Robust high tunnel greenhouse with generous protected growing space for vegetables, young plants and a longer gardening season

Our Bloomcabin polycarbonate high tunnel greenhouse is designed for gardeners who need a spacious, permanently protected growing area for vegetables, young plants and heat-loving crops. The three-metre-wide tunnel shape provides practical floor space for clearly arranged beds, a working path and irrigation. Unlike a flexible film cover, polycarbonate sheets with a thickness of six mm form a fixed covering over the galvanised steel structure.

The base length is 4 m and can be adapted to the required growing area with matching extension sections. The galvanised steel frame is anchored in the ground through its hoops. Together with the permanently fitted polycarbonate cover it creates a stable, protected growing environment. Explore our greenhouses and conservatories as well as our guides and planning advice.

More protection than a simple polytunnel – and substantially more growing room than many compact garden greenhouses

This model suits anyone who wants to use the space regularly for vegetables and plants. It provides room for permanent beds and working paths, while the selectable length still allows it to suit the property and the actual space required.

Key specifications of the Bloomcabin high tunnel greenhouse

Width: 3.00 m.

Height: 2.10 m.

Length: Base model 4 m; extensions in 2 m steps.

Frame: Galvanised steel, 1 mm material thickness.

Profile: Omega profile, 56 mm wide.

Hoop spacing: 1 m between hoops.

Snow load: 210 kg/m².

Ground anchoring: Each hoop extends approx. 35 cm into the ground.

Cover: 6 mm UV-protected polycarbonate.

Access: One door at the front.

Ventilation: Two side windows for temperature control and air exchange.

Warranty: 12 years under the applicable warranty terms.

A front door and two side windows simplify access and control of the internal climate

The internal height makes upright work easier and leaves room for tall crops such as tomatoes or cucumbers. The front door is the main entrance. Keep the area immediately behind it clear so watering cans, harvest containers and garden tools can be carried in and out without damaging plants.

Both side windows must remain freely accessible from inside and outside. Position plants, supports and stored items so the windows can be operated fully. When planning beds, also check that the windows will still be reachable when crops are fully grown.

Open and close the door and windows regularly to check that they work properly. Remove soil and plant debris from moving areas. If a component sticks, investigate the cause first instead of forcing it.

How to position crops for short routes and good access

When dividing the interior, consider not only plant type but also growth height, inspection needs and harvest frequency. This makes sensible use of the available space and preserves access to every crop.

Plan the location, ground and future use before installation

Measure the footprint for the selected tunnel length and prepare an area that is as level as possible. Adequate working room is needed around the structure during assembly so hoops and polycarbonate sheets can be positioned safely. Also plan surface-water drainage: rain from the fixed cover must not collect at the structure’s edge or in front of the door.

As the hoops extend about 35 cm into the ground, establish the route of underground electricity, water and drainage lines before work begins. Do not wait until assembly to remove larger stones or other obstacles. On uneven ground, prepare the area so all hoops stand on the same line and the specified installation depths can be achieved.

Plan how components will travel from the delivery point to the prepared area. Access must remain clear during assembly; soil, compost and garden equipment must not obstruct the working area. Remember that both long sides must remain accessible from outside for inspection and maintenance after installation.

Further advice on planning and ordering is available in our guides and planning advice.

When is a high tunnel the better choice than a classic aluminium greenhouse?

A classic aluminium greenhouse offers a linear appearance, varied design options and can become a visible feature within the garden.

With a high tunnel, the focus is instead on a large uninterrupted growing area, robust construction and the option of modular extension.

Choose the high tunnel when you need the greatest possible protected space for productive growing. A classic greenhouse is better suited where a straight-lined form and visual integration into the garden matter more.

Adapt use and care to the site and local weather conditions

Gardening conditions vary considerably by region and property in South Africa. Coastal sites may bring wind, humid air and changeable weather, while inland or sheltered locations can experience intense summer heat and colder winter nights. Use the high tunnel according to your garden’s microclimate rather than following a fixed calendar.

The protected space can offer a clear advantage for early crops in late winter and spring. Later in the season, heat-loving plants benefit because rain and wind reach leaves and fruit less directly. In autumn, many crops can continue producing for longer while light and temperatures remain suitable.

During the first season, record notable temperature patterns, particularly humid spells and areas with weaker plant growth. These notes help you adapt planting and care routines more precisely to the site in the following year.

Choose a sunny place and leave sufficient room for air exchange

A sunny position is particularly beneficial in winter, spring and autumn. Observe when buildings, hedges and trees cast shade over the intended area. At the same time, leave enough distance from obstacles for both side windows to ventilate effectively.

