While at the Washington State Hort Association meeting last Dec., I read an article entitled “Reasons for Tree Staking” by R.L. Norton, Extension Associate in the Cornell University Pomology Dept. The article made some points relevant to growing fruit trees in Alaska.
Dr. Norton mentioned that when trees are staked, better growth is noted. “The shaking effect of wind has always been a major factor in reducing tree growth.” Trees allowed to whip back and forth in the wind will develop a greater trunk girth, but the carbohydrates used to increase trunk girth must be diverted from producing shoot growth or setting flower buds. The stake can be used not only to support the central leader, but also as a point to which drooping limbs can be tied up, and upright limbs tied down. Heavy fruit loads can cause bending stress in the central leader and scaffold branches. This stress causes ethylene concentrations inside the tree to rise, which depresses growth. Staking can eliminate this stress.
After heavy rains, strong winds whipping around an unstaked tree can produce a funnel-shaped depression in the soil around the trunk, a problem especially severe in silt or clay soils. When water collects in the funnel, it can later freeze and form ice. Water and ice standing around the tree can enhance the development of phytophthora root rot.
In addition to Dr. Norton’s observations, I have some thoughts on staking. The staking of trees will allow the tree to develop roots without them being disturbed or broken by wind action. Furthermore, the very principle of espaliering fruit trees involves not only training and positioning the limbs, but also keeping them rigid. The result is that espaliered trees generally bear at a younger age than freestanding trees.
In late December 1989, I toured the Sundquist Orchard which adjoins that of Dan Whitney. Gene Cox, the orchard foreman showed me that the pear trees grown with support for the central leader were noticeably taller and broader than those grown without support. He also found that the older supported trees were bearing flower buds and fruit at a younger age than the unsupported ones.
Dr Curt Rom, formerly of the WSU Dept, of Horticulture, began a staking experiment in the WSU Orchard in 1988 with 4 different apple varieties grafted onto “Mark” rootstocks. The trees were given three types of support: none, support for 3 ft, and support for 6 ft of the central leader. During the second growing season, fruit yields in kg were as follows:
0 3’ 6’
‘Nicobel Jonagold’ 9 9.6 16.1
‘Early Red One’ 0 0 0.1
‘Imperial Gala’ 0.1 0.6 1.6
‘Ultragold’ 15.4 15.6 16.5
Combining all these numbers together, one finds that the fully staked (6 ft) trees produced 40% more fruit than the unstaked (0) ones.
Gene favors aluminum electrical conduit for staking. It is lightweight, cheap, and easily obtained. He binds the conduit to the leeward side of the tree trunk with horticultural tape and supports the bottom 6 ft of central leader. Unlike wooden 2´2’s, the conduit will not chafe against the bark. Furthermore, it is rigid and easily inserted between roots and in the root ball.