The bur-gambel oak is a naturally occurring cross between the bur
oak, whose native range is in the eastern U.S., and the Gambel oak,
whose native range is in the southwestern U.S. and Mexico. It is a
member of the white oak group and produces abundant acorns annually. The
mature size of the tree can vary from large tree (typical of bur oaks)
to medium tree/large shrub (typical of Gambel oaks) depending on its
environment. Both parents are known to be tough and drought-tolerant.

The genus Quercus
includes more than 600 species of the oak tree, of which 90 are native
to North America; the Chicago Botanic Garden's collection contains more
than 60 varieties and over 1,000 individual trees. Twenty oak species
are native to Illinois.

Oaks are slow growing, long lived, hard wood trees that produce fruit
we all know as acorns. Within the white oak group, acorns mature
annually; in the red oak group, acorns take two years to mature
(biennial). Oaks are often imposing shade trees at maturity and provide
habitat and food for a variety of wildlife.