Tag Archives: gardening

Plane Tree Dust – The Scourge of the Chelsea Cough

Platanus hispanica

So here’s an issue no official sources seem to be talking about: Plane Tree dust.

I work as a gardener in Central London and for me, and all gardeners who work beneath plane trees, the orange dust from Platanus hispanica causes huge issues. It leads to not just sneezing and itchy eyes, but uncontrollable coughing fits. I see colleagues of mine brought to their knees by coughing. I see their red eyes and hear constant sneezing. I’ve even heard cyclists complaining about it to each other as they whizz past.

Most worrying is that I think it may be getting worse, but there seems to be very little official recognition that there is a problem. A scout around the internet for information turned up almost nothing. The occupational therapist at my work had never heard of it. So I wanted to find out what is actually happening? Is this really only a problem for gardeners? Is climate change increasing the problem? And how worried should we be about it?

In this blog is everything I’ve discovered and I’ll be contacting anyone who might be able to tell me more, but if any of you out there have personal experiences or professional knowledge about plane tree dust, then please comment on here, or write to me – my email is at the bottom of the page.

Plane trees are beautiful, with their flaky bark, palmate leaves and dangly seed pods. They were planted in great number in London in the 18th century and are considered of great importance because they provide a huge canopy, are generally tough and resistant to pollution. There are roughly 115,000 in London. That makes up 1.4% of the capital’s tree population, but due to their huge canopies, they make up the biggest leaf area of any London tree species.

However to anyone working outside in London, they are known as serious trouble. Every gardener I have spoken to has described them as being their biggest hindrance to doing their job. Plus I know of a tree surgeon who refuses to work with them after being put in hospital with asthmatic fits. Around Chelsea Flower Show time, people talk about the Chelsea Cough. In Australia there have been protests and demands that the trees are banned.

There is some dispute over what causes this problem. When I started looking into this, I found plenty of research into Platanus pollen, but pollen isn’t the problem, it is the orange dust that floats down like snow and gets into the grass and coats the soil. The dust is largely made up of a fluffy coating in the seed pods (it helps the seeds float, like dandelion (Taraxicum officinale) seeds) but it also contain trichomes, tiny hairs that coat the leaves. These trichomes are thought to be the main cause of coughing. As James Wong explains here, antihistamines won’t work against trichomes, they are an irritant, which is more serious than an allergy.

The Reasearch

I found three studies into the effect of plane trees on the public. They include research from Australia, France, Spain and Italy. The effect of plane trees is acknowledged as often extreme, however all these studies focus on the effects of pollen. Some mention that it is odd that the reaction to plane trees happen outside of the pollen season, all find that plane tree pollen only affects a few people.

Australia 2011 study

Spanish1997 study

Spanish 2010 study

There are also scientific studies into trichome regulation, but these don’t seem linked to allergies.


Well, that’s all I have and it’s not much at all.

What worries me is that I think with the change in climate, this problem is getting worse. Because there are no studies I’m only going by what long-standing colleagues say, but the effects are so extreme and the awareness so small it makes me think it can’t have been as bad in the past.

Is global warming having an effect on the production of trichomes and the seed bristles?

And if so, do trichomes have an effect that lasts beyond the coughing fits – since prolonged exposure to dust can lead to long term health issues, should we be worried?

I shall continue to investigate and update later, but if you have information or personal experience, then either comment below or contact me via email on

therealtetrapod @ gmail .com


Why don’t we ban Glyphosate? (Round Up)

Mendoza GL 2

Abandoned station as the plants reclaim…

There’s been a lot of publicity surrounding the herbicide Glyphosate, the main ingredient in Round Up. A recent court case determined that it can cause cancer. It has also been found in streams and some water supplies. The media have been vocal in the dangers of this terrible chemical, and people must be wondering: why hasn’t it been banned?

The problem is, there is pretty much no other effective herbicide to use.

As someone who’s worked for a number of gardening companies and in a number of large gardens, it’s been the only non-selective herbicide I’ve come across (non-selective means it kills all plants). However, I was aware a number of countries had banned it, so I was convinced there must be something else to use. It’s been bugging me for a while, so thought I’d do a bit of investigating.

Why Do We Need a Herbicide Anyway?


Plants can grow anywhere

Naturally, when most people think about banning herbicides, they worry about the patios and paths in their gardens, but it’s a little more serious than that. It’s not surprising people think of plants as mostly well-behaved organisms, because that is how we keep them, manicured and contained. But plants have been colonising land since long before animals ever did, and they’re very good at it. If all humans suddenly vanished, it would only be a few years before plants had made headway in reclaiming roads and buildings.

Many plants don’t need a nice flowerbed in order to grow, plenty don’t need soil at all.

