Detailed Explanation of Key Technical Points for Transplanting Large Schrenk Spruce Seedlings

Schrenk spruce (Picea schrenkiana) is a tree species unique to the Tianshan mountain forests. It is an evergreen tree with needle-shaped, slightly curved leaves. The cones are oblong-elliptical and brown. Seedlings are shade-tolerant but intolerant of scorching sun, frost, and drought. They typically regenerate well under broadleaf forests and grow vigorously under moderately moist conditions and full light. The Schrenk spruce has a narrow, elongated crown, a thick, straight trunk, and a rugged, upright form.

With the improvement of the social economy and people's living standards, urban greening construction has received increasing attention. With its graceful, upright form and evergreen lush foliage, the Schrenk spruce has become a favorite among greening trees. However, because of its relatively high requirements for growth conditions such as altitude, temperature, humidity, and light, the survival rate of transplanted Schrenk spruce (the Schrenk spruce referred to in this article are all large seedlings with a diameter at breast height of 8 cm to 15 cm and a tree height of 2 m to 5 m) has long been unsatisfactory. The author has long been engaged in seedling cultivation and transplant management of Schrenk spruce. Through long-term experimentation and exploration, a set of scientific and effective transplanting methods has been summarized. Through practice, the transplant survival rate can reach over 90%.

I. Selecting the Transplanting Season and Weather

Schrenk spruce should be transplanted during the tree's dormant period. Generally, spring is the suitable transplanting period in northern regions. Experiments have shown that transplanting after the first snow of winter can also achieve a relatively high survival rate. After transplanting, Schrenk spruce grows vigorously and displays an excellent landscape effect. It should be noted that spruce should not be transplanted in areas whose longitude and latitude deviate greatly from the original growing site, otherwise survival is difficult. In addition, planting is best done in windless weather, preferably before evening.

II. Seedling Treatment Before Transplanting

Three to four days before spring transplanting, irrigate the spruce to be transplanted, following the principle of watering thoroughly and sufficiently so that the root system absorbs water fully. When transplanting in winter, if the soil ball lacks water and is loose, irrigation can also be carried out in advance before the soil freezes. If no irrigation was done beforehand and the soil has not frozen solidly, water should be splashed onto the soil ball to promote freezing.

Before transplanting, mark the south side of the seedling so that it can be placed into the pit in its original orientation during planting. This can effectively prevent possible summer sunscald (on the originally shaded bark) and winter freeze injury (on the originally sunny dry bark), and shorten the adaptation period. Remove diseased and pest-infested branches, dead branches, and dry skirt branches, and properly prune excessively dense and overlapping branches.

III. Preparation of the Transplanting Hole

Dig the planting hole one week before transplanting. The diameter of the planting hole should be 40 cm to 50 cm wider than the diameter of the large seedling's soil ball, and the depth should exceed the height of the soil ball by about 15 cm. When digging the hole, separate the topsoil from the middle and bottom soil, and clean out impurities in the soil (old gravel, bricks, tile fragments, grass roots, etc.). If the soil quality is poor, the soil must be replaced. If conditions permit, it is best to use original soil and apply about 10 kg of high-quality organic fertilizer at the bottom of the hole. When conditions allow, nutrient soil should be prepared in advance for later use. The specific method is: by weight ratio, take 50% sawdust, 30% plant ash, and 20% mature soil, mix thoroughly, and let stand for 2 to 3 days to promote high-temperature fermentation, then add an appropriate amount of chemical fertilizer as needed. For winter transplanting, the hole can be dug before the soil freezes, backfilled with loose soil after digging, and dug open again at planting time.

IV. Digging the Soil Ball and Packaging

When transplanting spruce, the soil ball should be made as large as possible. Planting with soil can ensure the integrity of the root system within the soil ball, keep the large seedling in close contact with the soil, and benefit survival and growth after planting. Generally, dig a round soil ball about 8 times the diameter at breast height of the seedling, retain the root system as much as possible, and prune and trim diseased roots, dead roots, and longer fibrous roots. The soil ball is packaged with non-woven fabric and nylon rope. When digging the soil ball in frozen soil, packaging is not necessary after the soil ball is dug. If the soil is dry and the frozen soil is not deep, water can be applied gradually until a complete frozen soil ball is dug out.

V. Loading and Transportation

When loading the seedlings onto the vehicle, the crown should face the rear of the vehicle and the roots should be near the driver's cab. Avoid damaging the tree body and root soil ball during loading, transportation, and unloading. For long-distance transportation, attention should also be paid to water spraying, shading, and waterproofing. In heavy rain, prevent the soil ball from being washed apart.

VI. Planting

First place the planting soil mixed with fertilizer into the bottom of the previously dug hole, then carefully place the soil ball into the hole so that its orientation remains consistent with the original orientation. The planting depth should be such that after the new soil settles, the original soil mark at the base of the large seedling is level with the ground or 3 cm to 5 cm below the ground surface. If planted too shallow, the root system is prone to drying out and losing water from wind and sun exposure. If planted too deep, the tree grows poorly and may even cause root suffocation and death. Backfill soil in layers and firm it (nutrient soil should also be spread around the soil ball and on the surface). For spring transplanting, when the backfill soil reaches 2/3 of the soil ball height, water once so that the backfill soil absorbs water fully. After the water has seeped through, fill the soil to the top (do not firm it at this time). Finally, build a berm around the outer edge and water a second time, thoroughly and sufficiently. After watering and settling, observe whether the soil around the trunk has sunk or cracked. If these phenomena occur, add soil promptly to fill and level it.