Crabgrass and henbit are common weeds found in lawns, gardens and ornamental plant beds. Although they may occur together in the same areas, they are very different types of weeds. They also require different types of herbicides for effective control. As with any type of lawn or garden chemical, follow the safety and application instructions on the herbicide label carefully.
Crabgrass (Digitaria spp.) is a summer annual “grassy” weed that reproduces by seed, with the seeds germinating in spring. Crabgrass thrives in warm weather and produces seeds from midsummer through fall. Crabgrass tends to die off by the first frost or freeze in fall. Over-watering and under-fertilizing your lawn can promote crabgrass growth. Mowing your lawn at the proper height for your type of turfgrass can reduce crabgrass seed germination and establishment as well.
Unlike crabgrass, henbit (Lamium amplexicaule) is a broadleaf weed that’s a winter annual, meaning that it reproduces by seeds that germinate during fall or winter. During warm weather in winter, henbit seeds will germinate, but it usually emerges in spring and dies off when temperatures warm during late spring or early summer. Henbit is highly invasive, often emerging in thin turf areas or landscape and garden beds. Henbit enjoys shady areas and lots of soil moisture.
To get rid of crabgrass in your lawn, you might use pre-emergent herbicides like bensulide, oryzalin or pendimethalin. These chemicals are found in products like Bensumec, Pre-San, Surflan, Weed Impede, Pendulum, Pre-M and Scotts. Dithiopyr, oxadiazon and prodiamine are also effective herbicides for crabgrass and found in the products Dimension, Preen, Ronstar and Barricade, but in most regions they’re reserved for professional use only. The best post-emergent herbicide for getting rid of crabgrass in your lawn is quinclorac, sold as Drive, Trimec Crabgrass and Momentum. Dimension and Preen are used by professionals for crabgrass in lawns.
For henbit in lawn areas, you can use a three-way herbicide containing the chemicals dicamba, mecoprop, or MCPP, and 2,4-D. This type of herbicide is marketed under the brand names Ferti-lome Weed-Out Lawn Weed Killer with Trimec, Bayer Advanced Southern Weed Killer for Lawns, Spectracide and Southern Ag Lawn Weed Killer with Trimec. These brands of three-way herbicides are typically safe for Bermuda, zoysia, St. Augustine, centipede and tall fescue grasses. Atrazine is another herbicide to control henbit in centipede and St. Augustine grass lawns. Metsulfuron -- sold as Manor or Blade -- is another post-emergent herbicide option for henbit in lawns, but it’s not registered for use in tall fescue.
If you have crabgrass in your garden or other landscape areas, you can use the pre-emergent herbicide chemical trifluralin, which is sold under the brand name Vegetable and Ornamental weeder. You might try the post-emergent herbicide called sethoxydim plus oil, sold as Fusilade, to get rid of crabgrass in garden or non-lawn areas. Another post-emergent herbicide for eradicating crabgrass in non-lawn areas is fluazifop, sold under the brand names Ornamec, Poast and Grass Getter.
To get rid of henbit in garden or non-lawn landscape areas, try herbicide products containing glyphosate, which is found in Roundup, Quick Kill, Eraser, Maxide, Bonide Kleenup and many other widely-available weed killers. Glyphosate is a non-selective or broad-spectrum herbicide, meaning that it will kill nearly all plants it comes into contact with. So you should apply glyphosate herbicides directly to the henbit weeds and be careful not to get it on any nearby desirable plants.