| The Ultra-northern pecan, northern pecan and the southern pecan are very different from each other in hardiness, nut size, and length of season required to ripen the nuts. The ultra-northern pecans suited to the growing conditions in Ontario are not only from the northern tip of the growing range of the northern pecan, but also from the earliest ripening trees from those areas.
A distribution map of the native range covers much of the Mississippi Valley, with fingers of distribution extending northward along the Mississippi River and major tributaries. It is in this area where the hardiest short season pecans are found. Though many of the pecans from this region are hardy in Ontario, it is the earliest ripening selections from there that get enough cooling degree days, to ripen in Ontario (zone 6-7).
The climate in the native pecan regions differed from the Ontario climate in three important ways:
1) The length of the growing season. This is calculated by the number of days above 28°F. (Pecan freezes at 26°F.) Zone 6-7 in Ontario averages 160-180 growing degree days. The commercial pecans in the native range require at least 180 frost free days. Only the southernmost tip of Ontario near Windsor meets this requirement.
2) The formula to calculate the # of cooling degree days is: (max temp + min temp)/2 - 65° Fahrenheit).
Zone 6-7 in Ontario averages about 600-700 cooling degree days. This is well short of the 1000 cooling degree days that most pecans require. That is the main reason that our pecan explorers (John Gordon, Gary Fernald and others) searched out the earliest ripening pecans near the northern end of the pecan distribution range. Pecans that drop in September in the native range have a good chance of ripening in zone 6-7 Ontario by late October. These early ripening pecans are renamed "ultra-northern" pecans to differentiate them from the "northern" pecans that grow successfully in southern Kansas but won't ripen in Ontario.
3) To ripen nuts, pecans require lots of summer heat including warm nights, something that is lacking in some zone 5 & 6 maritime climates.
Some of these early ripening ultra-northern pecans are small, about the size of a native shagbark hickory or large hazelnut, but they have the fine flavor for which pecan is known. Selections that were the earliest to ripen, were brought back in the 1980's from Green Island, Iowa by John Gordon, and other nut tree SONG member explorers. Some larger size nuts were discovered matching the normal native nuts in size but they require a longer season to ripen. These selections from the wild have become the selection base for promising new trees.
A few of the earliest ripening trees are propagated as grafted trees. These named selections are: 'Snaps', 'Carlson 3', 'Lucas' and 'Deerstand'. They have so far proved to be perfectly hardy and productive. The larger nut cultivars need a warm September-October season to properly fill the nuts.
Pecan trees planted from seed tend to take about 10 to 15 years to begin to bear, while grafted trees will bear in 5 to 10 years. As with most of the nut trees, the hickories and pecans will take two or more trees to set nuts.
Pecans like hickory trees are known for their long taproots. In transplanting bare root seedlings, the trees need at least a 50 cm long root. Grafted pecans from the Grimo Nut Nursery are grown in special long pots and so when they are out planted, the transplant shock is minimized.
Pecan weevils do not move far from their established trees, so it reduces the chance of them spreading to your trees, provided there are no weevils nearby. It is not practical for a homeowner to spray the canopy of large pecan trees in order to stop weevil feeding and egg laying. However, cultural controls significantly help control this late season pest. Prematurely fallen pecan nuts should be picked up weekly and discarded. This practice helps break the cycle by preventing larvae from entering the soil and completing their life cycle.
Research has revealed that 5% of adult weevils walk up the trunk, 77% fly onto the trunk to a height of six to eight feet, and 15% fly directly into the lower tree canopy. Once they reach the canopy, they begin feeding, find a mate, and lay eggs. Removal of low-hanging limbs reduces the ability of the adult weevils to reach the canopy. Tree limbs should be trimmed to six or eight feet above the ground.
By encircling the trunks with a sticky coating at a height of eight feet, the majority of the adult weevils will be trapped before reaching the canopy. Tanglefoot is an extremely sticky paste made from natural gum resins, castor oil and wax, and can be used on pecan trees for pecan weevil trapping. It is normally applied in a three inch wide band around the tree. For easy removal at the end of the season, apply Tanglefoot onto Tangle Guard or another banding material, such as duct tape.
For commercial plantings refer to Publication 360, the Ontario spray calendar chapter 7, Tree Nuts.
The pecan is a still largely experimental in Ontario. Continued work needs to be done to find new hardy ultra-northern selections with larger nuts that will ripen in Ontario. By crossing the best early pecans we have with larger northern pecans, new selections can be possible. SONG is always on the lookout for new cultivars.