Provided that the soil is in reasonably good heart, and rotted compost or similar organic material was used in its preparation before planting, there should not be any need to feed in the first year. Thereafter one feed in spring of a powder fertilizer, such as a slow-acting organic mixture should be all that is needed. However, some strong growing perennials need two of these in a growing season, the second in early summer, and if you have planted a vigorously growing species in a sandy soil, it will certainly need more than one feed, perhaps at monthly intervals from spring until midsummer.
This is vital to a border’s well-being – indeed, to that of any perennial – and should be done at least once a year. Perennials react more quickly to shortages of water than woody plants do, and mid to late spring mulches are essential to prevent what could quickly become a fatal drought. If there are weeds, clear these first, although in emergencies you can mulch on top of annual weeds: they will not survive the smothering. Any of the mulching materials available will be satisfactory, but bark is one of the best, as it is more discouraging to slugs and snails, and lasts two seasons at least.
The standard procedure applies, and there is no requirement specific to perennials.
Staking and supporting
Plants are generally chosen nowadays because which do not need to be staked, but Bamboo canes are used for tying up some of these perennials and other plants such as Dahlias and Chrysanthemums. Stakes must be inconspicuous and strong enough for their purpose. Sufficient support can be given by driving in three canes round a plant, sloping slightly outwards at the top. To make them inconspicuous, place one at the back and one at each side, where they can be partially concealed by the foliage. Tie a piece of garden string from cane to cane, possibly at three levels, bottom, middle and top, to form an enclosure. An excellent, inexpensive and inconspicuous method is to support the plants using twigs as stakes. Bamboo canes have a rather limited life, but you can buy plastic-covered steel rods made to look like Bamboo.
Treatment in autumn
As soon as possible after the foliage and stems have died, cut perennials down to within 7.5 cm (3 in) of the ground. Evergreen plants, however, such as Kniphofia (Red-hot Poker) should not be cut down and the foliage should be tied together over the crown to protect the plant during winter. In cold or exposed gardens, leave the stems on the plants, whether they are evergreen or not. If you don’t like the look of the border when it has been cleared in this way, leave the work until spring, but be prepared to deal with a fungus diseases or insect pests, which can over-winter in the remaining vegetation. In autumn, every three to four years, all perennials should be lifted and the soil redug and manured. The plants should be divided, to separate the inner and older stems, and the outer segments replanted, preferably in different positions, if possible.