University of Florida

Home > Nursery tree production > Specifications/standards > Developing quality standards

Developing quality standards for nursery stock

Edward F. Gilman
Professor, Environmental Horticulture Department
University of Florida, Gainesville, FL 32611

Many experienced, professional nursery operators and landscapers have been through this before. You bid on a job with a reasonably profit margin. You include in the bid high-quality plant material that you have grown or secured from other quality growers to fulfill the plant material needs. You even include a statement that all plants meet the national ANSI Z60.1 nursery stock standard. After all bids are in, a different firm is awarded the job.

While driving by the completed job several months later you find that inferior nursery stock was installed on the job. Your frustration is only matched by the passion to change this unfair, unprofessional, and unethical situation. I will present how explicitly-written nursery stock specifications have a role in changing this, and transforming our industry into a profession.

Few horticultural professionals in the US would argue that there are quality issues with some of the nursery stock that arrives at landscape sites. Many characteristics are associated with poor plant quality, and some of these can lead to unstable plants, unthrifty growth, or plant mortality. These include circling or kinked roots, deep planting in the root ball, codominant leaders on large-maturing shade trees, weak trees unable to stand erect, and other issues.

Some of these, such as circling roots or codominant stems, may not show any above-ground symptoms until many years after planting. Storms of many types often result in broken and uprooted trees. Whether it is true or not, some of this has been attributed to problems that began in the nursery. If this is indeed the case then urban foresters, arborists and others that care for trees for the decades following planting will demand better-quality nursery stock. Who can blame them?

Many arborists and urban foresters, and some landscape architects, from the across the country tell me that they are unable to find quality trees for their planting projects. They say they have written good specifications and sometimes they have. But I have seen many specifications that lack the detail necessary to ensure good stock is planted. So, maybe the buyers have not written the detailed specifications necessary to communicate to the growers what it is they want. Since urban foresters and others are mandated to plant trees, they sometimes settle for lesser quality material???.

There is another compelling reason to begin developing a uniform nursery stock specification-it will help customers evaluate quality more easily and separate those who grow good quality from those who do not. With more consumers understanding what quality means, more of them will demand quality and nurseries producing quality will sell out sooner. This already happens in our industry to a certain extent. These nurseries will grow more of the high-quality trees to meet increased demand. This is marketing 101 and should increase the quantity of high-quality trees on the market.

Side bar: The ANSI Z60.1 nursery stock standard it is not meant to be a gauge of plant quality. It provides buyers and sellers with a common terminology in order to facilitate transactions involving nursery stock. The standard defines terms and numerical relationships among tree parts.

The green industry has a nursery stock standard in the ANSI Z60.1, but like the ANSI A300 pruning standard used by arborists in the care of trees in landscapes, specifications should be written using the standards-the standard itself is not a specification. In fact the ANSI Z60.1 nursery stock standard states on the first page: "This standard does not provide buyers with any assurance of the health or quality of the nursery stock being specified or sold." That means we have to develop specifications to ensure quality gets purchased and planted.

Use the terms and numerical relationships in the Z60.1 standard when writing a specification to ensure that we are all using the same terms to describe common practices and procedures. That is the whole point of the standard! Most professions in this country do this. Even our own industry does this with plant names as we embrace the taxonomic tradition of referring to plant names in latin. Imagine going back to referring to plant names without latin.

What we are saying is that it no longer suffices to specify material in the following manner: Two-inch caliper Red Sunset™ red maple (Acer rubrum 'Franksred') 12 feet tall with an ANSI Z60.1 standard sized root ball. Although this references the nursery stock standard, this is not an adequate specification for nursery stock because it does not prevent the problems commonly encountered on nursery trees.

Essential items to include in a specification are statements about condition of roots, trunk and branches, canopy, and requirements that plants coming to the site are the correct species and cultivar and in good condition. Illustrations and/or photographs are essential components of any nursery stock specification because we simply do not have a universally recognized vocabulary to write a specification using only words.

There are some fine examples of specifications from around the country. If you read through good specs you find that there are common threads in all of them One of the first was published by Dr. R. W. Harris of the University of California in his popular Arboriculture book as appendix 1. Text descriptions of characteristics of the root ball, canopy, and size relationship between trunk and branches were included as well as other great ideas for quality evaluation. Later specification examples included illustrations and photographs ( and that make communication much easier for all parties. After all, good specs really come down to writing a document that can be easily understood by a large number of diverse people (Figure 1).

These might be good starting points for you to develop a specification for your region. This would be fairly easy to develop for a small region such as a state. However since there are many items that are uniformly desirable in a specification no matter where the landscape is located, why not develop a country-wide uniform nursery stock specification and publish it on the web? That way, all growers, buyers, consumers and others would have access to the same information and could come to a common understanding of what a quality plant is.

The items in this uniform country-wide specification could include those found in Table 1. Other items could be added as necessary. An industry-wide committee composed of growers, contractors, arborists, urban foresters, landscape architects, landscape management, educators, and other green industry groups would develop this uniform specification. Once the uniform spec is developed, a region of the country could start with the uniform spec and modify it as they see fit for their particular issues.

One of the downsides of a specification is that there is little room for compromise. The plant either meets the specification or it does not. Not meeting the specification is grounds for rejection at the planting site. The Florida Department of Agriculture and Consumer Services went a step further than a standard in an attempt to correct this. In 1998, following 9 years of discussion (sometimes heated), revision, and compromise, it published the second edition of the Florida Grades and Standards for Nursery Stock. Plants fall into one of four grades depending on their quality.

Landscape plants on many landscape jobs in Florida are specified using this document and have been since its introduction more than 40 years ago. It has become a generally accepted method for specifying plant material in the state. However, it is not a perfect document in that some of the important issues listed in Table 1 are omitted. This means that specifications should still be written to cover the issues not in the document.

The Grades and Standards document is transforming the industry in Florida. I have conducted tree seminars in 42 states in the last 10 years and have seen lots of nursery stock of various types. During this time I have seen the Florida tree nursery industry morph from producing some of the worst quality trees to producing some of the best in the country. The Grades and Standards for Nursery Stock document has been the driving force behind this change.

Some of the more progressive growers began to grow trees to meet these standards in the early to mid 1990s because they saw the future direction of the industry. They "pulled" the rest of the industry with them. Now, more than a few growers are producing the quality that trained urban foresters and other quality buyers are clambering for. The last all-day, outdoor tree production seminar in Florida April 4, 2002 drew more than 220 professionals from five states. At that program growers and buyers learned what quality trees look like and how to produce them beginning with liners and finishing with a 3 to 8 inch caliper crop.

Want to improve the quality of nursery stock and generate more profit at the same time. Create a uniform nursery stock specification or go with the full-blown grades and standards as Florida did. If your experience is like Florida's, more quality trees will be available, they will command fair prices, and buyers will be pleased. Everyone wins.