Eucalyptus dalrympleana - Mountain White Gum, Mountain Gum, Broad-leaved Kindling-bark, Broad-leaved Ribbon Gum, Kindlingbark, Seven-flowered Mountain Gum, White Gum (Southeast Australia and Tasmania) This large and fast-growing (to 150') tree has reddish-tinted blue-green leaves held in heavy tresses and very attractive white bark with grey, cream, and pink patches.  It is somewhat variable in its juvenile foliage.  The wood is somewhat useful but not of exceptional quality.  Very hardy but often fails to harden off before severe freezes.  Two subspecies exist, and the hardiest provenances of this species are probably from Tasmania.  3 to 12°F.
Photos of Eucalyptus dalrympleana

Eucalyptus dealbata - Tumbledown Red Gum, Tumbledown Gum (New South Wales) Fast growing medium tree, adapted to dry conditions but not excptionally hardy.  Possibly useful in Texas and the Southwest.  10 (?) to 16°F.

Eucalyptus deanei - Round-leaved Gum, Deane's Gum, Round-leaved Blue Gum, Mountain Blue Gum, Brown Gum (New South Wales) A very beautiful, large tree, with smooth attracive bark in colors of white, yellow and red, and pink-tinged juvenile foliage.  Extremely fast growing and adaptable.  Not fully tested for hardiness in cultivation, but it will probably tolerate 7 to 14°F.
Photos of Eucalyptus deanei

Eucalyptus deauensis - Mongamulla Mountain Mallee (New South Wales) A relative of E. alpina; hardiness not known but worth mentioning.  Extremely rare.

Eucalyptus delegatensis - Alpine Ash, Gum-topped Stringybark, Australian Oak, Tasmanian Oak, Whitetop Stringybark, White-top, Woollybutt, Blue Leaf,  Mountain White Gum (Southeast Australia and Tasmania)  This is one of the "half-barked ashes"--called so because, when the tree is mature, the bark is persistent near the base of the trunk, but shed annually above about 20 - 40' up the trunk.  The leaves are quite large (as eucs go) and curved, and have an attractive dark-pinkish-red tint.  White flowers appear in summer, in greater profusion than on most eucalypts.  This tree rapidly grows straight up, to a height of 100 to 150' with an enormous spread in maturity--its sheer size is incredible.  Tolerates exposure (where hardy) and poor soils, and also has potential as a timber tree for its high-quality wood.  It also holds up to freezing rain comparatively well.  Several specimens reached 70' tall at the University of Washington in Seattle in the 1970's, but froze in 1979.  Hardier provenances should be tried.  2 to 12°F.  Ssp. tasmaniensis (or tasmanica in some references) of Tasmania is less cold-hardy, but could be useful for its juvenile foliage which is very blue and resembles that of E. polyanthemos.
Photos of Eucalyptus delegatensis

Eucalyptus dendromorpha - Budawang Ash (New South Wales) Not commonly grown; probably hardy to somewhere around 5 to 12°F.

Eucalyptus denticulata - Shining Gum (Victoria) A recent classification differing only slightly from E. nitens in its fruit and adult leaves.

Eucalyptus dives - Broad-leaved Peppermint (Southeast Australia) As the name suggests, a peppermint with broad leaves, closely allied to the E. radiata group.  It grows fairly large and thrives on dryish sites.  Deep green leaves are not shiny but attracive.  Probably hardy to about 7 to 15°F.
Photos of Eucalyptus dives

Eucalyptus dunnii - Dunn's White Gum, Killarney Ash, Ribbon Gum, White Gum (southeast Queensland) a very fast-growing, large and beautiful tree, surprisingly hardy considering its place of origin.  Useful timber.  9 to 15°F.
Photos of Eucalyptus dunnii