PRESTON — When growing grapes in southeast Idaho it is important to remember you are growing grapes in southeast Idaho (Not a typo nor did I stutter). We just don’t have the growing season for much variety. Don’t expect grocery store grapes to be grown in your backyard. However, we can get good production on varieties that provide delicious grape juice and jelly, and passable table grapes most years.
For variety selection, refer to, “Grape Varieties for the Inland Northwest & Intermountain West” from the University of Idaho or, “Grape Varieties for Utah” published by Utah State University. In general, you must select a variety that is hardy to about -20° F with either an early-ripening cultivar or that requires less heat units. Concord is the standby for juicing, but it stretches our growing season to the max. If you have a known variety that performs well for you I’d like to know. Email me at email@example.com.
For now let’s talk pruning and training. This doesn’t need to be done until February or March. There are numerous systems for training and pruning grapes. The cane pruning system is the best for varieties that perform in our area.
The trunk is the permanent stem of the plant. Immature, soft stems of the current season are shoots. Shoots arise from buds on wood that is one or more years old. These shoots (first year growth) bear leaves, flowers and fruit. Pretty simple except that, on grapes, only the shoots from stems that grew last year will bear fruit this year. These shoots become fruiting canes. These should be allowed to produce one season and then be removed. For each fruiting cane on your plant, you need one renewal spur. The renewal spur is key to consistent future year production.
A renewal spur is created by cutting back a one-year-old cane to two buds. The shoots growing from these spurs become the fruiting canes for the following year, thereby renewing the fruiting canes. This is difficult to visualize but refer to the link, “Backyard Grapes” from University of Idaho or, “Grape Trellising and Training” from USU.
Grapes must grow on a trellis to be productive. They must have support to keep the wild vine growth off the ground. A chain-link fence is not the best support structure. While it does provide support, it does not lend itself to maintaining vines long-term. If you are planting a new vine and do not have a trellis, put in a stake or post to start establishing the trunk. For training and trellising techniques refer to the links I just mentioned. Use the techniques as a guide but don’t be afraid to adjust to fit your yard and preference.
During the growing season, the buds on the fruiting canes will send out shoots that have leaves and fruit. Because only the one-year-old wood produces fruit, you know exactly where the fruit will be produced. Fruiting canes only produce for one year. Therefore, during the dormant season, you are going to remove this cane and allow a cane that grew from the renewal spur to take its place.
Once you establish the system, grapes are the easiest fruit to prune. They are pruned very heavily. In many cases, you may remove as much as 90 percent of last year’s growth.
These are the basics but you will need to do a little homework before breaking out the clippers. Use the links below for more detailed information.
Because the links are long you may want to just search the title with the respective university.
Backyard Grapes (U of I): http://www.cals.uidaho.edu/edcomm/pdf/cis/cis0790.pdf
Grape Varieties for the Inland Northwest & Intermountain West (U of I): https://www.uidaho.edu/-/media/UIdaho-Responsive/Files/Extension/county/Bonner/NIFRC_GrapeVarieties.pdf?la=en&hash=2C7B287F508088F28D83F26581DBF8B24D83260D
How to Prune Grapes (USU): https://www.youtube.com/watch?v=VnWgaYOm0-M
Grape Trellising and Training Basics (USU): https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=2772&context=extension_curall
Grape Varieties for Utah (USU): https://digitalcommons.usu.edu/ cgi/viewcontent.cgi?referer=&httpsredir=1&article=2661&context=extension_curall.