plants are put into small pots and placed in a frame till the end of
May, when they are transferred to the border.
Nierembergia (Cup Flowers).--These elegant half-hardy annuals
grow well in any light soil, but prefer a mixture of sandy loam and
leaf-mould. Sow the seed in March or April in slight heat, harden off,
and plant out in May as soon as all fear of frost is over. They flower
in July. Height, 9 in. to 1 ft.
Nierembergia Rivularis.--This herbaceous plant is of a creeping
nature; it has deep green ovate foliage and large saucer-shaped white
flowers. It needs a moist position, and is increased by division. The
bloom is produced throughout June, July, and August. Height, 3 in.
Nigella.--These hardy annuals, a species of Fennel-flower, are both
curious and ornamental. Perhaps the best known among them is N.
Hispanica, or Love-in-a-Mist. They only require sowing in the open in
spring--but not before the middle of March--to produce flowers in July
and August. Height, 9 in. to 2 ft.
Night-scented Stocks.--See "Mathiola."
Nolana.--Hardy annuals that are suitable for the border, as they are
very showy when in flower. The seed should be sown in spring on a
gentle hotbed, and the plants transferred to the garden about the
middle of May. N. Atriplicifolia may be sown in the open in the
autumn. They flower in July and August. Height, 6 in. to 2 ft.
North Borders, Plants suitable for.--Hardy Camellias, Chrysanthemums,
black and green Tea Plant, Rhododendrons, Ferns, Red Currants, Morello
Cherries, and spring and summer cuttings of all sorts.
Nuttallia.--This early-flowering shrub is only hardy in the south and
south-west of our country. It requires a light, rich soil, and may be
increased by division. Racemes of white flowers are produced during
February and March. Height, 2 ft.
Nycterina.--Exquisite little half-hardy plants, suitable for pots or
rock-work. The seed should be sown early in spring on a gentle hotbed,
and the young plants transferred to the pots or open ground at the end
of May, using a light, rich soil. Height, 3 in.
Nymphaea Alba.--A hardy aquatic perennial, frequently found in our
ponds. It flowers in June, and may be increased by dividing the roots.
Height, 1 ft.
O
Odontoglossum Grande.--A most beautiful orchid, delighting in a
temperature of from 60 to 70 degrees and an abundance of water during
summer, but good drainage is essential. The blooms are yellow, spotted