Editing Tree planting (section)

== Season of planting ==
[[Image:Several people planting trees.jpg|thumb|Planting trees in USA]]

===Bareroot stock===
The classical silvicultural literature unanimously advocates spring as the time to plant bareroot stock, with lifting and outplanting taking place while the trees are still apparently [[Dormancy|dormant]].<ref name="Sutton 1984">Sutton, R.F. 1984. Plantation establishment in the boreal forest: glyphosate, hexazinone, and manual weed control. For. Chron. 60:282–287.</ref> This view, in which spring planting is implicit, was epitomized by Toumey and Korstian (1942):<ref name="toum">Toumey, J. W. and Korstian, C.F. 1942. Seeding and planting in the forestry practice. Ed. 3. John Wiley & Sons Inc., New York.</ref> "Almost without exception the most favourable time for ... planting is 2 weeks or more before buds [of the planting stock] begin their growth". Soil moisture conditions are generally favourable at the time when the growing season is about to begin, while dormant stock is less subject to mechanical injury and physiological shock.<ref name="Stiell 1976">Stiell, W.M. 1976. White spruce: artificial regeneration in Canada. Dep. Environ., Can. For. Serv., Ottawa ON, Inf. Rep. FMR-X-85. 275 p.</ref>

If the size of the planting program allows, there is little doubt that such scheduling would be advantageous in that it satisfies one, and commonly 2, of the factors essential for success: (1) the use of planting stock that is physiologically capable of responding to a growth environment at planting, and (2) planting when site factors favour tree survival and growth. The 3rd factor a good planting job, and although desirable in all plantings, is probably somewhat less critical in conventional spring plantings than at other times. If, however, a planting program cannot be completed in this way, there are other options: conventional fall planting with fresh-lifted stock; summer planting with fresh-lifted stock; and spring and summer planting with stored spring-lifted or fall-lifted stock.<ref name="Sutton 1984" />

===Conventional spring planting with fresh spring-lifted stock===
In the context of regeneration silviculture, "spring", "summer", etc. lack precise meaning. Typically, the spring planting season begins as soon as lifting becomes possible in the [[Plant nursery|nursery]], and ends with the completion of the program. At this time, planting stock is physiologically attuned to the oncoming growing season, and the outplant has the whole of that season in which to establish its root system before it is challenged by any frost heaving. In practice, ideals are seldom attained. That stock is normally [[Dormancy|dormant]] when spring-planted is a widespread fallacy. Active growth is commonly obvious at the time of planting, but in any case the metabolic activity increases in planting stock before the tops give visible expression to this. The difficulty of obtaining, in quantity, spring-lifted stock in dormant condition increases with increasing continentality of climate. In many areas, the period of springlike weather is unreliable and often short. As well, the soil moisture advantage claimed for spring planting is also insecurely founded. Soils that are sandy or gravelly, and shallow soils of any texture are highly dependent on current weather due to their limited available water capacities. Nor will a plentiful supply of soil moisture benefit an outplant whose roots are enveloped in anaerobic and/or cold soil, and mortality of trees outplanted into soil colder than about 6&nbsp;°C may be excessive.<ref name="Sutton 1968">Sutton, R.F. 1968. Ecology of young white spruce (''Picea glauca'' [Moench] Voss). Ph.D. thesis, Cornell Univ., Ithaca NY, Univ. Microfilms, Ann Arbor, Michigan MI, 68–11645. 500 p.</ref><ref name="Sutton 1969">Sutton, R.F. 1969. Form and development of conifer root systems. Commonw. For. Bureau, Oxford, U.K., Tech. Communication No. 7. 131 p.</ref> 

The [[spruce]]s may be planted not only throughout the spring planting period provided that the period of most active shoot elongation is avoided, but virtually throughout the whole growing season, with little loss of performance other than some reduction in increment.<ref name="mull3">Mullin, R.E. 1971. "Some effects of root dipping, root exposure and extended planting dates with white spruce." For. Chron. 47(2):90–93.</ref> 

