Page 39 - Simply Vegetables Summer 2022

Accessories
Electric is not essential but may be useful for lighting so work can be done in the evenings during the winter. It is also useful if lighting is needed for growing early crops like onions and leeks for exhibition; use the new LED types of lights. It is not economic to heat polytunnels as they do not hold the heat that well in the winter, but it can be useful for heating soil warming cables or heat mats in propagators for seed sowing and cutting propagation.
Irrigation can be by watering can, hosepipe or using an irrigation system of trickle, seep or drip irrigation. Porous pipe laid on the soil adjacent to the crop is very economical with water and avoids the polytunnel becoming too humid.
Propagators can be set up on a bench at a height for easy working, or if a large area is wanted, they can be on the floor. Use electric cables set in sand or a heat mat and have a cover to retain the heat.
Thermometers of the maximum and minimum type are very useful as they show how high and low the temperatures have been in the previous 24 hours if re-set
each day. Digital thermometers are also available.
Plant supports are useful for growing tomatoes, cucumbers, melons etc. as they should not be tied to the polytunnel hoops as it could bend them. A frame or crop support bars are available or can easily be made.
Polytunnel Erection
Instructions should be supplied with the kit and should be read carefully and followed, many suppliers also offer You Tubes videos showing how to erect the tunnel and are
well worth a look. Some companies have a telephone helpline service, but these are not often available at weekends. Most companies will also offer an erection service if required although
battens to the hoops and are easy to adjust. These battens or rails are commonly used if side vents are fitted.
When ready on a calm and warm day unroll the polythene and
at a cost. Depending on the size of the tunnel two or more people are required to erect the tunnel although a lot of the work can be done by one person.
carefully pull it over the hoops, fix one side in place and then as a team pull the polythene tight and fix it on the other side of the tunnel. Before fixing the ends fix the doors in position then pull the polythene tight
and pleat it to remove any slack, then nail it to the door frames and rails. Fix the doors in position and check everything is in place and tight.
Depending on the size of the tunnel a central path
or two paths will be required, these can just be compacted soil, but this tends to become wet and slippery after a while. Better are concrete paving slabs if available or woodchip, bark, Mypex or gravel. I have used an old dumpy bag cut into strips and pinned down which seems O.K. but it has only been down a month, so it is too early to say yet. Aim to make maximum use of the area so keep the paths narrow but wide enough to get a wheelbarrow along.
Soil Preparation
Once the tunnel has been erected there will be no natural rain or other weather on the soil and all watering will be by hand, hose or irrigation system. This tends to lead to the soil structure deteriorating over time. To avoid this happening add plenty of organic matter to the soil or construct some raised
Check the site is clear
and level first, clear any
obstructions and level if
required; measure and
mark out the tunnel and
hoop positions and ensure
they are square, double
check before knocking in
the sockets. If concreting
the sockets dig out holes to
the correct depth and use some hardcore to hold the sockets in position. Once everything is correct concrete the sockets in place, if the hoops can be held securely the framework can be constructed and then you are certain everything is right.
Irrigation can be by watering can, hosepipe or using an irrigation system of trickle, seep or drip irrigation
Allow the concrete to set before putting the polythene on, this is the point when help is required. There are two methods of securing the polythene one is to dig
a trench along the side and ends of the tunnel frame and the polythene edges are placed in the trenches which are backfilled with the soil which holds it tight. The second method which I prefer is to use timber battens fixed to the hoops and the polythene is fixed to the battens. I prefer this as it is easier to tighten the polythene later if it expands in the heat and becomes a bit loose. U bolts can be used to fix the
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