Smallholder advice – polytunnel growing tips

What you need to know to establish and maintain your planting paradise.

Polytunnels are an affordable way to boost your smallholding’s growing potential. Many smallholders swear by them as the easiest way to achieve year-round harvests, as well as cultivate crops that would otherwise not survive outdoors.

We share our top tips for polytunnel success.

Choosing your polytunnel

With some fairly basic DIY skills, it is certainly possible to build a polytunnel from scratch. However, with relatively low prices, most smallholders will probably opt for a self-assembly kit.

The quality of the structure is important to consider. Options range from flexible plastic poles to rigid steel. Your choice will ultimately depend on budget, how long you want it to last and its exposure to harsh weather conditions. It is important to ensure you have a safety management plan in place to protect you and your property.

Look for products with good ventilation to control humidity. Certain coverings also claim to prevent condensation build-up and the formation of droplets.

Crucially, it might be worth going bigger than you may initially be planning. Once you’ve created that productive little microclimate, you could easily fill it up and be wishing for more space.

Getting started

It is important that your polytunnel is both well-anchored and has a tightly fitting cover. Well-constructed and maintained polytunnels can last for decades.

Plan your layout in advance, ideally before choosing your polytunnel. You’ll find that planting space will be in demand very quickly, so use it wisely.

Paved or gravel walkways are a sensible addition, and experienced gardeners always recommend segmenting growing areas to aid crop rotation and limit the spread of disease.

Adding plant supports, such as canes, can help encourage vertical growth and maximise precious floor space.

If sufficiently rigid, you can make use of upper areas by suspending shelves, sprinkler systems and hanging baskets from the structure.

What to grow

You have the potential to grow practically anything in a polytunnel – popular crops among UK polytunnel users include cucumbers, tomatoes and even pumpkins. There are also people who have attempted to grow tropical plants, like coffee or cocoa, but not always successfully. Whilst possible, it is a lot more difficult to grow plants like these in a polytunnel.

By providing a warmer microclimate and added protection, the polytunnel encourages faster growth and higher yields of most plants. Polytunnels can extend a growing season by several weeks either side, enabling users to get improved harvests.

Common challenges

The enhanced growing conditions mean you will need to feed and water your soil more regularly than you might otherwise.

The enclosed space can also make humidity an issue, putting plants at greater risk of moisture-related issues. Good ventilation is therefore important.

If opening doors and vents, be careful not to allow birds and animals in. Covering openings with mesh/netting is a simple solution.

The warmth provides ideal conditions for troublesome pests such as aphids. Before introducing any new plants, it is good practice to thoroughly check them over and isolate them elsewhere for a couple of weeks. Attracting beneficial predators, such as ladybirds, will also help keep smaller pests under control.

Maintaining your polytunnel

Polytunnels are the preferred choice of plots particularly exposed to the elements. Their lack of glass and slight flexibility can actually make them more durable than greenhouses in some ways.

However, this durability depends on always maintaining a well-anchored and taut structure. Maintenance is therefore very important.

Before winter, and following any extreme weather, give the main structure a thorough check – right down to the tightness of structural bolts and screws.

Always be on the lookout for holes and tears – small holes can quickly become giant tears. Polytunnel repair tape is readily available – buy it before you need it.

To maximise light and limit degradation of the outer layer, you’ll need to clean your polytunnel at least twice a year. Dirt, algae and bird poo can easily build up over time and can be removed with an organic detergent and soft brush. For larger polytunnels, research the ‘floss method' which uses an old sheet and two ends of rope.