LAYING OUT THE INSIDE OF THE POLYTUNNEL

There are several options as to the ground plan and you should consider all these before making any definite decisions. Get out a pen and paper and make a few sketches to help in the decision-making process.

NOTE: It helps if paths are wide enough to push a wheelbarrow along.

Option 1: A single central path with a bed on each side. This gives the maximum amount of border to use for growing, but it might mean treading on the soil in order to reach all parts. This is the most appropriate plan for a small tunnel.

A single path

Option 2: Two paths running the length of the polytunnel, which effectively divide the floor plan into three long beds. This gives easy access to all parts of the tunnel, possibly without having to tread on the beds. This is a good plan for a wide tunnel.

Option 3: Individual raised beds, with paths running in between. This gives easy access to all beds; they need never be trodden on and they can be raised to a height that makes work easier for gardeners with back problems. It means that less ground is available for cultivation and the height of the beds might be an issue, in that they reduce the ‘head height’ available for tall crops. This is a good plan for a very large tunnel where maximizing space is less of an issue.

NOTE: Raised beds can be bought pre-made, or you can make your own. Never make them so big that you can’t access all points by reaching in from the edge, or so deep that they hit against the polythene sides.

Option 4: Let your creativity take you where you want to go. Some people have decking, some have hot tubs and some have deckchairs to enjoy the space inside the polytunnel!

Making paths

Some people choose to make a permanent path, using paving stones or tiles. Others simply leave a dry dirt path. The choice is yours and things can evolve over the years. It does make a certain amount of sense to dig out pathways and add the soil on to the beds at each side.

Before laying tiles dig down to a firm base and level this with sand if necessary. Boards can be fitted at each side of the path. Nail these on to posts knocked into the ground. Boards will act as retaining walls, to stop earth falling back on to the paths, and they will help keep the beds raised when compost, etc., is added over the years.

A water supply

If water can be piped to a tap by the polytunnel door, this is ideal. A tap on the inside of the structure means that you don’t have to keep running outside in bad weather to fill watering cans, and fittings are less likely to freeze in the winter. On the other hand, you can use hosepipes and watering systems to bring water from an outdoor tap.

Watering is a major job in a polytunnel and anything that helps with this is of course a bonus. There are lots of watering systems available, from the humble watering can to electronically controlled sprinkling devices, and I’m sure there are devotees to all forms. What follows are a few personal observations. The choice, as always, is with each individual polytunnel grower.

Overhead watering systems and sprinklers wouldn’t be my favourite for a polytunnel. The environment is already heading towards too damp for some plants, which fare much better if leaves are kept dry. Some of these systems offer the greatest degree of control, however, and they may be best suited to very large polytunnels, or those where a limited range of crops grow.

Pipes that drip or weep water at ground level do a good job, with two provisos: one is that a good pressure of water is needed to make them work well (usually no problem with a mains water supply); the other is that pipes have to be laid in an evenly spaced pattern to ensure equal watering for all plants. It would take a lot of pipe to water the whole of a large tunnel in this way, but selective use of this system can benefit thirsty plants like tomatoes.

A hand-held hosepipe and spray nozzle will mean hours spent spraying water around the tunnel, but it will also mean getting exactly the right amount of water to exactly the right points. Leaves can be dampened if necessary, or they can be kept dry while the soil is soaked.

Water reservoirs made from cut-down bottles can make handwatering easier. Reservoirs can be filled with a jet of water rather than having to sprinkle water slowly over the surface of the soil (a jet of water on to the soil can disturb plant roots). They cost nothing to make if you simply save milk and pop bottles: cut the bottoms off, remove the lids and put them spout end down into the ground.

The good old watering can might seem the worst method of all, but it has its advantages. If water is in short supply, watering with a can will ensure that every drop goes to a place where it is needed. Liquid feeds can be mixed with the water, so two jobs will be accomplished at the same time.

Water barrels and rain butts are vital where water supplies are low. These will collect water off any pitched roof, if gutters and downpipes are there to channel the supply. Some polytunnels can be fitted with gutters to do the same job. Wherever you put the barrels, try to choose a point close to the polytunnel, so that you don’t have to walk miles to fill a watering can. Alternatively, if you elevate the container, it might be possible to create a gravity feed to pipe the water down to where it is needed.

Don’t let water stand too long without using it. The idea is to have a good, fresh, clean water supply.

Top Tip

Put barrels of water inside the polytunnel to help raise temperatures through the winter months (see November).

Electricity

An electricity supply can be essential if you want to operate propagators, soil warming cables, lights, etc. However, the combination of electric sockets and a damp environment isn’t ideal. Consult a qualified electrician, or install an outdoor power kit, which has armoured cable and connectors suitable for using outdoors (available from Two Wests & Elliott, for instance – see list of suppliers).

It isn’t wise to use an ordinary extension lead inside a polytunnel.

Benches and shelves

A good potting bench isn’t essential, but it is a useful thing to have. It doesn’t need to be too big; nor does it need to be fixed to the structure. Freestanding units are available from many greenhouse suppliers. Choose one that is easy to scrub down and isn’t too heavy to lift if you want to move it.

If you fancy a bit of DIY, it isn’t too hard to make a bench. Just make sure that no nails or rough bits of timber are in a position to damage the polythene.

If your tunnel has horizontal bars running between the hoops, it’s easy to hang shelves from these. It’s easier still to rest a plank between the horizontal bars on two sets of hoops – although this might set the shelf too high.

Shelves can be fixed to the framework of a polytunnel. Use jubilee clips and hooks to get a fixing against the frame; these will ensure that the shelf doesn’t slip. A wooden shelf can be suspended with a length of rope, but watch out for it swinging if it gets a knock.

NOTE: It’s a good idea to protect the point between jubilee clip and polythene with a piece of hot-spot tape.