Planting Hardy Perennials: Many hardy perennials are nowadays sold growing in containers, and since there is no root disturbance, these can be set out at almost any time of the year. Dwarf subjects, in particular, can be set out even in full flower. But this cannot be recommended for the taller growers, which are almost sure to be blown around by wind and will have difficulty in anchoring themselves. In any case, with container plants, large or small, set out in late spring through the summer is always a danger of drying out independently of the surrounding soil; and if there is a period of drought at this time it means that they will have a struggle to become estab1ished, and may even die.
Throughout the first summer, then, it is essential that container-grown plants should be soaked several times after planting and not by light overhead spraying, as with a garden sprinkler, but individually soaked so that the root ball is thoroughly penetrated. Showers of rain at this time can be very deceiving. They may perhaps keep the surface moist, but do very little towards soaking the ground. It takes a lot of summer to have any real effect.
Planting time for dug-up-and-divided bare-rooted subjects can be either in autumn (October -early November), or in spring (March - April.) A few, such as scabious and Aster amelus prefer the spring move, but in general October, when most plants are becoming dormant and the soil is still warm, is a rood all-round planting month.
In the heavier, difficult-to work clay soils, it is a distinct teantage to make up a planting mixture a few days in advance, consisting of half peat or leaf-mould, and half sand or soil. As the plants are set in the hole, work in a handful or two, in immediate contact with the roots. This makes it easier for them to get a hold, and ensures a good start.
Roots, if free, should be spread out in the planting hole and even if from a container, it will pay lightly to tease a few away from the solid ball, encouraging them out into the surrounding soil,
It is difficult to generalize about planting depths, but they should never be shallower than they were previously. The same depth or very slightly deeper will not be far wrong. Firm the soil all round, and apply a pint or so of water immediately after planting to each plant, to bring the soil into sufficiently close contact with the roots.
A few slug pellets around is always a good insurance, particularly in the case of subjects with fleshy shoots, such as delphiniums. Bad attacks by this pest in the early spring can sometimes spell the sudden end of any new plant.
The spacing and arrangement of plants are also matters of individual decision, taking into account the height, spread and colors of the chosen subjects. No matter what the size of the patch, however, a group of three or five of one kind, set close enough together to mingle with one another when in flower is generally better than single dotted plants. And if there is a back and a front to the site, the taller things, of course, go at the back.
