1. Introduction
Adapting to climate variability means that producers are foregoing traditional tapping dates in favour of using the weather to make decisions. Significant sap flow events can be missed where producers are not prepared to collect sap.
The timing of the season does not predetermine the total volume or quality of syrup produced by each region. We will know the syrup crop results when the season is finished.
Earliest areas in Southwestern Ontario often begin tapping 2-3 weeks ahead of late-season areas in northern and northeastern regions. Tapping in earliest areas generally begins sometime after January depending on the weather. Good sap flow conditions can occur any time after early February in Southwestern Ontario.
Large operations can require several weeks to complete tapping in order to collect early sap flows and must plan accordingly.
2. Temperatures
- After January, watch long-range weather forecasts to determine when tapping can begin
- To predict sap flow events, watch for several consecutive days of thawing daytime temperatures with freezing nighttime temperatures of -5°C to -8°C
- Daily freeze thaw cycles are necessary to make sap flow and recharge the maple trees for consecutive release of sap
- Drilling tap holes and setting spiles into trees should only be done when the temperature of the wood is above -5°C to prevent splitting of the bark and wood at the tap hole
- The exception to this is very large producers, who will need to tap early
- When night-time temperatures are very cold (e.g. – 15 ⁰C or colder), maple trees will require several days of cool or warm conditions to thaw the bark and sapwood enough to allow safe tapping
- Wait until nighttime temperatures are above -5°C for a few days so trees can thaw
- Even gently installing spouts into tap holes, during very cold weather leads to bark splitting above and below the tap hole
- Larger syrup producers who have thousands of taps to install can consider increasing the size of their trained tapping crews, versus tapping when trees are too frozen and risk splitting the bark
- When sugarbushes are sheltered from the wind, increasing March sunlight can sometimes induce sap flow prevent sap from freezing in the lines
- Consider planting windbreaks around the perimeter of their sugar bush this coming spring or fall to help encourage earlier sap flow
- Once exposed and the trunk-root interface has thawed, sap will begin to flow more readily with each sap flow event
2a. Bark splitting
- Split bark will often cause a poor seal around spouts and the inner tap hole, and can severely affect vacuum pressures
- Bark splitting may not appear right away when taps are installed
- Split wood requires the tree to spend extra energy healing during spring and summer
Two growing seasons have passed since this tap hole was drilled into a sugar maple tree that was too frozen for tapping (left photo: one year, right photo: two years). Splitting of bark due to improper tapping causes significant injury and can open up the tree to decay organisms.
On a healthy sugar maple and with proper tapping practices, this tap hole has healed over with new sapwood after one growing season.
With splitting, vacuum in sap tubing can be reduced due to a poor spile-to-tree seal, and sap can leak down the trunk instead of into the spile.
3. Atmospheric Pressure
When you are watching the long range weather forecast for sap flow events, also keep an eye on the barometer to give you an idea of sap volume to expect.
- Low or falling atmospheric pressure = higher volumes of sap flow during freeze & thaw temperatures
- Due to a larger pressure difference between the inner tree and outside air
- High or rising pressure = low volumes of sap
- Due to lower pressure difference between the inner tree and outside air
- Vacuum tubing creates an artificial low external pressure even when surrounding air pressures are too high for good sap flow
- Without vacuum tubing, ideal thawing conditions can sometimes yield little sap where atmospheric pressure remains higher than the internal tree pressure.
4. Collection Method
4a. Vacuum tubing
- Used in conjunction with small-diameter spouts, can help prevent early drying of tap holes
- Useful for tapping ahead of normal dates
- Early tapping is now considered normal for the commercial vacuum collection industry
4b. Bucket collection
- Tap holes exposed to air, which can cause them to prematurely dry up when they’re installed too early
- Delay tapping until conditions are favourable
The written and graphic content in these pages was originally created by Todd Leuty (previous Agroforestry Specialist), and edited by Jenny Liu (Maple, Tree Nut, and Agroforestry Specialist).