Seeds and cuttings I collect around North Carolina, what they turned out to be, and how to grow them for a NC Piedmont native-plant nursery.
Carpinus caroliniana · Betulaceae
Smooth blue-gray trunk with muscle-like flutes, down in the creek bottom.
Community photos of Carpinus caroliniana to study before I head out: leaf, flower or bract, ripe fruit, bark, whole plant.
Common through the Piedmont wherever there is moving water. Person County iNat box holds 20 records; Orange/Durham box 718.
Best bet: Green seed kept continuously moist, then 4 months cold at 4 °C. Drying is what kills it.
FAC, zones 3a–9b, deep to partial shade, soil pH 4.0–5.6. Sensitive to drought, heat and soil compaction. Hard to transplant — move in spring. Roots are vigorous, so grow in fabric containers.
Each look-alike with the one character that settles it. Tap a photo to zoom.
Ostrya bark breaks into narrow vertical shreddy strips a fingernail can lift; Carpinus is unbroken tight skin over sinewy flutes. On stems too young to shred, check cross-section — Carpinus is fluted at one inch, Ostrya saplings are round.
Beech trunk is round, columnar and uniformly pale silver-gray, still perfectly smooth at three feet across; Carpinus is fluted and irregular. Beech leaves are singly toothed, one tooth per vein.
Birch bark exfoliates in curling papery salmon-cinnamon sheets; Carpinus never peels. Birch female catkins stand upright and shatter.
Elm trunk bark is furrowed into flat ridged plates, never smooth or fluted, and winged elm adds corky wings on the twigs. Elms fruit in March and are finished by summer, so a bracted fruit chain in August is not an elm.
Alder holds woody cone-like strobiles on its twigs all winter; Carpinus never carries a woody cone. Alder is a multi-stemmed shrub at the waterline with no fluted trunk.
Hazelnut is a shrub that never builds a single fluted trunk, and its new twigs and petioles are covered in stiff reddish bristles rough to the hand. Its nut is wrapped shut in two ragged bracts.
Cherry bark carries raised horizontal lenticel dashes running crosswise; Carpinus has only longitudinal flutes. A crushed cherry twig smells of bitter almond. **Cyanogenic foliage, twigs and kernels — wilted cherry leaves are the classic livestock poison.**
Serviceberry's smooth gray bark carries dark vertical stripes twisting up the trunk, and its leaves are singly and finely serrate. Weakest bark call on this list, so use the leaf.
Walk the water. This is a creek-bottom tree in practice, whatever the wetland indicator says. Streambanks, floodplain flats, ravine bottoms, the lower protected end of a slope where it stops draining. Almost always understory, under oak, beech and sweetgum. If I am on a dry ridge I am in the wrong place and should be looking at hop-hornbeam instead.
The trunk does the identification from thirty yards. Smooth blue-gray skin pulled tight over long ridges, so the stem looks like a flexed muscle. Cook says the bark is not similar to any other local tree and from every photo I have looked at that holds up.
Small tree, 20–30 ft, usually clumping or multi-stemmed, short crooked trunk, branches distinctly 2-ranked so the crown reads flat and layered. Expect a thicket of small fluted stems, not one specimen. In undisturbed stands 70–93% of stems are saplings under 5 inches dbh and under 1% ever reach 10 inches.
Right now, late August, the fruit is on it: pale green chains of paired 3-lobed bracts hanging off the twigs, loose enough that daylight shows between them. Not ripe by the book. See the collection note, because green is what I actually want.
Bark first, always. Smooth, thin, tight, blue-gray at every age and size, over irregular longitudinal ridges. The trunk is not round in cross-section. The fluting is present even on a one-inch stem, which is the check that works in a sapling thicket where nothing has bark character yet.
Leaf: alternate, simple, 2-ranked, ovate to elliptic, 3–12 cm long, doubly serrate with teeth that stay fairly blunt and primary teeth not much longer than secondary. Ten or more pairs of straight unbranched secondary veins, each running out to a tooth. Base symmetrical, rounded to cordate. Apex acuminate. Slightly hairy beneath on the major veins. Fall color orange-red.
Twig and bud: buds 3–4 mm, ovoid, sessile, imbricate, 4-angled in cross-section, no terminal bud. Pith round and solid. Twigs have lenticels even though the trunk does not.
Flowers are no use to me now but worth a spring note. Monoecious, wind-pollinated, no petals, opening with the leaves, March 20 to May 6 across the Southeast. Male catkins 2–6 cm, pendant, yellow-green, off lateral short shoots. Female 1–3 cm, erect and fuzzy, at the tips of new leafy shoots.
Fruit: a pendulous chain 2.5–12 cm long of paired foliaceous 3-lobed bracts, middle lobe widest, each bract 2–3.5 cm and subtending one exposed ribbed nutlet at its base. The bracts fall with the fruit. Nutlet 4–8 mm, deltoid, ribbed.
