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.
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.