May leaf out late. Aggressive roots preclude underplanting, but still needs deep soil. Very easy to transplant and adaptable to extreme soil conditions. Good compartmentalizer of decay.
'Valley Forge', 'New Harmony', and 'Princeton' (and possibly 'Jefferson' but it hasn't been tested enough outside Washington, D.C. yet) are the most resistant to Dutch elm disease of those cultivars commonly found in commerce... at least in the USA; apparently 'Princeton' is known to get infected in Europe, suspected to be due to the differences in the disease strains and/or main beetle vectors present on the two continents (Wikipedia). In controlled USDA tests, 'Valley Forge' was the most resistant cultivar, but it is also noted for being exceptionally vigorous and requiring pruning for good structure.
'Princeton' is also noted for being susceptible to storm breakage due to its branching habit. I have read that the wood of American elms is strong enough that most trees avoid this problem despite narrow crotch angles, but until I can find the source for this, I cannot in good conscience change the tags.
Sources: White Oak, Sunset, NCSU, Dirr, UFL, Missouri BG, UConn, Dirr/Warren, USDA.
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