Hop-hornbeam is the real one. Ostrya virginiana has bark that breaks into narrow vertical shreddy strips I can lift with a fingernail; Carpinus is an unbroken tight skin over sinewy ridges. On a stem too young to shred, use cross-section instead: Carpinus is already fluted at one inch, Ostrya saplings are round. In fruit, which is exactly the season I care about, Ostrya carries a hop-like cluster of closed inflated papery bladders while Carpinus carries open flat bracts with the nutlet showing. Habitat splits them too, dry rocky slopes against streambanks. In winter Ostrya's male catkins hang naked all season; Carpinus keeps its shut inside buds.
Beech is on the list because "blue beech" and "water beech" are both Carpinus names. Fagus grandifolia has a round columnar trunk, uniform pale silver-gray, still perfectly smooth at three feet across. Its leaves are singly toothed, one tooth per straight vein, and the nuts sit in spiny woody husks. It is a canopy tree.
River birch peels in curling papery salmon sheets and holds upright shattering female catkins. Elms have furrowed plated bark, and they flower and fruit in March, so a tree carrying bract chains in August is not an elm. Tag alder holds woody cone-like strobiles on the twig all winter and never builds a fluted trunk. Hazelnut is a shrub with stiff reddish bristles on new twigs and petioles, and its nut is wrapped shut in two ragged bracts. Black cherry has raised horizontal lenticel dashes across the bark and a crushed twig that smells of bitter almond, and it is the only genuinely toxic plant on this list. Serviceberry is the weakest bark call, smooth gray with dark vertical stripes twisting up the trunk, so I go to the leaf, which is singly and finely serrate.
Two routes, and they want opposite handling.
Mature seed ripens Aug–Oct, green to greenish-brown, and disperses November through spring. Dormancy sits in both the embryo and the endosperm. The Woody Plant Seed Manual figures for this species are worth reading carefully: 60 days warm at 20–30 °C followed by 60 days cold at 5 °C gave 10%, while no warm period at all and 126 days at 4.5 °C gave 58%. So skip the warm stratification. LBJ's simpler version is 2–3 months at 41 °F. GA₃ at 25, 100 or 500 ppm improves things further. Even so, published baseline germination on stratified mature seed often lands at 1–5%.
The green route is why I would go now. Silvics reports 100% germination from immature green seed. Collect while the bracts are turning yellow but are still soft and pliable. Never let the seed dry out — a hard seedcoat forms on drying, and that is what the 1–5% figures are measuring. Keep it moist from tree to flat. Fall-sow directly, or cold-stratify 3–4 months and sow in spring. Germination is epigeal. Naturally shed seed frequently waits until the second spring.
Roughly 30,000 cleaned seeds per pound. Minimum seed-bearing age is 15 years and heavy crops come every 3–5 years, so a young sapling thicket may hold nothing at all and I should look for the few larger stems.
One iNaturalist trap to keep in mind. NC fruiting annotations peak at May 51, June 34, July 25 against August 19, September 11, October 7. That curve tracks how visible a green bract chain is, not when the seed is ripe. Collecting off it brings home immature seed, which is fine only if I am deliberately running the green route and keep the material wet.
Vegetatively it regenerates hard from stump sprouts and root suckers, 4–5 ft in the first year after cutting. Useful to know for a coppice source. I have no rooting percentages for cuttings.
Person County first. The iNat bounding box holds 20 Carpinus records against 11 Ostrya, and those low absolute numbers are survey effort rather than scarcity. Mayo Lake Park and the Hyco Lake shoreline. The Hyco and Flat River bottoms, where Carpinus, Betula nigra and Alnus serrulata all sit at the water together, which makes it a good place to practice telling them apart. On the Person County game lands, Ostrya is up on the dry slopes, so drop into the creek bottom for Carpinus.
Further out, the Orange/Durham box runs 718 Carpinus to 356 Ostrya, the same rough 2:1 ratio. Eno River State Park and Occoneechee Mountain have both, with Ostrya on the rocky mafic slopes and Carpinus on the river flat. The Haw floodplain at Saxapahaw as well.
Name trap worth remembering out loud: "ironwood" means either genus and carries no information. "Musclewood" and "muscle tree" are Carpinus. "Leverwood" and "hardhack" are Ostrya.
For grow-out it is easy here. FAC, zones 3a–9b, deep to partial shade, soil pH 4.0–5.6. Sensitive to drought, heat and soil compaction, so no parking-strip sites. Difficult to transplant and should be moved in spring. The roots are vigorous enough that LBJ recommends water-permeable in-ground fabric containers. It tolerates flooding only up to about 24% of the growing season.