Although every garden should have its summer display of annual flowers, there should always be room for the early-flowering biennials, such as wallflowers and forget-me-nots, and the long lasting glorious variety of perennial flowers that form the heart of the herbaceous border.
Biennials are usually sown in a nursery area of the garden or seed bed where they can grow undisturbed until ready for transplanting. Seed sown in spring will result in plants that are sturdy enough to be moved to their flowering positions in autumn, normally when the summer bedding plants have given of their colourful best.
Sow the seed in drills using the technique described on page 10-11 and keep the bed watered during dry spells and weeded at all times. An occasional feed with a liquid fertiliser can be given during the early stages of growth, but refrain from feeding for at least six weeks before transplanting to avoid sappy growth that could be damaged by hard frost.
Some perennials can be treated as half-hardy annuals and sown indoors early in the year (see undercover sowing) in a propagator, greenhouse or indoors for transplanting in late spring to flower during the summer.
However, the majority of perennials, including the stately lupins, hollyhocks and delphiniums, can be grown in the nursery bed in spring, transplanted to their permanent positions in the border in the autumn, to flower the following season.
Remember these plants will lose their leaves in late autumn so it is prudent to mark the planting position with a label or stake.
Unlike annuals which complete their life cycle in one year, perennials will occupy the same site for years, so thorough preparation of the soil is important to ensure the plants enjoy a long and healthy life.
The site should be free-draining because waterlogging is fatal to this group of plants. Equally, it should not dry out too rapidly. The best way of achieving a well-drained but moisture retentive soil is to incorporate plenty of organic material into the top 6-12in (15-30cm). Well rotted farmyard manure, home made compost, spent peat from growing bags, and mushroom compost are all suitable for turning into the soil before transplanting the perennials from the nursery bed.
The addition of about 4oz (112g) to the square yard/metre of a balanced organic fertiliser, such as fish blood and bone or seaweed meal or the inorganic Growmore, worked into the top 6in (15cm) of the soil will help the plants to grow away strongly.
An annual dressing of the same fertiliser followed by a mulch of manure or compost will ensure your perennials have a long and healthy life. Successful management of the border perennials involves such things as slug control in the spring, staking and division of mature plants.