Proper plant spacing is a critical part of the planting process because it affects future maintenance requirements of the landscape. When plants are spaced too closely, they soon grow together and become thick and dense. When this happens, plants are more susceptible to insects and diseases. Junipers, for instance, will literally compete for space and will build up layer upon layer of foliage when planted too closely together. Spider mites and blight-causing fungi love this thick, dense foliage.
English laurel is another plant that suffers when planted too closely together.
This results in dense foliage and poor air circulation, making it more susceptible to a bacterial disease that makes the leaves look as though they were shot with bullets. Plants spaced too closely together also must be pruned more often to keep them separated from other nearby plants. When plants are allowed to grow together, their individuality and form are lost. Before you know it, the landscape appears to be made of big, green blobs instead of individual plants. When this happens, frequent pruning is required just to keep plants confined within an area, and the landscape becomes high-maintenance.