Spacing in the Shade
Gardeners often fudge a little (or a lot) by placing plants closer together than is recommended. Although you can sometimes get away with close planting in the sun, you definitely take your chances by doing so in the shade.
The combination of soil that stays damp for comparatively long periods of time and the reduced air circulation typical under canopies of large trees increases the possibility of disease. For this reason it is always best to err on the side of placing shade plants too far apart. The extra space allows for good air circulation (a deterrent to disease) and gives each plant the opportunity to receive its fair share of light and nutrients.
