Indigofera.--Beautiful evergreen shrubs. I. Australis has elegant,
fern-like foliage and racemes of pink or purple Pea-shaped flowers in
April. I. Decora Alba bears its white flowers in July. They require a
sandy loam or peat soil, and greenhouse culture. Cuttings of the young
wood planted in sand under glass will strike. Height, 21/2 ft.
Insects on Plants.--To destroy insects on plants wash the plant with
Tobacco-Water (_which see_). Or put 1 oz. of quassia chips in a muslin
bag, pour on some boiling water, and make it up to I gallon; dissolve
1 oz. of soft soap, add it to the chips, and stir well. Use it two or
three times during spring and early summer.
Inula Royleana (_Fleabane_).--A hardy perennial which flowers in
November. It will grow in any garden soil, and can be increased by
seeds, or by division of the roots. Height, 3 ft.
Ionopsidium.--These hardy annuals grow freely in any rich, damp soil;
a shady position is indispensable. Height, 1/8 ft.
Ipomoea.--These beautiful climbing plants are very suitable for
covering trellis-work, or for the pillars or rafters of the
stove-house. The seed is generally sown in April on a hotbed or under
glass, and the young plants set out in the border of the house in May
in light, rich soil. Success is mainly secured by allowing plenty of
root-room. The perennial kinds are increased from cuttings taken from
the small side-shoots placed in sand in a brisk bottom-heat. If grown
in the open they often shed their seed, and come up year after year
with but little attention. They make a good contrast to Canariensis.
The Ipomoea Horsfalliae, with its bright scarlet flowers, has a
lovely appearance, but must be treated as a stove evergreen. This is
propagated by layers, or by grafting on some strong-growing kind. It
thrives in loam and peat mixed with a little dung, and flowers in July
or August. Height, 6 ft. to 10 ft.
Ipomopsis.--A very beautiful half-hardy biennial, but difficult to
cultivate. Some gardeners steep the seed in hot water before sowing
it; but the best way seems to be to sow it in July in 3-in. pots in
equal parts of sandy peat and loam, ensuring good drainage, and place
it in a cold frame, giving it very little water. When the leaves
appear, thin out the plants to three or four in each pot. Replace them
in the frame for a week or so, then remove them to a light, airy part
of the greenhouse for the winter. During this period be careful not
to over-water them. In spring shift them into well-drained 4-1/2-in.
pots, using the same kind of soil as before, and taking great care not
to injure the roots; still give the least possible amount of water. If
plenty of light and air be given, they will flower in July or August.
Height, 2 ft.
Iresines.--Take cuttings of these greenhouse plants in autumn; insert
them thinly in 48-size pots filled with coarse sand, loam, and
leaf-mould, and place in a uniform temperature of 60 or 70 degrees.
When they have taken root place them near the glass. Height, 1-1/2 ft.
Iris.--The Iris is the orchid of the flower garden; its blossoms are
the most rich and varied in colour of hardy plants. For cutting, for
vases, table decoration, etc., it is exceedingly useful, as it is very
free-flowering, and lasts a long time in water. It thrives in almost
any soil, though a sandy one suits it best, and is strikingly
effective when planted in clumps. It soon increases if left
undisturbed. The English Iris blooms in June and July, bearing large
and magnificent flowers ranging in colour from white to deep purple,
some being self-colours, while others are prettily marbled. The German
Iris is especially suitable for town gardens. The Spanish Iris blooms
a fortnight before the English. Its flowers, however, are smaller,
and the combinations of colours very different. The Leopard Iris
(_Pardanthus Chinensis_)is very showy, its orange-yellow flowers,
spotted purple-brown, appearing in June and July. They are quite
hardy. The best time for planting them is October or November,
selecting a sunny position. Height, 1-1/2 ft.
Isopyrums--Hardy herbaceous plants of great beauty, nearly related to
the Thalictrums. They will grow in any ordinary soil, but flourish
best in vegetable mould, and in a moist, yet open, situation. They
are readily raised from seed, or may be propagated by division of the
roots in autumn. They flower in July. Height, 1 ft. to 1-1/2 ft.
Ivy (_Hedera_).--A deep, rich soil suits the common Ivy; the more
tender kinds require a lighter mould. To increase them, plant slips in
a north border in sandy soil. Keep them moist through the autumn,
and plant them out when well rooted. The following are the principal
choice sorts:--Aurea Spectabilis, palmate-leaved, blotched with
yellow; Cavendishii, a slender-growing variety, leaves margined with
white, with a bronzy shade on the edge; Conglomerata, crumpled leaves;
Elegantissima, slender-growing, with silvery variegated leaves; Irish
Gold-Blotch, large leaves, blotched with yellow; Latifolia Maculata,
large white-blotched leaves; Lee's Silver, silver variegated;
Maderiensis Variegata, leaves broadly marked with white; Marmorata,
small leaves blotched and marbled with white; Pupurea, small leaves
of a bright green changing to bronzy-purple; Rhomboides Obovata, deep
green foliage; Rhomboides Variegata, greyish-green leaves, edged with
white; and Silver Queen, a good hardy variety.
Ixias.--Plant out of doors from September to December, in a
sunny, sheltered position, in light, rich, sandy soil. For indoor
cultivation, plant four bulbs in a 5-in. pot in a compost of loam,
leaf-mould, and silver sand. Plunge the pot in ashes in a frame or
cold pit, and withhold water until the plants appear. When making free
growth remove them to the conservatory or greenhouse, placing them
near the glass, and give careful attention to the watering. Ixias are
also known under the name of African Corn Lilies.
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 delights in a rich, light soil. The purple Jacobaea is a great
favourite of the public. Flowers in August. Height, 1 ft.