Red Spiders.--These troublesome pests which appear in the heat of
summer, may be got rid of by constantly syringing the plants attacked,
and by occasionally washing the walls, etc., with lime or sulphur.
Retinospora Filifera.--A large-growing, hardy evergreen shrub. It may
be grown in any light soil, and increased by seed, or by cuttings
planted under glass in the shade. It flowers in May.
Rhamnus (_Buckthorn_).--Fine evergreen shrubs, of hardy habit and
quick growth. They may be grown in any soil, but prefer a sheltered
situation, and are very suitable for planting near the sea. R.
Latifolius has handsome broad leaves. Some, such as R. Alaternus and
R. Catharticus, attain large proportions, the former reaching 30 ft.
and the latter 10 ft. in height. They may be propagated by layers or
by seed.
Rheum Palmatum.--This species of rhubarb makes an effective plant for
the back portion of a border. It does well in rich loam, flowering in
June, and is increased by dividing the root. Height, 5 ft.
Rhodanthe (_Swan River Everlasting_).--These beautiful everlasting
flowers are half-hardy annuals and are suitable for beds or ribbons,
and make most graceful plants for pot culture, placing four plants in
a 5-in. pot. They thrive best in fibrous peat or a rich, light soil,
and prefer a warm situation. Used largely for winter bouquets, and are
perfect gems for pot culture. A succession of bloom may be obtained
by sowings made in August, October, and March. The temperature of the
seed-pots should be kept at from 60 to 70 degrees, and the soil
kept constantly damp with water of the same heat. After potting the
seedlings remove them to a cooler house and keep them near the glass.
Those sown in March may be planted in the open in June, where they
will flower in autumn. Height, 1 ft.
Rhodochiton--This evergreen climber makes a fine plant for
trellis-work. It is more suitable for the greenhouse, though it may be
grown in the open in summer. A light, rich, well-drained soil is its
delight, and it may be propagated by seed or by cuttings under glass.
In the greenhouse it should not be placed near the pipes. July is its
time for flowering. Height, 10 ft.
Rhododendrons.--Plant in October in peat, or in a compost of sandy,
turfy loam, with a good proportion of decayed leaves and charred
refuse. The best position for them is a sheltered one where they can
get a moderate amount of sunshine to develop the flower-buds. They
like plenty of moisture, but the ground must be well drained. If it is
desired to shift their position spring is the best time, the next best
being October. They are propagated by layers or seeds, and the small
wooded kinds by slips torn off close to the stems, planted in sand,
and placed under glass in heat. The seed should be sown early in
spring in pans of peat soil, and covered very lightly. Place the pans
in a frame, and when the soil becomes dry stand the pans in water
nearly up to the rims until the surface is moist. Pot off when strong
enough to handle, and keep close in the frame till fresh roots are
produced, then harden off. Rhododendrons may, when desired, be
transplanted in spring, even after the flower-buds are well advanced,
if care be taken not to break the ball of earth round their roots.
They bloom at the end of May. Height, 4 ft.
Rhubarb.--Seed may be sown thinly during April in drills 1 ft. apart.
Thin out the plants 12 in. from each other, and let them grow on
till the following April, then plant them out 4 ft. apart in deeply
trenched ground into which a good quantity of well-rotted manure has
been worked. Large roots may be divided in autumn or early spring;
every portion of the root that has a crown will make a fresh plant.
When the last of the crop has been pulled, fork in a dressing of old
manure. It may be forced out of doors by covering the ground thickly
with stable manure, and placing large flower-pots over the plants to
bleach them; but if forced in a frame the light need not be excluded.
None but the earliest kinds should be selected for forcing.