Ultradwarf bermudagrasses have shorter rhizomes, faster ball speeds, and are more heavily stoloniferous, and more prone to thatch and localized dry spots, than the traditional standard Tifdwarf.

Bermudagrass varieties for golf greens keep getting shorter and shorter.  In 1960, Tifdwarf was the ultimate in Florida.  But equipment manufacturers kept improving their products, and by the late 1970s it was clear that the demands were only going to increase.  Bermudagrass greens, especially 328 (Tifgreen) were getting clobbered by Bermudagrass Decline, at close height of cut, especially during the cloudy days of August and September.  In 1980, the late Monty Moncrief asked me to chair a USGA Greens Section seminar on the subject of Tifdwarf.   But what I remember was the agitation of the audience regarding Decline, and the fact that no one at that time had any answers.  It would be years later that Dr. Monica Elliott would come to Florida to solve the puzzle of Bermudagrass Decline.
Meanwhile efforts to grow bentgrass for year-round golf in Florida were doomed to disease, as was witnessed in a major televised tournament.  In 1987, I was strongly urged by my University administration to develop a bentgrass breeding program.  I ignored this advice because I felt it unwise to try to work against millions of years of evolution which has outfitted warm-season plants to grow in warm-climates.
Private consultants and golf course superintendents kept coming up with new types of bermuda.  Some felt that Tifdwarf was no longer genuine, thus a Classic Dwarf was marketed.  In the same way that Tifdwarf arose as an off-type in 328 (Tifgreen), superintendents such as Paul Frank were coming up with their own improved strains such as PF-11.  At times these new grasses seemed to be as much the problem as the solution.  Off-types that occurred on greens were sometimes more stoloniferous than the surrounding grass, thus causing hydrophobic spots.  But solid greens of the same grass didn't seem to have the problem.  Paul's work at Wilderness Country Club clearly showed that there were bermudagrasses that could survive at close cutting on greens in high humidity pockets surrounded by cypress swamps.  This was the perfect environment for Decline.  Within a few years, FloraDwarf was also recognized to be a big improvement in shortness, but it tended to be very difficult to aerify and overseed, at least with perennial ryegrass.  And there were other Ultradwarfs.
During the mid 1980s I was working almost exclusively on St. Augustinegrass.  Ironically this was on the advice of Dr. G. C. Horn, a widely respected consultant for golf course superintendents and former scientist with the University of Florida.  Whenever he talked at the turf show, it was standing-room only.  By 1985, I coined the term "Ultradwarf" to refer to dwarf St. Augustinegrasses shorter than Seville.   The term never caught on with Florida sod growers, as they were having enough problem with call-backs and lawsuits over the first Ultradwarf, Jade St. Augustinegrass.
Then by August 1996 I used "Ultradwarf" to refer to bermudagrasses shorter than Tifdwarf.  And the name stuck.  We were doing genetic fingerprinting studies to distinguish the new off-types, trade types, mutants, varieties, whatever they are called, and "Ultradwarf" helped to pigeon-hole a number of similar plants.  The danger of generalities is that once we understand the similarities of the Ultradwarf bermudagrasses, we ignore the fact that there are differences.
The first information I have accumulated here is on herbicide resistance.  We sprayed Ultradwarf bermudagrasses with way more herbicide than you would ever want, just to see how susceptible they are.  They are not highly susceptible, in  most cases, even to products applied at multiples of the label rate.  Don't do what we did, in fact you can see the results here without risking your job.
As an afterword, why don't I say "UltraDwarf" with a capital "D."  The business of capitalizing a letter in the middle of a word seems to me an unnecessary fad used in trademarks.  Part of the incentive is geek.  UNIX program such as perl take advantage of the case because UNIX operating systems and some languages such as JavaScript are case sensitive.  Somehow it helps the programmer distinguish variables from functions from operators and other stuff.   But to me, I just get tired trying to remember what letters to capitalize.  Whether Ultradwarf is a proper noun can also be debated, so perhaps it shouldn't be capitalized at all.

Philip Busey, turf@ufl.edu