By Jessica Clarke, Horticulturist
Colorado’s fall may not be as long-lived as those of
the East Coast, but it is a spectacular sight to see. Walking through a golden
aspen grove, listening to the crunch of leaves under your feet, and seeing the
snow-crusted mountain tops, you truly get a sense that Mother Nature is putting
on her crowning glory. The aspens and the mountaintops are not the only ones
putting on a show; many other natives are decked out and showing off their
grand colors before the long winter sleep. In the Foothills Garden at the
Gardens on Spring Creek, you can learn what natives to look for this fall while
you are out exploring nature’s goodies. Let’s begin with a showstopper that is
prevalent throughout the state of Colorado: Quercus, known commonly as
oaks.
Quercus are an interesting group of plants in general. One could do a whole thesis on the subject. Their ability to naturally hybridize with one another produces many different plants that don’t cleanly fit into our idea of a given species. This phenomenon can lead to any seasoned plant identification expert scratching their head when working with the group. Regardless, we have many great examples of these oaks in the Foothills Garden. If you are looking for one you can learn to identify while out hiking, start with Gambel oak (Quercus gambelii).
Quercus gambelii, can be found all along the foothills of the Southern Rocky Mountains. The species present as a deciduous shrub or small tree, typically growing between 5,000 – 8,500 feet in elevation. Gambel oak tolerates more moisture than other western oaks, and so can be seen on steep mountain slopes, which they colonize after forest fires. The trees light these slopes ablaze in fall when they color in shades of gold, orange, and near-red. Q. gambelii have alternate, deeply lobed leaves (compared to other native Quercus) that are two to four inches long, have a brown-grey bark, and produce long acorn caps that cover 1/3 or more of the nut in the late summer or early fall. A good example of Q. gambelii can be found right before you enter the Foothills Garden in the sedum slope closest to the stage.
The Rhus spp. (sumac species), that we have in
the Foothills Garden have some of the best fall colors in the garden. Even in late
September the leaves on the Rhus glabra, or Rocky Mountain sumac, have already
started to turn a deep, dark red. Just about all sumac species in the Foothills
Garden are Colorado natives. Rhus glabra f. lacinata, Rhus
glabra var. cismontana, and Rhus trilobata are three examples
of this. All three can be found in our foothill region from Arapaho & Roosevelt
National Forest to Pike – San Isabel National Forest here in Colorado, though
each prefers a slightly different habitat.
Rhus glabra, Rocky Mountain or smooth sumac, favor dry slopes in plains and foothill zones. They are a deciduous shrub that can grow 3.5 to 10 feet tall, the leaves are pinnately, toothed shaped, with cream-color, greenish-yellow flowers that shape into a pyramid. Their seed head forms the highly characteristic, cone-like cluster of red seeds that can be identified from afar. Rhus trilobata, three-leaved sumac, has two attributes that make it easy to recognize. As stated in the common name, three-leaved sumac has three leaves on each petiole. An alternate common name highlights its other identification trait: sometimes called skunk bush sumac, it has a very distinct smell. R. trilobata flowers have five fuzzy petals and form little clusters of orange-red, fuzzy berries. R. trilobata dwells along streams in the foothills and plains zones.
Rhus glabra, Rocky Mountain sumac in the Foothills Garden changing color
Speaking of plains dwellers, Prunus pumila var.
besseyi are for sure one to keep an eye out for this fall. You won’t have
to look very hard to find them in the Foothills Garden or in our foothills
zones that roll into the plains. We grow Prunus pumila var. besseyi, which
forms a mound to four feet high, as well as the nearly-flat growing
cultivar ‘Boulder Weeping’. Both are great additions to add to your fall
peeping list.
Prunus pumila var
bessey, ‘Boulder Weeping’ has outstanding deep red-orange fall colors.
This Colorado native was found just west of Boulder, Colorado. Considered more
of a groundcover, it grows less than two feet tall and spreads up to six feet
wide. If you are looking for a xeric groundcover, this is a great one to try. Both
sand cherries, Western and ‘Boulder Weeping’ are deciduous. They can be identified
by their simple, obovate leaves that are narrow on fruiting branches. In the
spring they have beautiful white, five-petaled flowers that transform into
purple-black fruit in late summer and, of course, their gorgeous red leaves in
the fall.
These are just a few examples of beautiful Colorado
natives to look for this fall. Hopefully, during your fall expeditions through
the Foothills Garden and through our foothills region, you will be inspired to
get outside. Maybe that inspiration will lead you even further by applying it
to your own landscape. All plants covered here are not only native but xeric
too. No matter how this little fall missive inspires you, hopefully, you find
the time this autumn to get outside and relish in nature’s beauty.