The jewel in The Brenton Arboretum’s crown is the Kentucky coffeetree collection. Our collection of nearly 100 accessions (and growing) was granted the prestigious status of accreditation by the international Plant Collections Network.

There are only three species in the genus Gymnocladus and only one of them is native to the New World; known to botanists as Gymnocladus dioicus. This graceful tree is native to a swath of North America stretching from southwest Oklahoma to Lake Erie.

The Brenton Arboretum’s Kentucky coffeetree collection focuses on the conservation of the unique genetics of wild populations throughout the plant’s native range. A joint partnership between The Brenton Arboretum and the National Plant Germplasm System (NPGS) has resulted in the collection of seeds from natural groves of Kentucky coffeetree throughout the US. Those seed are methodically cleaned and cataloged and then split between the Arboretum and NPGS.

The seeds that go to the National Plant Germplasm System are put into longterm storage at their facility in Ames, Iowa. Some of the seeds have even been sent to the famous Svalbard Global Seed Vault on a remote island in Norway! These stored seeds may prove priceless in a world full of environmental uncertainties. 

The seeds that remain with The Brenton Arboretum are planted and grown into seedlings. One lucky seedling from each wild population will be selected to be planted into the Arboretum’s thriving collections. No where else in the world can you stand among a grove of trees that represent such a complete collection of a species’ wild origins!

Click the link below to learn more about the Kentucky coffeetree, the partnership between The Brenton Arboretum and the National Plant Germplasm System, and the exciting collecting expeditions made by the project’s visionaries: Andy Schmitz and Jeff Carstens. The article, originally published in The Arnold Arboretum’s The Arnoldia, was written by these two botanists and is an excellent glimpse at the world of modern plant exploration and conservation.

The Brenton Arboretum hosts an impressive collection of oak species, hybrids, and cultivars. As a matter of fact the bur oak (Quercus macrocarpa) is the tree featured in our logo! Oaks are one of Earth’s most widely varied and dispersed tree species with hundreds of kinds native to almost all of the world’s continents… sorry Australia and Antarctica, you’ll have to import your oaks.

If you want to explore the Arboretum’s oak collection you’ll need to visit more than one area on the property. Our oaks are planted according to their growing requirements. Those that prefer moist soils can be found in the floodplains along the stream at the southern end of the property. Others prefer higher and drier ground and can be found closer to the Pavilion and O’Brien Nature Play area. Still others are rugged species and thrive in the strong west winds and poorer soils of the western edge of the Arboretum. Consult our Pocket Guide to Trees to seek out your favorite species.

Noted for its stately habit and sturdy wood the hickory tree (Carya spp.) is synonymous with strength, longevity, and natural grace. Like our oak collection, the Brenton Arboretum’s hickories will be found in more than one place. Part of the Carya collection can be found surrounding Overlook Pond along with a selection of upland oaks. The bulk of the hickory collection can be found just northwest of Walnut Bridge. Here you’ll find hickory species and hybrids that can easily tolerate occasional inundation from floodwater from the nearby stream.

The Brenton Arboretum Elm Collection

This article was written by Andy Schmitz, Director of Horticulture & General Manager of The Brenton Arboretum for the Spring 2015 Arboretum Newsletter

Unlike the other tree collections at the arboretum, where trees are grouped by species, the elm (Ulmus) collection contains numerous species, cultivars, and hybrids which combine to make a grouping of 80 trees. It is one of the most diverse and comprehensive collections at the arboretum. Actually, it is one of the most extensive elm collections in the Midwest.

The first elms (which the founder Buz Brenton brought back from the Morton Arboretum in Lisle, Illinois) were planted in 1997, the first year any trees were planted at the arboretum. All seven of these first elms are still alive and can be viewed on the south side of the arboretum along the stream. Accession number 1997-187 Wilson‟s Elm, Ulmus wilsoniana in particular is a beautiful specimen and is over 30 feet tall now.

The elm collection was greatly expanded in 2006 and 2007 with the addition of dozens of Asian elm species that Andy Schmitz, director of horticulture, received from Dr. George Ware, who was an eminent tree authority and whose primary passion was the elm genus. Andy visited Dr. Ware at the Morton Arboretum. All in all, 45 of the 80 elms in the collection have a direct connection to Dr. Ware. These Asian elms are typically smaller in growth form than the American elm, but are Dutch Elm Disease resistant. They have interesting names like small-fruited, Bergmann’s, and corkbark elm.

The elm collection includes five cultivars of American elm (Ulmus americana) which are also Dutch Elm Disease resistant. The American elms are “Jefferson,‟ “New Harmony,‟ “Prairie Expedition,” “Princeton,‟ and “Valley Forge.‟ All of these were selected from seedling-grown trees or from naturally occurring native American elms which showed resistance to Dutch Elm Disease.

On your next visit to the arboretum, be sure to visit this magnificent elm collection, not only to observe them, but maybe to decide if an elm tree might be right for your yard.

Large conifers are an important part of windbreaks that have protected Iowa farmsteads for more than a century. But did you know there’s only one species of conifer that’s native throughout the state? The Eastern Red Cedar (Juniperus virginiana) is a hardy and robust tree, but it doesn’t have many compatriots to help flesh out the much-needed hedgerows that block harsh winter prairie winds. That palette of plants has traditionally been limited to a limited selection of fir, spruce, and pine. This lack of diversity leaves windbreaks and other conifer plantings and populations around the Midwest susceptible to insects and diseases.

To try to help introduce new options and greater diversity for windbreak and landscape conifer options, The Brenton Arboretum teamed up with Iowa State University Horticultural Department and the Landscape Plant Development Center, in Chanhassen, Minnesota back in 2003. This collaboration involved planting scores of uncommon species of fir, spruce, pine, hemlock, and others at The Brenton Arboretum. Over a period of ten years each test plant was evaluated for vigor, disease resistance, and overall suitability for midwest landscapes.

As you can imagine, not all of the test plants survived and many failed to thrive. But at the end of the 10 year evaluation period there were definitely some great trees that made it to the head of the class. These trees were transplanted from the test field into the Arboretum’s public collection in 2013. Most of the trees continued to thrive and today you can peruse a wide variety of excellent large conifers that we would heartily recommend for your own landscape.

The Arboretum’s conifer collection can be found on the western side of the property near the crab apples and maples. Consult the Pocket Guide for a map of our collections.

• Crabapple (Malus sp.)
• Osage orange (Maclura pomifera)
• Maple (Acer sp.)
• Iowa Native Trees
• Aronia (Aronia sp.)