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  • Patrick Stoll

The Incredible Netleaf Hackberry

Updated: Mar 27, 2023

The comedian Rodney Dangerfield was best known for his signature saying, “I don’t get no respect.” I often think the same could be said for the incredible netleaf hackberry tree (Celtis reticulata). This western native is heat and drought tolerant, not picky about soil fertility, provides food and cover for wildlife, and is fire resistant. There are some who claim its often twisted and stunted appearance is unattractive. I think it gives the tree character.

Netleaf hackberry and Cooper's hawk
Netleaf hackberry and Cooper's hawk (Accipiter cooperii) in foothills above Boise, Idaho

My first experience with the netleaf hackberry took place years ago when I first ventured into the Boise foothills. While running in the rocky areas along the mesa above and east of the Idaho Botanical Garden, I noticed unusual little trees that almost always seemed to be growing from cracks or crevices among the rocks and boulders. I assumed this was an adaptive association that protected early growth from grazing herbivores. I later learned there was more to it than that. Referring to the netleaf hackberry, Boise botanist Ann DeBolt explained, “The presence of rock helps trees survive, first by providing a “safe site” for seeds to collect and germinate. Rocks also reduce competition with other plants, provide protection from grazing animals, help funnel moisture to tree roots, and protect plants from fire.” (DeBolt, personal communication).

Young netleaf hackberry along trail in Boise foothills

In the western U.S., netleaf hackberries tend to grow in rocky outcrops and draws in semi-arid locations. They are generally found near streambeds and hillsides with southern exposures. The hackberries near the Idaho Botanical Garden represent what is almost the northernmost range of the tough little trees (the northern range is fragmented with some pockets in eastern Oregon, southeastern Washington, and west central Idaho). One of the largest hackberry stands I have encountered was on the boulder-strewn trail on the north side of Idaho’s Snake River between the end of the road, downstream from Swan Falls Dam, and Halverson Lake.

Netleaf hackberries often grow amidst semi-arid rocky outcrops with southern exposures.

The rough, leathery leaves of the netleaf hackberry are alternate, growing from the stem in a zig-zag manner. It is one of the last trees to leaf out in the spring. The netleaf hackberry gets its name from the net-like appearance of the veins that are most notable on the underside of the leaves. This is also where you will commonly find hackberry “nipple galls” caused by hackberry psyllids - tiny, jumping plant lice. The hackberry psyllid lays its eggs inside the leaf buds in the spring. The larvae develop inside the leaves, feeding on the sugars and causing the nipple galls to form. As the name would imply, the hackberry psyllids are unique to the tree and do not seem to cause it harm.

As noted previously, hackberries provide a very important food source for wildlife. The fruit of the hackberry is a small, pea-sized drupe (a fleshy fruit with thin skin and a central stone containing the seed, e.g., a plum, cherry, almond, or hackberry). The immature seeds are green in color before turning reddish orange when ripe. The fruits remain on the tree, along with a few occasional leaves, well into winter. They provide food for many species of birds and small mammals.

Netleaf hackberry above east Boise's massive Harris Ranch development in winter

In addition to its importance for wildlife, the netleaf hackberry’s preference for semi-arid rocky habitats and ability to propagate from seeds or stem cuttings can make it a good candidate for the stabilization of certain disturbed sites.

So far, this story has focused on C. reticulata, the hackberry native to the west. A similar (but larger and faster growing) hackberry is native to eastern regions of the U.S. (Celtis occidentalis). Both species have long been considered to be members of the elm (Ulmaceae) family. This long-standing assumption is now being challenged by some upstart taxonomists who believe that hackberries belong, instead, to the Cannabaceae family. If true, would they get more respect?

Note: All photos (with one exception) were made with the iPhone 12 mini I always take with me when running or biking. The exception was the Harris Ranch development photo I made with a Sony mirrorless camera.



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