Potentilla.—Handsome herbaceous plants with Strawberry-like foliage. They will grow in any common soil, and may be increased by dividing the roots or by seeds treated like other hardy perennials. The shrubby kinds are well adapted for the fronts of shrubberies, and are propagated by cuttings taken in autumn and planted in a sheltered situation. They flower at midsummer. Height, 1-1/2 ft.
Potting.—Great attention must be paid to this important gardening operation. It is necessary that the pots used be perfectly clean, and, if new, soaked in water for several hours previously, otherwise they would absorb the moisture from the soil to the detriment of the roots. At the bottom of the pots place a few layers of crocks, and on these some rough mould so as to ensure perfect drainage. For all delicate, hard-wooded plants one-third of each pot should be occupied with drainage, but a depth of 1-1/2 in. is sufficient for others. Lift the plant carefully so as not to break the ball of earth round the roots, and fill in with mould round the sides. In order to supply water readily the pots must not be filled up to the rim. Pot firmly, and in the case of hard-wooded plants ram the earth down with a blunt-pointed stick; soft-wooded ones may be left rather looser. Give shade till the plants have recovered themselves. The soil used for potting should be moist, but not clammy. A rather light, rich loam is most suitable for strong-growing plants; peat for slow-growing, hard-wooded ones, like Ericas, Camellias, etc.; and a mixture of light loam, one-third its bulk of leaf-soil, and silver sand in sufficient quantity to make the whole porous for quick-growing, soft-wooded plants, such as Pelargoniums, Calceolarias, Fuchsias etc.
Pratia Repens (Lobelia Pratiana).—This pretty little creeping perennial is very suitable for the front of rock-work. It requires a well-drained vegetable soil and all the sun it can get. It is self-propagating. Though pretty hardy, it is safer to pot it off in autumn and place it in a cold frame throughout the winter. Flowers are produced in June, and are succeeded till cut off by frost.
Primroses.—See "Primulas," and "Streptocarpus."
Primulas.—This genus embraces the Auricula, the Polyanthus, and the Primrose. The greenhouse varieties are among the most useful of our winter-flowering plants. The seed may be sown at any time from March to July in a pot of two-year-old manure, leaf-mould, or fine, rich mould, but not covering it with the soil. Tie a sheet of paper over the pot and plunge it in a hotbed. Sufficient moisture will be communicated to the seed by keeping the paper damp. When the plants make their appearance remove the paper and place the pot in the shady part of the greenhouse. When they are strong enough to handle, pot off into 4-1/2 in. pots, and stand them near the glass. The roots may be divided as soon as the plants have done flowering. The hardy kinds may be sown in the open. It should be borne in mind that the seed must be new, as it soon loses its germinating properties. These flower in March or April. Height, 6 in.
Prince's Feather.—An ornamental hardy annual, producing tall spikes of dark crimson flowers and purple-tinted foliage. It is not particular as to soil, and merely requires sowing in the open in spring to produce flowers in July. Height, 2 ft.
Privet.—See "Ligustrum."
Prophet's Flower.—See "Arnebia."
Prunella Grandiflora.—A pretty hardy perennial, suitable for a front border or rock-work, bearing dense spikes of flowers from May to August. It grows well in any ordinary soil, and is propagated by division. Height, 6 in.
Pruning.—The main objects to bear in mind in Pruning any kind of bush or tree are to prevent a congested growth of the branches, to remove any shoots that cross each other, as well as all useless and dead wood, and to obtain a well-balanced head. It may be done either in August or in the winter when the sap is at rest, after the worst of the frosts are over, the end of February being usually suitable; but the former period is generally acknowledged to be the better, especially for fruit-trees. The cuts should be clean and level, and when a saw is used should be made smooth with a chisel and covered with grafting wax. In all cases as little wound as possible should be presented. Root-pruning has for its object the suppression of over-vigorous growth and the restoration of old trees to a bearing condition. It consists in taking off all the small fibres, shortening the long roots to within 6 or 8 in. of the stem, and cutting away any bruised or injured roots before the trees are first planted out. The mode of procedure in the case of old or unproductive trees is to open the earth in autumn 3 ft. from the stem of the tree, and to saw through two-thirds of the strongest roots. The opening is then filled in with fresh mould. Should the growth still be too vigorous, the soil must be opened again the following season and the remaining roots cut through, care being taken not to injure the young fibrous roots.