How to Choose the Right Containers For Growing Vegetables

, written by Jeremy Dore gb flag

Potting up

To most people plant pots are just throwaway items – flimsy bits of plastic packaging for houseplants bought from a garden centre or DIY store.  To vegetable gardeners, however, plant pots are an essential part of raising plants from seed - which often predominates the early parts of spring when the ground is still too cold for outdoor sowing.  Choosing plant pots and containers is something we may not give much thought to but there are a surprising number of options and choosing the best types can make a big difference to the success of young plants...

Seed Trays or Plant Pots?

Seed trays are the traditional way to start indoor plants and they are very economical on space and soil.  However, the tray depth is rarely more than a couple of inches and little seedlings soon outgrow the cramped conditions, needing to be ‘pricked out’ into pots while still small.

An alternative approach is to sow several seeds into each 3 inch (diameter) pot.  Once they are a couple of inches high you have a choice:

  • If the seed is cheap you can simply choose the strongest looking seedling to grow on and remove the others. This is best done by snipping them off with scissors at the soil level because pulling them out can disturb the roots of the remaining seedling
  • For more expensive seed such as capsicum, the extra seedlings can be pricked out into other pots in the same way as from seed trays.
  • Some herbs can be raised with several plants together to make them economical to grow.  I usually grow about 5 basil plants per pot and just ‘pot them up’ as a group when they need more space.
Repotting
When the roots hold the pot soil together it's time to pot up into a larger container

Potting Up

Most plants will outgrow the smaller pots in which they start life and ‘potting up’ is the process of transferring them to larger pots to give the roots sufficient room to continue to grow.  If the plants are destined for the garden then you may be able to harden them off and plant them out before they need this but most plants will need potting up at least once.  To do this choose the next size pot, add some potting compost at the bottom, position the plant so the top of the root-ball is still level with the top of the pot and push soil down the sides firmly until it is well supported.

As well as giving the roots more room to grow potting up serves a second very important purpose.  Even the best potting compost gradually loses nutrients as it is watered day after day.  By potting up plants every few weeks they get a fresh supply of new compost with plenty of nutrients to help sustain growth.  If your plants start to show signs of nutrient deficiency such as less vigorous growth or lighter patches on leaves then it is time to give them some fresh potting compost.

Putting Down Roots

Getting plants to grow downwards is as important as the growth above soil.  When they are planted out it will be the ability of the root system to access moisture and nutrients deep in the soil that will help them grow well so containers that have more depth can really help.  There are several commercial products that encourage strong downwards root growth such as Roottrainers which have a ribbed structure to the sides so that roots find it easier to turn downwards.   These work particularly well with peas, beans and sweet corn all of which benefit from deeper roots before planting out.

Plug plants
Plug plants are excellent for raising smaller seedlings like lettuce

On a smaller scale I have had much success with raising plug plants.  Smaller seedlings such as lettuce and flowers seem to be well suited to raising in these little modules and they are so easy to produce because the trays are compact and self-watering.

Biodegradable

For plants that don’t like having their roots disturbed a very effective approach is to use bio-degradeable pots.  These can then be planted straight into the soil and the roots will just grow through them. Various types are available but steer clear of peat ones because of the environmental impact - alternatives include recycled fibres, coir and even dried cow manure!  The main problem is that you can’t pot them up with fresh compost so I think these are best used for fast-growing plants such as squash that will be hardened off and planted out within a few weeks.

Pea seedlings in cardboard tubes

It is easy to make your own biodegradable pots.  There are simple instructions available for making pots out of newspaper but they usually need a firm tray to keep them upright and in my experience they are hard to make with enough depth for many seedlings.  An alternative is to use cardboard tubes stood upright in a tray with compost stuffed in as they provide better depth.  I use these for peas and beans in a similar way to roottrainers.

Recycle and Reuse

You can often reuse perfectly good plastic containers rather than sending them to landfill:

  • Almost any plastic container can become a plant pot as long as you punch plenty of holes in the bottom for good drainage.  This is important because soggy roots can’t get the oxygen they require and that will stunt growth.
  • Many thousands of plant pots and trays are thrown away every year by people who buy their bedding plants from garden centres.  Just ask any neighbour you know who does this and you can have an endless supply of perfect pots with perfectly fitting trays which make them easy to move when hardening off.
  • Old guttering can be used to raise peas and beans.  Once they are a few inches tall you can slide the plants out of the guttering into a trench for planting.  It’s a little tricky the first time you try it but it works well for succession sowing where the plants will be in the ground quite quickly and so don’t need a lot of depth for roots.
Plants in plastic pots

Over To You

Some plants such as root crops should almost never be started in pots but others, like tender basil, do best in pots on a sunny windowsill rather than planted outside.  You can mix and match - I grow some tomatoes for outdoors and others in large recycled pots in my greenhouse.  The trick of course is to experiment and work out what each plant type likes best. 

Do you have your own perfect containers for raising a particular plant or have you found a good way to use recycled items?  Please do add your ideas and tips below...

