Table of Contents

Theoretically, a forester has a range of stocktypes from which to select for a given reforestation project, i.e., those produced through sexual means, seeds and seedlings; and those resulting from asexual manipulations of plant material, cuttings and plantlets (tissue culture). In past practice, reforestation throughout the world, and especially in the western United States and Canada, was accomplished almost exclusively through the use of seeds and seedlings. However, during the last twenty years the use of seeds has been almost entirely abandoned and foresters have gone to seed produced stocktypes, either as bare-root or container grown stock. In the tropical and subtropical regions of the world where cuttings of many species may be induced to root regularly and where seed collection and/or storage is frequently limiting cuttings work best. Nor has this trend to cuttings been confined exclusively to the tropical regions. In countries such as Australia, New Zealand, and Germany, technology for rooting Pinus radiata and Picea abies has advanced rapidly. The rooting of Cryptomeria in Japan has been a forestry practice for centuries. Redwood is produced from cuttings by some nursery managers.

In the southern United States, cuttings have been used for a number of hardwood species such as Platanus occidentalis and Liriodendron tulipfera to establish short rotation plantations for biomass production, and with other species to regenerate bottom land hardwoods. However, the great majority of the reforestation in southern states employs loblolly pine seedlings.

In Canada, particularly Ontario, recent years have seen significant programs devoted to developing clonal techniques for black spruce.

However, in the Douglas-fir region of British Columbia, Washington and Oregon the present trend is for increased use of seedlings. The use of vegetatively propagated material has been confined almost exclusively to research. This is primarily because Douglas-fir has been both difficult to root if the ramets are taken from older ortets, and the incidence of plagiotropic growth habit in Douglas-fir cuttings is high. One exception to the foregoing involves the use of high yielding clones of Populus in plantations designed to produce raw material for pulp and paper.

Procedure

This unit will provide you with a summary of the strengths and weaknesses of the present regeneration systems and of the potential for those currently employed primarily in research. In addition, it will review the two commonly employed systems of seedling and transplant designation.

Objectives

Upon completion of this unit and the assigned material, you should be able to answer questions such as the following:

1. What are the major advantages and disadvantages of: seeds, seedlings, transplants, and cuttings as regeneration materials?

2. Name (with both the age and stock type, size, and year of planting classification systems) the seedlings or transplants most appropriate for:


a. Areas in coastal Oregon characterized by moderate to heavy rainfall and competing vegetation such as alder, salmonberry, thimbleberry, salal, vine maple.
b. Low rainfall areas in southwest Oregon.

Stocktypes

What is a stocktype? This word stocktype is so simple to use in conversation that it is not uncommon for practictioners to use it without fully knowing what it means. A stocktype designation tells the seedling grower or user only three things: (1) the age of the seedling, (2) how many times the seedling has been transplanted, and (3) if the seeding is bareroot or container or both. For example, a 2+0 (or 2-0) Douglas-fir seedling means that it was grown in a bareroot nursery for 2 years without being transplanted. A P+1 or plug + 1 is a containerized seedling of unknown cavity size (plug) grown for one year in a container and transplanted for one year in a bareroot nursery. A 1+1 seedling is a seedling grown in a bareroot nursery for one year, lifted, taken to the packing shed and graded, and the best quality seedlings are retransplanted and grown for one more year.

Understanding the stocktype system can be confusing at first. Some nursery managers will state that they have 160 stocktypes! This can be correct since they may have 160 different ways to grow seedlings. There are literally a hundred cavity types to choose from and growing phases that can range from only a few months to a couple of years. A good example is a Mini-plug + 1, a name copyrighted by Weyerhaeuser, that is grown in a special 1 cubic inch square cell for 4 months, transplanted to a bareroot nursery bed, and then grown for another year. A similar stocktype with an entirely different cell design is the 1 cubic inch Hahn 408. This styroblock container holds 408 individual cells. This stocktype is also grown for about 4 months, transplanted to a bareroot nursery, and then grown for another year.

