Chapter 89 Corylus species
89.1 American hazel (Corylus americana), beaked hazel (C. cornuta)
Corrugated leaves of an American hazel. Link to original image.
89.2 Soil: Moist Deciduous Mix
Ratio: 4 parts bark, 1 part grit
Add-ins: dolomitic limestone (~5 lbs/yd), Tree-Tone (15 lbs/yd)
pH: ~6.5 (slightly below neutral)
Moisture: average to moist. They are wet-adapted, and dislike drying out.
89.3 Light
Routine: full sun.
Summer: partial shade in summer.
89.4 Cultivation Notes
American hazel has a strong tendency to send up long, straight canes that extend from the roots to the crown rather than form low branches. New shoots will need careful attention to prevent them from bolting and to develop any movement or ramification.
89.4.1 Potting & Root Pruning
Schedule: every two years in early spring before leaf-buds extend.
Notes: look for new root suckers starting to emerge. These can be cut off and repotted, or allowed to emerge and grow on for a year, then removed and repotted. I personally have had better luck with letting them develop on the mother tree, but both work.
The roots will tolerate quite a bit of crowding. I kept a specimen 8 feet tall and 6 feet wide in a fabric bag that was 10 inches deep and 3 feet wide for
89.4.1.1 Top & Branch Management
The hazels tend to form multi-stem clumps in which each stem thrives for several years, then ages out and dies to the ground. Plan accordingly; manage the growth assuming that every stem will need to be replaced eventually.
Heavy pruning: hard pruning should be done after the catkins have finished but before new growth leafs out. In some years here, I have seen the catkins emerge in December, well before spring. Wait until after the mid-winter warm spell to do any heavy pruning.
Fine pruning: trim new growth through the growing season.
Leaf pruning: I have never tried it. I keep my Corylus in naturalistic styles.
89.4.2 Feeding
Forming hazel nuts. Link to original image.
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Mature hazel nuts. Link to original image.
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Feed on a biweekly (solubles) or monthly (organics) schedule. These shrubs like to have more phosphorus, so would do well with:
- Miracle-Gro Soluble Rose Plant Food (18-24-16), 1/2 strength
- Miracle-Gro Soluble Bloom Booster Food (15-30-15), 1/2 strength
- Holly-Tone (4-3-4) supplemented with rock phosphate (0-3-0)
89.4.3 Pests & Problems
Sources say they can be attacked by caterpillars, mites, sawflies and aphids, as well as by powdery mildew. I have never seen any of these problems on mine though.
89.4.4 Winter Storage
A hazel in winter, showing the branching pattern. Note how the branches are concentrated in the crown area with fairly straight stems. Cutting back stems when they emerge keeps the crown low and stimulates side branching. Link to original image.
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Store in mulch outdoors. Try to place in a shaded area so buds do not break in a mid-winter warm spell. No other special precautions are needed.
89.5 Propagation Notes
I have grown both species successfully from nuts that I collected in fall, sown in my standard mix, and let overwinter outside. Squirrels like to dig them up, so I keep both the trays with germinating nuts and the seedlings in a wire cage through their first full year.
Shrubs can be transplanted while dormant. Branches can be staked down in autumn to ground-layer them.
89.6 Artistic & Styling Notes
The hazels are thought to have leaves that are too large for bonsai, and that is true for traditional styles. They still work for more naturalistic styles. Also, the rough bark, twigs, and catkins give them a very interesting winter silhouette.
89.7 Additional Information
89.7.1 Natural History
Native to eastern North America, in USDA Zones 4 to 9. The largest shrubs reach 16 feet high and 12 feet wide, but most of the wild ones I encounter top out around 8 feet tall and wide. They have attractive corrugated leaves that can turn multiple colors in fall, including orange, rose, purplish red, yellow and yellow-green.
They are related to birches. Despite their names and superficial resemblance, they are not related to either the winter hazels (Corylopsis species) that are sometimes used in bonsai, or the witch hazels (Hamamelis species); both of the latter genera are in a different family.
89.7.2 In Cultivation
The hazels most often seen as bonsai are European common hazel (Corylus avellana), and corkscrew hazel (C. avellana ‘Contorta’). Given their similar habits, I think it is time to give the North American species a try.