Stellaria media 
The scientific name for the weed Common Chickweed.
Sun Spurge
An uncommon weed of newly sown areas which have been neglected in aftercare. An annual weed which is more common in borders which have had the soil disturbed. It flowers during May to October, with 5 yellow-green bracts beneath a capsule fruit. It grows over a wide range of soil pH levels, prefers moist conditions, in an exposed non-shaded situation. It is easily controlled by mowing or hand weeding out of sown areas. Its scientific name is Euphorbia helioscopia.
Taraxacum officinalis
The scientific name for the weed Dandelion.
Thistle
A number of species which can be a problem in longer maintained or neglected turf surfaces. Creeping Thistle and Spear Thistle are two common species which might, amongst others, be found within turfgrass situations.
Thrift
A common perennial weed of coastal turf surfaces. It has fine grass like leaves, to about 2mm in width, having a preference for sandier soil, but not acidic ones. It adapts well to dry and wet soils, salt sprayed turf, but needs to be in full light, not shade. It flowers from April to July with some flowering up to September, having pink flowers in a globe type head up to 25mm in diameter. Its scientific name is Armeria maritima.
Thyme Leaved Speedwell
A creeping perennial weed of turf surfaces, with a preference for damp and acidic conditions. Its leaves are 10mm - 20mm in length, and more or less hairless. It flowers during March to October, with whitish coloured flowers. Its scientific name is Veronica serpyllifolia.
Toad Rush
A fine bristle-like leaved rush that occurs in wet, poorly drained areas or damp thatchy surfaces. The scientific name for the annual weed is Juncus bufonius.
Tormentil
An uncommon perennial weed of longer amenity surfaces and lawns, and neglected surfaces. It has three leaflets, deeply lobed, with two smaller leaflets at the base of each leaf stem which are actually stipules, making it appear that it has five leaflets. Its scientific name is Potentilla erecta. It prefers free draining to damp soil, although these will mostly be acidic. The main flowering period is June to September, having yellow coloured flowers, having a median diameter of about 12mm, but being quite variable in size. It adapts to a range of soil conditions, from dry to wet, preferring sa
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Trefoils
Trifolium dubium