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Comments

 
"Last year I did highly unscientific, but equal tests of side-by-side trials to answer this question as it was bugging me. I had ceramic pots, plastic pots, net pots, newspaper pots, peat pucks and toilet roll pots. I found that seedlings germinated and grew faster in peat pucks, and this growth continued significantly faster in either toilet roll tubes or homemade newspaper pots. I came by this idea as my local plant nursery was selling young plants in expensive-to-buy, cheap-to-make cardboard tubes. I figured they need profit margins and so would adopt the method that was cheapest, easiest and had the most success. It was the best thing I did ... until... ... after some research I discovered aero/hydroponics yields the highest growth and so if I could replicate that in a soil pot I would be some way to getting the best out of soil container gardening and so I used those seagrass waste bins and those office mesh waste bins. This allowed me to drench the soil fully while keeping the soil safe and undisturbed, and it allowed for the fastest draining, letting the roots breath. It also gave the advantage of air-pruning the roots. When roots hit the sides of an 'open' container they get air-pruned and so develop side-roots on the main branches that have been pruned. This means a greater surface area for nutrient uptake, and greater growth. I only grow in this manner now and give away my cuttings in plastic plant pots to friends, thus reducing my stockpile. I did give some away in homemade paperpots but those were not so thankfully received - they thought I was being super-stingy! ah well!"
Kevin Hannan on Saturday 24 April 2010
"I have found that using cardboard tubes (loo rolls,kitchen papaer etc) very effective when sowing all types of bean.The problem I had was filling them with compost as a lot went between the tubes and was wasted.To overcome this I was advised to flatten the tube,fold the tube in half lenghthways then open it out and you have a square pot to sow into! This eliminates compost wastage and the added benefit is that you can get more tubes in whatever tray you use to stand them up in so you can sow more seeds .I tried this idea this year and ot works great.."
Melboy on Saturday 24 April 2010
"I followed my elderly father's idea. I took plastic yogurt containers (650g - about 5 inches tall) and cut out a small section in the bottom, while leaving the outer bit of the bottom intact. I then took the lid and crafted a piece that would fit into the tub at the bottom. In goes the dirt, the seed(s). When time to plant in garden, I push up on the bottom insert and the roots are pretty much undisturbed. I also use 1 litre milk containers and cut them down some, punch holes in the bottom. When it is time to plant, I just cut away the sides and the plant roots are undisturbed. This also saves on storage space as I just start saving these up starting at xmas."
Christina on Saturday 24 April 2010
"Some great ideas, thanks. Kevin - mesh bins are a really interesting idea that I hadn't considered before. Melboy - what a simple but clever idea to make the tubes square! Christina - that yoghurt pot method sounds very like a large version of the plug plant trays which push up the plug plants when they are ready to be planted out."
Jeremy Dore on Sunday 25 April 2010
"I gave myself an imaginary almighty slap on the forehead when I read Melboy's utterly brilliant and simple suggestion of squaring a round tube. I seem to recall from school (about 35 years ago!) that saves around 20% of space, which is fantastic. It goes to show that many heads are better than one and that's the value of places like GrowVeg.com. I must admit, though, I save on plastic pots all year round so that I can give away rooted cuttings for a good old fashioned nowt!"
Kevin Hannan on Sunday 25 April 2010
"Purely by chance, I received an email today of a friend who is now using flat-bottomed (milk) crates lined with gardening fleece/porous groundsheet for growing root veg. The 'open' sides are apparently proving more successful, and is a great 'modular' way to allow his garden to expand and contract as per his needs - on his balcony, garden and greenhouse. What a great idea!"
Kevin Hannan on Sunday 25 April 2010
"I find that the square pots better,you get more on a tray and they are less likely to move during transportation"
MARTIN FEAVIOUR on Monday 26 April 2010
"I use the plastic cups they give my kids when we go out to dinner. Most of them are more durable than regular plastic pots and they're taller. I drill four small holes in the bottom for drainage and voila - recycling! Plust I use a bulb planter to dig the holes. The bulb planter is the EXACT same size as the standard kids cup so the hole is the perfect size and really cuts down on transplant shock. Its also very fast to do the transplanting. "
Wade on Monday 10 May 2010
"I cut my cardboard loo roll centres in half and stick them in small yogurt pots with holes punched in the bottom. I then fill these with compost and they are then ideal for growing things in that don't like root disturbance such as sweetcorn. The pots keep the cardboard in shape and if you eat two pots at a timelike me,you can keep your trays nice and tidy. The cardboard and plant can then just be put in the soil when they're ready. New to vegetable gardening but learning! "
Estelle Fowden on Monday 7 June 2010
"I have a lot of people saving loo rolls for me for beans and look forward to making them square. Last year we grew three half row lengths of carrot seeds in gutter pipes, which were great to slide in. I grow herbs all year round in the plastic supermarket plum boxes. They already have holes in the bottom. Everything else possible starts life in other recycled food tubs. "
Lisa on Tuesday 22 February 2011
"i usethe cans from canned food. I punch holes in the bottom and i decorate the outside part rolling around some scrapbook paper or recycled paper from gifts or blackmail! I just made two today with antique pink shade and a pretty flower on top, and i make sometimes some witha picture of what i'm growing inside. Like the spicy pepper seed isaved from my mom's dried peppers, i took a pretty picture, printed it and applied some creativity around :) i also use half eggshells, and the cardboard rolls from the toilet paper. I encountered a problem though. I think it spreaded from an eggshell that i popped inside a cardboard tube... some red little particles started to form on the soil and the cardboard, and spreaded on the neighbor cardboards pots. I completely took apart the first one and put my poor little basil seedling inside a plastic pot, the others still have the dots on the cardboard but it doesn't seem that is growing anymore. Does anyone know what it could be?"
Silvia on Thursday 24 May 2012

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