Designing a field grown nursery

Raising field grown stock generally appeals to owners who are looking to establish a nursery without the high upfront costs establishment and labor that are inherent in a container operation. As opposed to growing plants in either above ground or fabric containers, field grown stock requires less irrigation (or none at all), fertilizer, weed control, disease and insect control, and concern over winter protection. Within the category of field grown, producers of groundcovers, herbaceous perennials, ornamental grasses, and Christmas tree seedlings prefer to raise bare-root nursery stock.

For shade trees, in-ground production generally results in a superior product, especially for the larger caliper stock. Shade trees can either be grown in plastic pot-in-pot systems (1) set into the ground, or entirely in the ground own their own. For the standard 2"-3" caliper stock root control fabric bags (2) have recently been introduced. Where trees were once dug by hand and sold as balled-and-burlapped stock, modern nurseries now use mechanical tree spades to dig larger trees. For shade trees over a 3" caliper, field production remains the preferred growing technique. Large capacity tree spades can handle the very large shade trees (3).

Even with the apparent ease of raising plants in the ground there should be a thorough plan for the layout of the field grown nursery before the first seed, seedling or rooted cutting is established.

Site selection for a field grown nursery begins with a close examination of the soil. Be sure to study a soils map, as well as ask the landowner what was raised previously on the site. Poorer sites can be used for buildings and roads.

Use a team approach to planning
Developing a plan for field grown nursery is similar to formulating the plans for building a house. A number of different specialists should be consulted with to come up with the most efficient plan for the intended business. A landscape architect should be employed to sketch out alternative plans for the production areas and the buildings. The larger Northwest wholesale nurseries often have a very well developed demonstration garden or arboretum displaying the trees and shrubs that they stock. A building architect should be utilized to plan out the office and shipping-receiving facilities. An interior decorator is utilized to make the office foyer and conference rooms suitable for conducting importing sales meetings with discriminating buyers. If bare-root stock will be dug up and stored over winter, a refrigeration contractor will be needed. If there will be a need for a greenhouse, a greenhouse supply representative should be consulted with. For roadways, a grading and paving consultant will need to be hired.

The goal is develop an efficient operation that not only optimizes plant growth, but also expedites harvesting and sales. A perfect nursery site will never exist. Nonetheless, by utilizing a diversified team (4) to develop a plan, the resultant operation should have a considerably improved chance for success.

Developing nursery plot map
Producers should first look at the entire parcel to note the natural features of the land. Invariably there will differences in slope, wind exposure, and native vegetation. A modern, inexpensive handheld GPS (global positioning system) unit can be used to record all of the important features of the field. What was once a time consuming task with tape and transit is now relatively easily accomplished in less than a day on a 10 acre parcel. The first measurement to record is the actual size of the field. By walking the boundaries of the field and then downloading the data from the GPS unit onto an office desktop or portable laptop computer, a very accurate nursery plot map can be developed. By knowing the size of the production unit the field supervisor can easily determine the number of plants per unit area that will be planted and latter harvested. A surveying company (5) can be hired to do all of the GPS and map development if the owner does not feel comfortable with the GPS unit. Differences in elevation can also be determined using a GPS unit. Steep areas will need to be either avoided if they have excessive slope, or terraced. All existing roads, culverts, fences, buildings, and wells should be noted as well.

A soils map can be used to determine the different soil types on the nursery parcel. The scale on Natural Resources Conservation Service soils (6) maps is detailed enough that the demarcation between two different types can be transferred over to the nursery plot map.

The direction of the prevailing wind should be observed and noted. On windy sites field stock can be deformed by prevailing wind. To block the wind a mixture of evergreens and shade trees should be planted on the windward side of the nursery. The growing area should be located no closer than 4-6 times the height of the tallest tree in the windbreak (7).

Mapping problem areas
If there are patches of noxious weeds on the property these should be surveyed and marked on the nursery plot map. Infestations of yellow nutsedge, field bindweed, horsetail, and bracken fern often require multiple applications of herbicides to eliminate them. On-line weed identification sites exist (8, 9). By including them on the nursery plot map, the field supervisor can go back at a later date and survey how well they are being controlled. Oregon State University maintains the PNW Weed Control Handbook (10) which lists control strategies for problem weeds. It's much easier to control problem weeds in a pasture before the field is plowed and planted. If problem weeds are not adequately controlled prior to planting with nursery stock, the weeds often come back to reestablish themselves.

If there are frost pockets on the property they should noted with the GPS. If early blooming stone fruit shade trees will be grown they could loose their bloom due to frost injury. Producers of Christmas tree seedlings are also very aware of frost hazards as their seedlings can be hurt severely. Cold air acts much like water in that it accumulates in low areas, or at the base of slopes abutting a grove of vegetation.

These field grown Japanese maples can suffer from the disease known as Verticillium wilt if they are grown for an extended period of time on this poorly draining piece of ground.

