Shagbark Hickory Tree - Carya ovata
Juglandaceae -- Walnut family
Height: to 100 feet, trunk diameter to 3 feet.
Shagbark hickory trees (Carya ovata) are well known to be desirable for shade, fall color, tasty nuts, and desirable timber, but perhaps their most valuable use is not well known. Mature shagbark hickory trees are natural roost sites for bats, and especially desirable as maternity roosts. Quality roost sites are key to maintaining and increasing a bat population, which in turn provides an effective natural control of mosquitoes and other night flying pests.
A bat house generally consists of one or more narrow chambers into which the bat may enter at the bottom, placed in a location with ample solar heating and reasonable protection from predators. A well pruned shagbark hickory essentially makes bat houses on the sides of the trunk. The bark "shags" off at the top and bottom leaving the middle quite firmly attached. A bat can find the side of the trunk with the most nearly ideal temperature, go up under the bark, and spend the day in relative safety and comfort.
Shagbark hickories have a large tap root that makes it difficult to transplant after the tree is more than 2 or 3 years old. Transplanted shagbark seedlings grow slowly for the first 2-3 years after transplanting, as the tree invests in a very large, strong, deep tap root. This foundation is necessary to support the natural habit of the tree, which is to grow slender, straight, and tall with a relatively narrow crown.
Shagbark hickories are high quality urban trees. They are strong, resist storm damage, have great fall color, and produce the sweetest and tastiest hickory nuts. They should not be planted where where the nuts would present a problem. Growth is initially very slow.
Growth is much faster after the tree makes the early capital investment in a large tap root. For protection and improved growth at low cost, slit a short piece of 4" diameter drainpipe, the black corrugated thin wall pipe used for French drains. Put this around the seedling, you may wish to use a couple of bamboo sticks to hold the tree protector in place. Thereupon put 1 or 2 bags of grass clippings around the tree protector 2 or 3 times a year. Any grass clippings is better than none, the amounts just stated are ideal for superior tree growth and vigor.
Most trees, including shagbark hickories, form a symbiotic relationship with mycorrhizal fungi. The mycorrhizal fungi tap into sugars from the tree, and in exchange bring back minerals and moisture, which can increase the effective area of the root system several times over.
When planting an area that has not had similar trees recently, you may need to inoculate the roots of the trees you plant. You can buy a commercial dip by going to http://www.forestry-suppliers.com and searching for inoculant. Diehard Ecto Root Dip is a great choice, a 15 oz. package costs $20 and treats 10,000 seedlings.
For more information on shagbark hickories see http://dendro.cnre.vt.edu/. You can also review the entry at http://en.wikipedia.org/wiki/Shagbark_Hickory, or just google "shagbark hickory." Photo by Oscar Stilley.
The dip is irrelevant if the tree is planted in forest soil, because all healthy forest soils have this fungi naturally. On degraded soils or soils that have not had trees for a long time, the introduction of a good mix of mycorrhizal fungi is key to survival and growth. If you are only planting a few trees, a small amount of healthy forest soil will provide the starter necessary for a healthy tree. More fungi to start with is not necessary, since fungi will expand to take advantage of its food supply, whether small or great.
The grass clipping mulch can be picked up for free on the streets of almost any American city, and provides the following benefits:
1. It feeds the mycorrhizal fungi, which in turn increase the effective area of the tree root system, often at several times the rate achieved in the absence of feeding.
2. It moderates the temperatures of the root system, lengthening the useful growing season in spring and fall, and for many heat sensitive trees, during the heat of summer as well.
3. It moderates soil moisture, keeping the soil moisture less during wet times and greater during dry times. It also greatly increases the total moisture capacity of the soil, in large part due to the great increase of beneficial worms, grubs, and other creatures that effectively till the soil near the tree.
4. It reduces competition from grass and weeds, which along with weed eaters and rabbits constitute the greatest threats to small trees.
I have gotten 30 foot oak trees in ten years with this system, on marginal soil with little watering and no fertilization other than grass clippings. I have not yet had this much time with hickories but believe that the same approach would likewise prove highly successful.
