With the variety of opening times we see from garden to garden, and even year to year in the same garden, keep in mind your mileage may vary on what is late for you or someone else. But, that being said, here are some that just started blooming (L or VL in my gardens, though the hybridizers' designations are earlier seasons) and that I really enjoy for their tardy appearance, strong bud count (15-30), saturated colors, and rust resistance potential:
Double Red Royal (tested very well for rust resistance by the University of Arkansas in 2001)
9am/82 degrees -- 10:30 am/86 degrees
Tremor (has parentage that was tested as resistant in 2001 U of A, and were given high marks in grower's survey)
6pm/86 degrees -- Varied eye patterns, different on each bloom
Mulberry Truffle has a good balanced parentage; bred with a selection toward tested resistance cultivars
-- depending on time of day, sun position, and from bloom to bloom, a nice range of colors
9:30am/83 degrees -- 10:30 am/86 degrees -- 3pm/93 degrees
Ferry Boat Ride also has parentage that tested well for resistance
7:30am/78 degrees -- Edge detail -- 2pm/99 degrees (blast furnace garden)