Other designations would be styro-2,styro-4, and sytro-8. "Styro" in the vernacular language of reforestation means styroblock container. The "8" means an 8 cubic inch cavity size. From this it is not difficult to see how it is possible to have well over a hundred different stocktypes from the very small transplants intended for nursery beds to very large 2+1s.

There are some key questions to ask about the stocktype nomenclature. What does a stocktype designation actually reveal about a seedling? Does the designation predict survival? Does it predict how the seedling will grow? Does it indicate the morphological shape of the seedling? Is it an indicator of physiological quality? Does it serve as a standard across all nurseries within a region or area? The short answers to these questions are as follows: (a) very little, (b) no, (c) no, (d) no, (e) no, and (f) no. In conclusion, the stocktype designation is useful, but still a very crude way of describing a seedling.

Outline of Different Plant Options for Reforestation

I. Seeds
Seeding is almost never used anymore. It occasionally gains limited interest after very large fires because it is hoped seeding will lead to a more rapid establishment of a young forest when there are not enough nursery seedlings available for planting. Experience has shown that the success rate is very mixed.

Advantages

1. Rapid, suited best to large burns or relatively inaccessible areas.
2. Relatively inexpensive.

Disadvantages

1. Seed-eating mammals may destroy most or all of the seed.
2. Regeneration often spotty-clumps interspersed with blank areas. 3. Relatively short period, mid-November to early February, is suitable for direct seeding. Weather may adversely impact project.
4. Not suitable for small areas, i.e., less than 100 acres unless seeds are protected in some type of spot seeding configuration.
5. Not suitable to areas with heavy plant competition or severe heat drought.
6. May require extensive site preparation.

Advantages

1. Permits rapid multiplication of desired phenotypes.
2. Has potential for asexual crosses, possibly across genera.

Disadvantages

1. Requires a high level of technology.
2. Currently relatively expensive.

Advantages

1. Allow replication of superior geno - or phenotypes.
2. With some species, i.e., sycamore, poplar, provide larger propagules than may be produced from seed in equivalent time.

Disadvantages

1. If taken from trees older than ca 10 years, plagiotropic growth habit is common.
2. If taken from trees older than ca 10 years, shoot growth is often significantly less than that of seedlings. However, recent New Zealand work suggests that this growth diminution may be due more to incorrect handling of the cuttings in the nursery rather than reduced plant vigor per se.
3. Possibly poor or inconsistent rooting, especially from material taken from trees older than 10 years.
4. More expensive than either seedlings or seeds.

Advantages

1. Vigorous seedlings, well-planted in areas properly prepared, are generally resistant to environmental stress.
2. Flexible-seedling or transplant types may be tailored for individual sites (see section in seedling classification below).
3. Close control of spacing is practical.

Disadvantages

1. Relatively slow, expensive when compared with aerial seeding. Requires 1-3 years advance planning. Survival in severe sites and growth dependent upon excellence throughout the regeneration system from seed collection through planting and post-planting plantation maintenance.

A. By age
First number indicates number of years in seed bed; the second number of years in transplant bed, i.e., 2-0 indicates a seedling which has spent two growing seasons in the seed bed, 2-1, a transplant which was in the seed bed for two years followed by one growing season in a transplant bed. Advantage: standard, reproducible. Disadvantage: substantial variation within each class.

B. By stock type, size, year of planting
The following is a description of the more detailed Canadian system of classifying seedlings.


• Stock type: B, bare root; C, container; BC, bare root transplanted to container; CB, container transplanted to bare root; BT, bare root transplant.
  
• Height measured to nearest centimeter.
  
• Diameter measured to nearest millimeter. Measurement made approximately one centimeter above the cotyledonary node.
  
• Shoot-root ratio. Measured by the volumetric method.
  
