If you think about it, most natural settings you see typically show groupings of similar plants. These plants are indigenous to the area (i.e. living and occurring naturally). This natural phenomenon gives us an excellent example and point of reference for our designed landscapes. If you’ve ever seen a mass of Native Rhododendron or Mountain Laurel growing in the woods, you know how beautiful “plant groupings” can be.
In this picture there are 3 Alberta Spruce grouped together to complement and soften a granite sign at a corporate center. One spruce would not have been enough. The 3 carry more weight to balance with the massive sign and the grouping looks more natural, especially with the woodland behind.
Less Is More
A plant grouping exemplifies simplicity and makes it easy on the eye and mind. The result is a pleasant and comfortable setting where “it just feels right”.
By arranging your plant groupings you can “lead the eye” to focal points or destinations in your design – in effect you can influence how people move through the gardens.
Beyond the design merits of grouping like-plants together are the practical gains. The intent is to have them ultimately touch one another. To that degree you must still be aware of their size potential and growth habit and, like always, arrange and space accordingly. (Have I ever said this before?) The point being you won’t feel compelled to keep each plant separate by aggressive pruning & trimming.
You may have noticed that in these examples all the groupings have been in 3’s. Generally speaking odd numbers do make for nicer groupings, especially in the smaller (“countable”) ones. Once your plant counts get bigger it becomes less of an issue. Below is a massing of azalea along a border. Whether there’s 7,8 or 9 azaleas is not an issue. And remember too, ideally they’ll grow together and become one beautiful form.