Poa Trivalis.—A very pretty, dwarf-growing, variegated grass. Plant in a moist situation in a rich, light, loamy soil. It is increased either by seed or division.
Podolepis.—Hardy annuals bearing yellow and red and white flowers. A mixture of loam and peat is most suitable for their growth. They are easily raised from seed sown in March, and bloom from June to August. Height, 1-1/2 ft.
Podophyllum Peltatum (Duck's Foot, or May Apple).—Grown chiefly for its foliage and berries, this hardy herbaceous perennial forms a pleasing spectacle when planted in moist soil under trees; it likewise makes a splendid pot-plant. A mixture of peat and chopped sphagnum is what it likes. The pots are usually plunged in wet sand or ashes on a northern border. It is propagated by cutting the roots into pieces several inches in length, with a good bud or crown on each. During May and June the plant produces small white Dog-rose-like flowers. Height, 1 ft.
Poinsettia Pulcherrima.—A stove evergreen shrub which produces lovely crimson bracts in the winter. (Poinsettia Care) – Plant in sandy loam, give plenty of water to the roots, and syringe the leaves frequently. In early spring cut down the branches to within three or four eyes of the old wood. These cuttings, if laid aside for a day to dry and then planted under glass, will form new plants. It flowers in April. Height, 2 ft.
Polemonium (Jacob's Ladder).—Hardy perennial border plants of an ornamental character and of the easiest culture. Any soil suits them, and they merely require sowing in the open either in spring or autumn. P. Richardsoni is most commonly met with, its blue flowers being produced in early autumn. Height, 1-1/2 ft.
Polyanthus.—Sow the seed late in autumn in well-drained boxes of light, rich mould; cover it very lightly, place under glass, and water sparingly, but give enough to keep the plants moist. The seed requires no artificial heat to germinate it. The roots should be divided each year as soon as they have flowered, and fresh soil given. The single varieties only are florists' flowers. The Polyanthus is a species of primrose, grows best in a rather shady position in a loam and peat compost, and produces its flowers in May. Height, 6 in.
Polygala Chamaesbuxus.—A hardy evergreen trailing plant requiring a peat soil in which to grow. It may be increased from seed or by division of the roots. May is the time at which it blooms. Height, 6 in.
Polygala Dalmaisiana.—This showy evergreen shrub needs a greenhouse treatment. Soil—three parts peat, one part turfy loam, and a little sand. It flowers in March. To increase it, top the shoots, which will cause it to throw out new ones. Take the new growth off when it is 3 in. long, and place it under glass in a propagating house. Height, 1 ft.
The hardy annual varieties of Polygala are obtained by seed sown in peat. These flower at midsummer. (See also "Solomon's Seal.")
Polygonatum.—These pretty herbaceous plants are quite hardy. The flowers, which are borne in May or June, are mostly white. Plants succeed best in a rich soil. They may be raised from seed, or the roots can be divided. Height, 1ft. to 3 ft.
Polygonum Brunonis (Knotweed).—This strong-growing creeping perennial plant is not particular as to soil so long as it can enjoy plenty of sunshine. The shoots root of themselves and must be kept in check, else they will choke other things. It flowers in August, after which the leaves assume beautiful autumnal tints. Height, 1 ft.
Pomegranate.—This requires a deep, loamy soil and a warm, airy situation. May be propagated by cuttings of the shrubs or the root, putting the cuttings into light, rich soil, or by layers. The double kinds of Punica, or Pomegranate, should be grafted on to the single ones. There is a dwarf kind, bearing scarlet flowers in August, which requires heat.
Portulaca.—The seeds of the hardy annual species of this genus may be sown in a sheltered open spot in spring. The half-hardy annuals should be sown thinly in boxes during March and placed in gentle heat. Harden off and plant out in May, as soon as the weather permits, in a light, dry soil where it can get a good amount of sunshine. Its brilliant and striking colour admirably adapts it for small beds, edgings, or rock-work; and it will succeed in dry, hot sandy positions where scarcely any other plant would live. It flowers in June. Height, 6 in.