How plants take over a hostile space

First moss and liverworts grow on bare rock, then when they die their decomposing leaves provide a little bit of soil for slightly bigger plants, which have more tenacious roots that ease into cracks. Then they die and create more soil. Soon there is enough soil for plants with tougher roots to sprout, and the cracks widen further. Once there’s a perfect environment for invasive weeds to take hold, it can be only a few months before waist high clumps are sprouting up in great numbers. And this can happen anywhere, on railway tracks, pavements, roads, even through walls.

Buddleia GL

Buddleia growing in railway arch walls

When it comes to invasive weeds, Buddleia (Buddleia davidii) and Japanese knotweed (Fallopia japonica) are the biggest problems, and a problem that only Glyphosate solves. Whereas plants such as Himalayan Balsam (Impatiens grandulifera) and Skunk Cabbage (Lysichiton americanus) tend to be confined to wet areas, Buddleia and knotweed can and do grow anywhere. Buddleia can grow in walls, knotweed can break through concrete. These plants are kept in check by Glyphosate, and whole companies exist to remove them. I studied for my spray certficate with a couple of guys whose sole job it was to inject Japanese Knotweed with Glyphosate. Without chemical intervention, these tough innovative plants would take over, and soon they would affect the running of trains, and damage buildings and roads. Pulling them out acheives little. Pull Buddleia out of a wall and you’ll damage the wall. Pull knotweed out of the ground and you’ll cause more shoots to sprout in their place like a Hydra from Greek mythology. A solution needs to be tough.

How Have Countries Banned Glyphosate?

Whenever trouble with Glyphosate raises its head, the media talks of countries which have banned it, so why can’t we? Looking deeper into this leads to some interesting caveats to the bans. Although 14 countries are reported as having bans, few have an outright ban.

Some countries, such as Belgium and the Netherlands have restricted use (only for commercial use or to treat invasive weeds). Some are undergoing the slow process to find alternatives and intend a ban in a few years time (eg France). Bermuda started out with an outright ban, then relaxed the laws. Canada has banned it except in the case of invasive weeds.

A number of countries such as Saudi Arabia, Kuwait, Qatar, Bahrain, Oman and the United Arab Emirates have an outright ban. I haven’t been able to find out why, but maybe there is a large lower-wage workforce there, who will do the weeding by hand. There are certainly invasive weeds in the Middle East, although many are dependent on irrigation provided by humans, so that may be  a factor. (If anyone knows the reason, please email me at the address at the bottom of this blog and I’ll update).

Despite headlines calling for a ban, it looks like the solution is more complicated.

What are the alternatives?

Salt – this is often cited, however, Sodium Chlorate, a derivative of salt used as a herbicide, is banned in Europe. Using it on a few weeds in one garden isn’t such a big deal, but using large amounts on train tracks could be an environmental disaster. It depletes the ozone layer and is harmful to aquatic life. It’s also toxic to humans.

Vinegarwas used in Bristol to control weeds for a year. It was found to be not cost effective and not have such a long-lasting effect as Glyphosate. Personally, I’d be concerned at the environmental effect of throwing large quantities of vinegar around. Large quantities of anything that kills plants can cause environmental harm.

Handweeding – this is incredibly slow and isn’t practical on a large scale. It would mean shutting down roads and train tracks and new purpose-built machinery and a lot of cheap labour. Fine for private gardens though.

Mulching – useful in flower beds, but useless on paths and patios and won’t stop plants that grow out of walls or through buildings.

Steam weeding (sometimes called Heat Weeding) – this involves a machine that sprays out water at 99 degrees. I’ve used one, it is effective, although still in its infancy, so the machine is cumbersome and not very versatile yet. It’s being trialled mainly in Australia and Sweden. Given time, it’s one of the best options and there needs to be investment, plus government incentives to use it.

Fire – not setting fire to the weeds, but running a flame over them. Another good possibility. Not something I’ve used, but I can see how it would work on open ground. I don’t know the logistics of using it on buildings, but it’s a possible solution.

And Finally…

I’m concerned that this blog may come across like I’m resigned to chemical use and I really don’t want that. This is a beautiful world, we’ve been messing with it for a long time and we’re starting to feel the terrible consequences of that. So it’s time to grow up as a species and start taking better care of our surroundings. One way to do that is to reduce chemical use and work with nature in a sustainable and less intensive way. There will be ways to reduce and eventually get rid of Glyphosate, but in order to do that, we need to accept it’s not just a matter of banning one chemical and then moving onto another.

If anyone has any knowledge or ideas to add to this, then drop me a line at therealtetrapod at gmail dot com. Thank you!

Mendoza Glyphosate

Another picture of Mendoza station, just because…