What’s the best container material?

Last month we looked at what size of container you need. Here we’ll look at your options in terms of container materials.

There is no perfect container material, each has different pros and cons. As well as the size, the main things you’ll want to consider when choosing a container is what it looks like, its weight, durability, water retention and cost.

Weight

Weight is likely to be important if you are growing on a roof terrace or if you’ll want to move your containers from place to place. Plastic, metal and fabric containers are light. Wood and terracotta are heavy, particularly in the large sizes.

Water and Heat Retention

Some materials retain water better than others. Unglazed terracotta pots are porous and dry out faster than plastic pots. Metal containers get very hot in the sun and cold in the winter – line with bubble wrap to prevent this. Wood is a good insulator and helps maintain a more even temperature.

These tins come from Pizza Express restaurants who'll often be happy to give them to you. They can look pretty - the downside is that the metal will heat up in the sun, and the tins are not very large - just about big enough for one chilli - or a very small baby bush tomato!

What they look like

This is an important consideration, particularly if you are growing in view of neighbours. If using recycled containers, use your creativity to make them look attractive. Decorate them, cover them with trailing plants or arrange them in attractive patterns.

Cost

How much you spend on containers is as long as a bit of string – you can do it for almost nothing or spend almost as much as you like. There are many excellent recycled options. Sometimes you may want to invest in containers for a particular space. For example, I started with home made wooden boxes on my south facing window sills but found they were very heavy and needed constant repairs. Last year, I bought Earthboxes – because they were light, strong, gave good yields, fitted the space perfectly and are supposed to last (according to the manufacturer!) many years.

Hand made terracotta pots like this can look great and will last many years. The downsides are that they are heavy, dry out quickly, and expensive.

Drainage holes and Feet

All containers need plenty of drainage holes in the bottom. Use a drill or a nail and hammer to make more if needed.

Water needs to flow freely out of the drainage holes. Stand the pot on feet if necessary. Take care not to let pots stand in water for too long – the soil will get water logged and the plants roots will suffocate.

Contaminants

You’ll also want to make sure that your containers are safe for food growing. Avoid re-using anything that has contained paint or chemicals. Also wood that has been treated with toxic preservatives (most external preservatives like creosote are toxic). And old tyres – tyres contain toxic chemicals that leach into the soil. You may be able to prevent some contamination by lining the tyres with strong plastic (eg old compost bags) to prevent the tyre being in direct contact with the soil.

Materials: pros and cons

Below is a table that summarises the pros and cons of each material.

In my next post I will share more ideas on recycled containers and where to source them (thanks for your ideas on Twitter!).

Material Pros Cons Notes
Plastic
  • Non porous
  • Light
  • Withstands weather if UV treated
  • Inexpensive to buy.
  • Easy to find in skips / scrounge in shops (eg buckets, veg trays, recycling bins).
  • Becomes brittle if not UV treated.
  • Offers little insulation to extremes of temperature.
  • Can be aesthetically challenging.
  • Best material to make self watering containers.
  • Most outdoor plastics (eg bins) are UV treated, most indoor plastics (eg storage boxes) are not.
Polystyrene
  • Very light
  • Good insulator
  • Long lasting
  • Trays available from fish mongers.
  • Aesthetics
  • Limited range of sizes
  • Potential fish whiff.
  • Trays are good for growing salads and other leafy crops..
Hard wood
  • Long lasting.
  • Useful to make window boxes ‘to size’.
  • Good insulator
  • Can look good.
  • Heavy
  • Time consuming to cut and make
  • Expensive / hard to find in skips
  • Most durable wood is oak & sweet chestnut.
Soft wood
  • Useful to make window boxes ‘to size’
  • Less expensive than hard wood / easier to find in skips
  • Good insulator.
  • Can look good.
  • Rots quickly
  • Heavy
  • Time consuming to cut and make
  • Line inside with plastic to enhance life.
  • Preserve if desired with linseed oil or Osmo wood protection oil
  • Scaffold boards are heavy but great if you can find them.
Metal
  • Strong and light weight
  • Old olive & cooking oil drums can be scrounged from shops & restaurants.
  • Prone to heating up  in sun, drying soil and stressing roots.
  • Line with bubble wrap to insulate or use out of full sun.
Woven sacks and bags
  • Strong, very light and easy to move
  • Readily available eg builders bags / old recycling bags.
  •  Unsightly
  • Good alternative to raised beds in temporary gardens
Unglazed terracotta
  • Good insulator
  • Often aesthetically pleasing
  • Wide range of shapes and sizes.

