- Author: John A Roncoroni
- Posted by: Gale Perez
“I hate crabgrass!” is a common lament I've heard from residents during my 35 years in UC Weed Science. However, four out of five times, the weed people are actually referring to is not crabgrass, but bermudagrass or dallisgrass. So why does knowing the name of the weed matter? It doesn't—unless you are trying to control it!
Crabgrass
There are two annual weed species of crabgrass: large crabgrass and smooth crabgrass. Large crabgrass, sometimes called hairy crabgrass (Digitaria sanguinalis), has leaves that usually appear grey with a hairy upper surface (Figure 1). If unmowed, the leaf sheath can grow upright to a height of 2 feet. Large crabgrass is commonly found in gardens and landscape areas.
While annual crabgrasses can be a problem, they pale in comparison to the perennial weeds bermudagrass and dallisgrass. Learn more about crabgrasses in the Pest Notes: Crabgrass.
Bermudagrass
Bermudagrass is hard to pull out and is very tolerant of both drought and mowing. The seed heads look very similar to those of crabgrass (Figure 4). Unlike the other two weeds discussed, bermudagrass can be very invasive in lawns and gardens. Learn more about bermudagrass by reading Pest Notes: Bermudagrass.
Dallisgrass
Dallisgrass is a problem in many areas because it is adapted to inconsistent irrigation and fairly close mowing; the seed heads grow almost parallel to the ground and are often missed by lawn mowers. Learn more about dallisgrass in the Pest Notes: Dallisgrass.
How do you tell them apart?
How are these weeds controlled?
Because crabgrasses are annual plants, reducing the amount of shallow irrigation helps reduce their germination and growth. In gardens, use drip irrigation, which works best when buried. In lawns, replace short, daily watering with fewer but longer (deep) irrigations. This allows the top to dry out, and encourages the deep-rooted perennial lawn species growth. To manage crabgrass, raise the height of your mower; this has been shown to make lawn more competitive.
Finally, many people use “crabgrass weed and feed” for weed control. This product is a combination of lawn fertilizer and preemergence herbicide. If applied before crabgrass emerges in your lawn, it can be very effective. However, if the weeds are bermudagrass or dallisgrass, the preemergence herbicide may control some of the emerging seedlings but will not control (and may actually increase) the infestation of these two weeds.
Proper identification and knowledge of weed biology, such as germination time and life cycle, is the first step in any effective weed management attempts. For more help identifying weeds, visit the UC IPM Weed Gallery.
- Author: John A Roncoroni
[From the Spring issue of the UC IPM Retail Nursery & Garden Center News]
Crabgrass
There are two annual weed species of crabgrass: large crabgrass and smooth crabgrass. Large crabgrass, sometimes called hairy crabgrass (Digitaria sanguinalis), has leaves that usually appear grey with a hairy upper surface (Figure 1). If unmowed, the leaf sheath can grow upright to a height of 2 feet. Large crabgrass is commonly found in gardens and landscape areas.
While annual crabgrasses can be a problem, they pale in comparison to the perennial weeds bermudagrass and dallisgrass. Learn more about crabgrasses in the Pest Notes: Crabgrass.
Bermudagrass
Bermudagrass is hard to pull out and is very tolerant of both drought and mowing. The seed heads look very similar to those of crabgrass (Figure 4). Unlike the other two weeds discussed, bermudagrass can be very invasive in lawns and gardens. Learn more about bermudagrass by reading Pest Notes: Bermudagrass.
Dallisgrass
Dallisgrass is a problem in many areas because it is adapted to inconsistent irrigation and fairly close mowing; the seed heads grow almost parallel to the ground and are often missed by lawn mowers. Learn more about dallisgrass in the Pest Notes: Dallisgrass.
How do you tell them apart?
How are these weeds controlled?
Because crabgrasses are annual plants, reducing the amount of shallow irrigation helps reduce their germination and growth. In gardens, use drip irrigation, which works best when buried. In lawns, replace short, daily watering with fewer but longer (deep) irrigations. This allows the top to dry out, and encourages the deep-rooted perennial lawn species growth. To manage crabgrass, raise the height of your mower; this has been shown to make lawn more competitive.
Finally, many people use “crabgrass weed and feed” for weed control. This product is a combination of lawn fertilizer and preemergence herbicide. If applied before crabgrass emerges in your lawn, it can be very effective. However, if the weeds are bermudagrass or dallisgrass, the preemergence herbicide may control some of the emerging seedlings but will not control (and may actually increase) the infestation of these two weeds.
Proper identification and knowledge of weed biology, such as germination time and life cycle, is the first step in any effective weed management attempts. For more help identifying weeds, visit the UC IPM Weed Gallery.
/span>- Author: Clyde Elmore, Extension Weed Specialist (Emeritus)
- Posted By: Gale Perez
We have all heard that turf grass is competitive to weeds and other plants in the landscape. There are several turf grass types grown in California. In southern California, Bermuda grass is the more common planting though Turf-type tall fesc ue is also used as well as other species to a lesser extent. Smooth and large crabgrass are the most prevalent summer annual grass weeds found in turfgrass in California. Can we devise systems using turf type, renovation (planting) time to establish a competitive, cool season, tall fescue turf and control crabgrass?
Several years ago with graduate student J. Graham Davis, and current farm advisor in Napa County, John Roncoroni, we developed experiments to study this concept. We chose different turf-type tall fescue varieties and planted them in the spring or fall at UC Davis and a university field station in Santa Clara, California. Secondly, we developed an established turf of medium vigor, tall fescue (variety Olympic) and evaluated the potential for large or smooth crabgrass establishing in different size “holes” or under three different management conditions (scalping the turf to thatch, clipping to 0.5 inches, planting and clipping again in 1 month, or removing the turf and placing clean soil in the holes.) Either smooth or large crabgrass seeds were planted in each treatment area. The turf areas were maintained to germinate and grow turf planted from seed.
Basically we found that tall fescue turfgrass planted in the fall of the year along with crabgrass at both sites established well with little or no competition from crabgrass. The older tall fescue varieties representing a more open growth habit (Linn variety) was less competitive than more vigorous tighter turf types (the improved turf-type fescues). As the fescue became more dwarf, they were less vigorous even though the culm count was high per surface area. More smooth crabgrass survived in these plots. There was more smooth crabgrass in the turf than when large crabgrass was planted in all varieties. Though there was more crabgrass establishing in the spring plantings, by the second season, crabgrass was not present in vigorous tall-fescue varieties. Smooth crabgrass was present in the open older varieties. Thus, fall planting of vigorous tall-fescue turf varieties controlled smooth and large crabgrass even if it was planted at the same time of planting the turf seed. It was less effective in spring plantings but by the second season with good management without herbicides, crabgrass was controlled.
Large crabgrass was most prevalent in large (10 cm and 20 cm) gaps. There was a significant difference in the number that germinated in the 5cm, 10 cm, and 20 cm gaps, but there was no significant difference in the number that germinated in the smaller gaps (
Take home story here is to plant and maintain a cool season turf that is vigorous. That is, a vigorous turf during the cool growing season, to maintain a vigorous turf and do not allow practices that might make “holes” in the turf to allow invasion of smooth or large crabgrass.