• Year seed sown. Calendar year in which the seed made first growth, i.e., seed sown in the fall of "77 or the spring of "78 would both be coded as 78".
  
• In British Columbia container seedlings are described by diameter & depth of cavity in cm. i.e. 313's are seedlings grown in cavities 3 cm in diameter and 13 cm deep. This description may also be modified by the number of cavities in block. In Pacific Northwest, styroplugs are described by volume, i.e., styro-2 indicates a 2 cubic inch container.

  With above code a bare root seedling 30 cm in height, 6 mm in caliper, a shoot-root ratio of 2.0, sown in 1975 would be listed as: BR-30 6 2.0 75.

Further, if the forester has determined that a bare-root 2-0 seedling is cost effective for his area, he may specify seedlings most appropriate for his site rather than just 2-0 Douglas-fir from a given seed zone. For example:

1. A droughty site in southern interior of B.C. is limited primarily by moisture stress. Therefore, the seedling with the highest prognosis for survival would be one with relatively large root system, short crown, and thick stem. Such a plant could be ordered as B 30 7 1.5 82.

2. A seedling destined for planting in the Coast range, where the chief limiting factor for survival is frequently plant competition could be characterized by a taller shoot and less well developed root system as: B 60 6 2.7 82.

3. Finally, a seedling to be planted in a medium elevation site with a slight northerly exposure in the interior where neither moisture stress nor plant competition are limiting in a properly prepared site could well be a well balanced plant as: B 40 5 2.0 82.

Disadvantage of both of the above systems is that they do not provide information with regard to the crop management in the nursery - seedbed spacing, irrigation, root pruning, all of which may dramatically impact seedling growth and survival potential.

VI. Seedling use (A-E bare root seedlings).

A. 2-0 Generally employed where there is no extreme environmental stress, where animal damage is not expected to be severe (may be combined with bud caps or vexar protectors if so) and where damage from ravelling slopes or falling debris is not expected. Seedlings destined for moderately droughty areas should be grown in wide spaced (no more than 10 seedlings per lineal foot) beds, hardened early. Great majority of planting stock is in this class.

B. 2-l Generally more resistant to environmental stress than 2-0's, especially if transplants have been grown to favor roots to increase survival potential in droughty areas. Transplants to be used in areas of heavy brush should be grown to favor a relatively high shoot/root ratio. Generally 50 - 100 percent more expensive than 2-0's so relatively small numbers employed in regeneration projects.

C. 3-0 Rarely used, but has potential where shoot/root ratio is not important and where a large shoot is desired to compete with brush species.

D. 1-0 Rarely used in British Columbia, although the Weyerhaeuser nursery at Armstrong produces 1-0 lodgepole pine seedlings, but the common planting stock in the South and in parts of California, and in New Zealand and Australia, where Pinus radiata, Pinus caribaea, and Pinus elliotti are all planted as 1-0 stock. P. ponderosa 1-0 stock has proven to be as good as 2-0 in parts of droughty SW Oregon [Picture at left is of 1+0 P.ponderosa.]. P. taeda 1-0 is used extensively throughout the South.

E. 2-2, 3-1 Use of these older seedlings confined to areas such as eastern Canada and Scandinavia where the climate dictates older plants because younger stock is too small to be plantable.

F. Container seedlings. The use of container seedlings was thoroughly discussed in an earlier section of these notes. The increased flexibility of this system vis a vis bare root grown seedlings, which is particularly important in reforestation projects in interior British Columbia, undoubtedly means that this class of propagule will become increasingly dominant in British Columbia forestry. Containerized seedlings are still used in the United States, but to a much more limited extent.

