You could not be faulted if you thought that the two ingredients needed for a rock garden are a garden and rocks. However, this is not the full extent to this specialized form of gardening as will become apparent in this article.
Rock gardens have been popular for many years as a way of introducing the grandeur of the mountain terrain into the home garden, albeit in a much reduced scale. Depending on the scope of the enthusiasm and resources in attempting to replicate what nature has spent numerous years achieving, some rock gardens are large and impressive, incorporating boulders rather than rocks and there are many such examples to be seen.
For the vast majority of us this is not possible or desirable. But it does not mean we have to give up the notion of having the beauty of mountain scenery as a part of our garden.
When I took my first stroll around the garden of the house I moved into eight years ago, as soon as I saw the bank of tall quack grass across the width of the backyard, "rock garden" immediately sprang into my mind. Actually, it was "rockery" because I'm a Brit and we give some things different names. Another thought simultaneously passed through my mind -- "hard work," and although this has been the case, it has been worth it.
Today the quack grass has been more or less eradicated and replaced by rocks and, for good measure, a trickling waterfall and stream. During the four-year period it took to achieve this, I made mistakes and would like to pass on the worst so you can avoid them when you launch into building your own rock garden.
One thing I did do right was to join the local chapter of the North American Rock Garden Society. There is nothing like rubbing shoulders with like-minded people and gleaning their freely given knowledge forged over many years.
On the basis that I had a garden, and now needed rocks, I set out to find them. You can go to a specialist and purchase rocks and have them delivered onto your driveway. Or you can ask everyone you meet if they have any rocks they don't want, which is a surprisingly lucrative method. It means you have to transport them and lug them into place. As a result, my rocks are generally only as big as I could lift. This is not a deterrent if they are placed carefully. As my rock garden is about 50 feet long by 10 feet wide this meant a lot of lugging.
My biggest mistake was not properly preparing the soil before placing the rocks. In my enthusiasm to make progress I neglected this basic need for the plants I wanted to grow. Alpine plants do not like our clay. Where they come from is, believe it or not, rocky and this provides fast drainage. I have corrected this by replacing the clay with a mixture of sand, gravel and peat to a depth of about 12 inches. The weeds love it!
Placement of the rocks is important. More rocks rather than less are best. I put mine in rough rows touching each other and slanting down from the top of the garden to near the front to try to emulate a strata formation. The rocks should lean back, so that rain drains to where the plants are located, rather than run off and away. This also helps to stop the frost toppling them over. All you need is imagination and a pleasing layout will be achieved.
I'm sure some of you are thinking that this all sounds like too much hard work, but as I alluded to above, there are alternatives. Crevice gardens use thin slabs of rock placed vertically close together with the plants grown in the gaps. A garden wall can be used in the same way. The size of the garden needed to achieve the pleasure to be gained from growing alpine plants is immaterial. It also means spending less on buying plants. I have seen many rock gardens the area of a bathtub; many older gardens are planted in stone troughs previously used for feeding and watering cattle.
If you have a small garden or like to have your plants nearby or inside the house, a popular method of rock gardening is to utilize containers. Troughs of many sizes, shapes and materials can be used. If you want a reasonably large area to grow in, decide on its final resting place first, as you are not going to move a concrete trough once it's full of soil mixture, rocks and plants.
Tufa, a variety of limestone, formed by the precipitation of carbonate minerals, is very popular rock. Its porosity is conducive to growing healthy plants. Hypertufa, typically made from a mixture of cement, sphagnum and pearlite, can be used to emulate natural rock and can be formed into troughs.
Styrofoam boxes can be used, modified to look as if they are concrete, and have the advantage of being lightweight. You can then move the trough to a more protected location during the winter.
Troughs are often referred to as miniature gardens. The design can be enhanced with dead branches and other objects. If they are whimsical, and incorporate miniature objects, such as gardening tools, benches and figurines, they are called fairy gardens. Children are especially enchanted by fairy gardens.
What plants to use? In addition to numerous alpine plants there are many choices. Irises, bulbs, hostas, aquilegias, heucheras and cacti are but a few. All come in miniature varieties, as do many different trees and bushes.
I hope this brief excursion into the pleasures of rock gardening has whetted your appetite for more information. A good start would be to attend the annual NARGS show and sale at Soergel Orchards on Brandt School Road from 9 am. to 3 p.m. today. Here you will find an exhibition of planted troughs, plants for sale and answers to your questions.
If you can't wait until then try: http://home.comcast.net/~sylvialynch/alpine_line.htm and read about the club's activities.