On wind-exposed sites, observe the prevailing wind direction and avoid unnecessary wind corridors between buildings. Natural wind protection at a suitable distance can help, but must not permanently shade the tunnel or block air circulation.

Also consider future maintenance when choosing the position. The front door must be easy to reach, and sufficient space should remain along both sides to inspect windows, polycarbonate sheets and fastenings externally.

Arrange tomatoes, cucumbers, peppers and early salads sensibly across 3 m width

The fixed 3 m width works well for two side bed rows with a central working path, or three narrower growing zones. Position tall plants such as tomatoes and cucumbers so they do not unnecessarily shade lower crops. If using strings or supports, plan their fastening before planting.

In late winter and spring, salads, kohlrabi, radishes, herbs and young plants can use the protected space before heat-loving summer crops take over. After the main season, part of the tunnel can again be used for hardy leafy vegetables or late herbs.

Mark occupied bed sections and note which crops stood there. This makes planning the next planting easier without having to reorganise paths or ventilation areas.

Respond early on hot days, before heat and high humidity build up

In South Africa, a closed tunnel can heat up rapidly on sunny days. Open the side windows before plants show signs of heat stress wherever possible. Early ventilation softens temperature peaks and removes humid air from dense planting.

Especially for tomatoes, it is useful to keep leaves as dry as possible and avoid encouraging condensation. Ventilate on mild days too when outdoor air allows good exchange. After watering, excess moisture should be able to escape from the crop.

During prolonged hot periods, adjusted watering times and temporary shading where needed can help. The suitable measures depend on region, orientation and the plants being grown.

Bring water directly to roots instead of dampening the whole interior

The polycarbonate cover keeps most natural rain away from the beds. Water supply must therefore be managed deliberately. Drip lines or targeted watering are especially practical because they bring water directly to the root zone and keep leaves drier.

Watering frequency depends greatly on soil type, temperature, crop size and density, and the season. Heavy soil holds water differently from sandy ground or a raised bed. Do not water to a fixed weekly schedule; check the actual soil moisture instead.

Collected rainwater can be used to irrigate beds. Position containers and route lines so paths and access to the front door remain clear.

Start with 4 m and match extensions to the real space requirement

The base length is already sufficient for several crops in many home gardens. Extra sections make sense when more cultivated bed space is permanently needed. The high tunnel can therefore grow with vegetable production or the gradual development of the property.

Nevertheless, consider the possible final length before first assembly. Paths, irrigation lines, compost areas and adjoining beds are easier to plan when a future extension direction remains clear.

For smaller self-sufficiency gardens, a longer version can be attractive when several crop groups are to be separated. Choose additional space only if it can genuinely be maintained, watered and planted.

Inspect the frame and fastenings before winter and after severe weather

In South Africa’s snow-prone areas, snow can vary greatly in weight with moisture, wind drifting and temperature, and may collect unevenly on the roof.

After heavy snowfall in snow-prone areas, or after severe storms, inspect the tunnel from outside. Unusual deformation, loose fastenings or one-sided snow build-up should be checked and remedied promptly. Remove snow without damaging the polycarbonate sheets or steel frame. Do not use sharp tools or walk on the cover, and avoid creating a heavily one-sided load while clearing.

Before the cooler season, systematically check M5 screws, D40 plastic washers, side windows, the door and ground anchoring. Clean the transitions between frame and sheets, remove plant debris and make sure all moving parts close. Loose pots, tools or support elements must not stand inside where they can strike the sheets. Work from the entrance to the end of the tunnel so less visible areas are included.

Replant beds in an orderly way and use the cleared tunnel for inspection

Decide the sequence of planned crops early. This lets you prepare a bed specifically for its next planting after harvest, without affecting neighbouring crops or the working path.

Clear harvested sections completely before the next crop moves in. Remove diseased plant material from the tunnel and prepare the soil for the intended follow-on crop. Also inspect supports and irrigation components within the relevant bed area.

After the final clearing, remove tying material, empty pots and labels, and clean work areas. Check irrigation for blockages or damage. Then use the open interior for a thorough visual inspection of frame, fastenings and sheets, as these areas are easier to access without dense foliage.

Generous protected growing space for community and home gardens

The high tunnel suits larger home gardens as well as plots where efficient use of the available growing area matters more than the decorative appearance of a classic greenhouse. Its functional shape puts protected plant space first.

Before assembly in a community garden, estate or managed development, check the applicable site rules. Confirm any requirements for size, position or boundary clearances before ordering a longer tunnel. Ask the local municipality whether the project needs approval.

The consistent width makes it easier to repeat a clear layout of paths, beds and irrigation, even when extending later.

FAQ – Bloomcabin high tunnel greenhouse