The Flowers “Nobody” Knows

Trees Producing Catkins Now At The Morton Arboretum

LISLE, IL (March 22, 2006) – There’s more to trees than new leaves this spring. Before their leaves start to come out, several species of trees at The Morton Arboretum are producing catkins – strikingly beautiful flowers that most people don’t recognize or even know about – and now is the time to start finding them.

Catkins are often “borne to blush unseen,” said renowned educator and naturalist Mary Theilgaard Watts in a 1944 Morton Arboretum bulletin.

Why aren’t more people familiar with these tree flowers? It might be that the popular idea of what a flower looks like doesn’t fit these catkins. They’re not rare, as up to half of all species of common deciduous trees will produce catkins anytime from late March through early June. Still, most people may be surprised at catkins’ color and attractiveness.

Catkins commonly grow in long, thin clusters that hang down from branches. The tiny flowers are usually yellow-green, red, mahogany or reddish-brown. To many, catkins look like thin, soft pine cones, or like last year’s seed clusters still hanging off the tree. Some catkins grow before leaves (as in alders, ironwoods and some maples) while others emerge at the same time as young leaves (on oaks and sycamores).

“Catkins are actually very conspicuous,” says George Ware, Ph.D., long-time researcher at The Morton Arboretum. “Yet because they only last a short time on the trees, and are gone by summer, most people don’t notice them.”

Catkins vary by species. Some trees contain catkins with stamens and pistils. Others have only stamens (“staminate” flower) on one tree, with the flowers containing the pistil (“pistillate” flower) on a separate tree. After releasing pollen, catkins dry up as the weather gets warmer, and then fall off the tree as the leaves fully develop. The seeds of the trees develop throughout the spring and summer; some seeds, or “fruits,” drop early like the fluffy white, wind-blown cottonwood seeds and the winged seeds of Silver maples. Others take until autumn to mature and drop, like oak acorns, walnuts and hickory nuts. In these late-fruiting trees, the female (pistillate) flower starts out as a single, or perhaps double, miniature nut.

One of the more handsome catkins blooming right now is on European black alders (Alnus glutinosa). These catkins are usually colored mahogany and yellow and should be opening to drop pollen over these next few weeks. The seeds develop over the next several weeks.

“European alders fill an ecological niche – growing along river banks – that has too few occupants among North American species,” Ware says. “At the Arboretum, alders are located along the East Branch of the DuPage River, and the catkins are already starting to shed pollen.”

The pyramidal European black alder (Alnus glutinosa ‘Pyramidalis’) is the Arboretum’s “Tree of the Month” for April. This tree is located in Godshalk Meadow.

Some of the trees at The Morton Arboretum that are producing catkins or clusters of tiny flowers now through April and May include:

• European black alder (Alnus glutinosa) – now into April; mahogany and yellow
• Silver maple (Acer saccharinum) – now into April; red, gold and white
• American elm (Ulmus americana) – late March to April; reddish-brown
• Ironwood (Ostrya virginiana) – April to May; yellow
• Eastern cottonwood (Populus deltoides) – April to May; red
• Black willow (Salix nigra) – April to May; yellow and yellow-green
• Boxelder (Acer negundo) – April to May; yellow-green with pink stamens
• Sugar maple (Acer saccharum) – April to May; greenish-yellow
• White oak (Quercus alba) – late April; silvery-green and yellow
• Sycamore (Platanus occidentalis) – May; red and green
• White ash (Fraxinus americana) – May; brown and green
• Black walnut (Juglans nigra) – May; green and purple
• Shagbark hickory (Carya ovata) – May to June; green

Catkins are a beautiful and not often noticed part of the seasonal cycle of trees. Visit The Morton Arboretum in March and April to check out these colorful flowers while they last.

NOTE: Staff at The Morton Arboretum Visitor Center Information Desk can help locate the exact location of tree species on your next trip to the Arboretum. You can also visit www.mortonarb.org for information by going into the “Plant Information” selection at the bottom of the Home Page. Select “Plant Collection Catalog”, then the “Plant Name” option. Type the name of the tree (Latin name such as “Acer Negundo” in the “Scientific Name Keyword”) or common name (“Boxelder” in the other box), with a space after the name. Once you’ve found the correct tree, click on one of the listed trees of that variety and a catalog location number (“R-99/43-13”) will correspond to the location on the plat map of the Arboretum.

The Morton Arboretum is an internationally recognized 1,700-acre outdoor museum with collections of more than 3,700 kinds of trees, shrubs, and other plants from around the world. The Arboretum's beautiful natural landscapes, gardens, research and education programs, and year-round family activities support its mission – the planting and conservation of trees and other plants for a greener, healthier, and more beautiful world. Conveniently located at I-88 and Rte. 53 in Lisle, Illinois, the Arboretum is open 7 days a week, 365 days a year, from 7 a.m. to 7 p.m. (CDT) and 7 a.m. to 5 p.m. (CST). The Children's Garden is open from 9:30 a.m. to 5 p.m. (CDT) and 9:30 to 4 p.m. (CST). Visit www.mortonarb.org or call 630/968-0074 to learn more.

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