Ever dreamt of buying a greenhouse and pottering around in your glazed sanctuary, whatever the weather? There are a few things to ponder before you take the plunge. Erecting a greenhouse is a commitment of your time, and a lot of work, so it is always worth checking any local planning or zoning regulations before you commit to a purchase.
In this article, we will consider where to locate your greenhouse; how to choose the right one for you; the advantages of buying new or second-hand; whether to build it yourself or call in the professionals; and the key considerations of greenhouse gardening, including water, heat, fertiliser, ventilation, and what to grow.
Where to put your greenhouse
Consider the practical and aesthetic considerations when siting your greenhouse. If you intend to have electricity, or an irrigation system that runs off mains water, this may have a bearing on the placement of your greenhouse. Providing power and water to a greenhouse can be expensive and lots of work, so aim to reduce that labour and those costs by positioning your greenhouse close to services. Fear not if you do not have the budget to connect to water or electricity: most people, including those who rent properties, make do perfectly well with watering cans and isolated heaters.
Site your greenhouse away from prevailing winds and in a sheltered spot in the garden. During high winds and storms, you don’t want to be looking out of your window fretting whether your greenhouse is safe. Avoid positioning your greenhouse under any trees, as they naturally shed branches which will damage your greenhouse.
Cold air will travel down a slope in the same way that water will, so don’t site your greenhouse at the bottom of a slope, particularly a north-facing one, as this is likely to be a frost pocket which will have a detrimental effect on your plants during the winter and early spring.
How to choose the right greenhouse
Research the pros and cons of the different types of greenhouses on offer, to work out which is the best one for you.
Aluminium-framed greenhouses
Aluminium frames are lightweight and low maintenance, with the ability to withstand stresses, and it is a material that will not rust. An aluminium frame will be solid enough to support polycarbonate or glass panels, and can be painted in a range of colours to suit your aesthetic tastes.
Advantages
• Aluminium is versatile with the ability to withstand all types of weather.
• It is rust and rot resistant.
• If cared for, the frame can last for many years and can be dismantled and re-erected on several occasions, if you move house or decide to sell the greenhouse.
Disadvantages
• With such a light frame, foundations must be robust and sturdy. This can often come with extra costs.
• It has very little insulation capability, creating colder environments in the winter compared to a wooden frame.
• Often in kit form, it is difficult to extend or customise an aluminium frame.
Wooden-framed greenhouses
Wood is a beautiful material to construct a greenhouse frame, but it isn’t without its drawbacks, often needing regular maintenance to keep it in good condition. Constructing a bespoke greenhouse frame out of wood gives the design great flexibility and the option for individuality. However, greenhouses are damp and warm environments that are conducive to rot, which can affect timber as a natural product.
Advantages
• A wooden frame can insulate and maintain warmer temperatures and does not lose heat as quickly as a metal frame.
• It offers great design flexibility.
• It’s available in kit form as well as bespoke.
Disadvantages
• Pest build-up can be an issue with a wooden frame, and it requires more intricate cleaning compared to a metal one.
• More regular maintenance will be required to keep the framing in good condition.
• Construction can be more time-consuming and specialist in comparison with a metal-framed greenhouse.
What to consider before buying a second-hand greenhouse
Customising or building your own greenhouse from scratch can be an incredibly rewarding experience, but you need to ask yourself whether you have the time, the expertise and the money to be able to pull all of the different components together to create an environment that grows plants successfully. Ventilation, heating, staging and light transmission all need to be considered.
Second-hand green houses are commonplace: like many absorbing hobbies, growing under glass becomes addictive, and gardeners soon realise that their original greenhouse has become too small to cater for their needs. This appetite for more space will often result in them selling their smaller greenhouse online or through a local advertisement.
When buying a used greenhouse, ensure that the frame is in good condition, without cracks or rust. A framework that is deteriorating will have a shorter lifespan and will end up costing you money if you need to replace any damaged parts. Replacement glass is easy to obtain through a local glass merchant, but the higher percentage of glass that you can retain from the used greenhouse, the better.
You can expect to pay a fraction of the cost of a new greenhouse when buying second-hand, often less than 50 per cent of the retail price, depending on whether you are required to dismantle it too, but do shop around and carry out your research to make sure that you are getting the best value for money compared to other greenhouses that are also for sale.
Building it yourself vs calling in the professionals
The cost of professional contractors may initially be offputting, but this is another opportunity to put your skills under the microscope and have an honest conversation with yourself. Do you have the ability to create a sound and level base that will last for a number of years? Do you have the logic and patience that is required to construct a greenhouse, particularly a second-hand one that may be missing parts?
