How to create a polystyrene box garden

While the premise of my blog was to move away from polystyrene box gardening, I know that a lot of people visit my blog in the search of PBG info.  Plus, while I've embraced earth-based gardening, I admit that some plants actually grow better in polystyrene boxes than the ground, for many reasons including portability, climate needs and isolation.  I have a list of vegetables that are particularly well-suited to PBG below.

It's not complex or expensive to set up a PBG, but here's my step-by-step guide:

You will need:
1. polystyrene box (or I've also used old council recycling bins or buckets)
2. newspaper
3. potting mix
4. seeds or seedlings
5. mulch (recommended but optional)

1. Go to your nearest greengrocer or anywhere that sells fresh fruit and vegetables, and ask for a polystyrene box (or two, or three or four).  The ones with holes in them are better, but if they don't have holes, the beauty of polystyrene boxes is that they're incredibly strong, but also very easy to cut.  If the greengrocer is a mingy pig and wants to charge you for the box, then go somewhere else.  They send hundreds of them to the tip, very few of them recycling them, so you're actually doing them a service by taking them away....

2. If your polystyrene box doesn't have holes in it, then cut some drainage holes in each corner and perhaps a couple in the bottom.  You don't want the box to become waterlogged.

3. I like to line the bottom with a few sheets of newspaper, because newly opened potting mix is usually very happy to escape through the drainage holes.  The polystyrene boxes with the pre-cut holes often have quite big holes, and so the newspaper allows drainage but prevents the soil from running away.  The newspaper will eventually rot away (which is good for the soil), but by then the potting mix will have compacted.  Note: do not use shiny magazine-style paper, or full-colour spreads.  For some reason, the coloured ink is not so water-soluble.

3. Tip the potting mix into the box, filling it to about 10-15cm to the top if you're planting seedlings, or 5-10 cm if you're planting seeds.  However, make sure you can lift the box without straining.  One of the joys of PB gardening is the portability of these light vessels.  Don't compress the soil but give the potting mix a bit of a water.

4.  If you're planting seedlings, then pull them out of the punnet by holding the plants by the base, turning the punnet upside down and gently squeezing the base to loosen the soil.  Hold each plant by the base at the level that you want the soil to end up, then tip some more potting mix into the box, filling in the space around the seedling.  Press down around each seedling so that it's firmly in place and give it a light water, preferably with some liquid fertiliser mixed in with the water.  I use Seasol.

If you're going down the seed route, then sprinkle the seeds where you want them across the top of the soil, and then add more potting mix over the top to the depth indicated on the packet (usually equivalent to the size of the seed).  Water lightly, again, preferably with fertiliser.  However, because the seeds you're sowing are usually quite small, it's better to use a fine spray of water.  I use one of those generic spray bottles used in hairdressing etc. You want to sow more seeds than you want plants, because some of them won't come up or others might be more puny than others.  Once the seeds have grown a little, thin the plants out, by either transplanting them or just pulling them out completely.  Don't throw them away though, just lie them on top as mini-compost.

5.  If you've planted seedlings, then you can place some mulch around the seedlings to keep the soil moist, prevent it from overheating, and deter weeds.  I like sugar cane mulch best. If you've planted seeds then don't use mulch just yet; wait until the seeds have grown into seedling-sized plants at least.

Easy, quick, cheap and delicious!

Plants (in my opinion) that are great for PBG, remembering that I live in quite a cool climate:

Pretty much all herbs
I still have my thyme in an old council recycling bin, for instance.  Because herbs take up a relatively small amount of space, you can usually plant multiple plants in the one box.  Herbs are wonderfully suited to PBG because they have a great space/value ratio and potentially save you a lot of money.  If you've ever spent $4.50 on a bunch of thyme, used one sprig, and then watched the rest rot in your fridge, you'll know what I mean.  For $4.50 you could set up a thyme PBG and be able to eat it at your leisure without any waste. The photo below shows my thyme plant.  It started off as a small 5cm round bush and used to share its box with some chives (long gone), and now it's filled the entire tub!  I now sell bunches of this thyme at markets for $1 bunch.  It's paid itself off many times over.

Old recycling boxes, for instance, make great pots. The recycling box holds Thyme, the lemongrass is on the right, and 'Figly' the Genoa Fig is on the left.  I have a tendency to name my plants....
A note on companion planting for herbs.  Because some herbs are quite invasive, and others have their own way of quietly progressing or bolting to seed etc etc. there are certain herbs more suited as 'box-mates' than others.  Mint and Oregano, for instance, are good box-mates.  I wouldn't plant mint in my garden because it spreads so readily, so I have a couple of boxes of different varieties of mint just outside my back door.  Coriander and Rosemary are also good companions.  I keep my box of coriander in a coolish spot, because it tends to bolt to seed if it gets too hot.  I keep my basil and lemongrass together because they both hate frost. In autumn, I'll bring them both inside and stick them on my window sill (although I keep them in smaller planter boxes for that reason)

Lettuce and small green leafy vegetables such as spinach
You want one leaf of lettuce for your lunchtime sandwich? done.  Lettuce is relatively expensive, goes off quickly, and is super easy to grow.  It also does well in the space/value ration.

You know how you can buy those expensive do-it-yourself 'mushroom kits'?  Well don't.  Just buy some mushroom compost from any nursery, tip it into the box, keep it in a cool, darkish area of the garden, and you'll grow delicious mushrooms.

Capsicum, Chilli, Tomatoes
They don't have much space, but I've grown some of my best tomatoes in polystyrene boxes.  In my last rental house I had two polystyrene box tomatoes and two ground tomatoes, side-by-side.  Guess which ones did better? Yep, the PBG toms

Spring Onions
This last year I've had spring onions in the ground, but I'm about to switch back to keeping my spring onions in a polystyrene box.  I believe they grow better in a box.  Also good in the space/value ratio.