These weeds have aggressively colonized our lot. They are a thorny species, extremely drought tolerant and very prolific. With the unprecedented moisture falling daily from the sky, these weeds and others have started to take over, especially areas that are not under cultivation.
According to city law, once the weeds pass 4 inches in height they are illegal. This is in part rational because weeds do tend to be a major source of airborne pollen, a leading cause of allergies.
However, when I mowed the weeds down the first time I left some along the edges because they provide great habitat for beneficial insects, especially bees. I’ve seen all sorts of bees coming to these flowers to collect pollen and nectar: bumblebees, honey bees, and other bees that I’m not familiar with.
The city of course, doesn’t care so much about beneficial insect habitat as they do about compliance, so naturally we got a notice saying that we need to mow the weeds down.
Weed management is a tricky area. I’ve seen projects dedicated solely to the sustainable management of weedy species for soil conservation. That’s because weeds serve an important natural function. They are the first colonizers of ground laid bare (often by human activity), acting to stabilize the soil, prevent water and wind erosion, and they add valuable nutrients to the soil through nitrogen fixation and organic matter production. Mowing weeds, therefore, causes Nature to react in a predictable fashion: they grow back, and fast.
Using weeds as a green manure is a viable strategy if you have access to intermediate technologies like small tractors or roto-tillers. But the best low-input strategy for a situation like ours, where only relatively small areas are actually under cultivation, is a sheet mulch of wood chips or some other biodegradable material. Yes, some weeds will make it through the mulch, but the mulch will change the species composition and greatly reduce the quantity of weeds.