Teucrium

Chamaedrys Germander
Perennial.  This plant has tiny leaves, but they make up for size with shine. The pink/ purple flowers cover the foliage from summer through fall. It can be trained as a small shrub or as a ground cover. Full sun to part sun. Zones 5-10 Height 10-12". 

Thalictrum

Perennial. A relative of Columbine, this genus has very distinct, beautiful flowers. It is the plant of choice for height in the perennial shade garden. The leaves are bluish in hue and are softly lobed. The flower spikes resemble Baby's Breath. Shade to part shade.
aquilegifolium Fluffy lavender flowers. Height 24-36" Zones 6-10
diperocarpum Nodding rose-violet flower clusters with distinct yellow stamens. Finely dissected leaves. Height 36-48" Zones 7-10

Thelesperma

Greenthreads burridgeanum 'Brunette'  Annual. A beautiful cushion of brown and yellow bicolored daisy flowers will greet you every time you walk into the garden. The foliage is very fine, similar to Coreopsis rosea. It also makes a great cut-flower. Full sun to part shade. Height 16-20".

Thermopsis

lancelolata False Lupine Perennial. This mid-sized member of the pea family is an excellent choice for the perennial garden. It's large yellow flower spikes attract bees, & butterflies as well as people. The foliage is palmate. Full sun to part sun. Height 14-16" Zones 7-10.

Thunbergia  

A genus of mostly vines and clumping shrubs native to Africa, Asia, and Madagascar. Their leaves are entire or lobed and the flowers trumpet shaped. They prefer reasonably rich soil and good drainage. They do best with a little protection from the sun in summer when liberal water should be provided. Zone 10
Orange
White

Tiarella                       

Foamflower, North American native that thrives in cool climates in shade and humus rich soil with ample water. Tiarella resemble Heuchera, a relative, but have airy sprays of white to pink flowers. Ht. 12” Zones 3-9

Tithonia                      

Mexican Sunflower ‘Fiesta del Sol’  -The most compact Tithonia with bright orange flowers. Very heat tolerant but needs ample water. Ht. 30”. Zones 8-10

Torenia

hybrid Wishbone Flower Annual. A great shade performer and it has bright flowers too!  What more could you ask for. These little guys are a great alternative shade bedding plant. Part shade to part sun. Height 6-8" Zones 9-10
‘Clown Mix’ good performer in most weather conditions, compact, densely branched 8-10” tall.
'Duchess' Series great for the shade garden, 6-8” tall, available in pink or blue.

Trachelium

Caeruleum ‘Devotion Blue’ plants have a central umbel surrounded with smaller side umbels. This is a selected deep blue variety. Grow in full sun to part shade in very well drained soil. Zones 9-10

Tradescantia           

Spiderwort 'Shimmer Series’a perennial for the sun or a partly shaded garden. Flower stems can reach to 24”. Spiderwort prefers fertile, moist to dry soil. They may be cut back severely when they become straggly. Zones 7-10

Turnera

Ulmifolia Yellow Alder Perennial. This small shrub will brighten your breakfast; its large yellow flowers are only open in the morning. The leaves are hairy and medium green. Full sun to part sun. Height to 2'. Zones 8-10.