Consistently producing line-out stock for species shrubs and trees and understocks for budding have been a part of Bailey Nurseries Inc. since the beginning. I worked at Bailey from 2004 to 2013, and it was great to be a part of that tradition of starting durable and dependable seedling line-outs. Most of those line-outs are developed solely for bare-root field planting, sales and for container planting. At the propagation facilities in Cottage Grove, Minnesota, the seedling department is a small, dedicated operation that focuses on cost effectively managing the production of roughly one million seedling line-outs in single year production cycle. What follows is a description of my experience in helping Bailey to make that happen.
At the Minnesota seedbeds, Bailey grows 80 species of trees and shrubs from seed. Seedling crops are regularly monitored in the seedbeds throughout the growing season to evaluate acceptability for continued use as a seed source for the future. Several selections of sugar (Acer saccharum) and red (Acer rubrum) maple were made, from Minnesota-originated sources, for superior plant growth characteristics. Two or more selections of each maple have been cloned and lined in Bailey’s orchards in Sunnyside, Washington, to rear the highest quality seed and seedlings for the company’s bare-root production. Around 30 percent of Bailey’s annual seed needs are supplied by the Sunnyside orchard, and that percentage is growing. Roughly 40 percent of annual seed needs are hand-collected from trees and shrubs located around the greater Twin Cities area in Minneosta, as well as a select few from the northern part of the state. Scouting for superior landscape-adaptable plants becomes as much of a pastime as it is a component of routine trips to check on the current year’s seed crop.
During my tenure at Bailey, we operated on a parcel of land with 31 tillable acres. At the time, production levels allowed us to plant 17 acres of land in seedbeds, annually. Postharvest, we ripped each field in the fall to a 24-inch working depth and chisel plowed and lightly cultivated in the spring to plant a cover crop of Glyphosate®-resistant corn or daikon radish, depending on the most persistent field issue. Post cover-crop, each field was chopped, chisel-plowed and cultivated to a finished bedding condition for bed forming. Fields were bedded 4 to 6 weeks in advance of planting to manage weed pressure before and, if possible, after crop sowing.
We mechanically sowed about 90 percent of our annual seedling production schedule, using a common hopper gravity-fed vegetable planter. This seed planter was capable of sowing seed from the size of Populus tremuloides to Prunus americana. With this equipment we were able to uniformly apply seed sowing densities in rows at planting depths of our choosing, or surface scatter the seed. We found that six, double-shoe planted rows worked the best for our situation. A uniform seed flow rate is critical to achieve consistent densities. When necessary, pre-moistened seeds were sown with a light coating of talc powder or powdered graphite. After sowing, we covered each bed with 3/8 to 1/2 inch of coarse grade sand.
Weed control is paramount in consistently producing a high quality seedling crop in a single growing season. Common groundsel (Senecio vulgaris) and purslane (Portulaca oleracea) were our top weed issues in the seedbeds. In an effort to reduce the economic impact of hand-weeding labor costs, we utilized charcoal and herbicide banding on row-sown beds. These are liquid applications that are applied at the time of sowing and are then covered with a layer of sand. Application rates of herbicide will vary with the timing of sowing, but the charcoal layer is consistent. Careful attention to irrigation volume is needed to promote activity of the herbicide between the rows and to prevent lateral migration of herbicide in the bed profile. This technique was a work in progress, but at the time it was applied to approximately 60 percent of all of our row-sown crops.
Minnesota winters can be a harsh environment for growing in seedbeds. The months of cold are not as critical as long as there is enough snow. We tended to have poor germination where the seedbeds were exposed to the harsh winter with little snow cover. A uniform stand of seedlings is best achieved in a cool and evenly moist seed stratifying bed. In Minnesota, we used an even layer of rye or wheat straw at a depth of 3 inches over every surface of the bed. That straw was windrowed on each bed; it was then spread via a tractor-drawn hydraulically operated rake. The rake has two multi-axis articulating drums that operate perpendicular to the bed for covering the bed evenly in a single pass. To uncover seedbeds in the spring, the drums move the straw from the bed to the furrow when each drum is turned at 45 degrees to the length of the bed. This single-pass covering and uncovering allowed for timely and cost-effective winter protection of Minnesota seedbeds.
Bailey Nurseries’ success in growing is based on building and establishing a good root system. The growing and plant cultivation strategies are dedicated to building a high quality root system. For the crops that were undercut, root pruning timing is what makes the difference. If the plant is severed later in the growing season, size yields are certainly going to be reduced and the recovery period is long. Bailey’s practice is to head the root radicle back when the plant is young and the roots are fleshy. Small cuts made in the earlier part of the season still have an effect on size yields, but not as much time passes waiting recovery from the procedure. Ground moisture is important to reduce excessive plant and soil shifting, but is balanced against the potential for soil glazing from the passage of the blade.
Grading seedlings at Bailey Nurseries is still done in a similar format to the way the company has graded for the past 30 years. One grader is responsible for every grade. Each plant type is graded in order of the most prevalent size relative to the order on hand. We only processed as many seedlings as we had orders. Each plant type was graded, prepared for planting or sales, and packaged away for winter storage in a single handling. Plants are held at varying storage conditions based on what works most successfully for the company’s own needs.
A version of this report was previously published in the Proceedings of the International Plant Propagator’s Society, Volume 63, page 263.