Seed and stock

Early in the planning stages, contact and confirm the nursery that will be supplying planting material. The relationship you build with your nursery will be important, as well as determining their production capacity. It is also important to review the tree stock you’re interested in purchasing before ordering. This is usually done by visiting the facility or speaking with their representatives and other clients who order their stock from the same nursery. Several important questions to ask are: 

Any reputable nursery will be able to answer these questions, and any others you may have, when contacted.  Choosing a nursery with a good reputation for providing native trees for Canadian tree planting projects will ensure the highest likelihood of success. A good nursery will participate in sustainability practices, grow from a variety of local and climate-ready seed sources, illustrate an ongoing commitment to research and development, and can offer you a reliable variety of tree species you’re looking for. To find out more about tree nurseries in Canada, visit the online resources provided by the Canadian Tree Nursery Association (CTNA).

Selecting the right species for your project is critical, but choosing the stock type that will give the greatest chance of success with the site conditions, is also essential. Nurseries can grow a variety of stock types suitable for various conditions. For example, if the soil on the site is heavy, fertile and exhibits high levels of competitive vegetation, then larger, more robust stock may be more appropriate to combat and compete in this environment. In comparison, a site with very shallow soil and low fertility may be more supportive of smaller stock with a shallower root system.

For mass tree planting projects, you may be using a combination of stock types ranging from greenhouse plugs, bareroot stock and, less commonly, potted stock or cuttings. Table 1 summarizes the four main stock types used in Canada for large-scale tree planting projects.

If you find that your nursery has the species you’re looking for, but not in the ideal stock type/size, consider the pros and cons of proceeding with this alternative stock type and determine if it’s worth the risk. If you plant a stock type that is not best suited for a site and there is high mortality, then there will be the added costs to returning to replant vs. taking an extra year or two and having the right stock grown.

It is important to confirm with the nursery what stock types they grow, but also be able to have conversations about what may work best for your sites and if they are able to grow those other types as well. As mentioned, often a 2-year lead time is needed for the nursery to plan and organize your production numbers. If that lead time is not possible, then the only stock available may be less than ideal stock types and seasonal surpluses.   

Visit your stock supplier prior to ordering trees or receiving planting material. There needs to be a clear level of expectations set between the grower and tree planting organization. Most of the time, this will include signing growing agreements that outline the size specifications and agreed-upon targets of the final product.  When visiting the nursery, time should be taken to ensure the stock is free of insects and disease or physical damage, foliage is healthy (lush and vibrant colour), and buds are developed well. Inspect the root system to make sure it is well-established, but not bound and there is sufficient volume to support the tree size. If you're using larger potted material, familiarize yourself with the Canadian Nursery Stock Standard to ensure planting material supplied is meeting specifications and measurements. These standards were developed to ensure plant material is set up for success after planting and provide consistency within the industry.

When stock is received from the nursery during the planting season, time should be taken shortly after the shipment is received to review and assess the planting material. This is an opportunity to ensure stock is in good condition, meets expectations, and is ready to plant. If there is a problem, then the grower should be contacted immediately to discuss the issues and identify opportunities to resolve the situation.

Often, tree planting organizations are so focused on sourcing specific tree species for their tree planting programs that they don’t consider the original parentage and source of the seed and stock.  When planting trees, knowing the seed source and making best management decisions based on the genetic zone and provenance of the trees being planted is paramount in ensuring a successful project. If a seed source is used that is not adapted to the area or moved too far from its natural range, it can have a detrimental effect on the long-term success of the planting site. 

Urban tree planting project managers primarily use the cold hardiness zones to guide their species selection.  These are based on monthly means for the minimum temperature in the coldest month and maximum temperature in the warmest month, number of frost-free days, rainfall during the growing season, snow depth and wind gusts. The hardiness zones only reflect the climatic factors affecting a tree’s survival and performance but lack information about genetic adaptation to the region. In large-scale tree planting projects in Canada, genetic seed zones are used instead.

Sourcing trees from appropriate genetic seed sources and provenance is important for establishing healthy forests in order to maximize adaptation to the local conditions, comply with applicable provincial regulations, enhance biodiversity, mitigate invasive species and disease, and enhance overall health and performance of the trees during the growing stages. Some provincial regulations can dictate what species and seed sources are used on crown land planting areas. For example, in BC, anyone who uses seed to establish a forest under the Forest and Range Practices Act (FRPA) must consult and apply the Chief Forester’s Standards for Seed Use ensuring that the species and seed source selected for planting are adapted to the environment where they’re being planted. Ensure nurseries supplying your stock consider seed sources when growing trees and provide this information prior to ordering your trees. 

Historically, most provincial governments were directly involved with supporting conifer seed production to assist the forest industry in their reforestation mandates on crown land. Often this involved establishing tree improvement seed orchards and facilities to process and store seed.  Due to a reduction in funding and resources, many provincial governments are focused more on the policy and governing the industry instead of being directly involved with seed production. Depending on the province, the forest industry tends to still have good access to conifer seed, but many tree planting organizations do not have the same opportunity.  Therefore, it is often the nursery growing the trees that supplies the seed for tree production, but species and seed source options can often be limiting. 

Many tree planting organizations are getting directly involved with seed collection to ensure that they have the specific species and sources they are looking for.  There are many different functions of seed collection that you can get involved with, such as collection site opportunities, crop forecasting, collection, transportation, processing, storage, and testing.  Because conifer seeds are orthodox in nature (can be stored long-term when managed properly), good seed crops can be utilized, and multiple years' worth of seed collected in one season. Unfortunately, most deciduous tree species are often recalcitrant in nature and cannot be stored long-term, so you are reliant on the crop periodicity and annual climatic conditions, which can be inconsistent from year to year.  It is important to have discussions with your grower to determine who is supplying seed and if there is an opportunity to work together to support seed collections. 

For more information about seed sourcing, talk to your nursery or reach out to the Forest Gene Conservation Association (based in Ontario) or the National Seed Centre (based in New Brunswick).