Poa Annua (Annual meadow grass) is a common grass that is part of the Poaceae family. This family of grass provides staple foods, from domesticated cereal crops such as maize, wheat, rice, barley, and millet, to feed for animals.
For some, Poa is a turf manager’s daily grass; for others it may be their enemy. It all depends on you personal prefrence, topgrapthy and available resources. Some choose to embrace Poa and use it to thier advantage; others decide to control it. On today’s educational card, we’ll be treating it as a weed’ Like most weeds, it’s really about getting ahead and then continuing to follow processes of management. Even the best looking swards of grass can be susceptible to being invaded by this weed grass, and controlling it, preventing it and eradicating it can sometimes be a bit of a fine art which can cause many a headache in the process. Here we give you a few of many options that may work for you. To prevent, you may choose to use pre-emergance to kill the poa as it trys to germinate.
How to recognise annual meadow grass
Annual meadow grass is usually easy to identify. The youngest leaf will appear in a folded shape. There are no auricles at the base of the leaf, and the underside of the unribbed leaf is matte and often pale green in colour. This colour difference is often clearly visible in a field. Furthermore, Poa annua has a long and milky-white ligule. In a field, annual meadow grass can easily be identified by its abundant seed formation. After all, it flowers year-round. The leaves are unribbed, which means that they are soft and wavy.
Low wear tolerance
The wear tolerance of annual meadow grass is moderate to low, partly for reason of its shallow roots. This means that the grass is easily kicked or hit away, which may result in many bare spots that will significantly reduce the quality of play on a sports field or golf course. In addition, annual meadow grass has an unattractive appearance.
Appearance of annual meadow grass
The appearance of annual meadow grass is unattractive. Poor nutrition will change its mid-green colour to a lighter green. The colour will change in dry conditions and when there is insufficient moisture in the top layer, annual meadow grass will immediately turn light green and then begin to flower profusely.
Early germination
Annual meadow grass germinates at soil temperatures as low as 7 – 8 °C. When the fields have been played bare, annual meadow grass will often be the first to appear as most grass mixtures germinate at higher temperatures. This means that the bare patches are filled in fast and the good thing is that there is a green field, which is always better than nothing. However, this benefit does not outweigh the disadvantages.
Less sustainable
In recent years, sustainable control of grass has increased significantly in importance. Annual meadow grass needs large quantities of water and fertiliser. Sustainable grass management is not possible with annual meadow grass. Environmental damage is therefore the result of this grass plant.
A major stress factor for annual meadow grass is drought. Its reaction to drought is to flower profusely, and all these flowering tufts don’t do much for the visual appeal of the field. Stress factors cause annual meadow grass to reproduce. It will try to maintain itself by forming seed heads. When this happens a lot, there is no stopping annual meadow grass and it will appear everywhere.
Annual meadow grass is very sensitive to diseases. Fusarium and Dollar Spot are the most occurring diseases in fields that contain annual meadow grass. These diseases can seriously damage a field.
Tolerates close mowing
Annual meadow grass can flower even at a mowing height of 0.5 cm or lower and deliver germinable seed, and several times a year! Many grasses do not survive close mowing, but annual meadow grass does.
Thatch build-up
Naturally, extended rainfall leads to the formation of a wet top layer. A wet top layer is more sensitive to compaction than a dry one. Wet conditions hinder the decomposition of dead stalks and roots, and this results in a thick thatched, matted layer. There is now a situation in which annual meadow grass can grow with ease because of its shallow roots. The thatch prevents water from reaching the unsaturated areas, which in turn may lead to water problems.
Control options
Verti-Cutting
Done properly, this is one of quickest and most effective ways of removing the seed and the stalks from within your sward. Verti-cutting allows for deep penetration through the sward to the soil and removes various unwanted weeds, weaker grasses and invasive species, leaving you with a clean profile. Doing this thoroughly is key to its success. Where possible, cut in a diagonal across the usual cutting direction as pictured. Usually 2-3 passes will have removed 95% of the problematic weed growth using a verti-cutter or similar machine. After this, you should mow to collect remaining debris. Following this quite heavy process of verti-cutting, if the sward looks thin, this may be the perfect time for an over seed if you have the means to do so. Note that it’s possible that after verti-cutting you may find some standing poa seed heads; using a rotary or and a power brush is more effective at collecting seed heads than cutting with a cylinder mower.
Fraise/Koro Mow the Surface-End of Season
Koro’ing a surface is quite expensive and some would see as an extreme measure to remove annual meadow grass. Ultimately, though, without it, you will never really regain control of a healthy grass growth as weeds will find it easy to germinate within the sward. This problem will continue if the sward is already saturated with Poa and other weeds. In many cases, the most effective way for you to eradicate the problem is to koro the surface and start afresh. if you do go down this route, you’ll need to take action once every three years or so, by hiring a specialist contractor. This will remove the shallow rooted weed grass, and if you’re lucky, the process will leave the ryegrass to regrow back, but you shall also need to over seed. This is also a great way of removing thatch, and many sports clubs do this on a yearly basis.
Other Annual Meadow Grass Control Options?
1-Starving it out – as Poa is shallow-rooted, this is an option that may be worth looking into, but unless thorough renovations and seeding is done, you could end up with additional problems and maybe more Poa.
2-We all hear of groundsmen carrying out total weedkilling and removing all vegetation from their squares. The concern would be leftover vegetation and organic matter so take this into account.
3-Use of a growth regulator will stop Poa from seeding on existing plants, so a process of removal will still be needed. PGRs to be applied by a certificated spraying operator.
4-High phosphorus levels are said to contribute towards high levels of Poa. Annual soil nutrient testing is the only way of monitoring and managing this. Testing usually takes place when the plant is more dormant i.e. winter.
5-Use of a good scarifier to a semi “kind-of” effect, meaning it won’t completely remove the top profile, but done enough times in enough directions, it will remove the vast majority of the weed grasses and thatch.