Saturday, April 11, 2020

A South American engulfed my resting vegetable beds

I had put my veggie beds to rest for the winter. What could go wrong?

I knew we were going to be out of town for the first three months of 2020, so I did not plant our normal winter crops. After the last summer/fall crops in three of the beds, I weeded them trying to disturb the soil as little as possible and then covered them with a four-inch layer of pine needles. (6 reasons to use pine needle mulch in edible gardens) In two of the other three beds had the native salvia and other wildflowers growing, so I did some light weeding and left them alone. In the last bed I planted some wildflower seeds and I'll cover this bed in my next post.

So in those three beds, a visitor from South America came calling...

This innocent-looking plant is a monster! The native range for this oxalis is shown in green while the purple areas show where it's escaped. 

Look how pretty the pink woodsorrel (Oxalis debilis) is. It's been a frequent weed in the edible beds because it loves the disturbed soil, but I have never been too concerned about it before, and over the years, I even added it to pestos and salads for its sour tang. (You don't want to eat too much of it, though because it contains oxalic crystals, which are irritating to our digestive systems. Spinach also contains these crystals which is why we add vinegar or cook them.)

But while we were gone, the oxalis formed a solid mat in those three beds that I'd put to bed for the winter.

Wow! The oxalis formed a solid mat on three of my resting vegetable beds.
I expected some weeds, but not this... Time to get to work!

I scooped out sections of the oxalis mat a garden fork so I could shake off the soil and keep the plants in one piece. I pulled out the pine needles from the plants when possible. It was a tedious process, Then I scraped the soil away from these raised beds down to the ground level and removed more oxalis bulbs and pieces that were deeper.

The oxalis had become entangled in the pine needles. I pulled out the pine needles so I could use them again.

Here's the underside of a scoop of the oxalis, which reveals the bulbs and bublets. 

Trying to extract  the mat of oxalis to ensure that the bulbs were kept intact was not easy because at this stage, most the bulbs had shed their outer skins and the tiny bublets were prone to falling away to start a whole new generation of these aggressive plants.

After removing the oxalis, it was time to prepare the bed for planting.

Adding a layer of leaves to enrich the soil and to retain moisture. After spreading out the leaves evenly, I shoveled a layer of soil on top.

I scraped away the soil from half of the bed down to the ground level and removed remaining oxalis bulbs and pieces from deeper in the soil as I spotted them. I raked some leaves from the yard and added about three inches on the bed. This leaf layer will help retain moisture and add humus to the soil. I shoveled the removed soil back in place and repeated the process for the other end of the bed.

The hydrophobic soil needed to be carefully wetted so the seeds would be able to germinate. Building swales to prepare for okra crop and wetting the seed planting sites at the corners and intersections around the edges of the swales.
The soil was so dry that it was hydrophobic, so I spent an extra day working to get the soil wetted with rain barrel water so the seeds would have nice even moisture so they could germinate and get a good start. It's important to use rain barrel water because in organic gardening, we want all the soil microbes, but water from the faucet includes purification chemicals so we don't get sick from the water. Those purification chemicals will reduce the population of soil microbes. Learn more by reading my post, Dealing with hydrophobic soils.

On one end of the bed I created four swales for my okra crop. This creates nine planting sites for the seeds at each intersection of the raised beds and nine to twelve okra plants is plenty for the two of us. The swales will make it easy to water the okra and over the next week or so, I will add a bucket of kitchen scraps in the bottom of each swale to add more nutrients. Those scraps will have plenty of time to decompose before the okra roots are long enough to reach the bottom of the swale. And since the extra irrigation will be in the swales, the roots will go in that direction. One advantage to this arrangement is that there are very few weeds outside of the swale areas.  Learn more by reading: Okra swales and Trench composting in the vegetable garden.

Okra swales at one end and two wide rows for New Zealand spinach on the other. After the wetting treatment, the seeds were planted and pine needed were added in all the non-growing areas.
If you need some guidance for Florida
vegetable gardening, because
it is different here, here's a link

Lessons learned:
- When it comes to oxalis, light weeding is a wasted effort and pine needles are not a deterrent.
- I will be less tolerant of the beautiful oxalis from South America in and around our edible beds.

I hope you are working on your warm-weather crops,  because every pound of food you grow and harvest offsets up to two pounds of greenhouse gas emissions. 

Green Gardening Matters,
Ginny Stibolt


  1. Did you get rid completely of this oxalis? I also have it in my vegetable garden. Because of this oxalis, I opened up another veggie garden area on the opposite side of the house (with no oxalis) where I'm planting carrots, lettuce and other low vegetables. On the veggie area with the oxalis I decided I will plant taller vegetables such as beans and tomatoes.

  2. There is no chance of getting rid of it. It's in our freedom lawn and growing at the edges of wooded areas. But, as I said, I will be less tolerant of it in my vegetable beds and other garden areas.
    Good luck with your bed on the other side of the house.

  3. Will the book above help me if I've never gardened before or will it leave me with more questions? We are wanting to start prob next year or later this year. Its all grass where I want to put my vegetables at and full sun.

    1. We desinged this book so that it's easy to understand by beginners, but has enough information for people who are ready to move to the next level.

  4. How do you keep rodents out of your swales when you add the kitchen scraps? We have everything from possums, armadillos, rabbits and rats and raccoons at different times of the year. I have to keep my compost bin tightly closed. I'm wondering if chicken wire would be enough to stop them.

    1. We do not compost any meat or meat products. If you bury it a little more deeply, the odors are less likely to attract unwanted visitors. We have armadillos and sometimes they dig in the trench composted area, but usually they are looking fr bugs, elsewhere.

  5. Darn oxalis. I am in Bermuda and it is growing everywhere. Disturbing it only encourages multiplication, as the tiny bulblets invariably end up getting scattered in an ever-expanding area. What a nightmare. Napalm might be the solution.

    Repeated weeding passes (I mean dozens) can weaken it. I am adopting a zero-tolerance stance. Hopeless, I know.

    1. Flaming it with a propane torch would be one way to de-weed without using pesticides. Another would be to solarize the soil. But you're right, it's tough to get rid of. Now, a few months after my extreme weeding, there is more oxalis sprouting between my okra and New Zealand spinach crops. I'm keeping after it with more effort than I might otherwise have made in the past.

  6. I use a soil sifter and if necessary, I will weed it every single day for weeks, just checking the spot, raking weeding, digging out all the soil one cubic foot at a time. I just go after it, go after it, go after it.. it becomes me or the weed, and eventually it just gives up and goes away. I stay extremely diligent and do extreme weeding early and often. Weeding can be about the timing more than anyhing else. If I pull out that "first Bidens alba", you know, that big one that is going to propagate a field if allowed. If I am paying attention and get that big "first weed".. then it saves me from 50 more plants it may produce. "early and often".. winning by due diligence. I know many others do this too, but I tell people new to gardening that it is work. If you don't want to work it.. your success rate will be exemplified often times by how much effort you put into the soil.