Q. Please tell me how to plant and space Matteuccia struthiopteris and Trillium erectum in a shade garden.
Two lovely plant choices!
Matteuccia struthiopteris is likely to grow to four feet or more and as wide as 3 feet. It grows on rhizomes and will produce offset plants four to eight inches from the parent plant, so there is a lot to consider when planting. These ferns look best, to my eye, when gently touching rather than pushing into eachother, so allow at least two feet between plants if you can wait for a sense of fullness in the garden, and closer if you need more instant coverage each year. Look out for the offsets and divide the clumps in early spring to use elsewhere in the garden. Partial shade in humus-rich, well drained soil will produce the best results.
Trillium erectum is a far smaller plant and grows about 20 inches tall and 12 inches across. It is quite upright and not dense in form and can tolerate some gentle overlap with other plants so plant about 8 inches apart.
Good luck with your garden!
Courtesy of NYBG Plant Information