First thing I would ask is which way the flat faces. This is important for
shade considerations. Some pants love full sun, others semi shade, and some
can only tolerate evening sunshine. Also what kind of fertiliser will you
use, buy a soil testing kit, or are you just using compost and growmore for
growth and feed. Height is obviously important as a large plant can be used
as a backdrop while others can be small and delicate, Do you want flowers
or ferns and greenery for background colour. For summer growth you cannot
beat bedding plants available form any garden centre,these are small plugs
of plants with minimal roots easy to plant right away and be grown on
annually. these however generally die after the summer season. Go for
perennials which mean they bloom and flower every year. You could also go
for some shrubs which are flowering although these can come in various sizes
from 1 metre to 5 metres high. Go for forsythia = a lovely yellow colour
which blooms every year, ceanothus known as Californian lilac which flowers
twice a year and is evergreen, and some flowering currants or ribes, or
pieris which are multi coloured foliage also known as flaming flowers of the
forest. Hope this helps.

Angela