A container-grown perennial is a plant which has been raised as a seedling or cutting and has then been potted on until it is housed in the plastic or metal container on display. It should not have been lifted from the open ground and its roots plus surrounding soil stuffed into the container. Such lifted plants are sold and can give successful results, but they should neither be called nor be priced as container-grown plants. The true container-grown hardy perennial can be planted at any time of the year as long as the ground is neither frosty nor waterlogged. The most convenient of all the planting types, but also the most expensive.
A pot-grown specimen is a miniature version of the container-grown plant. It may be a mature rockery perennial or the juvenile form or a border perennial, annual or biennial. This is the best way to buy a rockery perennial, and it is generally more economical for border perennials than container-grown plants. It is the dearest way to buy annuals but the flowers are earlier and larger.
SEEDS: The seed packet is one of the corner-stones of gardening and is the standard method for raising annuals and biennials. You can obtain a much wider range of varieties from seed than is possible if you rely on buying bedding plants. Some perennials can be readily raised from seed. Look for types marked F1 hybrid, this means that the variety has been carefully bred to have more vigour and produce more attractive blooms than the standard types. Expensive, but usually worth the extra cost. Starter Kits are widely available at seed sowing time. Plastic trays have been filled with Seed Compost are are pre-sown. The transparent lid is used to provide cover during the germination stage.
The pre-packaged perennial is the standard planting material sold by hardware shops, supermarkets and department stores. They are also available at garden centers. It is a bare-rooted plant with moist peat, sphagnum moss or compost around the roots and the whole plant housed inside a labelled polythene bag.
Such plants are cheaper than their container-grown counterparts but there are drawbacks. You can't see what you are buying and premature growth may begin in the warm conditions which occur in the shop. Planting time is the dormant season between autumn and spring.
LIFTED PLANTS: Small clumps and divisions of large clumps of perennials are sometimes lifted and placed in polythene bags for sale. The problem here is that some roots will have been broken during the transfer and so tap-rooted varieties may take a long time to become established in their new home.
Bedding annuals and biennials are sold in wooden or plastic trays ('flats'). Buy from a supplier with a good reputation or one who has pleased you in previous years. You are bound to be disappointed if the seedlings have not been properly hardened off.
Never buy half-hardy annuals before the recommended planting time. If you can, buy a whole box and not just a few plants wrapped in newspaper.
BULBS: Make sure that bulbs and corms you buy are firm at the base. They should not have started to grow and the surface should be mould-free. Large-sized bulbs are usually the best choice, but buying a mixture of bulbs, which you can grow on, is the more economical way of covering a large area. Outdoor Hyacinths should be the medium and not the large grade. It is of no importance if Tulips have lost their brown skins. The outer scales of Lily bulbs should be firm and succulent, do not buy bulbs if they are covered with withered scales.