The great indoors: how to pick the best glasshouse for your garden

I was a student at the National Botanic Gardens in Glasnevin when I first discovered the magic of glasshouses. Entering its great Palm House on a icy winter’s morning felt like slipping through a portal into an exotic world filled with the gentle fug of warm, humid air and plants that soared skywards in a tropical tangle of leaves and arching fronds.

It was then that I learned to love the peculiarly addictive smell to be found inside all glasshouses – that sweet yet tangy whiff of new growth, decay and damp soil – as well as their cloistered, otherworldly atmosphere. No matter if it was snowing, raining, or even freezing hard outdoors; enclosed within the protective carapace of those high glass walls even the most tender plants grew with lush abandon.

Most glasshouses, of course, aren’t of such lofty dimensions as those belonging to the Bots, but even in an average-sized domestic garden their many charms are undeniable. The best, for example, are pleasing to the eye in a way that no polytunnel (much as I love the latter) could ever be, combining functionality with good looks so that rather than detracting from the overall appearance of a garden they do much to enhance it.

They are also longer-lasting than polytunnels (the latter typically need their plastic skins replaced every six to eight years) while their construction allows for much easier exclusion of cold draughts and more effective heating when plants need to be protected during the frostiest of winter nights.

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When a garden belongs to an historic property or listed building a glasshouse can also be made to a design that complements those all-important period details, from decorative embellishments such as cresting and finials to the pitch of its roof. For keen gardeners possessed of deep pockets, it can even be custom-built to a shape, size and design that fits seamlessly into an awkward site or to replace an original period glasshouse that’s long beyond repair.

An outstanding example is the bespoke service offered by family-owned British company Alitex (alitex.co.uk), whose beautiful, elegantly engineered glasshouses can be found in historic gardens around the world, including many large RHS and National Trust properties in the UK, as well as here in Ireland.

Manufactured from long-lasting, light-weight, polyester powder-coated aluminium and toughened glass, they are available in a wide range of colours (for an additional charge, the company offers a colour-matching service).

Models can be freestanding or lean-to, with a range of different roof pitches and add-ons such as rain-harvesting systems, external shading (to protect plants on very hot, sunny days), tiered display and work benches, external cold frames and different internal growing zones (to suit the requirements of different plants) as well as heating and lighting systems.

Considered the crème-de-la crème of glasshouses, the Alitex range comes with a lifelong warranty for the aluminium structure and a 10-year warranty for the paintwork. It is a particular favourite of Dundalk-born, Chelsea gold-medal winning designer Paul Martin, who describes these "long-lasting, beautifully-crafted statement pieces as the horticultural equivalent of an Aga or a Rolls-Royce".

Such exquisite craftsmanship doesn’t come cheap; the starting price for a bespoke Alitex glasshouse is £800-£3,000 per sq m, or equivalent to that of a new car. More within reach is its off-the-shelf National Trust collection, which starts at £16,000 for installation of the compact “Hidcote” model. (2.6m x 3m), with initial groundworks/foundations to be carried out by a local contractor/landscaper (expect to pay about €4,500 for these).

Also more affordable is the UK-manufactured Gabriel Ash range of glasshouses, which are built from sustainably sourced, long-lasting Western red cedar. The only range of timber glasshouses to be endorsed by the RHS (the UK’s Royal Horticultural Society), it includes a selection of handsome models suitable for historic/listed properties, while the firm also offers a bespoke design service.

Among its most popular designs are the compact RHS Rosemoor (standard size 198cm  x 2.36m), which Owen Chubb, the Dublin-based landscaper and Gabriel Ash’s Irish agent, calls “perfect for the smaller urban garden”m and the larger RHS Wisley model (standard size of 2.7m x 3.55m).

All Gabriel Ash glasshouses are made with toughened glass and come with a 10-year warranty and a lifetime expectancy of 25-35 years, as well as fully automated full ridge-length ventilation. Standard models can also be customised in a variety of ways, including adding extra length, extra windows, extra louvred vents and wider/wheelchair-accessible doors, cold frames and external rain-harvesting systems.

Chubb, who has installed Gabriel Ash glasshouses all over Ireland (including in Helen Dillon’s new Monkstown garden and at the GIY headquarters in Waterford), has noticed an increasing demand for high-quality, long-lasting, elegant glasshouses that enhance the overall design of a garden .

“People get so fond of them that they decide to take them with them if/when they move,” he says. “One of the many great features of the Gabriel Ash range is that they can be dismantled and rebuilt.”

Orders have a lead-in time of six-eight weeks, with prices for the RHS range (including installation and VAT) from €8,500-€16,000 and preparatory groundworks/foundations an additional €1,500-€2,000. Prices for the more affordable Classic range are €4,500-€12,000, with preparatory groundwork a further €1,000-€1,500. Display models can also be viewed by appointment at Owen Chubb’s showrooms in Rathfarnham (see owenchubblandscapers.com and gabrielash.com).