===Conventional fall planting with fresh-lifted stock===
The fall planting season is generally considered to begin when nursery stock has hardened off and soil moisture reserves have been replenished by autumnal rain. It then continues until the planting program has been completed or is terminated by freeze-up or heavy snow. The advantages of fall planting were once considered "To outweigh those of spring so certainly" that in the National Forests of the Lake States almost all planting was done in the fall,<ref name="Kittredge">{{cite journal |last1=Kittredge |first1=J |date=1929 |title=Forest planting in the Lake States |journal=U.S.D.A., for. Serv., Washington DC, Agric. Bull. |issue=1497 |pages=87 p}}</ref> but in spite of some success, operational fall plantings in North America have tended to be less successful than operational spring plantings.<ref name="leb">LeBarron, R.K.; Fox, G.; Blythe, R.H. 1938. The effect of season of planting and other factors on early survival of forest plantations. J. For. 36:1211–1215.</ref> On certain sites, a major disadvantage of fall planting is that the root systems of outplants have little time in which to become firmly anchored before being subjected to frost heaving. Such plants are also vulnerable to "winter browning", which may occur in the fall soon after planting, especially among stock having high shoot:root ratios.<ref name="rud">Rudolf, P.O. 1950. Cold soaking – a short-cut substitute for stratification? J. For. 48(1):31–32.</ref> Relationships between dormancy progression and physiological condition, including root-growth capacity, are much less clear in the spruces than in the pines, but certainly there is good evidence<ref name="Baldwin 1938">Baldwin, H.I. 1938. Planting experiments in the northeast. J. For. 36:758–760.</ref><ref name="mull">Mullin, R.E. 1968. Comparisons between seedlings and transplants in fall and spring plantings. Ont. Dep. Lands For., Res. Div., Toronto ON, Res. Rep. 85. 40 p.</ref><ref name="sin">Sinclair, C.; Boyd, R.J. 1973. Survival comparisons of three fall and spring plantings of four coniferous species in northern Idaho. USDA, For. Serv., Intermount. For. Range Exp. Sta., Ogden UT, Res. Pap. INT-139. 20 p.</ref><ref name="McClain 1975">McClain, K.M. 1975. Continuous planting of seedling black spruce. p. 177–194 ''in'' Black Spruce Symp. Proc., Can. Dep. Environ., Can. For. Serv., Sault Ste. Marie ON, Symp. Proc. O-P-4.</ref><ref name="McClain 1979">McClain, K.M. 1979. A review on the possibility of extending the planting season. Ont. Min. Nat. Resour., Northern For. Res. Unit, Thunder Bay ON. 44 p.</ref> that, in the absence of frost heaving, plantings of spruces can be just as successful in fall as in spring.

===Summer planting with fresh-lifted stock===
Conceptually and logistically, the simplest way of extending the conventional planting season is to extend lifting and planting of fresh stock through summer until the planting program has been competed. Summer planting has also been successful in a number of research studies with white spruce, e.g., Crossley 1956;<ref name="cross">Crossley, D.I. 1956. The possibility of continuous planting of white spruce throughout the frost-free period. Can. Dep. Northern Affairs National Resour., For. Branch, For. Res. Div., Ottawa ON, Tech. Note 32. 31 p.</ref> Ackerman and Johnson 1962;<ref>Ackerman, R.F.; Johnson, H.L. 1962. Continuous planting of white spruce throughout the frost-free period. Can. Dep. For., For. Res. Branch, Ottawa ON, Tech. Note 117. 13 p.</ref> Decie 1962 cited by Revel and Coates 1976;<ref name="rev">Revel, J.; Coates, H. 1976. Planting white spruce throughout the growing season on high site areas in the Sub-Boreal Forest Region of B.C. B.C. For. Serv., Res. Div., Victoria BC, Rep. E.P.668. 37 p.</ref> Burgar and Lyon 1968;<ref name="bur">Burgar, R.J.; Lyon, N.F. 1968. Survival and growth of stored and unstored white spruce planted through the frost-free period. Ont. Dep. Lands Forests, Toronto ON, Res. Rep. 84. 37 p.</ref> Mullin 1971,<ref name="mull3" /> 1974;<ref name="mull4">Mullin, R.E. 1974. Some planting effects still significant after 20 years. For. Chron. 50:191–193.</ref> Revel and Coates 1976.<ref name="rev" /> Success depends on minimizing stresses to planting stock at all stages from lifting through planting and on planting when site conditions are conducive to survival and growth.{{cn|date=September 2024}}

