CO-Horts

CO-Horts

Friday, September 7, 2018

Tree Seeds of Fall

Posted by: Alison O'Connor, Larimer County Extension

The end of August and early September can be pretty "blah" in the garden. While we're harvesting zucchini and tomatoes up the wazoo, the perennials and shrubs are looking tired. That is, until we start seeing some fall color.

But the tree seeds have been growing all year and will soon be fully mature. They are beautiful in their own right and some can be quite attractive and showy. Some seeds are persistent through winter, adding interest.

Here's a few of the common tree seeds you'll see around the landscape:

Oaks

There are two groups of oaks--red and white. Red oaks include the red oak (Quercus rubra), pin oak (Q. palustris), and scarlet oak (rare in Colorado) (Q. coccinea). Red oaks have pointy leaves and the acorns are usually in pairs on the tree, taking two years to mature. The red oaks, in general, have a "classic" acorn. Red oaks are not always a great choice for Colorado landscapes, though some species, like Texas red, are more tolerant to high soil pH.
Pin oak leaves and acorns
The white oak group includes bur oak (Quercus macrocarpa), swamp white oak (Q. bicolor) and English oak (Q. robur). These species tend to have lobed leaves and are MUCH better choices for Colorado landscapes. They are more tolerant to high soil pH and do better with dry climates. The acorns of white oaks vary, but take one year to mature, and leaves from these trees can persist on the tree through winter. Fall color for white oaks is usually yellow and they don't get the brilliant reds and maroons of red oaks.
Bur oak and acorn. 
The bur oak acorn is very large (macrocarpa is Latin for "big fruit"). The cap of the acorn (scientifically called the involuchre) nearly covers the entire nut and is very hairy. As the acorns mature, the cap and seed will turn brown/tan.

English oak and acorn.
I adore English oak for many reasons, but I find the acorns to be particularly endearing. They are long and skinny with a small cap on top. The way I remember this tree are two-fold: 1) the leaves have "earlobes" at the base where the petiole (stem) attaches to the tree. I was taught to remember Prince Charles's earlobes; 2) the acorn, being long and skinny, reminds me of a tall Frenchman with a beret on his head. England, France....both located across the ocean. We don't have a French oak, so this is my association.

The acorns of bur oak (top left), English oak (bottom) and pin oak (right).
Buckeyes/horsechestnuts

Buckeyes and horsechestnuts are great trees for Colorado. They have showy flowers in early spring and are tolerant to our soils. The Ohio buckeye (Aesculus glabra) is a fairly common species, though could be planted more. (And for the record...Go Bucks!)

Buckeye fruit has small spines. Towards the end of the fall, the capsule will break open and reveal the shiny brown nut inside--keep one in your pocket for good luck. Squirrels go crazy for these nuts and bury them all over. If you have a buckeye in your landscape, you'll likely get volunteer seedlings.
Ohio buckeye leaf and fruit (seed not mature).
Horsechestnuts are very similar, but the fruit capsule has more spines and there are multiple fruits in one capsule.

Catalpa

Catalpa (Catalpa speciosa) is one of the bigger trees in our landscapes. Mature catalpa can reach heights of 50 feet or more. They are very showy with their white orchid-like flowers in June. Catalpa are drought tolerant with huge leaves and cigar-shaped fruit. (Disclaimer: Growing up in Minnesota, our neighbors had a catalpa in their front yard and we would either pretend to "smoke" the fruit or use them as swords--neither practice is recommended.) Many find the leaves and fruit to be messy, but it's just something to consider before planting.

Catalpa leaves and seed pod. The leaves can be much larger than this, about the size of an adult's face. The seed pods will mature and turn brown, but often hang on the tree through late fall and into winter.
Maples

Oh maples (Acer sp.). I do love this tree, even though it's one that can get sickly in our dry, high pH soils. Seeing the sugar and red maples along the St. Croix River bluffs on the Minnesota/Wisconsin border in fall was always a highlight. Most everyone knows maples have samaras (you may call them "helicopter-whirly-gigs") but samaras come in all shapes and sizes. Tatarian maple (A. tataricum) has small cherry red samaras in clusters; Norway maples (A. platanoides) have wide samaras that you can perch on your nose.

Norway maple leaf and samara--the one you can perch on your nose.
Ash

Ash (Fraxinus sp.) are still a very common landscape plant in Colorado and this year, the green ash (F. pennsylvanica) had a seed heyday. This happens every few years--generally when we have good spring moisture. The ash seed is also called a samara, but it's a single fruit, unlike the maple. Many of the newer ash planted are male clones, which do not form seed.

Leaves and seeds from green ash.
Kentucky coffeetree

Another drought tolerant, tough-as-nails tree for the landscape, Kentucky coffeetree (Gymnocladus kentukea) has amazingly thick, chunky seed pods that are retained through the winter. The structure of the tree is very coarse, so the seed pods give it great winter interest. The green seed pods turn into a chocolate brown color. Squirrels also love the seeds. The leaves of this tree are considered as doubly compound, where the leaf branches twice. If you grow this tree, be patient. It doesn't look like much for a few years.
Kentucky coffeetree leaf (one leaf!) and seed pod.
There are many other trees in the landscape with interesting seeds, leaves and fruit. Take a closer look into the tree canopy and see what you find. If you ever need help identifying trees in your landscape, contact your local Extension office!
Maple the Beagle. Not the tree. 

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