Crab Grass

[SkunkedAgain]

Wow - maybe I'll finally have to start spraying chemicals on my lawn. We've never had a problem with much of anything before, but this year a crab grass explosion has hit our yards and many of the lawns on our block. In a few weeks time, our backyard has gone from none to roughly 30% crab grass!

Do I really have to start using all of these broad-leaf preventers or are there alternatives? What can be done this summer/fall?

[reinhard1]

i'm having the same problem. i will be interested in the info. also. thank and good luck.

[Tom7227]

based on a lot of the info on this HSOforum I used a product from Lesco that contains Dimension. I am amazed at how few pieces of crab grass I have, and they all seem to be on the edges where I didn't put down the stuff.

I have used some past emergent stuff about this time of the year in the past. The best solution I've found for this time of the year however is a blow torch. Literally toast them before they release the seeds. It may be too late or there may be too much for you to use it this year. You end up with some brown holes in the lawn but you also don't have seeds for next year.

[SandBayFishCamp]

The best approach is to put down a pre-emergent crab grass preventer in the spring, around the time lilacs are blooming.

[Powerstroke]

Prevention is the key. The easiest and most effective way is to apply a pre-emergent in the spring. It kills the sprouts before they hit the surface. WOrks like a charm and super easy.

Post-emergent can work (spraying large plants) but it is expensive and needs to be timed right.

[hotrod1]

I just applied Momentum Q last week at work for all the grassy weeds and broadleaf weeds. I was worried about the timing of the application being it is best to apply around the begining of July or end of August but took care of about 90% of the crabgrass and clover.

Cost was about $100/acre.

If you have just grassy weeds like crabgrass, Drive will work great for you.

[LwnmwnMan2]

This year is going to be bad for crabgrass, even with a decent pre emergent.

With all of the rain we've been having, it's broken the chemical down quicker than normal.

For next year, I would recommend a split application of pre emergent.

Meaning for both the first AND second applications, use a decent product.

Personally, I would recommend the Dimension that Tom mentioned before.

Also, we had quite an early spring this year, so when the chemical barrier is still in force at this time of year, in a "normal" year, we're coming to the end of its viability.

When spreading along curblines, I always put down a double dose, as that's 90% of where you're going to have issues down the road.

A straight broadleaf herbicide will do nothing against crabgrass. It has to be labeled for crabgrass prevention.

Also, be sure you're talking about crabgrass. I've seen A TON, and I mean a TON of annual bluegrass pop in the last 2 weeks, more than I've ever seen, at least as far as I can remember.

Crabgrass looks a bit like a king crab turned upside down. 1 main plant with bunches of "legs" or stalks coming off of it.

Annual Bluegrass pretty much looks like regular grass blades, but wider and a light green color, but for the most part, each blade is seperate.

[IcePro]

LwnmwnMan2...

Annual Bluegrass pretty much looks like regular grass blades, but wider and a light green color, but for the most part, each blade is separate.

This description sounds more like quack grass than annual bluegrass. Annual bluegrass or annual poa does not have wider blades.

I have seen a lot of quack grass in the last couple of weeks in neighbor’s yards. I have been battling poa for a few years and it is not wider than KBG.

[LwnmwnMan2]

Here is an article from UC Davis that I use when talking with customers... But yes, I agree, it could be either one. Pics would be helpful, although neither are going to be easy to rid.

Annual Bluegrass / Poa Annua

Annual bluegrass, Poa annua, is one of the most common weeds of turf, ornamental plantings, and gardens in the United States. It is native to Europe but is distributed worldwide. Commonly referred to as "Poa," it is a particular problem in golf course greens and fairways throughout the world. It also can be a weed in vegetable crops and agronomic crops. Though present in tree and vine crops in California, it is usually not a significant problem. The genus Poa consists of about 200 species worldwide. Their typical "boat-shaped" leaf tips, which curve up like the bow of a boat, are a distinguishing characteristic of the genus.

Three members of the genus Poa are commonly found in turf. Kentucky bluegrass (Poa pratensis) is a common cool-season turf species that is well adapted to cool, well-watered sites such as coastal and intermountain areas. Rough bluegrass (Poa trivialis) is a less desirable turf/weed species that does well in moist, shaded areas, but lacks heat and drought tolerance. Annual bluegrass is a weed species that, unlike Kentucky and rough bluegrass, is able to survive low mowing heights (less than 1 inch) and still reseed. A fourth species, bulbose bluegrass (Poa bulbosus) is sometimes found as a weed in northern California turfgrass.

IDENTIFICATION AND LIFE CYCLE

Annual bluegrass is a misnomer because there are two plant types of annual bluegrass: a true annual (P. annua var. annua) and a perennial type (P. annua var. reptans). While the two types are not easy to distinguish from each other, the annual type is more upright in its growth habit and produces more seed than the lower-growing perennial type. The annual type also tends to produce a higher percentage of dormant seed. The perennial type produces seed that germinate readily under optimum conditions. Depending on the site there may be a predominance of one type or a mixture of both. The perennial type is common in such sites as golf course greens, while the annual type may be more common in lawns and parkways (although both types can be found in either of these situations).

Annual bluegrass starts germinating in late summer or fall as soil temperatures fall below 70°F. It continues to germinate throughout winter, allowing several flushes of germination at any one site throughout winter. Annual bluegrass grows to a height of 6 to 8 inches when left unmowed. It has light green, flattened stems that are bent at the base and often rooted at the lower stem joint. Leaf blades are often crinkled part way down and vary from 1 to 3 inches in length with typical Poa, boat-shaped leaf tips. The inflorescence (flowering structure) is a terminal panicle that varies from 1 to 4 inches in length. Seed head initiation can start as soon as plants are 6 weeks old in early fall and continue until early summer, but most seed heads are formed in spring.

