Sturdy crop shelter with ample room for vegetables and seedlings, helping extend the productive garden season

For gardeners, the Bloomcabin high tunnel greenhouse with polycarbonate panels provides a generously sized, permanently sheltered place for vegetables, seedlings and crops that enjoy warmth. The 3 m-wide tunnel accommodates beds, an access path and irrigation in a practical layout. Unlike a flexible film tunnel, it uses rigid 6 mm polycarbonate panels fitted to a galvanised steel frame.

The standard length is 4 m and compatible extension sections let the growing area follow your needs. Each arch of the galvanised steel structure anchors into the soil. Combined with the permanently fitted polycarbonate cover the frame forms a stable enclosure for growing. Browse the Bloomcabin greenhouse and conservatory collection or consult our practical guides for planning.

A tougher enclosure than basic film and more crop space than many small garden greenhouses

Gardeners who intend to cultivate vegetables and other plants regularly will find this model practical. There is sufficient space for established beds and access paths, while the choice of length lets the footprint reflect both the property and the area genuinely needed.

Key specifications for the Bloomcabin high tunnel greenhouse

Width: 3.00 m.

Height: 2.10 m.

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

Frame: 1 mm-thick galvanised steel.

Profile: 56 mm-wide Omega section.

Arch spacing: 1 m between arches.

Rated snow load: 210 kg/m².

Anchoring in soil: Each arch is set roughly 35 cm below ground.

Cover: 6 mm UV-protected polycarbonate.

Access: Single door at the front.

Ventilation: Two side windows provide adjustment of temperature and airflow.

Guarantee: 12 years under the applicable guarantee terms.

Entry is through the front, while two side windows help manage airflow and temperature

With its interior clearance, the tunnel supports upright tasks and taller crops, including tomatoes and cucumbers. Entry is through the front door. Leave an open landing just inside so you can move watering cans, produce tubs and tools without brushing against the plants.

Keep each side window reachable from outdoors and within the tunnel. Arrange crops, trellises and stored equipment so neither opening is restricted. Your bed layout should also allow the windows to be reached after the plants have attained their full size.

Test the door and both windows from time to time. Keep their travel areas clear of soil and vegetation. When something begins to bind, find and remedy the reason before applying more force.

Position crops for short routes and good access

Crop species are only one consideration when dividing the interior. Allow for mature height, how often each planting needs inspection and how frequently it will be picked, so all available space remains useful and every crop can be reached.

Assess the location, soil conditions and intended use before building

Mark out the footprint for your selected tunnel length, then make the area as level as practicable. During construction, leave safe working clearance around the frame for handling arches and polycarbonate sheets. Consider where runoff from the solid roof will go as well; water should not pool along the edges or at the entrance.

Because the arches penetrate about 35 cm, locate buried electrical cables, water pipes and drains before starting. Deal with large rocks and similar obstructions during site preparation rather than while erecting the frame. If the terrain varies, level it sufficiently for the arches to align and reach their intended embedment depth.

Before work starts, decide how each component will travel from the drop-off point to the prepared site. Keep that route and the assembly zone free of soil, compost and equipment. Once built, the tunnel also needs exterior access along both long sides for checks and upkeep.

For more help with selection and preparation, visit our planning and ordering guides.

Which situations favour a high tunnel over a conventional aluminium greenhouse?

Conventional aluminium greenhouses bring a crisp architectural shape and a range of styling choices, allowing the structure to contribute visibly to the garden design.

By contrast, this tunnel prioritises an expansive uninterrupted crop area, durable framing and the flexibility to add modular sections.

Select the tunnel when productive, sheltered growing capacity is the chief concern. Choose a conventional greenhouse instead when straight architectural lines and deliberate integration with the surrounding garden carry greater weight.

Let local weather and the individual site guide operation and maintenance

Australian gardens encounter markedly different conditions across regions and properties, from humid coastal or tropical districts to hot inland areas and cool temperate locations. Wind and exposure also vary from one block to another. Manage the tunnel according to its observed microclimate rather than relying on one nationwide planting calendar.

Where spring sowing is appropriate, shelter can give early crops a useful start. As the season advances, warmth-loving crops receive less direct rain and wind on their foliage and fruit. In districts with a suitable autumn, production may continue while available light and temperature still support growth.

Keep notes during the first growing season on unusual temperature patterns, periods of high moisture and patches of poor development. Use those observations to improve the next season’s planting positions and maintenance routine for this particular site.

Look for sun while preserving clearance for ventilation

Sun exposure is especially valuable during spring and autumn in temperate regions. Check the proposed footprint at different times to see where trees, hedges or buildings create shade. Provide enough separation from obstructions for both side windows to exchange air effectively.

