One of the major benefits of building your layout outside is that much of the scenery is already in situ and you just need to add a few buildings and some figures to create a realistic model railway. Well yes and no. In fact, it is sometimes easier to create realistic scenery on an indoor small-scale layout indoors where you have total control rather than compete with nature in the backyard.
Unless you are extremely lucky in having the perfect site to create you layout or opt to modify your design to take full advantage of the existing topography you are likely to find yourself involved in a considerable amount of physically arduous work. This is especially the case where you are intending to build a raised layout, or the physical attributes of your chosen site are incompatible with your layout design (i.e. hills where you wanted a flat terminus and goods sidings (marshalling yards) or low terrain in just the spot you planned to install a steep grade to a high mountain plateau.
The prospect of hard work should not discourage you unduly as there is usually a solution, but this can often prove expensive to implement in terms of materials. Once you moved 10 tons of soil (or ‘dirt’) from one part of the garden to the other in a dodgy wheelbarrow with a spade that has seen better days, perhaps in inclement weather, you may wish that you hadn’t pursued this approach.
If you can round up a few friends to help so much the better.
You also need to consider whether the existing garden needs any modifications in order to fit the railway in and landscape the surroundings to give a natural look. Perhaps move that water butt or realign the garden path? Remove the bird table or water fountain (currently occupying the spot where it would be nice to have a garden pond?). If there is some physical structure limiting your design it is probably a good idea to relocate same if at all possible rather than compromise a good design.
Of course, if you just want to run trains al fresco that is a personal choice. If, however, your aim is to achieve a sense of realism then to borrow a quotation by Ian Stock from “Garden Railway Realism”, build “A real railway in miniature: realistic operation of realistic trains in a realistic landscape” then we need to turn the realities of nature to our advantage by using natural light and sounds, seasons and weather, trees and plants to give an immediacy and impact that could never be boxed-up indoors.
The essential problem (or challenge) with achieving realism is that the garden environment is in 1:1 scale whereas your model trains are to a much smaller scale – possibly 1:16 right up to 1:32 – and if the scene is to look right you need to miniaturise the natural landscape to align more closely to your chosen scale.
This is a tall order if your garden site is home to large trees or overgrown bushes but even grass is likely to grate when viewing everything in situ. As Jack Verducci observes in “Garden Railroading – Getting Started in the Hobby (Kalmbach Publications) a well designed garden railway will stand on its own as a beautiful landscape even without a train.”
He rightly points out, with good reason, that the majority of the time you will see the landscape with no train present, so it is well worth the effort to make landscaping a high priority in your own plan in order to create a scene that is co-ordinated and pleasing to the eye. He likens garden railroad landscaping to Japanese-style gardens where the use of miniature features is used to make a space look larger.
So where to start? I would suggest searching the web for images of garden railways round the world, ideally with similar climates to your own, to see what can be achieved and get some practical ideas for your own layout. Indeed, I would strongly recommend that you also establish a realistic budget for at least partial implementation of your scenic and horticultural plans lest you find yourself with insufficient funds having invested it all in locomotives, rolling stock, track and power and control equipment.
There is a vast amount of information out there and I will append a list of the sources which I found to be informative but if you are in lock-down or whiling away the winter months indoors this would be a valuable exercise.
Here are just a few of the “garden scenic images” I came across whilst doing my research but there are thousands of others on the world wide web waiting to be discovered. Remember, the principal aim is to create an impression of a landscape and a pleasing and complementary composition rather than try to create a miniature version of all the flora and fauna.
Pay particular attention to slow-growing trees that have conical appearance or upright (erect) a habit which might lend themselves to judicious pruning and herbs which can be a godsend when seeking to provide perennial groundcover. Be careful when selecting your trees as “slow-growing” does not necessarily mean small or dwarf. In 10 years the amount of growth achieved can be surprising.
As a rule, try to avoid using annual bedding plants which can be difficult to control and rarely look convincing although there are bound to be exceptions.