Yellow Woodsorrel

About

Yellow woodsorrel is a small, shamrock-leaved native with little yellow flowers that pops up in lawns, beds and containers. Its seed pods fling seeds several feet, so one plant quickly becomes many.

Also called common yellow oxalis, oxalis, wood sorrel, sourgrass, lemon clover

How to identify it

Look for

Each leaf has three heart-shaped leaflets that are often partly folded along the middle. Upright, sometimes hairy stems are green to purplish, and the flowers are bright yellow with five petals. Slim, upright seed capsules about half an inch to an inch long split open and shoot out seeds.

Look-alikes

White clover and black medic have rounded, not heart-shaped, leaflets.

Where it grows

Lawns, garden beds and moist, fertile soil, though it tolerates many conditions.

When

It flowers from spring through summer, roughly March or May through September depending on the area.

How it spreads

Exploding seed pods that throw seeds up to about 12 feet, plus slender underground stems.

Most common in

What to do, gentlest first

Start at the top. Weed killers are a last step; always read and follow the label.

1. Stop it before it seeds Prevent

   Keep turf thick and remove plants before they have a chance to spread seed.

2. Pull early and often By hand

   Pull or dig plants when the soil is moist, getting the underground stems, and do it before the pods ripen.

   Pulling after pods form can scatter seed.

3. Mulch beds Barrier

   A 2- to 3-inch mulch layer in beds keeps flung seeds from rooting.

4. Vinegar on young plants Organic spray

   Horticultural vinegar kills small seedlings; bigger plants often regrow.

   Strong vinegar (over about 11% acetic acid) can burn skin and eyes, so wear gloves and eye protection. It browns any leaves it touches, grass included.

5. Pre-emergent plus spot sprays Conventional spray

   In lawns, a dithiopyr or isoxaben pre-emergent stops new seedlings, and triclopyr or a 2,4-D/MCPP/dicamba product can be spot-sprayed on actively growing plants.

   Read and follow the label. Many lawn weed killers also harm vegetables, flowers and shrubs, so don't let spray drift into beds, and keep dicamba products off the root zones of trees and shrubs.

Uses, wildlife and pets

Edible?

UMN and NC State say the leaves, flowers and pods are edible with a sour, lemony taste, but eat only small amounts because of oxalic acid. Pick only from unsprayed ground.

Not 100% sure? Don't eat it. Never pick from ground that may have been sprayed, or along roads and railways.

Pets

Toxic to dogs, cats and horses (ASPCA, listed as Oxalis spp.): it contains soluble oxalates, and serious problems usually need a large amount eaten.