Potatoes.—Ground intended for Potatoes should be dug deeply in the autumn, thoroughly drained, well manured and trenched, and left rough on the surface during the winter. At the beginning of February stand the tubers on end in shallow boxes, and expose them to the light to induce the growth of short, hard, purple sprouts. Allow one sprout to each tuber or set, rubbing off the rest. They may be planted at any time from the end of February to the end of March in rows 1-1/2 to 2-1/2 ft. asunder, placing the sets 6 in. deep and from 6 to 9 in. apart. As soon as growth appears keep the ground well stirred with the hoe to prevent the growth of weeds, and when the tops are 4 to 6 in. high ridge the earth up about them. Directly flower appears, pick it off, as it retards the growth of the tubers. They should be taken up and stored in October. If short of storage room dig up every other row only, and give the remaining ridges an additional covering of earth. They keep well this way.
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.
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.
Prunus.—Beautiful early-flowering trees, which will grow in any soil, and can be increased by seeds or suckers.
Ptelia Trifoliata (Hop Tree).—This is very suitable for planting on the borders of still waters, where its long frond-like leaves, which turn to a golden yellow in autumn, produce a fine effect. It blooms in June, and is propagated by layers. Height, 10 ft.
Pulmonarias (Lungworts).—Hardy perennials that require but little attention; may be grown in any common soil, and propagated by division at any time. They flower in April and May. Height, 1 ft.
Pumpkins.—Valuable for soups and pies in winter, and in summer the young shoots are an excellent substitute for Asparagus. For their cultivation, see "Gourds."
Punica Granata Nana.—A greenhouse deciduous shrub which flowers in August. The soil in which it is placed should be a light, rich loam. It can be most freely multiplied by layers, and cuttings will strike in sand under glass. Height, 4 ft.
Puschkinia (Striped Squills).—This charming bulbous plant may be grown in any light, rich mould, provided it is drained well. The bulbs may be separated when the clumps get overcrowded, late in summer, after the tops have died down, being the most suitable time to do so. If planted in a warm position it will begin to flower in March, and continue in bloom till May. Height, 8 in.
Pyrethrum.—The greenhouse kinds grow in any rich soil, and young cuttings planted under glass root readily. The hardy kinds are not particular as to soil so long as it is not cold and wet, and are increased by seeds sown in heat in February if wanted for early use, or in the open during March and April for later growth. The crowns may be divided either in autumn or spring: each eye or bud will make a fresh plant. Young plants produced in this way in the autumn require the protection of a frame during the winter. They flower in July. Height varies from 6 in. to 3 ft.
Pyrola.—A handsome hardy plant, suitable for a moist, shady situation. It is raised from seed, or will bear dividing, but is rather hard to grow. Height, 6 in.
Pyrus Japonica.—See "Cydonia."
- Letter U | Flowers Encyclopedia U Ulex Europaeus Flore Pleno (Double Furze).—This elegant, hardy, evergreen shrub likes a rich, sandy soil, and may be increased by cuttings planted in a...
- Letter X | Flowers Encyclopedia X Xeranthemum.—These charming everlasting annuals retain, in a dried state, their form and colour for several years. They are of the easiest culture, merely requiring...
- Letter “J” – Encyclopedia J Jacobaea (Ragwort).—May be raised from cuttings in the same way as Verbenas, and will grow freely from seeds sown in autumn or spring. It...
- Letter “D” | Online Flowers Encyclopedia D Daffodils.—These will grow in any good, cool, moist, well-drained garden soil if sand be put round their roots, but thrive best in a moderately...
- Letter V | Flowers Encyclopedia V Vaccineum Myrtillus and V. Uliginosum.—Attractive deciduous shrubs. They require to be grown in peat or very sandy loam. In April or May they produce...