Planting seedlings is a big deal in a tree-growing state such as Oregon. According to the Oregon Department of Forestry, between 30 and 40 million new seedlings are planted each year! The reasons for planting are many – reforestation after a timber harvest, conversion of a field to a forest, filling in tree-less openings in a stand, and many others. Whatever the reason, the success of your planting effort depends on choosing the right seedling and planting it properly.
There are several decisions to make in choosing a seedling, including species, seed zone, and stock type. The choice of species depends on the objective of your planted forest. Do you want to maximize the future value of your planting investment? Perhaps you want to mimic the diversity of species found growing in your area. Choose your species accordingly.
Tree seed zones refer to the geographic area where seed was collected and can be safely outplanted. These zones are based on areas of similar geology, climate and native vegetation. Seed zones are broad areas, and differ by species. Maps of seed zones for most commercially-grown species may be found on this Oregon Department of Forestry web page.
Seed zones are further refined by elevation bands, again reflecting the area where the seed was collected. As a rule, it’s best to select seedlings grown from seed collected in the same seed zone and elevation as your planting site.
There are two basic types of planting stock: bareroot and container-grown seedlings. Bareroot seedlings are sown and grown in nursery beds, lifted, and then sold without soil on the roots. Container-grown or “plug” seedlings are normally grown in a greenhouse. The container’s cavities are filled with growing medium and the seed is sown on top. Nurseries extract plug seedlings from the containers before shipping them for out-planting.
Bareroot seedlings are typically classified by the number of years grown in the nursery or transplant bed. A seedling grown in the same bed for two years is referred to as a “2+0” seedling, while a seedling transplanted after its first year to a lower-density bed is referred to as a “’1+1.” A “1+1” seedling will generally be larger and more expensive than a “2+0” seedling of the same species.
Most plug seedlings are grown for a single year in the greenhouse. Plug types vary by the size of the container the seedling was grown in. For instance, a “styro-8” plug is grown in a styrofoam cylinder eight cubic inches in volume. In general, a larger growing container equates to a larger – and more expensive – seedling.
A third variation is a combination of the two: a plug seedling grown for a year in a greenhouse followed by a year in the nursery bed. Such a seedling is referred to as a “plug+1.”
For a discussion on the pros and cons of various stock types, seedling sizes, and containers see the “Guide to Reforestation in Oregon 2006” by Robin Rose and Diane Haase. This guide is also available from your local Oregon Department of Forestry stewardship forester, OSU extension agent online.
There are many nurseries in Oregon that grow forest seedlings. One excellent resource for finding your desired seedlings is the “Sources of Native Forest Nursery Seedlings” catalog produced annually by the Oregon Department of Forestry. Keep in mind that seedlings often sell out long before planting season, especially for less-common species.
Lastly, if you can predict your seedling needs one to three years in advance (depending on the stock type), consider having your seedlings contract grown. Seedlings grown under such an arrangement are typically much less expensive than seedlings grown “on speculation” by the same nursery.
The first key to planting is proper storage and handling of your seedlings from the nursery to your planting site. Seedlings should be kept cool, but not frozen, and out of the sun and wind until they get planted. Cold storage at temperatures in the mid-30s is best. Bags or boxes of seedlings should be handled carefully so as to not damage the living plants inside. Plan your seedling delivery to minimize storage time before planting.
Remember that seedlings like to be planted in mineral soil with straight roots. Seedlings are best planted in the winter months on cool, damp days when your planting site is not frozen and has little to no snow.
A final consideration for a successful planting show is weed control. Moisture throughout the growing season is often the limiting factor for seedling survival. One or more years of grass and weed control is generally a good idea.
Special thanks to OFRI.org for images used on this page.