Plastics on your allotment & the environment.
Many people will have been very concerned to see on the Blue Planet how plastics are having a
devastating effect polluting our seas & oceans. Environmental groups like FOE & Greenpeace had
been trying to alert people for many years to this growing disaster but it took the clout of David
Attenborough to really make the general population finally sit up & take notice of the negative
effects of a substance we use once & then throw away with gay abandon.
With the exception of PVC, the majority of plastics are relatively benign & non-toxic for their
original purpose. They are after all widely used for food packaging. It’s what happens to them
when they’re disposed of that is the real problem. It’s not enough to assume that it’s ok to keep on
& on buying single use plastic & throwing it into the recycle bin. The recycling process is VERY
imperfect. As little as a third of plastic sent for recycling in the UK is actually recycled. You the
consumer have no control over whether your bottle ends up being turned into an inferior bottle,
landfilled, incinerated or shipped to the far east & illegally dumped in a river or on a beach there.
We should all be doing our utmost to reduce the amount of plastic we buy in our lives & bring
onto our plots. Ultimately the only way to control the torrent of single use plastic is for
governments to tax it into oblivion which will encourage the development of benign alternatives.
Looking around the back ends of members’ plots, there is a very worrying build-up of abandoned
& decaying plastic & fibres from carpets around the whole of our allotment site. Information on
the effects of plastic pollution in soil is still being researched but a few facts are worth
- It’s downhill all the way to the sea via our site’s drain. Plastic bags & particles, once they fall into
water become ensnared & are carried away with the flow. Larger pieces may be filtered out at the
sewage works but during storms, even these are carried with the overflow straight into the
- Earth worms behave differently when the soil contains micro plastics.
- In the marine environment, Persistent Organic Pollutants with hormonal effects have been
observed to be adsorbed onto the surface of plastic micro particles. These particles are then
ingested by simple organisms like plankton & so the POPs are carried further & further up the
food chain & eventually into the fish we eat ourselves. Remember too that as plastic breaks down
into smaller & smaller particles, its overall surface area increases. It’s very likely this process is
happening in the soil too. Not hard to see why cancer rates are on the rise.
- Nearly all plastics are affected over time by being exposed to the Ultra Violet content of sunlight.
This typically causes the outer layer of plastic to weaken, become brittle & flake off thereby
exposing fresh plastic underneath. Transparent & light coloured plastics generally have the least
resistance to the effects of UV. Always try to buy dark or preferably black plastic items. The dark
pigment reduces UV penetration. A good example of this is an orange builder’s bucket I had that
obviously came from the same mould in the same factory as my regular black ones but after only 2
or so years it became bleached, then cracked & useless whereas the black buckets are still perfect.
Don’t go for the gaudy option if you want items to last. Always try to store all your plastic items –
watering cans, hose, sacks etc – away from strong light. Some plastics have additives to resist the
effects of UV but infuriatingly, there are no markings to indicate this. You must be prepared to
keep an eye out for evidence of the decay of all plastics on your plot over time. If this seems
tedious to you then seriously reduce the amount of plastic you have there.
The following notes on the stability & longevity of the different types of plastic commonly
encountered on allotments are mostly based on observations & mistakes made by me over the
years. I’ve spent many hours on my knees picking up scraps of decaying plastic & particularly tufts
of carpet from my own soil & compost. Never bring hessian backed synthetic carpets onto site. I’d
strongly recommend that plot holders always have a bucket near to hand to collect bits of plastic,
carpet fibres & glass into whenever they’re working their soil or compost. The codes & full
chemical names of plastics are given below so people can do their own further research.
Polythene, Polyethylene, LDPE & HDPE.
This, the simplest plastic, exists in High Density & Low Density forms. Used for cheap
greenhouses, bubble wrap, milk bottles, thicker non-rustling type of plastic bags, compost sacks &
smooth heavy-duty sheeting. Polythene in its non-UV stabilised form appears to degrade in the sun
faster than any other plastic. It can lose all its strength & fragment entirely away in about two
years. Black (builders) HDPE sheeting seems the most stable form & is useful for warming the
soil & excluding light from weeds.
