs located near the base. The blades are typically folded near the base. Leaf blades are very fibrous and difficult to cut cleanly, causing them to fray and give turf a rough appearance. Bahiagrass has an extensive deep root system and is very drought tolerant. Bahiagrass is often identified by the distinctive “V” shape (see seedhead insert) created by the two slender spiked racemes (sometimes there are three, but not often) with two rows of oval seeds. The tall seed stalks are a problem due to their rapid growth and require constant mowing in fine turf. Bahiagrass produces seedheads from June through November. Bahiagrass reproduces from seed and from short rhizomes and stolons which are so stout they are almost woody. Since old leaf sheaths persist at the base, they tend to have a woody appearance as well. Introduced from Central and South America as a forage grass in the early 1920’s. Fine turf areas, roadsides and pastures are easily invaded by this aggressive plant. Bahiagrass is found along coastal states from southern Virginia to Texas and in California.

Weed Photos: Courtesy of Dr. Lambert McCarty . Clemson University. Clemson, SC.

Herbicide Use

Mid-summer is the optimum time for a post-emergence application of metsulfuron to control bahaigrass which has invaded bermudagrass. For renovation of areas containing bahiagrass, use a glyphosate product.

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Bahiagrass Control – How To Eradicate Bahiagrass In Your Lawn

Bahiagrass is most commonly grown as forage but it is sometimes used as erosion control on roadsides and disturbed soils. Bahiagrass has excellent drought tolerance and can be grown on a variety of soils. The grass seeds prolifically and spreads into turf areas.

Unfortunately, it has a rough, unattractive appearance that can invade green lawns. Control of bahiagrass is important in lawns to minimize competition. Bahiagrass control is achieved with a two-prong method of cultural and chemical means.

Recognizing Bahia Grass

The Y-shaped seed heads it produces easily identify bahiagrass. Unfortunately, the species is at its most invasive by the time you see the seeds.

Control of bahiagrass rests on identification of the plant. The grass is mat-forming and spreads by rhizomes. It is a light green color, coarse, and spreads in tufts or clumps. Efforts to eradicate bahiagrass in sod is foiled by its consistent use in warm-season climates.

A useful bahiagrass preventer would be the suspension of its use in open settings.

Bahia Grass Control

A natural bahiagrass preventer is with cultural methods. Bahiagrass does not tolerate shade and high nitrogen soils. When the grass is found in garden beds, it may be hand-pulled but you need to be careful to get all the rhizomes.

Organic mulch over six to eight layers of wet newspaper is also useful to smother the plants. Consistent lawn mowing prevents the formation of seed heads and the further spread of the plant. Annual fertilization and proper watering techniques will keep sod healthy and help eradicate bahiagrass.

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There are numerous chemicals that can kill bahiagrass. The perennial grass is controlled with pre-emergent or post-emergent herbicides. In a vegetable garden, it is best to use a pre-emergent chemical and wait to plant. Bahiagrass control in garden beds is achieved with spot spraying of a chemical like Glyphosate. Any product with Atrazine is effective in lawns as a pre-emergent treatment. You can kill bahiagrass with Imazaquin in any setting except where food items are grown. Follow up spraying may be required with any chemical.

Bahiagrass is a perennial grass and manual removal is difficult because of the rhizomes. The best way to kill bahiagrass in most lawns is by applying a product with MSMA. If it is applied three times in seven to ten day intervals, the bahiagrass will die. Any application of chemical treatments should be consistent with the product’s instructions. The best time to apply post-emergent products on lawns is when the selected species has just begun to green up after winter.

Control of bahiagrass requires vigilance and repeated applications of treatments. Be sure to read the packaging to make sure the product will not adversely affect your turfgrass species.

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