Tricyrtis.—­These greenhouse herbaceous plants bloom in May.  A rich, light soil suits them.  Height, 6 in.

Trientalis Europaea (Star Flower).—­To grow this native perennial to advantage, it should be planted in leaf-mould with which a large proportion of sand has been mixed.  Confine the roots to a narrow compass by means of slates placed just beneath the surface of the soil.  Let the ground be kept moist, but well drained.  The bloom is produced during May and June, and it is propagated by runners.  Height, 6 in. to 8 in.

Trifolium Repens Pentaphyllum.—­A showy, hardy, deciduous perennial.  It thrives in ordinary soil, puts forth its white flowers in June, and is propagated by seed or division.  Height, 6 in.

Trillium Erectum (Wood Lily).—­This tuberous perennial is quite hardy, and flourishes in partial shade.  The soil must be light and rich, yet moist.  The plant does not increase very fast, but the roots of good-sized plants may be divided.  It flowers in May and June.  Height, 6 in.

Tritelia.—­A charming spring-flowering plant, bearing pretty white star-like flowers on slender stalks.  It is used largely for edgings.  It looks well in clumps on the front of borders.  Plant in autumn, and divide the bulbs every two or three years.  Height, 6 in.

Tritoma (Red-hot Poker, or Torch Lily).—­Requires a rich, sandy soil, and to be protected in a frame from wet and frost in the winter.  Increase by division or by suckers from the root.  The flower spikes grow 18 to 27 in. long.  The crown of the plant should not be more than 11/2 in. in the soil, which should be dug deeply and mixed with rotted manure.  In winter, if it is left in the ground, surround the plant with 2 in. of sawdust, well trodden.  Remove this in May, and water liberally with liquid manure till it blooms.  The best time to plant is March or October.  By many it is considered advisable not to disturb the plant too often.

Tritonias.—­These somewhat resemble miniature Gladioli, and are among the most useful bulbs for pot-culture.  Plant from September to December, placing five or six bulbs in a 5-in. pot, and using a compost of loam, leaf-mould, and silver sand.  Plunge the pots in ashes in a cold pit or frame, and keep them dry until the plants appear.  When in full growth they may be removed to the conservatory, placing them near the glass, and giving careful attention to watering.  For outdoor cultivation choose a sunny, sheltered position, with a light, rich, sandy soil.  Give protection in frosty weather by covering with dry litter.

Trollius Altaiense (Globe Flower).—­A pretty, hardy herbaceous plant, with very handsome foliage.  It likes a light but moist soil, may be increased by seed or by dividing the root, and flowers in May.  Height, 9 in. to 2 ft.

Trollius Asiaticus.—­A very pretty herbaceous plant, suitable for the border.  It may be raised from seed sown in the autumn, and grown on in light, moist soil.  The plant is hardy and flowers in May.  Height, 1 ft.