Growth characteristics of short-stem apple trees

Firstly, spur-type apple trees are more compact, with a dwarf growth habit. Mature trees typically reach a height of about 3 meters, with a crown diameter ranging from 3 to 3.5 meters—roughly 4/5 the height and 2/3 the width of standard apple trees. This size is similar to that of medium-sized rootstocks like M7 or MM106. The planting density is higher, with between 825 to 1,335 trees per hectare—two to three times that of conventional apple trees. This allows for more efficient use of space and better light penetration.

Secondly, these trees have an upright growth pattern, with main branches that open at a narrow angle. Varieties such as Yanqing, Smoke Red, and New Red Star are commonly upright, with base angles typically between 35 to 45 degrees. This makes it essential to use techniques like support, spreading, or bending during pruning to improve branch angles and promote better canopy development.

Thirdly, spur-type apples have a high bud germination rate but low branching efficiency. For example, the germination rate of tobacco variety is 74%, which is 19.4% higher than green banana. Similarly, red tobacco has a 71.8% germination rate, surpassing red banana by 6.5%. Additionally, 79.4% of the trees are good dwarfs, 17.3% higher than red banana. Buds on these trees can germinate in the same year they form, making it easier to produce secondary shoots after planting. This trait is beneficial for summer pruning, shaping the tree, expanding the canopy quickly, and achieving early fruiting.

Moreover, the branching power of short-stemmed apple trees is relatively low. After one-year-old branches are cut back, the average number of long shoots produced is around 1.5 to 1.8, which is only 64% of that seen in green banana. For Smoke Red, it's 2.1, still just 65.6% of red banana. However, these trees have a higher number of short branches, with a short-branch coefficient usually above 50%. A four-year-old young tobacco sapling, for instance, had a short-branch rate of 91.8% and a short-branch coefficient of 65, significantly higher than green banana. Proper pruning is necessary to encourage more branching, which helps develop fruiting branches and ensures stable, high yields over time.

Lastly, spur-type apple trees tend to flower earlier, with flower buds forming easily in the same year they are developed. This leads to early fruiting. According to surveys, grafted seedlings (semi-mature) typically start producing fruit within 2 to 3 years, and full production is achieved in 4 years—about 2 to 3 years earlier than short-branched varieties. These trees are dominated by short fruiting branches, with fewer medium or long fruiting branches. They have a high flower bud formation rate and fruit set, with some varieties reaching up to 92.7% flowering and over 60% fruit set. Once they begin bearing fruit, their yield increases rapidly, entering full production in 6 to 7 years—about 5 to 6 years earlier than normal types. However, heavy fruiting can reduce tree vigor and lead to alternate bearing. Therefore, careful management is needed: increasing branch numbers and expanding the canopy early to boost photosynthesis and achieve early high yields, while controlling flower buds after heavy fruiting to avoid excessive results and maintain consistent production.

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