New Chestnuts for Connecticut

 

Sandra L. Anagnostakis
Department of Plant Pathology and Ecology
The Connecticut Agricultural Experiment Station
123 Huntington St.
P.O. Box 1106
New Haven, CT 06504-1106

Voice: (203) 974-8498 Fax: (203) 974-8502

E-mail: Sandra.Anagnostakis@po.state.ct.us

The Experiment Station has had scientists working on chestnut trees for a long time. First, on the best way to manage woodlots that were nearly pure American chestnut, and then on ways of using the dead, standing trees killed by chestnut blight disease from 1908 to 1913. In the 1930s, experiments were begun on breeding chestnuts for resistance to blight; crossing susceptible American and European trees with resistant Chinese and Japanese trees. For several years the breeding program has had a two fold mission: breeding blight resistant trees for timber and for their nutritious nuts. The ideal timber tree is tall and straight, with a strong central leader, and flowering is delayed until the tree is quite tall. Thus, all the energy is put into vertical growth and not "wasted" on making flowers and nuts. An ideal nut tree is short and spreading, and starts flowering when it is only a few years old. Most of the tree’s energy goes into nut production. I’m going to talk today about the nut producing trees, and some of our recent results in this part of the breeding program.

Why grow chestnuts? A few acres of land can yield nuts for your own enjoyment, or for sale at the side of the road or to your local market. Chestnuts are a good food, as shown in this table:

Species	Fiber %	Protein %	Fat %	Carbohydrates %	Calories per ounce
Chinese	14	8	2	65	66
European	14	6	4	66	57
Japanese	14	8	0.4	90	114
American	19	10	10	40	70

They are high in fiber, have a good amount of protein, and the fats are more than 90% unsaturated fatty acids.

There are seven species of chestnuts, native to the temperate zone around the world.

This is a list of their scientific names and their common names.

Castanea dentata (Marshall) Borkhausen American chestnut

Castanea seguinii Dode Dwarf Chinese chestnut

Castanea Henryi (Skan) Rehder and Wilson Chinese chinquapin

Castanea sativa Miller European chestnut

Castanea mollissima Blume Chinese chestnut

Castanea crenata Siebold and Zuccarini Japanese chestnut

Castanea pumila (Linnaeus) Miller

var. pumila Allegheny chinquapin

var. ozarkensis (Ashe) Tucker Ozark chinquapin

The experiment Station has specimens of all of these, due to the foresight of Arthur Graves and Donald Jones, and the work of Hans Nienstaedt and Richard Jaynes. Trees that they planted here and at our Chestnut Plantation at Sleeping Giant make my work much easier.

As you look around Lockwood Farm you will see that many of the chestnut trees have white paper bags on the tips of the branches. These are covering female flowers that received specific pollen to make new hybrids. Kate Edgerly is standing in the small orchard of hybrid chestnuts on the other side of the barns [plot # 49], and can show you these. The female flowers look like small pineapples, and the male flowers are on long catkins, with the anthers (containing the microscopic pollen) on long stalks. The female flowers are usually receptive at the end of June through the first week of July. Normally the pollen is carried by the wind, and by bees and beetles that feed on the pollen. there are always a lot of Soldier Beetles, which look like Lightning Bugs, on the catkins here at Lockwood Farm. All species of chestnuts can pollinate each other, but they are "self-sterile." That is, no chestnut tree can pollinate itself or its clone. Hybrids often produce no pollen (are "male sterile"). Several of the important cultivars of chestnut are male sterile.

When a tree is determined to be especially good, it is often "named" as a cultivar, and cloned. Since cuttings of chestnut will not easily form roots, the cloning must be done by grafting the cuttings onto compatible seedling trees. All of the clones of a tree are identical, and since chestnuts will not self-pollinate, two or more cultivars (or some seedlings, which are all different) must be planted to provide pollen for each other.

The International Society for Horticultural Science has designated The Experiment Station the International Registrar for Cultivars of Chestnut. This means that people wishing to register a new cultivar send their application to us, we certify that there have been no other chestnut cultivars with the same name, and register their tree. A list has been made from the literature, and with a little help from our friends, and will soon be posted on the Station web page. Currently the list contains 1,176 names. I have also made a list of cultivars sold by nurseries, and you may call or e-mail me for a copy. The Experiment Station released cultivars to growers in the 1950’s, and several are still being propagated and sold. Recently released cultivars include ‘Lockwood’ which is a broadly spreading tree that has really large nuts, and ‘Little Giant’, which is an extremely small tree with decent sized nuts. the originals of these are growing on the hill behind me. Pam Sletten is standing there in Plot # 51 and can show them to you.

