Khakiweed

What is khakiweed?

Khakiweed is a mat-forming perennial in the amaranth family that came to the United States from Central and South America. It is a turf weed across the southern United States and also shows up in pastures and along roads. khakiweed identification comes down to three things: a flat mat of hairy, often reddish stems; opposite, glossy leaves that are frequently mismatched in size; and stiff, spiny white flower heads tucked right into the leaf joints that turn into prickly burs.

It is a problem for two reasons. First, the dense mat crowds lawn grass and leaves the turf thin. Second, it is tough to kill: a deep woody taproot and a thick waxy coating on the leaves make it highly drought resistant and make it harder for herbicides to get in, and stems root as they go, so plants regrow from fragments. Add burs that ride out of the yard on pets, shoes and equipment, and one patch easily becomes several.

Khakiweed identification: what to look for

Look closely at the leaf joints along a stem. The giveaway is the cluster of stiff, chaffy bracts around the tiny white flowers, which feel prickly when the plant matures. Then check the root: a hard, woody taproot going straight down tells you this is not a simple summer annual.

• Leaves: Opposite and smooth-edged, roughly 1/2 to 2 inches long, often one larger than the other. Prominent vein underneath; older leaves glossy from a thickening wax layer.
• Stems: Heavily branched and spreading flat; green, brown, reddish or purple, finely hairy, rooting at the nodes.
• Flowers: Tiny, white and stalkless, set in the leaf joints singly or in twos and threes, each surrounded by spiny bracts up to about 1/5 inch long.
• Burs: The bracts harden into small burs that ripen in fall and stick to fur, socks and tires.
• Roots: A deep, woody taproot that is hard to pull and lets the plant ride out drought.

Where it grows in the United States

In the United States, khakiweed is documented in Florida, Georgia, Alabama, Texas and California, and Extension specialists in New Mexico and Texas publish guides for it. Outside the US it grows in Cuba, Jamaica and eastern Mexico and has spread to parts of Asia, Africa and Australia.

It shows up in turf, pastures and roadsides, most often on sandy soil. Its waxy leaves and deep taproot make it very drought tolerant, and seeds usually germinate after spring or summer rains.

Khakiweed look-alikes

A few plants get mixed up with it:

• Spotted spurge (Euphorbia maculata): Another flat summer mat in lawns, with opposite leaves. Spurge leaves usually carry a reddish spot, the stems bleed milky sap when broken, it does not root at the nodes, and it is an annual with no spiny burs.
• Prostrate spurge (Chamaesyce humistrata): A close relative of spotted spurge that, like khakiweed, roots where its stems touch the ground. Check the leaf joints: prostrate spurge has none of khakiweed's spiny, chaffy flower heads or burs.

How to get rid of khakiweed

Pulling, digging and mowing: Hand removal can work on scattered plants, but only if you get as much of the root system as possible. Follow the taproot down with a weeding tool and pick up stem pieces, since rooted nodes and fragments can regrow. Work before fall so you are not spreading ripe burs, bag the plants, and clean shoes, tires and mower decks before moving to clean areas.

Cultural control matters most, because the right conditions keep it from coming back.

• Keep turf dense; healthy grass shades the soil and leaves less room for seedlings.
• Mow at the recommended height and never take off more than a third of the blade at a time.
• Water deeply and less often instead of lightly several times a week, which encourages weed seed to germinate.
• Fertilize and lime based on a soil test so the lawn can fill thin spots.

Herbicides: Expect to treat more than once. Texas A&M AgriLife reports no preemergence products labeled for khakiweed; isoxaben may help if applied as seeds start germinating, around soil temperatures of 60 to 70 degrees F, and watered in well. For established plants, active ingredients with activity include 2,4-D, MCPP, MCPA, carfentrazone, dicamba, metsulfuron, triclopyr and fluroxypyr, and products combining two or more are more likely to work. In research, two metsulfuron applications about four weeks apart gave the most consistent season-long control. Start in spring while plants are small, growing and the soil is moist, then follow up about four weeks later. Because of the waxy leaves, add a non-ionic surfactant if the label calls for one. Glyphosate kills khakiweed but also any grass it touches. Metsulfuron can damage trees and shrubs if it reaches their roots, and most of these products can delay spring green-up of warm-season lawns; St. Augustinegrass is especially sensitive. Use only products labeled for your site and grass type; the label is the law. If you hire someone to spray, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Keeping it from coming back

Burs are how khakiweed moves. Stop plants before they set burs in fall, and keep pets, boots, tires and mowers from tracking burs out of infested spots.

A thick, well-fed, properly watered lawn leaves little room for seedlings. On dry, sandy sites, scout in spring after rains and deal with young plants while they are small.

Questions we get about khakiweed

Similar weeds

Spotted SpurgeEuphorbia maculataBurcloverMedicago polymorphaChamberbitterPhyllanthus urinaria