Another reputable Irish supplier of quality glasshouses is Greenhouse Ireland, which acts as agent for several excellent ranges including the Belgian-manufactured Janssen brand and the British-manufactured Griffin range. Both are made of long-lasting powder-coated aluminium and can be similarly custom-made to a wide variety of specs as regards ventilation, roof pitch, pane widths etc.

Prices for the handsome, high-end Griffin range, particularly suitable for period properties, start at around €22,000 including installation (this does not include laying the foundations/building plinth walls, for which the company suggests employing a local builder). The far more affordable Janssen range starts at around €1,800 for the smallest model (1.62m x 2.36m), which comes in kit form (installation on site would be about €600).

Based in Birr, Co Offaly, Greenhouse Ireland also has its own showrooms with a wide range of models on display (see greenhouseireland.ie). Lead-in times for the Janssen range is no more than a couple of weeks, but several months for the Griffin houses.

Whichever model of glasshouse you do plump for, the same rules hold true as regards careful site selection. So choose a sunny, open, level and easily accessible spot well away from overhanging trees or large shrubs, with enough space to roughly orient the glasshouse on an east-west axis to maximize winter light (north-south is better if you only want to use it during the late spring/summer months).

It’s also well worth installing lighting and some waterproof sockets; a nearby tap is essential. Unless you plan to grow directly in the ground, some sort of internal paving is also a good idea.

Size is also important; Alitex recommends a minimum width of 2.5m-3m to allow sufficient room for a central path wide enough to access with a wheelbarrow.

Last, but not least, make certain that the model you choose comes with more than sufficient ventilation, a painful lesson that too many Irish gardeners learned to their cost during last summer’s searing heatwave.

THIS WEEK IN THE GARDEN
Even in the mildest gardens the time has come to clear away the frost-bitten remains of summer bedding plants. Short-lived annuals can be simply pulled out and put on the compost heap, while half-hardy/tender perennials such as pelargoniums, fuchsias,  plectranthus and canna lilies can be overwintered in a cool glasshouse or porch, and tuberous begonias and dahlias can be stored in a cool, dark, frost-free shed cover of a cool glasshouse, all to reuse next year.

To keep the displays going over the winter and early spring, refill any freshly-emptied pots or window-boxes with hardy winter varieties chosen for their colourful evergreen foliage or pretty flowers. Examples include skimmia, winter-flowering pansies, trailing ivy, heuchera, winter-flowering heathers, hellebores, evergreen ferns, sarcococca and cyclamen (in milder gardens). Pop in a sprinkle of spring-flowering bulbs  (tulips, narcissus, chionodoxa, crocus,  hyacinths) for some extra flower power.Late autumn is a time to appreciate the beauty of the many kinds of berrying or fruiting trees and shrubs that add colour and texture to the garden.

Examples include the many decorative varieties of mountain ash (Sorbus), crab apple (Malus), Euonymus, Skimmia, holly (Ilex), Cotonesater  and certain species of dogwoods such as Cornus kousa chinensis and the lovely Himalayan strawberry tree (Cornus capitata). As long as the ground isn’t badly waterlogged or very frozen, November is an excellent time to plant any of these trees or shrubs.

Chrysanthemums are enjoying a resurgence in popularity as gardeners rediscover their usefulness as long-lasting, very late-season flowering plants. Many varieties of these sun-loving perennials also make excellent cut-flowers with a very long vase life.Some such as ‘Spartan Fire’,  ‘Ruby Mound’ and ‘Emperor of China’ are hardy enough to grow outdoors, while the tender or half-hardy types can be kept outdoors as container-grown plants during the summer months but should be moved into a glasshouse, sunny porch  or  polytunnel in late September.

Overwintered under cover in this way, some of the latest-flowering varieties such as the blush-peach ‘Avignon Pink’ , ‘Pandion Bronze’ and ‘Minstreel Red’ will keep blooming right up until Christmas. Plants are best bought as young rooted cuttings in spring, and can also be very easily propagated from cuttings . Recommended suppliers include chrsyanthemums.direct.co.uk and sarahraven.com (via ParcelMotel).

DATES FOR YOUR DIARY
Thursday, November 15th (8pm) in the Artane Beaumont Family Recreation Centre, Kilmore Road, Artane, a talk on garden photography by David O'Flynn on behalf of Dublin Five Horticultural Society  (admission €5).
Wednesday, November 14th (3pm) in the Visitors Centre, National Botanic Gardens, Glasnevin, Dublin 9, "Is the Scots Pine an Irish Pine?", a lecture by Dr Colin Kelleher as part of Science Week on how Trinity College uncovered the true history of this handsome native tree. See botanicgardens.ie