How to get rid of nuisance weeds Pink and Creeping woodsorrel
This time of year is made less glorious by all the plant problems that are rearing their ugliness and keeping us away from the fun stuff like planting new beds, redesigning old ones and just generally spending as much time as possible in the nurseries.
One such problem that pops up every spring and seems like it just doesn’t go away is oxalis. In fact, that was the subject of my friend’s question posed last week.
“I have clover coming up all through my yard. The tiny pink flowers are so cute, but it’s really getting out of control!”
I hated to tell her, but clover and oxalis are commonly mistaken for one another. The leaves look similar, but oxalis lacks a stipule (a small usually leaflike appendage at the base of the stalk that attaches a leaf to a stem). In short, you’ll need a magnifying glass. More apparently, oxalis generally has a more pronounced indentation at the top of each leaflet.
There are over 800 different species of oxalis worldwide, eight of which have been documented in Florida. Since these pests grow year-round in Florida, we need to learn about the few most common in our lawns.
The oxalis plants with pinkish flowers belong to Pink woodsorrel (Oxalis debilis Kunth). It was introduced to the US as an ornamental plant and was documented in Florida as early as 1930. Within this species, there are two varieties, neither of which is native. Both are perennial bulbous plants from the mountains of South and Central America. What was once an ornamental is now a weed that has escaped into the landscapes of several southern states.
The leaves, flowers and stems of oxalis are edible and have a tart, lemony flavor. The roots taste nutty. But before adding them to this evening’s salad, understand their oxalic acid content (like that in spinach, broccoli, grapefruit and rhubarb) could be harmful for those inclined toward kidney stones and calcium deficiency.
Despite these culinary attributes, once pink woodsorrel is established in the lawn it is a pain in the back to get rid of. The more you pull the plants out the more they multiply. These enemies of good posture reproduce by bulbs and seeds. If you leave a bulblet behind it will grow into a plant.
Also popping up in yards and potted plants everywhere is Creeping woodsorell (Oxaslis corniculata L.) It has delicate yellow flowers with five petals and often reddish or purplish leaves. It has a more spreading habit and produces stolons (aboveground plant stems that root at nodes). This one is a Florida native weed and will be found throughout the state, especially in undisturbed natural areas. The nuisance factor of Creeping woodsorrel is it can form dense mats, competing for water, food and light with our cultivated plants.
For both types of oxalises, hand weeding, if you’re up to it, is the first approach to weed management. Do this when the soil is moist to ensure that all parts of the plant (roots, rhizomes, bulblets, etc.) are removed. Collect all debris and leave nothing behind. If the seedlings are
young, shallow mulching can help suppress germination by blocking the light.
If that doesn’t work, there are many preemergent herbicides labeled for landscape use that can be successful. The UF publication, “Biology and Management of Oxalis” (https:// edis.ifas.ufl.edu/publication/EP514) includes tables listing the commercial names of a variety of products.
There are many postemergence herbicides that provide effective control of oxalis. Products that contain glyphosate, glufosinate, diquat and pelargonic acid among others are available at local nurseries and big box stores. Both systemic and contact herbicides will work. Postemergence herbicides are most effective when the weeds are small and actively growing. Be sure that the product you select lists oxalis as one of the plants the herbicide is designed for.
Whenever using chemical controls, follow the label instructions and take all safety precautions such as wearing masks and gloves.
There are few things, plants particularly, that are intrinsically bad without any positive attributes. So it is with oxalis.
As published in a blog from Wild South Florida, “People around the globe have found yellow wood sorrel medicinally valuable … The Cherokee used it internally and externally to treat hookworms, sore throats, to stop vomiting, as a cancer drug and with sheep’s grease, to treat sores. The Cherokee and Iroquois used it as a food; the Menominee made yellow dye from it.”
This little factoid is nice to know but I’m sure it wasn’t what my friend wanted to hear.
Paula Weatherby is a Master Gardener Volunteer with the Duval County Extension Service and the University of Florida/IFAS. For gardening questions, call the Duval County Extension Office at (904) 255-7450 from 9 a.m. to noon and 12:30 to 3:30 p.m. Monday-Friday and ask for a Master Gardener Volunteer.