Creeping woodsorrel (Oxalis corniculata), often simply called wood sorrel, is one of the most persistent weeds in the garden. Here is how you can combat this annoying weed.
The creeping woodsorrel originates from the Mediterranean region and is considered a neophyte or archaeophyte in Central Europe, as it has been present specifically in the wine-growing regions for centuries and is considered naturalized. Creeping woodsorrel is a typical example of plants that benefit from climate change. Due to its Mediterranean origin, it is well adapted to longer periods of drought and is spreading further and further to in previous days colder region because of increasingly dry, hot summers and mild winters. The plant wilts during drought and retreats into its fleshy taproot. As soon as the climate then becomes wetter again, it sprouts anew. The reddish-brown leaves are also an adaptation to strong sunlight.
Creeping woodsorrel has also developed an ingenious strategy for spreading its offspring: It flings its ripe seeds several meters when the capsules pop open. The seeds are also carried away by ants, they are keen on the fatty appendage, the so-called elaiosome. In addition, the creeping sorrel spreads in the nearby environment by root runners. In the garden, wood sorrel is often found in lawns and paving joints, but sometimes in flower beds as well, provided enough sunlight reaches the ground. It does not thrive in very shady locations.
How to get rid of creeping woodsorrel?
Check pot root ball for creeping woodsorrel.
In most cases, creeping woodsorrel is brought into the garden by newly purchased plants. Therefore, check the surface of each pot ball and pluck out horned wood sorrel along with its taproot before placing the new plant in the bed. To exclude the possibility of further seeds in the potting soil, it is best to completely remove the top layer of soil with few roots and dispose of it in the household waste.
How to remove creeping woodsorrel from beds?
Once creeping woodsorrel has established itself in the garden, it is extremely troublesome to combat it. Therefore, become active as soon as you discover the plant: as long as it has not yet flowered, it cannot spread further, at least via seeds. Chop off the plants above ground in the bed with a sharp hoe or, ideally, pluck them right out of the ground with their roots. However, the latter is only possible on very light, humus-rich soil, in loamy soil, the root is usually so firmly anchored that it breaks off at ground level.
If the creeping woodsorrel forms individual closed areas, it is worthwhile to loosen the soil piece by piece with a small hand fork and then pull out the plants together with the root. Once you have cleared the bed of the plant, you should immediately plant larger open areas with perennials or ground-cover plants so that the soil soon disappears completely under the plant cover. In addition, you can cover the soil about 5 cm (2 in) high with bark mulch, to suppress the new sprouts.
How to control creeping woodsorrel on paved areas?
The heat- and drought-loving plant is particularly fond of settling in pavement joints. Here, of course, it can be controlled in the traditional way with a good joint scraper, but this is quite tedious. Faster is the flaming with a special device. Hold the gas flame on each plant for only one or two seconds at a time, that’s enough to destroy the cell structures, even if the creeping woodsorrel initially shows little outward sign of damage. It dies above ground within the next few days. However, heat does not allow for root-deep control, so flaming must be repeated several times a year.
What to do about creeping woodsorrel in the lawn?
It is often recommended to simply lime the lawn if it is riddled with creeping woodsorrel. However, this doesn’t do much good, because creeping woodsorrel is by no means an acidophile. It also grows without problems on calcareous soils. Nevertheless, the main thing to do is to improve the growing conditions of the lawn grasses if you want to combat creeping woodsorrel. So, first measure the pH of the soil and sprinkle garden lime as needed. After that, keep your lawn well supplied with nutrients. About 14 days later, when the green carpet is well grown, renew your lawn by mowing it down deeply, scarifying thoroughly and reseeding completely. Where the creeping woodsorrel is particularly dense, after dethatching, you should peel the entire turf flat and apply some new topsoil. What creeping woodsorrel does not like is very wet soil. Therefore, water the newly seeded lawn generously as needed until the grasses form a closed turf again.
Control with herbicides?
Whether to fight creeping woodsorrel in the garden with chemical herbicides, each gardener must decide for themselves. Even if these are agents that are approved for home gardens, their use is generally not recommended. The situation is different with biological products based on acetic acid or pelargonic acid. However, they only cauterize the above-ground part of the plant, so the taproot will resprout after a certain time. In addition, it is important to note that herbicides in the bed do not treat only the unwanted plants, they do not distinguish between “friend and foe”. For lawns, on the other hand, there is a chemical preparation that eliminates dicotyledonous plants, but has no effect on monocotyledons, which include all grasses. By the way, the use of herbicides on paved areas is prohibited in many countries.