 

  • Porous – dries out faster in warm weather, and needs more watering.
  • Cheaper terracotta often cracks after a few years – particularly in frosts.
  • Relatively expensive.
  • Glazed terracotta has similar properties, except it is not porous.
Woven willow
  • Attractive material to weave round sacks and other less visually appealing  recycled objects.
  • Requires time and skill to use.
  • Find a willow weaving course!

 

 

10 comments… add one

  • Loved your articles ( ones I read so far…) thought you might have an idea how to fix my problem… I’m a new indoor grower ( herbs for cooking! LOL house plants and a few veg.) have a small child and two dogs so pesticide is not a good idea I think… HAVE A NASTY INFESTATION of gnat fly and some kind of soil mites ( root eating buggers Grrr ) tried all kinds of things doesn’t seem to work, just tried the 1 part hydrogen peroxide to 4 parts water waiting to see if it’ll work next going to order the Food Grade Diatomaceous Earth and buy sand and peat moss instead of the potting mix of miracle gro I used before. If these steps won’t work I’m booking a room at the psych ward

    Reply
  • Tjere’s a major slug problem, along with high rainfall where I live. Have found that slugs don’t seem to like metal. So built large containers ( 2′ by 3 or 4′) out of scrap roofing metal, secured at corners with scrap lumber. Pieces of 1×3 ( or approx) laid along top edges and nailed into corner posts make a safe and attractive edge.

    Also, have cut up some metal sidewalls from discarded above ground swimming pools. Cut into 2′ strips, easy to wrap into a circle,varying diameters depending on how long. Good for compost bins too, cut about 3′ wide. Tied with rope, easy to release when time to dig it out.

    Reply
  • The motor on my ShopVac, died, so hoses got put aside for other project, leaving the bottom half- the part that contains the stuff vacuumed up. It has wheels. Drilled holes in the bottom and filled with soil- about 3 gallons. Totally perfect!

    Reply
    • Love it Teresa – that’s the first time I’ve ever heard that one!

      Reply
  • Thanks for the interesting article. I wrote about it on my blog.
    /Mattias

    Reply
    • Thanks for sharing that on your blog, Mattias, appreciated. Very best, Mark

      Reply
  • Hi Mark,
    Great article!
    I am curious, I’ve not gone down the metal path with pots as I am concerned about rust. Do you have anything to share on that? I like the idea of bubble wrap as an insulator tho.

    Also I had a chat with someone the other day who attended a Michael Reynolds Earthship seminar a week or so back and from what I gather they said once a tyre has worn down beyond road worthiness that most if not all chems will have already leached.

    Re hardwood, not sure what it’s like over in the UK but you can sometimes find hardwood in the form of old fence palings that have been taken out of a property (usually to be replaced with treated pine :( Fencing contractors a a good source for these – saves them taking it all to the tip) Hard to cut but use a hire or loan site to find a dropsaw.

    Catch you on twitter :)

    Steve

    Reply
    • Hi Steve
      Thanks for stopping by! I have found that metal tins often do rust after a few years. From what I’ve heard the rusting doesn’t release dangerous chemicals into the soil. Having said that, I don’t have categorical proof of this. But if you line first with bubble wrap then with a food safe plastic inside that should help minimise issues, if there are any.

      I hear lots of different things about tyres, some people say they’re safe, some not. I guess nearly all containers have some element of risk attached – and its interesting to hear that the chemical residues in tyres can reduce over tine. Thanks for sharing.

      Great idea for the hardwood palings – not so common here in the UK – but a great tip for readers in Australia and other countries where they are. I have occasionally found old oak floor boards chucked in skips in the UK!

      Cheers!

      Mark

      Reply
  • I see you grow in a very tight area, and I came across a web sight you may be able to get an idear or two from. It grows great stawberry’s in not a lot of space. http://lifeonthebalcony.com/how-to-turn-a-pallet-into-a-garden/

    Reply
    • Thanks for sharing Martin, that’s a nice idea – and a great use of an old pallet! I’ve been meaning to try something like this for a while, so your comment is also a timely reminder that I must get on and do it!

      Reply

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