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. 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.