Arbor Vitae. See “Thuya.”

Arbutus (Strawberry Tree).—­Elegant evergreen shrubs with dark foliage of great beauty during October and November, when they produce an abundance of pearly-white flowers, and the fruit of the previous year is ripe.  A. Unedo is particularly charming.  They flourish in the open in sandy loam.  The dwarfs are increased by layers, the rest by seeds or by budding on each other.

Arctostaphylos.—­These evergreen shrubs need the same treatment as Arbutos.  A. Uva-ursi, or Creeping Arbutos, is a pretty prostrate evergreen, which flowers in May, and is only 3 in. high.

Arctotis.—­A showy and interesting half-hardy annual.  Raise the seed in a frame in March, and transplant in May.  It succeeds best in a mixture of loam and peat.  It flowers in June.  Height, 1 ft.

Arctotis Grandis.—­A very handsome, half-hardy annual producing large daisy-like flowers on long wiry stems, the upper part being white and the base yellow and lilac, while the reverse of the petals are of a light lilac.  The seed should be sown early in spring on a slight hot-bed, and the plants potted off, when sufficiently strong, using a rich, light mould.  They may be transferred to the border as soon as all fear of frost is over.  Height, 2-1/2 ft.

Ardisia Japonica.—­An evergreen shrub which delights in a mixture of loam and peat.  Cuttings will strike if planted in sand under glass with a little bottom heat.  It flowers in July.  Height, 6 ft.

Arenaria Balearica (Sand Wort).—­A hardy evergreen trailing plant of easy culture, provided it is favoured with a sandy soil.  Its cushions of white flowers are produced in July, and it may be increased by seed or division.  Height, 3 in.  It is a beautiful plant for moist, shady rock-work.

Argemone.—­Interesting hardy annuals, succeeding well in any common garden soil.  Are increased by suckers or by seed sown in spring.  Height, 6 in. to 3 ft.

Aristolochia Sipho (Dutchman’s Pipe).—­This hardy, deciduous climber grows best in peat and sandy loam with the addition of a little dung.  It may be raised from cuttings placed in sand under glass.  Height, 30 ft.

Armeria (Thrift).—­Handsome hardy perennials for rock-work or pots.  They require an open, rich, sandy soil.  Bloom June to September.  Height, 1-1/2 ft.

Arnebia.—­Ornamental hardy annuals, closely allied to the Anchusa.  The seeds are sown in the open in spring, and flowers are produced in July.  Height, 2 ft.  There is also a dwarf hardy perennial variety (A.  Echioides) known as the Prophet’s Flower, growing about 1 ft. high, and flowering early in summer.  It needs no special treatment.

Artemisia Annua.—­Pretty hardy annuals, the silvery leaves of the plant being very effective on rock-work.  Sow the seed in spring where it is to flower.  Height, 6 ft.

Artemisia Arborea. See “Southernwood.”