Oftentimes, when people are thinking about planting chestnuts, the first thing they do is start looking for nursery sources and reading variety descriptions in catalogs. The decision of where to plant them is almost an afterthought. This is not the order in which these decisions should be made. If you are thinking about planting chestnuts, the very first thing you should do is find out if you even have a site suited to chestnuts—or, if you don’t yet have land you need to locate and acquire land suited to chestnuts.
Chestnuts absolutely require well drained soil on the acid side of the pH scale. The site needs to be located within the USDA plant hardiness zones 4b-9a and maybe the northern fringes of 9b. For most people, the biggest challenge in site selection is identifying whether a soil is well drained or not. People often tell me they know their soil is well drained because, “it’s sandy” or “it’s on a slope.”
While soil texture and slope are two factors affecting drainage, neither is definitive, and it is possible to have poorly drained sandy soil on a steep slope.
In most cases, the easiest way to evaluate the soil drainage characteristics of a site is to use a soil map to identify the soils on the site, and then look at the description for the soil series. If you have a USDA Soil Survey book for your county, you can find a soil map of your farm, identify every soil type on every site you are considering, and read the description for each soil type. The drainage characteristics will always be given in the very first sentence of the description. For example, “The Fayette series consists of very deep, well drained soils formed in loess.” In that first sentence, you may find the words (ranging from wettest to driest) “very poorly drained,” “poorly drained,” “somewhat poorly drained,” “moderately well drained,” “well drained,” and all the way to “excessively well drained.”
An added benefit to the Soil Survey book is that you can get a feel for potential productivity of a site by consulting the table near the back of the book (usually Table 7., but not always) with the title “Woodland Management and Productivity.” One column in the table has the title, “Site Index.” If a soil series appears on this table, it will have a number corresponding to a species of tree (or maybe a couple of numbers corresponding to a couple of tree species). These site index numbers represent the height in feet that that tree will grow in 50 years, on that soil. This is a very good indication of how well a tree will grow (and how well a nut tree could produce) on a given soil type. You will not find a site index number for chestnuts on this table, but you can use upland oaks (white oak and red oak in Iowa) as a proxy for chestnuts. You will find site index numbers for upland oaks ranging from 45 (marginally acceptable) up to 80 (the very best). If you are a landowner, you should be able to go to the USDA Service Center for your county and request a free copy of the Soil Survey book from the NRCS office.
If you don’t have and are unable to acquire a Soil Survey book, but you have access to a computer and internet, you can find the drainage characteristics for the soils on your farm from the Web Soil Survey www.websoilsurvey.nrcs.usda.gov. You may need to take the tutorial on the home page to learn to use the site. A list of soil types will appear to the left of the soil map for your farm. If you click on the name of the soil type, a lot of technical information about that soil will appear. You will find the drainage characteristics for that soil under “Properties and Qualities.”
A definitive test of soil drainage is to dig a 3’ deep “post hole” and slide a 4” X 3 ½’ piece of PVC pipe down the hole, instead of a fence post. It’s best to put a removable cap on top of the pipe to prevent small animals from falling down inside and getting trapped. Monitor the bottom of the pipe several times per year, especially after heavy rain events. If the pipe fills with water you can be sure that site won’t be suited to chestnuts. On the other hand, if the water in the bottom of the pipe always drains away within a day or two following heavy rains, it is probably well drained.
If you live in Iowa you have an additional tool for evaluating sites for chestnuts. All of the soil series in Iowa have been divided into 10 classes based on how well suited they are for growing trees. Once you have identified your soil series you can go to the “Iowa Woodland Suitability Recommendations” and look it up and see in what class your soil has been placed. Class 1 is “somewhat poorly drained” and unsuited to chestnuts. Class 2 includes the poorly drained and very poorly drained soils. Class 3 is the best for chestnuts and most other trees. These soils are deep, fertile, moist but well drained, and have a good balance of clay, silt, and sand particles. These soils also have the highest site index numbers. Classes 4-7 are suited to chestnuts, but differ from Class 3 soils: Class 4 soils have higher clay content. Class 5 soils have higher sand content. Class 6 soils have bedrock 2’ to 3’ below the surface. Class 7 soils are very sandy and excessively well drained, and would require irrigation to be productive of chestnuts. Classes 8-10 are not suited to chestnuts. You can use this link to the Woodland Suitability Recommendations or search for it elsewhere on the internet.
Once you have determined you have a site suited to chestnuts, then you are ready to develop a planting plan and start looking for nursery sources and varieties.