Rooftop Gardens and Roof Gardening Ideas

Container Gardening for Rooftop Gardens

With regard to the plants and their containers for your rooftop garden, the choice is not nearly so narrow as you might think, given the exposed site. The choice of garden container is endless – indeed anything will do – depending on the strength of the roof, but for your own well-being, the lighter they are the better and the less risk you take of back-strain, when lugging them about.

For the heavier garden containers, remember to spread the load and give them a small deck of their own if the roof is not already covered in this way.

Raised Beds for Rooftop Gardens

If your rooftop garden is strong enough to take a raised bed, you are in luck, for most plants will be happier with their roots less confined and the compost will not dry out so quickly, especially if you line the beds with plastic sheeting or a coat of bituminous paint.

All the usual methods of making a raised bed can be used, but remember that if one side of the bed is against an existing structural wall, you must install a serious vertical damp-proof course if you are not to cause real problems. Take expert advice, but in many cases you can give the wall two or three coats of an exterior wall-proofing substance such as Aquaseal or Synthaproof and then line the bed with plastic sheeting. This should do the trick, but it is worth making sure by checking with your builder. rooftop gardens

Ideas for roof gardening could include lightweight raised beds, albeit a little primitive, but they can be made quite cheaply by using chicken-wire, strengthened in some way by timber battens or strong galvanised wire, which you then line with plastic and fill with compost and drainage material in the usual way. These can then be disguised by some lightweight ‘hide’, such as skip timber trellis, or a roll of half logs which you can buy at garden centres, etc., or by planting directly through the mesh and plastic with trailing and mat-forming plants, so that the unattractive outlines of the bed are hidden.

Ivy of course, Vinca, Cerastium tomentosum, Aubrieta, Alyssum and all the other bushy, spreading little plants would do the trick. The effect should be something like a natural mound rather than a bed, and would fit quite well into an informal scheme. If your roof is concrete, you could consider covering it with gravel which would complete the rustic effect, but you would have to fit some metal gauze over the drain-traps and down-pipes to prevent the gravel being washed into them.

A bed of peat blocks is another possible solution for a raised bed. The blocks are light to handle when dry, but once they are on the roof they must be soaked before use. They can be laid like bricks or stone, and the walls should slope slightly backwards with soil sprinkled between each layer and plants inserted as you build. Their roots will grow into the blocks and help to bind the wall. You will have to keep the bed well watered as the blocks would shrink and eventually crumble if allowed to dry out. One way to prevent this would be to provide the bed with a length of perforated hosepipe which you could easily connect to a tap and so keep them gently irrigated.

Whatever kind of raised bed you decide upon, they will all need a good layer of drainage material at the bottom and some weep-holes as well, although these will not be necessary for a bed made of peat blocks. Weep-holes are placed at the bottom of the retaining walls to allow surplus water to drain away. This is particularly necessary in the wet, windy months, when the plants could drown if not given effective drainage.

Another idea is to place lengths of plastic piping at the bottom of the beds. These should be perforated at the top and sides to allow the water to enter the pipes and to be carried out through the sides of the bed at a point which will drain to the nearest outlet or down-pipe. These pipes should be covered by a good layer of drainage material which can be crocks, bits of old bricks, stones, pebbles, gravel or fired-clay granules, such as Hortag. Even broken-up bits of polystyrene foam can be used and these would be especially light. Odd lengths of plastic piping are often found on skips and so are broken bricks and other rubble, so you should be able to do all this cheaply enough. For an added precaution, I would place a small piece of metal or nylon gauze over the inside of the weep-holes and indeed over the drainage holes of any roof-top containers, as the less gunge that escapes the better. You could also use the thin fibreglass carpet-underlay that I mentioned earlier for this purpose.

Roof Gardening Plant Ideas

It is amazing how many plants will thrive on a rooftop garden if you site them sensibly and give them a little care and attention. The outer ring of planting will have to be able to stand up to the wind and many of our native plants will do this. However, leylandii is a good tough evergreen plant, and makes a solid barrier. Thuja occidentalis and its cultivars are also good. These conifers are best planted when small, before their roots have been constricted by a container.

rooftop gardens Hollies, cotoneasters, viburnum tinus, the taller euonymus, yew and pittosporums are all tolerant of the winds and, although Privet is not always regarded as being especially wind resistant, I have used it on some very exposed roofs with good results. Tough climbers include the Ivies, Clematis montana and its varieties, Honeysuckles, Jasminum officinale, the dreaded Russian Vine and the delicate looking Passion Flower will all do well in rooftop garden situations.

Within these outer windbreaks, a vast range of plants will thrive, and many will particularly enjoy the good drainage that raised beds and containers provide. You will be able to find plants for both shaded and sunny positions, as well as those that will be happy in either. I have grown the eucalypts, fatsias, mahonias, ligustrums, choisyas, yuccas, cordylines, skimmias, roses, rhododendrons, hebes, hydrangeas, a variety of silver darlings and a host of others, as well as fruit, vegetables, herbs, bulbs and bedding plants of all kinds on a rooftop garden with much success.

Roof gardening can be very rewarding – many fruit and vegetables are as charming as they are useful, whilst the herbs are both, and fragrant as well. Potatoes, strawberries, alpine strawberries and many herbs, especially parsley and the thymes, can be grown in barrels of wood, plastic or clay, which have had planting holes provided all over their sides.

These days, you can buy fruit-trees grown on dwarfing-rootstocks, and these are the ones to go for. It is even possible to buy trees where two or three varieties have been grafted on to a single trunk. Tomatoes do well on a rooftop garden and are easily grown in Gro-bags. Last year’s Gro-bags can be used for filling a container the following year.

You will have to choose your compost according to your plants. While the peat-based composts are light to handle and excellent for many plants, they do not have much holding power for large plants, which need something a bit more solid to help them withstand the winds which may whip up around your rooftop garden. Whatever garden container and soil you choose, try to fit some kind of drip tray underneath the container, as this will help to prevent the roof becoming stained and slippy, which can easily happen as a result of the constant watering and feeding that the plants will need on your rooftop garden.

Furthermore, if you are interested in extending your home and potentially bringing some of your garden indoors, you could consider adding a conservatory to your property.  Read more here …  For information on styles of conservatory for the home, click here.

13. October 2010 by Dave Pinkney
Categories: Roof Gardens & Balcony Gardening | Tags: , , | Comments Off on Rooftop Gardens and Roof Gardening Ideas

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