How to Maintain a Lawn Without Herbicides or Synthetic Fertilizer, Version 2

Although I can appreciate the benefits of grass around the home, I am not a big fan of big lawns. They demand lots of energy and water, and in return, our family, which consists entirely of humans, cannot eat grass. For this reason, we have devoted most of our backyard to a vegetable garden, shrubs, berries and fruit trees. Unfortunately, a borough by-law prevents us from growing tomatoes or other produce in front of our home, so I maintain a small lawn.

Here’s what it looks like today, in early September.

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Although not “impeccable” by conventional standards, it’s quite green, and yet it has not ever received any herbicide or pesticide in its entire 21-year existence. For the last 15 years or so, it has not received any synthetic fertilizer either. So how do I keep it green?

I add used coffee grounds to my lawn throughout the summer. In the spring I also spread a few composted chicken manure pellets with my backyard’s compost in areas that have mostly grass. It also gets some urea(a nitrogen-source) from dogs who pee on my front yard during the winter. What’s wrong with synthetic fertilizer? Aside from being expensive, it inevitably spreads beyond the lawns’ borders, eats away at sidewalks, and runs off into our storm drains and river.

Next we come to the subject of “weeds”. Using such a term demonstrates ignorance of botany, which is a beautiful but underappreciated science. By not using herbicide, I save money, don’t risk health effects and allow plants like bird’s foot trefoil (Lotus corniculatus) to survive. Before flowering it looks like this patch from my lawn:

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It is a legume so it provides some of its own fertilizer thanks to a bacteria in its roots. If I don’t mow the lawn for a while, the trefoil produces attractive flowers that look these:

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Other non-grass plants worth tolerating are herbs like oregano, which spread to the lawn from the rock garden. If you look carefully, there is also parsley at the bottom center of the picture.  P1170382.JPG

There are three plants that I treat as “weeds” because they would otherwise grow at the expense of the grass, oregano and trefoil. They are dandelions, plantain and crab grass. To remove dandelions and their entire root, I use a tool. But trefoil does compete with them nicely. The other two have shallow root systems and are easy to pluck out with my thumb and index:P1170378.JPG

These were removed a little late. They have flowered and could have already spread their seeds. It’s best to learn to recognize them and pull them out earlier and donate them to the compost pile.

To encourage a deeper root network, I rely on rain, and even during dry spells, I water grass only every second day.  To conserve more water I use some water from a rain bucket positioned below the roof gutter. Since the patch of grass is only about 300 square feet, it takes me less than 15 minutes to hose it down.

Hopefully, if you haven’t already adopted similar practices, you will now be willing to save money, learn some botany and spend a little more time outdoors.

Side-Benefits of Birches’ and Beans’ Friendships

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Frankia bacteria with vesicles

Although it’s common knowledge that there is a beneficial relationship between members of the legume family and Rhizobium bacteria, less people are aware that there is a similar relationship between the members of the birch and alder family and a bacteria called Frankia. What’s noteworthy is that in both mutualisms, legumes and birches gain more than just ammonium, which the bacteria form by converting nitrogen from the air with their special enzyme nitrogenase. (For those of you who are also salivating to find out what plants do with ammonium, they use it to give glutamate an extra amino group as it becomes glutamine. The latter yields an amino to α-ketoglutarate which regenerates glutamate as it transfers it to variable intermediates. Those finally become a variety of essential amino acids. )

Before revealing the other benefits, let’s look at the Frankia nodules that form around the roots of Alnus glutinosa, the common alder tree. They are the orange clumps you see throughout the picture below.

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A mutualism between alder roots and Frankia nodules

When alder or birch trees are still young, it’s been shown that the Frankia infection lowers their ability to produce tannins and other compounds, making them more appetizing to herbivores. But the drawback is short-lived. The synthesis of deterrents accelerates as the treelings quickly mature, thanks to the extra nitrogen from Frankia, and this allows the trees to survive.

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a Mexican Bean beetle

Lima beans, which form nodules with Rhizobium, use the nitrogen-bonanza to make their leaves richer in cyanogenic glycosides that are poisonous to Mexican Bean beetles. The more nodules they have, the more protective compounds they produce. Researchers confirmed that hypothesis by chemically degrading the poisons with enzymes in closed Thunberg vessels and then using spectrophotometry to measure the amount of hydrogen cyanide  HCN released.

Having more nodules also improves bean plants’ ability to make volatile organic compounds when they first get attacked by the beetles, which drives them away.  Meanwhile, the more “infected” lima beans become with Rhizobium, the less extrafloral nectar they produce.  This makes them less attractive to ants, who otherwise farm aphids at the expense of bean plants.

Sources:

  • Ballhorn, James and al. Colonization by nitrogen‑fxing Frankia bacteria causes
    short‑term increases in herbivore susceptibility in red alder
    (Alnus rubra) seedlings. Oecologia. 2017 https://cbs.umn.edu/sites/cbs.umn.edu/files/public/downloads/Ballhornetal2017.pdf
  • Thamer, Sylvia and al. Dual benefit from a below-ground symbiosis: nitrogen fixing rhizobia promote growth and defense against a specialist herbivore in a cyanogenic plant. Plant and Soil.  April 2011.
  • James Mauseth. Botany, An Introduction to Plant Biology. Jones and Bartlett. 2008

Why I Keep Trying to Grow Poplars

P1160987Pictured is my fourth attempt at growing a poplar from seed. The seed, which was within a capsule-like fruit, landed in my garden after it drifted in the wind, courtesy of an attachment to a cottony puff. Most people, if they notice them at all, think they are an annoyance that have to be skimmed off  swimming pools. They are in instead another species’ way of perpetuating itself. And they are more ephemeral than most flowers. In fact, prior to germination, the soil must have been moist because poplar seeds are only viable for a few days.

The third attempt failed. After germinating in the same manner and location, I transplanted a one-foot poplar to the green strip between the sidewalk and the street, in the spot where a city tree had died. But after 5 years of neglect, officials decided to finally plant a new one where my poplar stood. I moved it to my yard, but my neighbour’s dog chewed a ring around its  bark, removing the phloem, which led to the starvation of its roots.

The second attempt was a prequel of the first third one’s history, with the same cause of death—girdling, it’s called—but with a different perpetrator. A city worker with a noisy, fossil fuel-powered weed wacker inadvertently killed it. It’s why I surrounded the vulnerable trunk of Poplar Number 4 with a mesh, in case the neighbour’s dog returns with the same intention, which it already has, or in case the cord of the weed wacker somehow slips and covers three times its intended radius.

Attempt number one happened decades ago when I was still a teenager living at my parents. I had been watching its quick growth when one day I found it in the garden with its roots pointing to the sky. I revived it temporarily, only to be told by my father that it was  a useless tree. It’s not, actually. Aside from its beauty and ability to remove carbon dioxide from the air and convert water to oxygen, the wood can be used for plywood and matches. But that was never my reason for caring about poplars.

Between the ages of 5 and 10, there were hundreds of poplars in what we considered to be our backyards, given that there was no fence separating our properties from the woods. In those woods we built cabins and fires, ate berries, climbed trees. My grandmother even taught us how to make bows and arrows from the soft, easily peeled wood of poplars. Then one spring, a bulldozer, in a matter of hours, wiped out the natural playground of our childhood. Three of us screamed at the operator. When he told us to get lost, I picked up a small rock and threw it at him with Rusty Staub-like accuracy. Luckily, it did not hit him in the head but in the back. He tried to chase us, but we ran away like rabbits. The exhilaration from the escape was short-lived, but the urge to spread poplars all over the city has never gone away.

 

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