Monthly Archives: June 2021

Weeds Have Jobs #2

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This week we’ll talk about spurges, also called sandmats. There are two types that seem to be prevalent in the gardens I’m tending in Tulsa, Oklahoma. The first, Euphorbia maculata, with purple spots on the leaves.

Spurge – Euphorbia maculata

The second is Euphorbia prostrata, that tends to have a spreading, spiderlike, form.

Euphorbia prostrata

The third type is the Euphorbia serpens, or creeping spurge.

Euphorbia serpens

So what is this about spurges? What are they all about and why do they grow where they are? In other words, what is their job?

Euphorbias are prostrate and spread.  They can have a taproot up to 2 feet.  They are not edible (and are toxic – the milky latex sap contains diterpene estersin, which can be irritating to the skin). 

Spurges tell us that the soil is clay, loam, and sand. Which can be good. But …

Generally spurges indicate low calcium, very low phosphorus, very high potassium and magnesium, high sulfur, high copper, and a hard layer in the soil (thus the long taproot to break up the soil).  They also grow where there is poor drainage, which is a symptom of a hard soil layer.

So when you see a lot of spurges in your garden or in your lawn, think about having the soil tested for mineral content, and dig down a bit to see if there is a hard layer just under the top soil.

Want to read more? My favorite references are John Beeby’s Test Your Soil with Plants (Willits, CA: Ecology Action, 2013); and Jay McCaman’s Weeds and Why They Grow (Sand Lake, MI: Jay McCaman, 1994.

Weeds Have Jobs

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Weeds as soil indicators

I’ve recently taken a deep dive into weeds that I’m finding in the garden. I’ve skimmed over this subject for the last few years, but now I want to really understand why weeds are growing in my garden. Each “weed” is actually there for a reason – to bring a mineral to be used by other plants, to cure a mineral deficiency in the soil, or use long roots to open up compacted soil. Weeds have jobs and if you know how to read the weeds, you can find out more about your soil – sort of a DIY soil test with plants! I’m going to post some of my discoveries here in the next few weeks. We’ll start with Wood Sorrel.

Oxalis stricta (common yellow wood sorrel)

This plant grows in sandy soil.  It is perennial and thrives in slightly alkaline soils with a pH of 7-8 (an indicator that we would need to work on acidifying the bed if we want to grow strawberries or spinach, which like a lower pH soil).

According to Weeds and Why They Grow (Jay L. McCaman, 1994), wood sorrel grows where there is very low calcium and phosphorus, but very high potassium and magnesium.  The flowers are visited by bees, ants, and butterflies. 

Wood sorrel is edible (in small amounts, because it contains oxalic acid) and is a source of vitamin C, and is regarded as a medicinal plant.  The yellow flowers also can be boiled to produce a yellow to orange-red dye.

Okay …. I’ll add another “weed” in the next week or so.