The garden gives the railway life; the railway gives the garden purpose. The two must be integrated with great care. It is not the purpose of this work to suggest specific plant material for your railway. That you must choose yourself after much research and study. Think in general terms, though, about the kinds of plants to use in any given setting.
Groundcovers are just thatthey cover the ground. They come in all shapes, sizes, and colors. If you are choosing something to carpet a station area, pick a small-leaved, tightly knit plant. If you want to cover a large rural area, you can use something that has larger parts. If the effect you are trying to achieve is homogeneous, use a plant that lies flat and presents a smooth upper surface. Plants that stick up more will give more texture to an area. These can often be used in conjunction with flatter-growing plants. However, they will want to grow into each other, so careful and meticulous maintenance at their boundaries will be an ongoing necessity. Many groundcovers are invasive, so plant accordingly. Again, maintenance will always be necessary, particularly if you are trying to achieve a neat and tidy look.
Trees provide verticality in a scene. They can be used individually as landmarks or focal points, in groves to accent a larger area, or in forests to cover a mountainside. When choosing trees, try to find those that have scale-sized components. A larger tree with tiny needles or leaves will read better in the railway setting than a smaller tree with big leaves.
A tree can be selectively pruned to enhance its appearance and make it look more treelike. Dense spruces can have their foliage trimmed up from the bottom, exposing the trunk. Remove branches to reveal the trees structure. Look at the tree carefully before cutting. Once a branch has been removed, its hard to put back. A carefully pruned tree can become a point of interest or famous landmark on the railway, resembling a gnarly old pine or a venerable oak. A poorly pruned tree can become landfill.
When planning the railway garden, the concept of scale must be kept firmly before you. The most effective railway gardens are planted in tiers or zones. Three zones are typically used. Zone 1 is closest to the track; zone 2 is a transitional zone that can be near the track or between zone 1 and 3, depending on its context; and zone 3, which is farthest from the track.
In the area closest to track and structures (zone 1), plants must be chosen, placed, and maintained with the greatest of care. These are the ones that relate directly to the railway and lend scale to surrounding structures. A too-small plant will look silly. A too-large one will dwarf the scene and look out of place. This is tricky ground, fraught with hazard. Full-size trees often radically dwarf structures like houses. On the railway, plants often need to be underscale to appear right. A 100' tree in 1:20.3 scale would be 53" inches talltoo tall for most scale scenes. Be careful.
Certain mosses can make convincing lawns, and groundcovers can become open meadows. Upright thymes can form shrubbery and miniature hedges. Constant maintenance in this first zone is a must.
Flowering plants should be avoided in this zone. Flowers are almost universally out of scale and, despite any individual beauty, destroy the illusion. A scene composed of different textures and shades of green, silver, and yellow is much more effective than one littered with blossoms. Of course, a plant will want to reproduce itself, so, if you must, choose plants with the smallest flowers possible and dont photograph your line until the blossoms have gone to seed.
This first zone is most important in developed areas. A miniature garden suggests miniature people, habitation, and civilization. Areas on the railway that might be considered out in the country can have a less-well-defined first zone.
The second zone is away from the track a bit, and away from scale habitation. Plants here can be generally larger, lending a wild atmosphere to the scene. They should still have scale-sized components, however. Even though they are over-scale in stature, they are still an integral part of the scale scene. The second zone can often encroach on the first without jarring the eye. A hint of wildness will make the developed areas that much more attractive and will help to give them a distinct sense of place. Also, when following a train from one developed area to another, passing through a wild, overgrown area (zone 2 adjacent to the track) helps with the illusion that you have been somewhere.
The third zone is well away and can be just about anything. Avoid garishly colored flowers, though. They will look unnatural. This zone forms a backdrop for the railway. It becomes a barrier between the garden railway and the outside world. Use it to hide visual distractions like houses, clotheslines, and the neighbors fence.
Consider the formal and informal usage of plant material, particularly in zone 1. Formal usage can include manicured lawns; trees planted in galleries or in pairs, framing an important building; tightly clipped hedges (yes, they can be done in miniature). Pathways lined with geometrically placed plants, combined with arbors or stately fences, will also denote formality.
Informal plantings can include trees planted as if volunteers, raggedy hedges of thyme, meadows, groundcovers used as fill, and just about any other non-rigid application you can think of.
As in the real world, formality is often intermixed with informality, adding interest to a scene. The courthouse with its plantings in a grid is across the street from the casual city park.
When placing plants, think about their immediate surroundings. Where would a tree near a house be planted? It should be close enough to relate to the house and be part of the scene. But it shouldnt be so close that it dominates or endangers the house. Look around as you drive.
Main streets in towns often have little by way of plants on them. An area of your railway without plantings provides contrast and interest for those that do.
Plant material near the track can seriously affect the look of the railway. A full-size railway recedes into the landscape when viewed from afar. However, when seen close up, you realize the plants are kept at bay. A poorly maintained line might have plants encroaching while a well maintained one will have a sharp delineation between plant and railroad. Observe reality.