Areas with poor air circulation should be noted as well. In areas west of the Cascade Mountains ornamental dogwoods, photinia, and hybrid roses are very prone to damage by leaf spotting fungi when they don't receive good air flow in the spring as they are budding out. Growers trying to raise these types of plants will have to spend more time applying fungicides to keep the new foliage from becoming infected with leaf spotting fungi.

If the site review is conducted during the wet months, as it should be, any soft areas (springs, compacted ground) can be noted with the GPS unit and marked accordingly on the nursery plot map. If there are seasonal streams on the property their location can be plotted out on the nursery map using a GPS unit. Often these small streams dry up during the summer months. The Japanese maples are very prone to Verticillium sp. root rot if they are grown on wet ground. Noble fir Christmas tree seedlings can suffer extensively from Phytophthora sp. root rot as well. Areas with wetter ground are best suited to shade tree species such as red maple, birch, bald cypress, willows, and sweet gum. A complete list of trees and shrubs which can tolerate wet ground has been developed at the University of Georgia (11).

If there are year-round streams on the property there course should be plotted as well. State environmental agencies are contemplating establishing buffer zones along water courses to protect fish and reduce agricultural run-off.

A detailed nursery plot, developed using modern equipment, will become a very valuable record of the nursery enterprise. Financial loan officers will appreciate having a very detailed summary of the entire operation literally at their finger tips as they will be able view the plot map from a CD on their desk computers. All facets of the production cycle can be recorded and stored easily on a computer for latter reference.

Developing a layout
With a computer generated nursery plot map the layout of the entire operation can proceed. A whole host of different factors must be included in the layout:

By some estimates the room required for roads, borders, buffers along water courses, and areas too steep to farm can account for 30-40% of a nursery field, leaving only 60-70% available for field production (12). Obviously the best land should be reserved for the planting beds, while the poorer ground should be used for the office, shipping and receiving facility, and parking areas (13).

Rows should be set out to run on the contour of the sloping ground. A group of rows is considered a block. Each block is separated by roads that should be 15-20' wide in order to handle trucks, field trailers, tractors, loaders, tree spades, and spraying equipment. Roads will have to graded and may need a cover of gravel to make them accessible during the winter months. In general blocks should not consist of more than 8-10 rows wide. Blocks that are too wide make digging large trees too difficult. A number of large holes will result during the harvest of shade trees with a tree spade. These holes can become a danger especially in blocks that don't have all the trees harvested at the same time.

Planning for expansion
All too often the field run nursery is designed for the purchased or leased parcel size. After the first stock has been harvested it's not all that uncommon to find that sales have been good enough to consider an expansion. With a shipping and receiving facility, purchase of digging equipment, a good sales staff, and a dependable field work force, the business may find that expansion makes very good business sense. The nursery owner should look at surrounding parcels as possible sites for expansion. It's much easier to expand from the original site than it is to move equipment to a site further away.

After a shade tree nursery has been extensively harvested, or "mined" as such (14), with a mechanical tree spade, a soil rebuilding program will have to be started. After bringing in soil or compost to fill the holes, the field should probably lie fallow for a year while cover crops (15) are grown to replenish the soil organic matter. It is not advisable to simply re-grade the harvested field without bringing in soil as they could mix in subsoil which generally has poor tilth.

References
1. The pot-in-pot production system. 2003. Mark Holcomb, University of Tennessee.

2. Root-Maker Products Company, LLC., Lacebark, Inc., Stillwater, Oklahoma.

3. Optimal Tree Spades. Gatlinburg, TN

4. Nursery site selection, layout, and development. F.E. Morby. Forest Nursery Manual, USDA Forest Service.

5. Harvest Geographics. This company does GPS surveying and GIS mapping for the entire Pacific Northwest. Canby,OR.

6. County soils maps. Natural Resources Conservation Service. Washington, DC.

7. Nursery design and layout. 1995. Tom Landis. The Container Tree Nursery Manual: Volume 1, Nursery planning, development, and management. U.S.D.A. Forest Service, Agriculture Handbook 674.

8. New Jersey Agricultural Weed Gallery. John Meade, Rutgers Cooperative Extension.

9. Weed Photo Gallery, University of California Integrated Pest Management Program, Davis, CA.

10. Pacific Northwest Weed Control Handbook. 2004. Oregon State University, Corvallis, OR.

11. Selection, production, and establishment of wetland trees and shrubs. 1999. Mel Garber and D. Moorhead. University of Georgia Cooperative Extension Service.

12. Nursery field production. Mark Holcomb, University of Tennessee Agricultural Extension Service.

13. Starting a nursery enterprise: Specializing in shade trees. 1994. Stanton Gill, David Ross, and James Hanson. University of Maryland, College of Agriculture and Natural Resources.

14. Pot-in-pot container culture. Hannah Mathers, The Digger, trade association magazine for the Oregon Association of Nurseries, November 1999.

15. Nursery Management Administration and Culture. 1994. Harold Davidson, Curtis Peterson, and Roy Mecklenburg. Prentice Hall Career and Technology, Englewood Cliffs, New Jersey. Distributed through the American Nurseryman Publishing Company.

First posted: December, 2004.