Clarkia.--These hardy annuals make a pretty display in the borders
during summer. Seed ripens plentifully, and merely requires sowing in
the open in March, or in September if protected in winter. The bloom
lasts from June to September. Height, 18 in.
Claytonia Sibirica.--A hardy herbaceous plant which yields light
yellow flowers in June. It is not particular as to soil, and may be
raised from seed sown either in autumn or spring. It stands division
of the root. Height, 4 ft.
Clematis (Virgin's Bower).--These plants like a dry situation. They
will grow in smoky districts, and may be increased by cuttings of firm
side-shoots under a glass in summer or by layers in September. With
the protection of a greenhouse they come into flower early in spring.
They are the most beautiful of all flowering hardy climbers. The stove
and greenhouse varieties are best planted in loam and peat, though
they will thrive in any light soil. Any good garden soil suits the
hardy kinds. The herbaceous varieties are increased by dividing the
roots early in spring. They bloom at various periods. After they have
ceased to flower, the Jackmanni and Viticella sections should be cut
down to within 9 or 12 in. of the ground. The Patens and Florida
do not require pruning; those of the Lanuginosa should be cut back
moderately, but not too close. A good dressing of leaf-mould and
manure should be dug in about November. Heights vary from 2 ft. to 20
ft. (See also "Traveller's Joy.")
Cleome.--The species of this genus are very pretty and free flowering,
some being half-hardy climbers notable for their foliage. They like
a rich, light soil. Cuttings of the stove kinds root freely under a
glass. Some of the annual species require to be sown in a hotbed frame
or in a hot-house, then potted off and placed with tender annuals. The
hardier ones may be sown on a hotbed, and afterwards planted out in a
sheltered position. They flower in May, June, and July. Heights vary
from 6 in. to 8 ft.
Clethra Alnifolia.--This hardy deciduous shrub bears in September
deliciously scented pure white flowers on the side-shoots of the
previous year's growth. It needs a light soil and a dry, sunny
situation. It may be propagated by cuttings placed under glass in
sandy loam, or by suckers taken when the leaves have fallen, but is
more generally increased by layers. Height, 3 ft.
Clianthus.--A genus of very elegant, free-flowering, evergreen
greenhouse shrubs. They flourish in the border of the conservatory (or
against a south wall if protected from cold) in an equal mixture of
loam, peat, and sand. Cuttings root freely in the same soil under
glass. Seed sown early in spring produce flowers the first year, in
May. Height, 3 ft. to 4 ft.
Clintonia.--Very pretty half-hardy annuals; useful for beds, edging,
pots, or rock-work. They produce an abundance of Lobelia-like flowers
in August. Sow the seed in the open in spring. Height, 6 in.