Chapter 84 Celtis occidentalis, C. sinensis
84.1 Common hackberry (native to eastern US); Chinese hackberry
A Chinese hackberry. Link to original image.
84.2 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. Does not like to dry out.
84.3 Light
Routine: Mostly to full sun, but keep roots cool.
Summer: Mid-day shade, especially for the pot and roots.
84.3.1 Potting & Root Pruning
Hackberries tolerate agressive root pruning if done early in the season.
84.3.1.1 Top & Branch Management
Heavy pruning: cut branches late winter.
Fine pruning: hackberries develop very fine ramification when regularly pruned. Trim back shoots that outgrow the intended shape all season long.
Leaf pruning: trim back new shoots to shape. Leaves are large but reduce quickly after leaf pruning. Responds well to repeated pruning and defoliation. This can cause 3 or 4 new shoots to emerge at the same point; it is important to reduce this to two.
Flowering: small flowers in late spring become small bright orange fruits.
84.3.2 Feeding
Fertilize in spring, after new leaves have begun to emerge. Do not fertilize after repotting. Wait 3-4 weeks. Then feed sparingly til mid-summer.
Use:
- Slow release shrub and tree fertilizer, applied at half the recommended rate.
- Organic plant food that must be broken down by soil microbes, such as Epsoma Tree-Tone.
- Inorganic, water soluble fertilizers at half strength rather than full strength.
For example, feed with 18% N, 6% P, 12% K controlled release granules at half normal dose just after spring leaf-out. In late June or early July, and early August, feed again with 0.5x Miracle-Grow.
84.3.3 Pests & Problems
Chemical Warnings
84.3.4 Winter Storage
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.
84.4 Propagation Notes
Dark orange fruits are ready to collect after mid-summer. Gently mash then soak fruits overnight to ferment away the seed coat. Wash clean and store seeds dried. Sow seed outside in autumn. Alternatively, soak seed overnight in hot tap water, then stratify in moist sphagnum or peat for 60-90 days at 4oC. Plant 1/4 inch deep in fertile free-draining soil at 20oC. Seeds will germinate in 30-50 days. Expect less than 50% germination, and possibly <30%.
84.5 Artistic & Styling Notes
84.6 Additional Information
84.6.1 Natural History
Celtis sinensis is a spreading, deciduous tree native to E. China, Korea and Japan where it reaches heights of around 40 feet in woodland areas. Celtis occidentalis is native to North America. Both species of hackberries are woodland understory trees. They are adapted to withstand very cold conditions. Hackberries do better in areas with warmer summers, which increases vigorous top growth. Ironically they suffer when overheated, which is why it helps to keep the roots shaded, or grow them in a deeper container than usual.