===Spring and summer planting with stored stock===
Refrigerated storage of planting stock has been developed largely with the aim of overcoming problems experienced in using flushed planting stock. Storage provides a means of holding stock for use when fresh stock is either unavailable or at a stage of development that renders it unsuitable for planting. It also offers possibilities of manipulating the physiological condition of the stock. However, there are problems associated with storage, e.g., mold, cold injury, desiccation, and depletion of food reserves. The rate of deterioration depends very much on the physiological condition of the planting stock at the time of lifting, as well as on the storage environment and duration of storage.<ref name="mull5">Mullin, R.E. 1978. "Tests of frozen spring storage for white spruce and red pine planting stock." USDA, For. Serv., Tree Plant. Notes 29(4):26–29.</ref>

Mullin and Forcier (1976)<ref name="mull6">Mullin, R.E.; Forcier, L. 1976. Effect of lifting and planting dates on survival and growth of spring stored nursery stock. Ont. Min, Nat. Resour., For. Res. Branch, Toronto ON, For. Res. Notes 3. 4 p.</ref> and Mullin and Reffle (1980)<ref name="mull8">Mullin, R.E.; Reffle, R.J. 1980. Effects of dates of lifting and planting on success of frozen spring storage at Swastika Nursery. Ont. Min, Nat. Resour., Toronto ON, Nursery Notes 66. 5 p.</ref> examined the effects of spring-lifting date and planting date on several species, including 3+0 white spruce after frozen storage, with fresh-lifted controls planted on each planting date for comparison. In all plantings, the earliest (2 May) lifting gave highest average second-year survival in all species. In another study, Mullin (1978)<ref name="mull5" /> found that outplantings of frozen-stored 3+0 white spruce were consistently successful to the end of July only with the earliest-lifted (25 April) stock. Sutton (1982)<ref name="Sutton 1982">Sutton, R.F. 1982. "Plantation establishment in the boreal forest: planting [[season extension]]." Can. Dep. Environ., Can. For. Serv., Sault Ste. Marie ON, Inf. Rep. O-X-344. 129 p.</ref> also used 3+0 white spruce in outplanting every 2 weeks from the end of June through the growing season in 3 successive years on a variety of sites in northern Ontario. Despite variation in planting stock, poor storage environments and adverse weather, 4th-year results showed a consistent pattern of reasonable survival and growth rates among trees planted through July, with a rapid decline in performance of trees planted thereafter. Overwinter storage of stock has also been employed. It has the advantage of lifting stock at the end of the growing season when physiological processes are invoking natural dormancy.<ref name="mull7">Mullin, R.E.; Parker, J.D. 1976. "Provisional guidelines for fall lifting for frozen overwinter storage of nursery stock." For. Chron. 52(1):22–25.</ref>

Natural refrigerated overwinter storage has been used in root cellars and snow caches. Using natural refrigeration in root cellar storage, Jorgensen and Stanek (1962)<ref name="jorg">Jorgensen, E.; Stanek, W.K.L. 1962. "Overwinter storage of coniferous seedlings as a means of preventing late frost damage." For. Chron. 38(2):192–202.</ref> kept 3+0 and 2+2 white spruce in dormant condition for 6 months without apparent detriment to performance after outplanting. Moreover, the stock was highly resistant to spring frost damage. Natural cold storage for overwintering 3+0 and 2+2 white spruce was also used by Mullin (1966).<ref name="mull1">Mullin, R.E. 1966. "Overwinter storage of baled nursery stock in northern Ontario." Commonw. For. Rev. 45(3):224–230.</ref> Unlike Jorgensen and Stanek's (1962)<ref name="jorg" /> stock, which was raised 550&nbsp;km to the south of where it was planted, Mullin's stock was raised in a nursery at about the same latitude as the planting site; the stock experienced inside-bale temperatures down to -15&nbsp;°C in mid-winter, but still showed first- and second-year survival rates of 85.9% and 65.9%, respectively, compared with 91.4% and 76.2%, respectively, for fresh-lifted stock. However, Mullin's stored stock was much more damaged by spring frost than was fresh-lifted stock and it "showed a reduction in vigour as measured in terms of survival, susceptibility to damage and growth".