Hilling Up for Vigour

One of the perennial struggles an apple grower is faced with is how to keep trees from becoming too growthy and vigorous. Trees of most cultivars and their rootstocks left to their own ways will for the most part have a tendency to put on too much growth with an inevitable drop in fruit quality and crop volume in the process. Over the years, strategies for controlling tree vigour have varied considerably. They include root pruning, summer pruning, withholding of nutrients, shallow planting and the use of size controlling rootstocks just to highlight a few.

Just to complicate the problem even more, some cultivars are not known to be not nearly vigorous enough particularly if they are budded to a more size controlling rootstock like B9 or M9 and planted fairly shallow.

Most of the apple trees planted in Ontario for the last two decades have been planted with bud union well above the soil line. This strategy does not work for all cultivar/ rootstock combinations. The lack of vigour of the Honeycrisp cultivar has been known for some time and trees planted too shallow on size controlling rootstocks can result in plantings that are too slow to establish in some situations.

One method that may help with this problem is to hill around the base of the tree with soil. The idea here is to have greater root volume and to give the tree more push where a planting appears to be slow coming along. Figure 1 shows soil hilling of Honeycrisp on M9 for this very reason. The desired growth response may take a couple of years but may be entirely worth the effort.

Figure 1. Honeycrisp/M9 with soil hilling to improve tree vigour

For more information:
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