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I have exciting new grass seedlings sprouting, some weeds appear to be gaining:

Oxalis in new seeded lawn How far do I have to pull Oxalis to kill it?

My basic questions:

  1. Is it better to manually pull the oxalis, or let the grass try and compete?

  2. If I pull, how much do I have to get out? Is it better to wait for the plant to grow big and easy to pull?

  3. As an experiment I created a cardboard ring to protect the grass, and sprayed Glyphosate carefully. The clover turned sort of yellow but that's it. What should I expect?

  4. As an experiment, I use a "natural" weed killer. This rots the leaves and stems the same day (much faster than the Glyphosate). I used "EcoLogic" a concoction of rosemary oil and sodium laureth sulfate (sodium lauryl ether sulfate ).

The seed bed was prepared by mechanically removing the turf, watering for 2-3 weeks to sprout weeds, mechanical removal, then 2 inches of fresh soil and a high quality deep rooted grass seed variety. The garden all around has clover everywhere on all sides, and has for decades.

If I dig enough, I can often get the onion like bulb at the base of each "clover":

Cover or oxalis

But the basic question is if I pull the weed and it breaks above the bulb, is the bulb going to sprout again? Some start tiny and don't seem to have bulbs, is this rhizome spread?

2 Answers 2

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First off, the "clover" in your photo is actually not clover, it's oxalis. This explains the bulb you're finding when you dig it out. You also have nasturium and, oddly, something that looks like sagittarius, which is usually associated with water, in that photo. Where did your two inches of fresh soil come from?

There are many oxalis species, and some are considered good garden plants. I'm wondering if the ones in your garden self-seeded from a long-ago garden oxalis and have now moved into the lawn. There is one that's also a common lawn weed (yellow woodsorrel), and yours could be those, too.

Because oxalis has a bulb, it is difficult to eradicate unless you manually remove every bulb in the lawn AND prevent any plants from going to seed. I have a weed with a bulb in my garden and yard (Ornithagalum, AKA Star of Bethlehem) and it has been a many-year project to remove it from the garden. After seven years, I'm not free of it yet. Don't ask about the lawn... (at least it goes dormant in early summer).

Clemson University has an excellent page on controlling oxalis (they concentrate on yellow woodsorrel, but their recommendations should be applicable to any other species in the genus). During the time you're spraying it with herbicide, you need to make sure that any of the plants in the lawn (and in your garden) do not set seed, or the seeds will almost certainly infiltrate your lawn. You'll then need to treat with both pre- and post-emergent herbicides.

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  • The 2" of soil came from American Soil Products, a local respected garden supply house. The oxalis bulbs were present in large numbers in the native soil, we removed as many as possible. (A gardener dumped some potted plant soil on the native soil thinking it was good, and it was filled at levels with the bulbs). The bigger "clover" seems to have a bulb below, the smaller does not.
    – Bryce
    Dec 2, 2021 at 18:11
  • Note in my tests, glyphosate seems to have little to no effect on the clover/oxalis. I tried a "natural" herb based spray that actually did far better, actually wilting and rotting the weed.
    – Bryce
    Dec 2, 2021 at 18:16
  • The gardener's potted plant soil must be the source of the nasturtium and sagittarius (?) that are in the photo. I can see nasturtium seed being part of that soilless mix, but the sagittarius is a mystery. I agree that the oxalis must've been in the native soil. Clover does not have heart-shaped leaves, so if the lower-growing plant does indeed have heart-shaped leaves then it is more than likely to be yellow woodsorrel, else it is white clover. Anything with a bulb is oxalis. Would love more details on your herb-based herbicide - maybe add an update to your post?
    – Jurp
    Dec 2, 2021 at 23:10
  • Added "EcoLogic". Most online resources about Oxalis don't mention the bulb. I think I'm getting growth through all 2 inches of the new topsoil. The oxalis if pulled always breaks at the joint with the bulb. Will this "exhaust" the bulb, or is the bulb too hardy?
    – Bryce
    Dec 3, 2021 at 8:25
  • It could, but it might take a couple of years. That's a lot of pulling, unfortunately. And if you miss a sprout, the bulb will quickly bounce back to normal. Oxalis is almost as tough to eradicate from a lawn as field bindweed is from a garden.
    – Jurp
    Dec 3, 2021 at 14:32
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Couple of points. First, many weeds can't cope with being regularly mown. So you might want to wait for a while to see how much of a problem there is before resorting to weedkillers, hand weeding, etc. Second, unless you're managing sports turf (where weeds are a real problem), you don't really need a weed-free lawn. In other words, it's not written in stone that a "good" lawn consists of nothing but grass, and a "bad" lawn is full of weeds. As the RHS put it:

One gardener’s weedy lawn is another's wildflower meadow. The more plants grow in your lawn, the more biodiverse it will be. If you really want to remove the plants you consider weeds, try hand weeding first and, as a last resort, selective lawn weedkillers are available to use.

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  • Didn't read the link in my answer, did you? Oxalis cannot be easily hand-weeded, and mowing doesn't kill it. OTOH, I agree with you and the RHS on a "weedy" lawn - my own lawn does contain woodsorrel, creeping charlie (which I do try to kill, BTW) and violets, and I used to be a proponent of white clover until the clover overran the grass and infiltrated my gardens. But my lawn isn't your lawn isn't the OP's lawn. Everyone has their own tolerance for how weedy their lawn can be., and I'm going help them achieve that if I can.
    – Jurp
    Nov 30, 2021 at 15:13
  • Sadly mowing will not control clover, it just grows lower. I learned to live with it.
    – kevinskio
    Dec 1, 2021 at 15:43

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