When it came to building the recycled concrete slab base and the adjoining piece of recycled crazy paving for my greenhouse, I chose to engage with a contractor to put the base down. This contractor had machinery such as dumper trucks, diggers and lasers to ensure that the levels were absolutely spot on. The sheer weight of the concrete slabs was quite sobering and I’m glad that the group of contractors put that base down as I think I would have physically struggled to do so on my own.
Erecting the frame of my greenhouse was a methodical process but took a lot longer than I had anticipated. With each different greenhouse kit you learn the method as you go. This takes time and more often than not you need to retrace your steps and sometimes undo the previous task to enable you to move on to the next one. The cost of a contractor to build the greenhouse was not one that I could justify, but in hindsight I appreciate that the greenhouse would have been erected much quicker due to their experience and skills.
Key considerations when growing in your new greenhouse
We are creating an artificial environment with our greenhouses, in order to get the best from our plants. The way in which our plants respond will be directly linked to the type of conditions that we provide. When gardening under glass there are certain aspects and considerations that must be considered and manipulated to achieve success.
Light
Consider light levels: getting this right for the types of plants that you want to grow is one of the most fundamental elements in greenhouse growing. It is essential, particularly during the winter and early spring, to maximise the amount of light transmission through the cladding of your greenhouse, whether that be glass or polycarbonate. If your glass is dirty, that will hinder the amount of light that can penetrate through to your plants and cause weak and leggy growth.
In complete contrast, during the summer light levels can be too intense and lead to scorching and damage to the plants. During the period of the year when temperatures are high and light levels are more intense, it is essential to restrict the amount of light that comes into the greenhouse to reduce the amount of stress on our plants. Shading by netting or by paint during the height of the summer will create conditions of less extreme heat which will be more comfortable for plants and for you to inhabit the greenhouse at this time of year.
Water
We can’t grow plants in greenhouses without water. Being able to supply our plants with their hydration needs is a key component when growing plants under glass. Being able to react to your plant’s needs, depending on the time of year is this skill that gardeners hone over time, and as you inhabit your greenhouse you will become more attuned to your plant’s hydration levels. Excessive watering during the more dormant season of growth in the winter and early spring can be detrimental to plants, and in contrast, not enough water during the highly active summer will lead to drought conditions, causing the plants to deteriorate and eventually die.
Water is a precious resource, and our greenhouses demand a great deal of water at a time of year when there is often little rainfall, so it is essential that we mitigate this by harvesting as much rainwater during the winter months to sustain us during the summer as possible. This can be achieved through guttering and down pipes which feed water butts and tanks.
Heat
Different plants will require different temperatures to thrive. Most domestic gardeners will be able to provide a moderately heated environment during the winter, often enough to keep the greenhouse frost-free but not much warmer than that. The reality for most gardeners is that their greenhouses will be bright but cool during the winter, but then incredibly warm during the summer. We can manage these environments by choosing the plants that we cultivate in the greenhouse at any given time of year.
What to grow for beginners
Bright and cool conditions during the winter are perfect for overwintering plants, and growing hardier salads and herbs, as well as spring-flowering bulbs and cut flowers. During the summer, with much warmer conditions, we can turn our attention to more tropical and heat-loving crops which will favour the conditions. Tomatoes, cucumbers and peppers will not only grow but thrive in conditions that are much warmer than the garden outside.
Fertiliser
When growing in containers – and, to a lesser extent, borders – in the greenhouse, the way in which we intervene and expose plants to different nutrition levels will affect the rate and the type of growth that we encourage. Most peat-free composts, although free-draining, have very little nutrition that can sustain a plant over a long period of time. To this end, we need to supplement our plants with nutrition as they grow in our greenhouses.
Ventilation
Gentle and consistent air movement around our plants will encourage healthy growth, reduce pests and diseases, and help with pollination. In the same way that we tune into our plants’ watering requirements, we also need to tune into the way that we can manipulate the greenhouse environment to deliver the right amount of ventilation given the conditions inside and outside the greenhouse. Cold draughts during the winter can be harmful to sensitive plants, but a lack of ventilation during the summer can exacerbate the hot and dry conditions, which will cause our plants to suffer. It all comes down to the right amount of ventilation to encourage healthy growth in response to the conditions outside our greenhouses.
The Greenhouse Book by Tom Brown is out now, published by DK