Plane Tree leaf mulch

This post is about using Plane Tree leaf mulch to make vegetable gardening easier and less weedy.

Introduction

As children, we often encountered the fluffy stuff from the crushed fruit of Melbourne’s ubiquitous London Plane Trees. We quickly learned its properties and called it ‘itchy wool’. We did not try to smoke it, but to our shame, we put it to other irritating uses.

Now some 60 years later, Plane Trees are justifiably getting a ‘bad wrap‘ because of the allergic response that their pollen, but more particularly the ‘itchy wool’, can produce in a substantial portion of our population.

Researchers are even inoculating trees with hormones in order to eliminate fruiting. This is for trees around city streets that are frequented by the ‘latte and smashed avocado set’. “That’s the bad news. Now for the good news.”

The leaf of the Plane Trees

If you have experience with the autumn fall of Plane Tree leaves you will know the mess they make and how they are so slow to break down if added to compost.

In my childhood, the smoke from the now-discontinued practice of burning (or more correctly ‘smouldering’) piles of leaves was the normal backdrop for Melbourne weekends in autumn. The days were often sunny, but with early forming mists that mingled with smoke. The background also included the sounds of football umpire whistles and periodic cries from supporters in the still and smoggy air. “My senses told me that winter and snow, that I now love so much, was just around the corner.”

My garden as a testbed for mulch

The soil in my garden is a heavy grey loam (not much real clay content). It quickly consumes organic matter that I put in or on it.

“I remember that I dumped a free trailer load of wood chip garden mulch beside my vegetable garden. I was busily building my home at the time. By the time I got back to spread the mulch a few months later, it was nearly all consumed by the soil. Similarly, if I leave firewood in my paddock too long, it will be ‘eaten’ by the soil.”

Consequently, if a Plane Tree mulch survives a long time in my garden, it is indeed a persistent mulch. As for any plant-based mulch, to be effective, the garden beds need high borders, mesh or netting borders to prevent birds from scratching the mulch away.

Plane trees mulch makes a cheap and persistent garden mulch.

For three years I have been collecting plane tree leaves to mulch my vegetable garden. The layer of leaves slowly breaks down but the cover will last for a year until the next lot of leaves are available. After the year the soil below is damp, friable, looks good and has a nice population of worms. It is difficult for me to determine the compositional quality of the soil resulting from this treatment. However, most importantly for me, the mulch greatly reduces weed propagation and growth that I would otherwise have to endure. The friable soil also means that any remaining weeds are easy to pull out. “It works like magic on asparagus beds.”

Magic chemicals from nature

The success of Planetree mulch may be that it just acts as a persistent weed mat. However, I consider that there may be some plant chemistry contributing to its success. “See, chemistry keeps popping up everywhere, it’s all around us and in us.”

I heard this little story on ABC radio when they were celebrating the 150th anniversary of the periodic table of the elements. The story went like this. George (still walking) and Bill (in a wheelchair) were 95+ year war veterans. Bill started to reminisce. “Do you remember the story that we soldiers were being fed bromine supplements in our food to make us less randy? Well, I did not believe it at the time……but you know, I think it might just be beginning to work!” Back to mulch

Many plants make chemicals that can suppress the germination and or growth of other competing plants allelopaths . These chemicals can often be distributed via fallen leaves. Some of these chemicals can even suppress the growth of their own species, for example, to prevent overcrowding autoalleopaths.

I have not found any documented evidence for alleopaths in plane tree leaves (“maybe you can”). Nevertheless, I consider they are likely to be part of the success of the mulch that I use.

Victoria’s botanic gardens have giant Plain Trees that were planted by the botanist Baron Ferdinand von Mueller. Local tales suggest that the giant Plane and Oak Trees on my farm (and around Victoria) were probably planted at the same time at the instigation of the Baron. He was also credited with the introduction of blackberries to Australia. I thank the Baron for my Plane Trees and their abundant leaves that fall each year to a ground where nothing else grows. No thanks for the blackberries. I have continued like the Baron, planting Oak Trees from acorns from under my favourite Oak Tree at Carnegie Primary school.

I hasten to add that seedlings planted through the Plane Tree mulch and into the soil continue to grow very well. It is possible that the chemicals only suppress the germination of weed seeds rather than inhibiting general plant growth.

Direct planting through the mulch with seed such as corn, peas and beans may be a problem and is something that I should test.

Have a listen to my garden bird chorus.

For more on my tree plantings see from little acorns big trees grow.

If you are a keen gardener you may like my Pickled fig and Fennel or Rocoto chilli sauce recipes :

Pickled figs with fennel recipe

Sweet Rocoto chilli sauce

Tim