Growth characteristics of short-stem apple trees

Firstly, spur-type apple trees are generally more compact and dwarf in stature. Mature trees typically reach a height of about 3 meters, with a crown diameter of 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 around 825 to 1,335 trees per hectare, which is two to three times the density of conventional apple plantings. This makes them ideal for high-density orchards where space is limited.

Secondly, the growth habit of spur-type apple trees is usually upright, with a narrow angle between the main branches and the trunk. Most varieties, such as Yanqing, Smoke Red, and New Red Star, have a base branch angle ranging from 35 to 45 degrees, making them less open than other types. To encourage proper development, pruning techniques such as support, spreading, and drooping should be used to widen the main branches and improve light penetration.

Thirdly, these trees have a high bud dormancy rate and low branching efficiency. For example, the germination rate of tobacco variety is 74%, which is 19.4% higher than that of green banana. Similarly, red tobacco has a 71.8% germination rate, 6.5% higher than red banana. The short-branched type also shows better dwarfing, with 79.4% of the trees being dwarf, 17.3% higher than red banana. One notable feature is that the buds of spur-type apples can germinate in the same year they form, allowing for quick growth and early fruiting when planted as seedlings or saplings.

Spur-type apple trees have low branching power. After one-year-old branches are pruned, the average number of long shoots per branch is only 1.5 to 2.1, which is significantly lower than that of green banana (around 2.3). However, they produce a large number of short branches, with a short-branch coefficient often above 50%. A 4-year-old sapling of young tobacco may have a short-branch rate of 91.8% and a short-branch coefficient of 65, far exceeding that of green banana. This means that young spur-type trees need careful pruning to promote branching and develop a strong framework for future fruiting.

Fourthly, these trees tend to flower early and produce fruit on short branches. Flower buds form quickly, leading to an earlier start of fruiting. For instance, grafted seedlings (semi-mature) can begin bearing fruit within 2 to 3 years and fully fruit by the fourth year—two to three years earlier than standard apple trees. The fruiting pattern is dominated by short fruiting branches, which contain many flower buds. This results in a high fruit set rate, with some varieties achieving up to 92.7% flowering and over 60% fruit setting. As a result, these trees can reach full production in 6 to 7 years, about five to six years earlier than normal types.

However, after heavy fruiting, the growth of the tree may decline, and the phenomenon of alternate bearing (large and small crops each year) may occur. Therefore, it's important to manage the tree carefully during the early stages by increasing the number of branches and expanding the canopy to enhance photosynthesis and support early fruiting. Once the tree starts producing, strict control of flower buds is necessary to avoid overbearing, which can lead to smaller fruits and reduced yields in the following year.

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