I am looking for suggestions for a perennial or shrub planting for a narrow and long (6 inch x 15feet x 20 feet) second floor planter. It is heavily shaded by oaks and is south facing and windy. There was a boxwood planting but they all died. It is also a high 4 foot planter viewed at that level or from below when sitting at the table. Person does not seem to like grasses. I thought maybe lime corral bells or christmas ferns? Can you make some other suggestions? Must also be a mono planting.
for your help
Container plantings in full shade can be a big challenge, and the fact that the planter you are working with is only six inches wide limits your choice of plant material even further. Toronto’s recent winters have been very hard on boxwood, which is hardy to Zone 5. In containers they are of course more vulnerable given the freeze-thaw cycle that makes it difficult for even hardier perennials to survive. Shrubs and perennials that are hardy to a zone or two below our own will have a better chance of survival in containers.
Your suggestions are both great ideas to try. The Christmas fern, Polystichum acrostichoides, is very hardy and will tolerate shade conditions. You could also consider Adiantum pedantum, the Northern Maidenhair Fern, another very hardy native which does best in light shade, but can tolerate deeper shade conditions.
There are several Coral Bell cultivars that are very hardy will tolerate a range of shady conditions, for example, ‘Lime Marmalade’ and ‘Dolce Key Lime Pie’.
A couple of other suggestions, both of which have very lovely foliage, are Foam flower, Tiarella cordifolia, which is very hardy and grows in shade/part shade conditions, and Brunnera, in particular ‘Jack Frost’, with its light green leaves overlaid by silver: it is hardy and grows in shade to part shade.
In terms of evergreens, you could consider trying one of the dwarf cedars, for example, Thuja occidentalis ‘Little Giant’, hardy to Zone 3, or one of the Cotoneaster cultivars that are hardy to Zone 4, both of which will tolerate part shade: you will need to determine whether these are too large for your narrow planter.
Here is the Toronto Master Gardeners’ fact sheet on perennials for shade: https://www.torontomastergardeners.ca/factsheet/perennials-for-shade-in-dry-or-moist-areas-a-toronto-master-gardeners-guide/ .
This site gives some good practical advice for overwintering perennials in containers: