12th January - Blowfly Grass - A Case Study

Briza maxima, Quaking or Blowfly grass has been my most difficult grass pest. It is native to the Mediterranean. It is a glabrous annual, usually 20-60 cm high; panicle 1-sided, simple or slightly branched, 2-8-flowered;spikelets 10-20 mm long, drooping, on filiform pedicels, 9-17-flowered, golden, 8-10 mm broad at the base; glumes dark-brown or purplish.

Blowfly grass germinates after the April rains. It grows quite slowly through the colder months and becomes quite visible by August. In September-October it forms a head. In November-December its seeds mature. As its seeds mature its pedicel lengthens. At this stage the spikelets dance around a lot and hence its common name.

By the time the seeds are ripe its pedicels are very long. The spikelet articulates above the glumes. If an animal or machine moves through the grass at this time the seed heads break off and are fired a considerable distance. This means blowfly grass can spread very quickly.

As with any annual, its control simply entails stopping it from seeding. One advantage with annuals is that they rely on germinating, maturing and seeding as quickly as possible. They do not need to spend time developing a root system to tide them over Summer.

There are therefore three stages in its growth. The first stage is before flowering is visible. The second stage is after flowering is visible but before the seeds are viable. The third stage is after the seeds are viable.

Control in the first stage is simply by removal of the plant. It doesn't need to be disposed of but I have found this helps me to get a better result since I can then see where I have been. Of course it is necessary to be able to identify them but this is always necessary before any plant is removed. It is important to remove the whole plant or it will simply grow multiple stems and produce more flowers. There is no point in mowing at this stage as it will simply increase their capacity.

The second stage is much more visible and probably the easiest time to remove the plants. It is important to remove the whole plant. Every gardener knows that the best way to get a second crop of flowers is to harvest the first crop. Unless the season ends abruptly it will simply produce a second crop. Mowing can be helpful at this stage however my article on mowing may help with this decision.

The third stage gives a opportunity to finish off the job. Providing the crop is thin enough to allow removal of the seed heads without firing them everywhere, they can be plucked off and disposed of reasonably easily. Mowing again with a catcher can be helpful, but again refer to my article on mowing.

Providing all seeds are removed a few years of intense and complete removal will reduce the problem to an occasional walkthrough. I will say a bit more about this under maintenance.