I'm gonna wash them weeds right out of my soil...

Or that's the idea anyway. I certainly washed plenty mud right into my hair - and every other exposed surface... I posted earlier about Cameron Colson's brainwave to adapt an industrial sized power washer to use in invasive weed control, creation of firebreaks, and such. Yesterday I had a go using our domestic sized power washer, in two areas of disturbed soil where the opportunists had colonized.

One area is between the neighbor fence and the swimming pool fence (yes, a swimming pool came with the house - I have a harebrained scheme to convert it to a natural pool one day...). The deer occasionally use this passage, though they can move freely through our property in other areas. A bit too freely sometimes...

The other area (not shown) is behind the pool fence to the north, where the land slopes down to a valley of mixed-evergreen forest and redwood habitats. I've been removing non-native weeds and poison oak there for the past few years. (I can't live with poison oak where I garden.)

I washed down our entire cedar-shingled house with this power washer a couple years ago to great - and lasting - effect. So I was ready to take on the oxalis.

I discovered that the width of the nozzle and the angle, and the distance from the soil all have a large effect.

Holding a narrow nozzle vertically and close to the soil dug out great channels about 6 inches or more deep. A slight angle, a slight distance, and moving the nozzle rapidly and in a rotating manner all helped. Also harder ground was - obviously - less disturbed than softer ground by the blast.

Here's a link to a video of me power washing the soil. Turn down the volume - the sound of the power washer isn't too amusing. The video shows the other area, which I did first. I tried out different ways of working - in the end I found that standing on the not-washed soil and working backwards worked best (as shown in the picture).

Well, in the end it looked a lot better than in the beginning. But I'm not sure what I've done as yet in terms of ridding the soil of weeds. Cameron recommends three applications about 45 days apart, so I'll have to follow up to complete the experiment.

I did feel sorry for the soil critters I blasted. I didn't see any, though, so the part of me that believes in fairies also believes that they all heard me coming and slithered away to a safe place.

But here's the thing...
THIS TOOK ONLY ABOUT 20 MINUTES!

Comments

Town Mouse said…
Very impressive! Maybe it would be good to plan on sowing some native annuals after the 3rd application...
Country Mouse said…
Yup - good idea, though deer do walk through here.
ryan said…
Bold idea. We usually newspaper mulch oxalis. That power washing looks a little scary.
Anonymous said…
How has the power washing worked out on the Oxalis? We ususlly use newspaper and mulch after pulling much Oxalis first. Perhaps power wash and then newspaper/much?

a native plant gardener
Country Mouse said…
Yes I would do that, use mulch once you're done, and papers make all the difference.

I'd treat maybe two times. I got it pretty early in the year and it did come back but not so strongly. We let it sprout and did a retreatment. The place where I did this is mostly on a rather steep slope and I haven't mulched there. I would certainly do the newspaper/mulch otherwise and you should see much less regrowth.

Places where I hand pulled then mulched 3 years in a row are looking better but not perfect. The newspaper makes a huge difference. I think it will be better again next year. It's a pain in the neck having Oxalis for sure.

I think the treatment might not pulverize the nasty root nodules. I got em now on my property where there are surviving oxalis plants. But it would still destroy the plants and prevent more nodules forming.

So - If you get it early, and do two or more treatments - letting it resprout each time - then use paper and mulch - I think you would have good results and make progress towards eradication. The pulverizing is SO FAST you can get so much more done - and time is of the essence when it comes to Oxalis. Get em before the root nodules form.

I'm trying different approaches on different parts of my property - being blessed with copious amounts of the darned stuff.

Ms C.mouse
Linda said…
i worked with cameron colson at the boulder creek museum removing ivy from redwoods and was totally amazed at how effective his method is. huge ivy roots completely encircling the redwoods--below the surface--that i would not in a hundred years have been able to remove were removed without injury to the tree. cameron has stumbled onto an environmentally safe means of removing invasive plants beyond the quick pull. he should be commended for thinking outside of the box.
WiseAcre said…
I've got to try using it to weed the garden paths. Then myself.