Unlike our previous piece about choosing the appropriate compost bin, the decision to invest in a greenhouse is an altogether larger investment and the greenhouse you choose will be dictated largely by the parameters of space and budget. You also need to think about what you will be using the greenhouse for, as there are other factors that will also take priority in the design of your greenhouse, such as temperature control and stability.
Generally a hot greenhouse will maintain a minimum temperature of around 65 degrees Fahrenheit, while this temperature can be increased to suit your needs, this greenhouse is generally favoured by gardeners in a cold climate or with a desire to raise really tropical species. However, in moderate climes this temperature can be regulated by careful ventilation to make best use of the local sunlight.
A warm greenhouse, as its named would suggest, caters for a much larger variety of plants and can be used to house more tender species brought in from the garden over winter, or for raising half-hardy plants. You should be careful to plant with an eye for space though, as it can become a temptation to house many cultivars that may not require the extra attention and will thrive just as easily outdoors!
The cool greenhouse is the artificial answer to frost damage, ideally suited for the incubation of hardy seeds and saplings until they have a chance to germinate or form a solid root foundation. Really a form of training wheels before its charges are ready for exterior planting.
Once you’ve decided what you’ll be growing you can look at the other deciding factors. Where size is concerned, the cost is relative and so there are a variety of designs for the shape and dimensions of a greenhouse.
Types of Greenhouse
The detached ‘Quonset’ type is the most common design in commercial horticulture and agriculture, however their size and shape is perhaps not very suitable for the domestic garden. More commonly seen is the basic rectangular model with pitched roof, although they can come in both very decorative, and very basic styles.
While the simple lean-to design isn’t perhaps commercially viable, and therefore not a common sight at gardening warehouses, it is very practical for the hobbyist, particularly one seeking a heated space. It can be attach to the walls of any structure or even a freestanding wall on your boundary, and the replacement of glass on one side with sturdier materials will make it far more heat efficient. Similar to the lean-to, a furrow roofed greenhouse attaches to a permanent structure whilst sacrificing an interior wall. These designs are particularly suited to areas with heavy rainfall as their furrows can attach directly to the guttering of a house and with a little ingenuity can feed an irrigation system below.
Greenhouses are available as either permanent or collapsible structures that can be stored when not in use. Personally I would recommend the collapsible variety, as the materials required for a detached greenhouse of any longevity make the whole project rather costly, not to mention the convenience of having a greenhouse you can erect at whatever time and location you deem fit.
Of the permanent varieties, the customisable, the do-it-yourself nature of greenhouses is one of their greatest attractions. It feeds the constructive instinct inherent to any gardener and all of these designs can be tailored by way of structural materials such as timber or aluminium, glass or plastic, to make them more personal to you. Each of these materials has their own characteristics which should be considered based on the garden they will inhabit – while wood framed is traditional, it is, of course, prone to rot and is a much heavier material to erect. Aluminium tends to be more expensive, but will not rot and is much more lightweight. Glass can easily get broken, but plastic will degrade over time. So, the choice is yours!
Of course, if a full size greenhouse seems too great a commitment to you, then there is always the option of cold frame storage. Typically providing anywhere between 5 and 10 square feet and sheltered growing space these low-level boxes are favoured due to the fact that they are easily and simply constructed and many of the building materials can even be salvaged – if you know of a neighbour or friend who is having windows replace or double glazing fitted, for example, then you can offer your gratitude and perhaps some cash to the builders to ensure that the old windows leave their frames in one piece. These glass sheets can then be used for your cold frame’s lights.
So, as you can see, greenhouses can be your doorway to growing cultivars otherwise unsuitable for your environment or, failing that, it can just provide a shelter for more delicate plants over the winter period. But do bear in mind the added costs of a heated greenhouse as many temperate climates are still too frigid to support a warm greenhouse on their own and also, the smaller the space, the easier it is to keep warm.
By Josh Ellison