Widely used for many larger moulded plastic products on allotments – compost bins, watering
cans, buckets, plant pots, clematis netting, hose reels, bottle tops, vermin netting, woven Ikea blue
bags, giant cubic metre builder’s aggregate sacks & estate agent sale boards. It’s also used to make
the twisted film type of plastic string & rope. Probably due to its high surface area in this state, PP
string & rope degrades particularly rapidly in sunlight – shedding tiny fibres from the outside
which blow around or drop into the soil & the string completely disintegrates in as little as 2 years
of sunlight exposure. Don’t use such string or rope for the long term tieing together of things
unless you’re prepared to renew it every year or two. Best use natural jute string for tieing plants,
runner bean poles etc. All of the plastic netting I’ve encountered seems to be UV stable but the
consequences of it not being so are so serious that you should avoid buying it from cheap sources
such as the hateful pound shops that sell mostly short-lived rubbish that soon breaks & ends up in
landfill. Also never buy the very wasteful plastic pea & bean climbing netting as it gets thrown in
the skip after a single season. There are always twigs & sticks to be had from the green waste
heap. I find the giant PP builder’s bags particularly useful for containing leaves rotting down into
leaf mould. Kept in a shady position these can last 3 to 4 years. However, because of their limited
life, it’s imperative that you should test them each year by attempting to rip them. If they tear or
make a cracking sound then they should definitely be disposed of very soon. Don’t use these bags
to store compost that contains food scraps as rats & mice will chew their way through the fabric to
reach the food. The plastic fragments are particularly fiddly to pick up. Estate agent sale boards
crumble very quickly so don’t bring onto site for compost containers etc.
PET, Polyethylene Terephthalate
This is used to make the thin rustling plastic bags that blow everywhere & also the clear plastic
used for drinks bottles that are used once then thrown away. Rats & mice like chewing up plastic
bags into tiny pieces for their bedding so keep carrier bags etc in vermin proof containers such as a
biscuit tin. I gather 5 litre mineral water PET bottles up as they blow around in the street near me,
cut the bottoms off & use them as cloches to protect tender seedlings from slugs & cold nights.
Never be tempted to leave the caps on as I lost most of my seedlings one year through overheating.
Remove film labels as these disintegrate very quickly. Such bottles used to quickly yellow & go
brittle in the sun but modern ones seem good for about 5 years but you must always keep checking
them for brittleness. On no account buy hideously destructive bottled water yourself as clueless
people with more money than sense can be relied on to keep doing this & then scatter such bottles
around. If you’re concerned that tap water is polluted then it’s because there are diesel burning,
water laden lorries thundering across Europe & plastics factories making bottles at a furious rate. I
laughed out loud when I read that bottled water contains plastic particles.
PVC, polyvinyl chloride.
Used for hose pipe, cling film, cable insulation, window frames & waste & rainwater pipes &
guttering. Like many halogenated organic compounds, the manufacturing process for PVC is very
polluting involving carcinogenic ingredients. This is why I get particularly annoyed to find
perfectly good hosepipe regularly thrown away in the skip. If a section of your hose leaks or splits
then it’s very easy to cut the damaged section out & join the two ends with a hose joiner rather
than buy an entire new hose & cause several more kilos of polluting PVC to be manufactured.
PVC is generally one of the more light stable plastics but after many years of exposure to UV the
surface can start to dull & have a crazed appearance. PVC should be disposed of when this
happens as it’s likely to shed toxic micro particles into the environment & your soil.
Compostable plastic bags made from corn starch.
These have the look & feel of condoms. They’re supposed to naturally decompose but in practice
this only happens in properly hot compost heaps so best put these into council compost bins rather
than your own heap.
If you’re desperate to know the type of plastic an unmarked item is made from then the simplest
way is to melt a tiny sample & compare the smell to that from a known sample. Be cautious of
breathing in PVC vapour though because of its toxicity.
Finally please remember that our skips go straight to landfill & are therefore an absolute last resort
that should only be used for mucky non-recyclable items. People living within a mile of landfill
sites have a 15% raised chance of developing leukemia. Casually dumping your picnic rubbish in
the skip is lazy, thoughtless & selfish as we all have to pay about £300 each time it’s unnecessarily
bulked up & filled & we’re presently filling about four skips a year. Put such rubbish in your
domestic bins at home. Your council will properly dispose of any item you take to their recycling
depot for FREE.