Nut Trees|Iowa Arboretum & Gardens

NUT TREE GROVE

What is a nut tree?

Nut trees are a group of woody plants that produce a nutrient rich, edible seed as part of their reproduction. Many of these species evolved with animals, which are responsible for planting new nut trees. For example, many of our native hickories and walnuts rely on birds and mammals to collect nuts, cache or bury them, and then forget where they were stored. The next spring, the forgotten nut will germinate and grow a brand new tree! Many nut trees are considered mast species, meaning the go through waves of highly productive years creating lots of nuts, and years of less production where they focus on growing. Humans have been using nut producing species for thousands of years, and they have become an irreplaceable food source for much of the world.

Despite popular belief, nut trees are a diverse group of trees from several different plant families. For instance, almonds are closely related to peaches and come from the rose family. Pistachios come from the cashew family, the same family as sumac and poison ivy! Chestnuts come from the beech family and are related to oaks. Hazelnuts come from the birch family and are related to hornbeam. And finally, walnuts and hickories are both a part of the walnut family. Even ginkgo and pines are considered a nut tree in many parts of the world!

While the nut tree category is relatively diverse, many species are not cold hardy in Iowa. The most commonly grown nut trees commercially here are walnut (Juglans spp.), hickories/pecans (Carya spp.), chestnuts (Castanea spp.), and hazelnuts (Corylus spp.).

The Grove

The Nut Trees were established in 1982 in the far southwest corner of the cultivated 40 acres. Several hybrid and cultivar introductions by the late Archie Sparks, the late Al Ferguson, and Ward Mally exist in this planting. Their involvement in the Iowa Nut Growers Association and Northern Nut Growers Association gave them great access to the best nut tree genetics at the time. Particular favorites of theirs to propagate were black walnut (Juglans nigra), shagbark hickory (Carya ovata), northern pecan (Carya illinoinensis), and chestnut (Castanea). Their love of the state and exploring its untapped potential led to the creation of many nut tree selections named after local landmarks near where they discovered superior trees. Many of the trees are reproduced by grafting, and in some cases the graft union where bark texture changes can still be viewed on mature trees. Cultivars in this collection were selected for their large, edible fruits. Other selection features include ease of cracking and self-hulling. Now that the grove has reached maturity, further selection is being done for the potential for ornamental trees, with considerations like small nut size, fall color, and final tree size/shape all being considered.

Unique Specimens

While many of the tree specimens in this grove have been the favorites of many plant professionals and visitors, there are several notable trees growing. The first is a Japanese wingnut (Pterocarya rhoifolia). Planted in 1979, this tree hails from Japan where it is commonly used as an ornamental tree and for lumber. Belonging to the walnut family, this species does produce nuts that are paired with little wings. The nut is edible, but is very small making it difficult to shell. A fast grower, it makes a stunning shade tree with great horizontal architecture.

Another specimen worth noting is a little known Iowa State University introduction called Stark Northern Prize Persian Walnut (ISU71-E18). A selection of the Persian walnut (Juglans regia), it was selected in 1971 at the Ames Horticulture Station by Dr. Paul Domoto. Proving to be a cold hardy variety, it was quickly picked up and distributed by Stark Brothers Nursery for decades. Now a rare tree this far north, interest in cold hardy Persian walnuts has regrown with the hopes of one day creating additional selections for Iowa.

One specimen particularly important to the Arboretum is a selection of butternut (Juglans cinerea) likely collected on Arboretum property. Named ‘Herrick’, the tree is known for large nuts and resistance to butternut canker, a deadly disease for butternut. The variety was brought to the United States Department of Agriculture National Clonal Germplasm Repository for preservation by the Iowa State Horticulture Society in 1990. The story goes that the plant was named Herrick butternut because the plant was collected on the Arboretum’s very own Herrick Memorial Trail.

All of these nut trees and more are a part of the Iowa Arboretum & Gardens Nut Tree Collection. Learn more about the whole collection here.

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Plant List:

Carya cordiformis – Bitternut hickory C. cordiformis x C. ovata (C. x laneyi) Carya x laneyi ‘Vermace’ – Vermace Laney’s hickory Carya illinoinensis – Northern pecan Carya illinoinensis ‘Donnellson’ – Donnellson northern pecan Carya illinoinesis ‘Gibson’ – Gibson northern pecan Carya illinoinensis ‘Le Baeu’ – La Baeu northern pecan Carya laciniosa ‘Kaufman’ – Kaufman shellbark hickory Carya laciniosa ‘Ross’ – Ross shellbark hickory Carya laciniosa ‘Selbhers’ – Selbhers shellbark hickory C. laciniosa x C. ovata (C. x dunbarii) Carya x dunbarii – Dunbar’s hickory Carya ovata – Shagbark hickory Carya ovata ‘Abundance’ – Abundance shagbark hickory Carya ovata ‘Hopson’ – Hopson shagbark hickory Carya ovata ‘Silvis 303’ – Silvis 303 shagbark hickory C. ovata x C. illinoinensis Carya ovata x illinoinensis ‘Henke’ – Henke hican Carya texana – Black hickory Carya tomentosa – Mockernut hickory Castanea dentata – American chestnut Castanea mollissima – Chinese chestnut Corylus americana ‘Purpleleaf Bailey Select’ – Purpleleaf Bailey Select American hazelnut Corylus avellana – Common hazel Corylus avellana ‘Contorta’ – Corkscrew hazelnut Corylus colurna – Turkish filbert Juglans ailanthifolia – Japanese walnut Juglans cinerea ‘Herrick’ – Herrick butternut Juglans nigra – Black Walnut Juglans nigra ‘Cranz’ – Crans black walnut Juglans nigra ‘Davidson’ – Davidson black walnut Juglans nigra ‘Eldora’ – Eldora black walnut Juglans nigra ‘Minnesota’ – Minnesota black walnut Juglans nigra ‘Prairie’ – Prairie black walnut Juglans nigra ‘Sparks #127’ – Sparks #127 black walnut Juglans nigra ‘Sparks #128’ – Sparks #128 black walnut Juglans nigra ‘Sparks #147’ – Sparks #147 black walnut Juglans nigra x regia Juglans nigra x regia – Hybrid walnut Juglans regia ‘Stark Northern Prize’ – Stark Northern Prize Persian walnut Juglans x quadrangulata (J. cinerea x J. regia) Juglans x quadrangulata ‘White’s Hybrid’ – Whites Hybrid walnut Pterocarya rhoifolia – Japanese wingnut