On an exposed block, identify the usual wind approach and avoid siting the tunnel in a channel formed by buildings. Distant natural screening may be beneficial, provided it does not leave the greenhouse in persistent shade or impede ventilation.

Future upkeep also matters when choosing the position. Ensure easy approach to the front entrance and retain exterior clearance on both sides for checking panels, windows and their fasteners.

Arrange tomatoes, cucumbers, capsicums and early salad crops across the 3 m width

Across the 3 m width, you can set out a centre path between two edge beds, or divide the floor into three slimmer crop strips. Position tomatoes, cucumbers and other tall plants where they will not cast avoidable shade. Arrange anchor points for twine or trellising before planting.

Spring space can go first to lettuces, kohlrabi, radishes, herbs and seedlings, then to summer crops that prefer warmth. Once peak harvesting has passed, return part of the tunnel to resilient leafy greens or herbs for the later season.

Label the occupied sections and record the crop previously grown in each. Those notes make the next rotation easier to organise without shifting the access route or areas needed for ventilation.

Act ahead of hot conditions so heat and moisture do not become trapped

Under Australian sun, temperatures may rise rapidly inside a shut tunnel. If outdoor conditions permit, adjust the side windows before the crop displays heat stress. Prompt airflow limits the highest temperatures and carries moisture away from closely spaced foliage.

Tomato foliage in particular benefits from remaining as dry as practical, so avoid conditions that promote needless condensation. Mild weather can still provide a useful opportunity for air exchange. Following irrigation, allow moisture held around dense plants to disperse.

During a prolonged hot period, changing irrigation times or adding temporary shade may be useful. Base the response on the district, tunnel orientation and quantity of foliage.

Apply water at root level without dampening the entire enclosed space

With the polycarbonate roof excluding most rain from the beds, irrigation must be managed intentionally. A drip hose or other localised method is convenient because moisture reaches the roots while less water lands on foliage.

There is no single watering frequency: season, temperature, soil characteristics and the size and density of the planting all influence demand. Heavy earth retains moisture differently from sandy soil or a raised garden bed. Inspect the soil itself instead of watering to an inflexible weekly schedule.

Rainwater collected for the garden may also supply these beds. Locate tanks and irrigation runs where they will not narrow the aisles or interfere with the front entrance.

Begin with 4 m, adding sections only where more cultivated area is justified

For many household gardens, the starting length accommodates several different crops. Extension bays are worthwhile when extra bed space will be cultivated consistently. This allows the structure to expand as vegetable production increases or the property is developed in stages.

Even so, consider the likely finished length before the initial build. Keeping one extension direction available makes it easier to position paths, watering pipes, compost storage and beds alongside the tunnel.

A longer layout may suit a small productive garden whose crop groups need separation. Add that capacity only when there is enough time and water to plant and maintain it properly.

Check steelwork and fasteners before winter and again following severe conditions

The mass of snow changes with its moisture content, temperature and wind-driven distribution, and roof accumulation may be uneven.

After major snow or storms, examine the structure from outside. Attend promptly to distortion, loosened attachments or snow loading concentrated on one side. Clear snow only by methods that protect both the sheets and steelwork. Never stand on the covering or use implements with sharp edges, and avoid shifting the load in a way that heavily weights one side.

Before colder weather, work methodically through the M5 screws, D40 plastic washers, two side windows, front door and ground anchors. Clear plant matter and clean each panel-to-frame junction, confirming that moving components close correctly. Position loose pots, tools and trellises where they cannot strike the cladding. Inspect from the entrance towards the rear so less visible points are not overlooked.

Prepare beds methodically for their next crop, using empty space to inspect the structure

Set the intended cropping order in advance. After harvest, each bed can then be prepared for its successor without disrupting plants nearby or obstructing the access aisle.

Once a section is harvested, empty it before installing the following crop. Take diseased material out of the tunnel, then condition the soil for what will be planted next. While that bed is open, inspect its irrigation parts and any supports.

At the season’s final clear-out, collect ties, labels and empty pots, then wipe down work surfaces. Test irrigation for damage and blockages. With foliage gone, inspect the frame, panel fixings and sheets carefully; the cleared interior exposes areas that are otherwise difficult to reach.

Extensive protected crop space for home gardens and shared plots

This tunnel works in sizeable household gardens and on plots where efficient cultivation is valued above the ornamental presence of a conventional greenhouse. Its purpose-led profile gives priority to sheltered room for plants.

For a community garden, consult the site’s own requirements before building. Confirm any conditions governing dimensions, placement or clearances before committing to an extended configuration.

Because the width does not change, paths, growing beds and watering systems can follow the same orderly pattern when extra sections are added later.

Bloomcabin high tunnel greenhouse FAQ