As part of our study of old cultivars and our search for new ones, volunteers from The American Chestnut Foundation have made crosses three years in a row, to see which combinations of four of our cultivars result in the most nuts. ‘Eaton’ was an exceptionally good pollen parent in both 1997 and 1998, and ‘Eaton’ and ‘Sleeping Giant’ crossed well in both directions. These are the two cultivars that I usually suggest for people who only want to plant a few chestnuts. Our two new cultivars, ‘Lockwood’ and ‘Little Giant,’ had an unusually high percentage of filled nuts when the pollen sources were ‘Sleeping Giant’ and ‘Eaton.’

in 1994 we did some chemistry with nuts which showed that the fats in chestnuts are unsaturated fatty acids that are known to be important to the flavor, nutritional quality, and storage quality of nuts. The individual fatty acids were quite different from species to species.

Species	Total Fat (%)	Palmitic %	Steric %	Oleic %	Linoleic %
American	9.50	1.05	0.08	5.70	1.91
European	2.95	0.43	0.04	0.88	1.26
Chinquapin	4.01	0.53	n.d.	1.68	1.22
Chinese	2.17	0.22	n.d.	0.91	0.77

The sugar levels in the nuts of the species that we tested were all the same, but the American chestnuts tasted much sweeter. The chemist in that study was Samuel Senter, who tells me that the fatty acids are the factor that make the American chestnuts taste sweet (notice that the American chestnuts had much more oleic acid than the others). Last year we had some nutritional analyses done by a commercial laboratory on the 1998 nuts. There was very little difference in fiber, protein, and carbohydrate between nuts from the same cultivar with different pollen parents. There were big differences in the amount of fats. For example, nuts from ‘Sleeping Giant’ by ‘Little Giant’ had seven times as much fat as ‘Sleeping Giant’ by ‘Eaton’, and ‘Lockwood’ by ‘Sleeping Giant’ had twice as much fat as ‘Lockwood by ‘Little Giant’. We obviously have to repeat these tests, but this was a very exciting result. Maybe genes in the pollen parent affect the amounts of fatty acids that determine flavor.

This year we will be testing the nuts for sugar content and I hope to have tests made for specific fatty acids to see whether the "flavor components" are under simple genetic control. This would allow us to more easily design crosses to improve our nut-producing cultivars.

addendum:

Tree shelters can be made of wire or plastic, or can be as simple as piled brush to protect the trees from deer. The plastic tubes cost about $3.00 each and are easy to install, but must be lifted each fall to allow the grafted trees to harden off properly. They frequently harbor wasps, and provide a nice environment for rodents who then eat the tree bark. A better shelter may be a stiff plastic net now being tested by some companies.

An irrigation system is essential for a commercial orchard, even if you live in a region where rainfall is fairly dependable.

Plant your trees in well-drained sandy loam, better drained than apples require. Sites with clay may be tolerated if there is good surface drainage (slope). Chestnuts need a soil pH of 5.5 to 6.5 and absolutely won’t tolerate limestone soils. If your soil pH is much higher than this, consider another crop.

Space the trees at 40 feet apart, or start at 25 feet apart and remove trees, as they mature, to 35 feet apart.

Fertilize (SPRING ONLY) with one pound of 5-10-5 or 10-10-10 per year of tree age, or one pound per inch of tree trunk diameter.

Pruning should be done only when it is hot and dry, in early summer. This reduces the chance of infection.

The area around the trees should be kept mowed, and a circle about three feet wider than the diameter of the trees should be kept weed-free. Mulch can be applied to help with water retention, but should not be deeper than two inches, and should not be up against the trunks (allowing easy access by rodents in the winter).

The value of the nuts is directly related to the size, but is usually at least $1.50 per pound wholesale and up to $5.00 per pound retail. Yield will start to be significant after the trees are 10 years old, and yields have been reported of from 14 pounds per tree to 138 pounds per tree.

The traditional method of harvest is to allow the nuts to fall to the ground, and employ people to pick them up. For a few nuts for your own table this is not a bad system, but commercial orchards need more efficient methods. Nets can be suspended under the bottom branches of the trees to collect the nuts (they should be removed from the nets every day), or some of the marketed ground-collection systems can be used (see advertisements in the Northern Nut Growers Newsletter).

Marketing chestnuts is easy if you already have a farm stand for selling produce, but if you have to sell them to local food stores, you will have to work a little harder. Nuts should never be allowed to dry out, and markets must be convinced to display and store them in plastic bags in refrigerated cases.