By Martin Shervey
Why grow Common Hackberry
With the increased population in cities, more trees are needed that can withstand the stresses that a city produces.Common Hackberry or Celtis occidentalis is a good tree that does well in the urban environment.Common Hackberry is very urban tolerant, has rapid growth and establishment, and is very cold hardy.It is also a large shade tree, which can help reduce the temperature in “heat islands.”
Common Hackberry needs full sun but is tolerant of partial sun in it youth.It prefers moist, rich soils but is highly adaptable to many adverse conditions.Common Hackberry has low water requirements and is highly tolerant to salt and alkali soils, which allows it to grow almost anywhere.It is native to zones 2 to 9, but grows at different rates in different zones.
The tree can be propagated by both seed and cuttings grafted onto seedling understock, or they may be rooted.The soil should have mycorrhizae induced to help it grow more vigorously in pots.
Common Hackberry, when fully grown, is about 70 feet tall with a 50-foot wide crown.The trunk diameter can be over 3 feet wide.When planted by itself, in the open, it will tend to grow shorter with a wider crown.It is not uncommon for Hackberry to grow over 70 feet tall in ideal conditions.A smaller variety of Common Hackberry, georgiana Ahles, grows to 40 feet to 60 feet in height with a trunk diameter of 1 foot to 1.5 feet.This smaller variety grows in zones 5-7.
Some limitations of Common Hackberry are they are susceptible to several aesthetically unattractive conditions, such as witches’ broom and nipple gall.Even though it is susceptible to some diseases and insects, none of these are life threatening to the tree.Another limitation is it is somewhat sensitive to being transplanted in autumn.The tree should then be planted in the spring if possible.If not possible, the tree should be fertilized, watered thoroughly, and mulched adequately in the fall to enhance survival chances during the first winter.Even though this tree provides large amounts of shade in the summer, it has a poor fall color.Other trees should be planted if you desire high quality fall color.
Warts caused by nipple gall.
Growing in the Greenhouse
To get the best results, cuttings should be grown n a greenhouse under moist conditions.If propagating Common Hackberry by seeds, the seeds should be germinated in clay loam soil, or something similar.An acrylic greenhouse should be used and it should have a low ceiling for a smaller area to heat.The smaller area will reduce heating costs.Plantings will take place in the late winter to early spring.The seedlings should be placed outdoors in mid to late summer to harden them off.This will also reduce heat damage to the roots on warm summer days.Soil used in the greenhouse should not be completely sterile, but should have mycorrhizae induced into it to help the tree absorb nutrients.The mycorrhizae used should by ectomycorrhizae.
Before the first winter, the new seedling should be brought inside the greenhouse, while allowing the greenhouse to cool down to around freezing.This will increase the survival rate of the seedlings for the first winter in harsh climates while allowing acclimation to take place.The next spring, the seedling should be taken outside before bud break.While moving the seedlings outside, they should be planted into larger containers, which should be done every spring.Be sure to always use soil-containing mycorrhizae.
Cultivated hackberry can grow up to 1.3 feet per year, so the plant should be about 2.5 to 3 feet tall after 2 years.This rate of growth prevents more than two years of growth in the greenhouse, because the seedlings will take up so much space.Pots used for growing the seedlings must be deep because hackberry is a deep rooting species.A heavier soil may be used to slow root growth down towards the bottom of the pot.
The soil in the seedling post, in the greenhouse, should not be saturated because the new seedlings’ roots are more sensitive than the older trees, to saturation.Severe injury can take place within 60 days to the hackberry seedlings’ root system and they are often unable to recover.
While in the greenhouse, hackberry should be watched to prevent gall mites and powdery mildew outbreaks.This can cause “witches-broom” which will decrease the value of the tree and lower your profits.
Using greenhouses to grow seedlings will increase the seedling size and allow more seedlings to survive.Common Hackberry can grow for longer periods of time and more vigorously if grown in the greenhouse under optimal conditions.This will increase the value of the seedlings and increase the number of sellable seedlings.
Benefits of Growing
Common Hackberry is an excellent urban tree because of its ability to grow to a large size in many different conditions.Its wood strength is much greater than that of Silver Maple; another large tree that is highly adaptable to poor soil.The tree can also be used for windbreaks and help in erosion control.
Its large size and ornamental bark makes it an authentically pleasing tree to look at.
It also attracts many different birds by producing fruit.Some of the different birds that are attracted by the fruit are wild turkeys, pheasant, quail, grouse, and bluebirds.The large size also provides cover and shelter for these birds.
Common Hackberry can be sold as bare root seedlings, in wire baskets, and containers.The average price of a two-year-old bare root seedling is $2.50.Wire basket prices for a 2-inch diameter tree are $78 and $87 for a 2.5-inch diameter tree.Container grown trees are $21.40 for a 7-foot tall tree grown in a 10-gallon container and $34.90 for a 1.5-inch diameter tree grown in a 15-gallon container.