Matching Planting Stock to Site

Adaptability of seedlings to post-logging or site prep environment

1. Environment is characterized by a set of physical parameters projected forward in time. Vegetation controls moisture, light and temperature factors increasingly after disturbance. Falling trash is a problem in dead brush or steep slopes. Worst in shade.
a. Species differ in tolerance to shade. Momentary survival and subsequent growth and ability to evade shade are important.
b. Caliper of stock influences ability to withstand bending, browsing.
c. Height of seedlings influences degree of shading from low cover and vulnerability to browsing and clipping. Large stock has greater potential growth rate, especially if large in caliper. However, large stock also has a potential for greater planting shock, so high growth rate may not be expressed for two/three years after planting.

d. Stock can be managed in nursery for hardiness or rapidity of take-off, depending on habitat need. Hardiness may be critical in locations other than coastal or climates of high summer rainfall.

2. Environments change, and with them change the seedlings. It is important that seedlings be able to maintain dominance throughout the establishment period. Compare dominance potential of residual brush with planted stock:
a. Growth curve of seedling expected.
b. Growth curve of brush based on crown height and volume.
c. Distribution of brush.
d. Expected mortality of seedlings from animals, misc.
e. Expected mortality from moisture stress.
f. Degree of suppression tolerated.

1. Limitations of seedling choice arise.

a. Because of short planning horizon, new program, fire, etc.
b. Because of limitations of species adapted to long-term needs of site.

2. Site prep can be modified to allow for seedling limits.

a. By reducing physical debris problems.
b. By leaving shade or removing it as needed.
c. By modifying animal cover.
d. By manipulating frost protection to some degree.

Planting Techniques and Seedling Root Systems

We have emphasized through the course that satisfactory regeneration required good planting stock, good site preparation, and good planting. Thus far, however, we have not defined what we mean by "good planting".

Seedlings are relatively fragile organisms; therefore these guides should be followed to maximize seedling survival and minimize planting shock:

1. Seedlings should be maintained in cool, moist conditions until planted. Even a few minutes' exposure of the root system to desiccating conditions may cause significant mortality of fine roots. Seedlings should not be planted during weather extremes i.e. soil frozen below surface, dry desiccating winds, high temperatures.

2. Every effort should be made to avoid physical damage of seedlings. Containers should not be handled like sacks of potatoes. If root systems are too long for proper planting, they should be trimmed with a sharp knife, not torn off.

3. Seedling roots should be planted straight, i.e. "J" or "L" configurations should be avoided (this is especially important with tap rooted species such as some of the pines). Trials which have examined the possible benefit of planting roots in a three dimensional configuration (more nearly natural than the more common two dimensional root system which results from split planting) have yielded conflicting results.

4. Root systems should be planted in mineral soil which is pressed firmly about the roots to obviate possible air pockets.

5. Only favorable microsites should be planted. Where practical, stumps or debris should be utilized to provide shade, especially on southerly slopes.

Readings

Rose, R. 1992. Seedling handling and planting. In Reforestation Practices in Southwest Oregon and Northern California, Ch 14, (eds) S.D.Hobbs, et al. For. Res. Lab., Oregon State University, Corvallis, OR. pp328-345.

Mitchell, W.K. et al. 1990. Planting and Seeding. In Regenerating British Columbia's Forests, Ch 18, (eds) Lavender et al. Univ of British Columbia Press, Vancouver. pp 235-255.

Scagel,R., R.Bowden, M.Madill, and C.Kooistra. 1993. Provincial seedling stocktype selection and ordering guidelines. B.C. Ministry of Forests. Silviculture Branch. Province of British Columbia. 75p. (look through this and see what you can learn)

Additional Information

Lopushinsky, W. and T. Beebe. 1976. Relationship of shoot-root ratio to survival and growth of outplanted Douglas-fir and ponderosa pine seedlings. USDA Forest Service Research Note PNW-274. PNW Forest and Range Experiment Station, Portland, Oregon. 7pp.

Cleary, B.D., R.D. Greaves, and R.K. Hermann. 1978. Regenerating Oregon's Forests. Chapter VI. pp. 75-80.

Updated: July 26, 1996

- Sa'Di