The annual form of annual bluegrass is a rapid and prolific seeder. Each small plant can produce about 100 seeds in as few as 8 weeks. Viable seed can be produced just a few days after pollination, which allows the plant to reseed even in frequently mowed turf. The seed is amber colored and about 1/16 inch long.

Annual bluegrass has a fairly weak and shallow root system and needs available moisture from rainfall or frequent irrigation to survive. It grows well in moist areas in full sun. However, it can also do well in semi-shaded conditions. Annual bluegrass also can grow in compacted soil conditions. In coastal regions or in moderate temperature areas where turf is frequently irrigated, annual bluegrass may persist all year. In warmer areas, it usually dies in summer.

IMPACT

Annual bluegrass can be a major weed problem for turf and landscape managers. In turf it forms a weak sod that provides poor footing for athletic fields and golf courses. In addition, unsightly seed heads of annual bluegrass reduce the aesthetic quality of the turf. Because of its winter growth habit, it is more competitive than warm-season turf cultivars (common bermudagrass, zoysiagrass, and hybrid bermudagrass) during the cool season. This accounts for the severity of annual bluegrass invasions during winter. Although annual bluegrass can be a problem in all turf species, it is most obvious in bermudagrass and bentgrass. In the cool season, annual bluegrass grows faster than warm-season turf cultivars, which gives infested turf an undulating or irregular surface in as little as 2 days after mowing.

When annual bluegrass infests ornamental plantings, it forms a dense mat that can reduce the vigor of desirable landscape plants by reducing available nutrients in the soil surface. Because dense seedling infestations can occur, hand-pulling or hoeing to remove annual bluegrass is often futile as new flushes of seedling plants germinate after the older seedlings are removed. Hoeing or hand-weeding must be done frequently to be successful. Thus, controlling it manually is very expensive in commercially maintained landscapes and not always successful. In established woody shrubs and trees, annual bluegrass probably has little detrimental effect but may be aesthetically distracting.

Once a few annual bluegrass plants become established in turf or ornamental areas, spread can be rapid because of its prolific and rapid seed production. Seeds are spread by mowing, foot traffic, birds, and cultivation.

MANAGEMENT

A primary method of control is the prevention of new infestations. Mowers and cultivation equipment should be thoroughly cleaned before moving from infested to weed-free areas. If solitary plants of annual bluegrass are found, they should be removed before seed production starts. Isolate small infested areas until control can be accomplished. Maintaining turf and ornamental areas properly assures their maximum vigor, which helps these plantings become as competitive as possible and slows invasion of the weed. Dense turf and ornamentals shade the soil surface, making the establishment of annual bluegrass seedlings difficult.

Overwatering, especially in shady areas, will predispose turfgrass to annual bluegrass invasion. Use deep and infrequent irrigation to discourage the development of the shallow-rooted annual bluegrass populations. Withhold water until the desirable species are beginning to show drought stress. Avoid fertilization and don’t aerate turf during the peak of annual bluegrass germination. Avoid cultural practices and use patterns that might tend to promote soil compaction.

Turfgrass

No single control procedure has been successful in controlling annual bluegrass in turfgrass. Early removal of solitary infestations has been successful when practiced diligently. Open spots should be overseeded to establish a vigorous turfgrass. Removal of grass clippings may help reduce the number of seeds that reach the soil. Check the irrigation output to be sure shady areas are not getting too much water.

Preemergent herbicides such as benefin, bensulide, DCPA, dithiopyr, oxadiazon, pendimethalin, and prodiamine have been successful in limiting germination of annual bluegrass, but they must be applied before weed seeds germinate to be effective (Table 1). Pronamide is also available for preemergent use, but it can only be applied to warm-season turf. These herbicides (with the exception of pronamide) will not control emerged plants. To limit bluegrass germination during winter, apply preemergent herbicides in late summer or early fall when soil temperatures drop below 70°F. Where the perennial type is a large component of the bluegrass population, preemergent herbicides will be of little or no benefit.

[lindy rig]

Looking ahead for next year... Can you use crabgrass preventer in a vegetable garden? (obviously just putting in established plants)

[reinhard1]

thank you all for the time you took to inform people like me who knows little on the subject. thank you and good luck.

[SkunkedAgain]

You know, my wife said that it was crab grass and I believed her because she knows a lot more than me about plants and gardening. However, I think that it may be the bluegrass. I'll take a picture and post it. Thanks for all of the info everyone!

[SkunkedAgain]

Here are two pictures, a lawn shot and a close up:

[lindy rig]

That does not look like crab grass. Looks like quack to me.

[Tom7227]

Intersting question. Maybe after eating some of the food your swimmers would be all kaput and you'd not have to worry about having any kids for a while!!!

[hotrod1]

Let some grow to produce a seedhead and then post a picture if you are still unsure.

I am going to guess either Foxtail, Sandbur, or Crabgrass.

[echo2010]

Mine looks a lot like that..... but is in clusters... or bunches..

[LwnmwnMan2]

If it's in clumps, are the leaves smaller, all tucked close together? Or does it have "stalks" of grass spreading out like an upside down spider / crab?

[echo2010]

Mine is light green in color. The blades are wider the the other grass and it is kind of ....spreads to the side... like fingers out.... in areas where it got into my rocks... it does look like stalks... like little corn stalks