In order to make an ideal roost tree, the shagbark hickory should have the trunk pruned clean up for about 20 to 30 feet or more, pruning perhaps 2-3 feet every couple of years depending on the total growth rate. This reduces the threat of predation and also ensures that the ideal roost locations get the best solar heating.
The first 8 feet are easy for most landowners, the later prunings may require a professional. Pruning should be done in the wintertime both for the health of the tree and to ensure that roosting bats are not disturbed.
Shagbark hickories can be bought in quantity from ArborGen. They have an enormous selection and produce very high quality seedlings. Shagbark hickories are available for $450 per 1,000, $100 per 100, or $60 per 25. The per thousand price is excellent, especially when you consider the quality of their product, but smaller quantities are more economically procured on Ebay. Selection declines early in the year, so don't wait until spring to call.
For smaller numbers of seedlings, start with Ebay. Don't forget you are likely to have some mortality, buy a few extras to keep in a garden or flower bed, just in case. If you can't find what you want on Ebay, take a look a http://www.willisorchards.com or http://www.tytyga.com. Improved cultivars are available at various places including http://www.grimonut.com. You can find shagbarks for sale from a number of other vendors by simply typing in "shagbark hickory nursery" on google.
The adventurous may wish to try seed. F. W. Shumacher (http://www.treeshrubseeds.com) is probably the best source of seed for this and a huge selection of other species. They not only sell seed at very reasonable prices, they have information about the trees, including germination requirements. Shagbark hickory seeds require 90-120 days of cold moist stratification (conditions that mimic winter) in order to germinate.
You can direct seed, or plant in the garden and then transplant. Don't forget that squirrels and other rodents love the nuts and will eat them if they can. For most of us, seedlings are a better choice. However, direct seeding is cheap, gives you the option of economically starting several different hard to find trees at once, and gives you years to find them a permanent home.
Don't forget to look for existing trees. You may have one or more shagbarks nearby that would perform well if it was released from competition, pruned, and mulched. If you are so fortunate, this will put you years ahead in the quest for permanent bat housing.
By Oscar Stilley, an attorney from Fort Smith Arkansas better known for his advocacy for taxpayers than for his love of trees. However, he writes a piece on trees from time to time. This article is dedicated to the public domain and may be reproduced in hard copy or otherwise by anyone, so long as credit is given to Oscar Stilley, with reference to http://oastilley.wordpress.com/?s=shagbark+hickory.
Bats rely upon forest resources for summer (and winter) roosts in cavities, under bark, and among foliage (including leaf-litter). Bats have lost these roosts which occur in extremely low densities in todays younger forests. As natural roosts have been disturbed or destroyed, many bats have moved into man-made structures, especially old style wooden buildings and bridges. As man-made roosts are being replaced by modern concrete and steel structures, or being destroyed due to liability concerns, bats often lose these refuges of last resort as well. Man-made bat houses and other roosts are becoming increasingly important for many of our remaining bat populations. However, the ultimate long term goal for conserving species like the Indiana bat and the little brown bat is propagating natural tree roosts that will carry bat populations well beyond any artificial roost lifespan.
Shagbark hickory trees are perhaps the most valuable roost tree for Indiana and little brown bats known. Regardless if you are a homeowner interested in a specimen tree for the backyard, or a developer wishing to enhance a property and mitigate for Indiana bats, the Shagbark hickory is the ultimate bat roost. This tree naturally features peeling bark after approximately 20-30 years of age and progressively becomes a living bat house with age. Most other trees in a forest stand do not provide ideal bat roosting characteristics until the tree actually dies. Shagbark hickorys are slow growing but long lived, and a properly managed stand is an investment in bat conservation for hundreds of years.
When mitigating for Indiana bat habitat disturbance, it is best to install an appropriate number of well placed metal or plastic bat houses to provide a temporary (20 year) roost alternative. Meanwhile, a number of Shagbark hickory should be planted in areas appropriate for long term (200+ year) bat management. Similar to a bat house, at least some Shagbarks should be planted where direct southern exposure will be guaranteed when the tree matures enough to start becoming attractive to bats (20-30 years old). Ideally, shagbarks of various ages (seedlings to 10' tall or more as available) should be planted so the stand is sustainable.
Plantings should be done in fall or spring. Contact Willis Orchard or a local nursery to find out about obtaining trees of various sizes.