The first tapping of sugar bushes has begun in early southwest regions of the province where thawing temperatures occurred prior to the current deep cold on March 5 and 6. Later regions including central Ontario, north and northeastern areas will have temperatures suitable for tapping maple trees over the coming weekend and next week as cold winter temperatures begin to subside and thawing temperatures are more frequent.
Where night-time temperatures drop to very cold freezing levels, such as – 15 ⁰C or colder, maple trees will require several days of cool or warm conditions following the deep freeze, to thaw the bark and sapwood adequately to allow safe tapping.
Be patient and wait for thawed tapping conditions. Larger syrup producers who have thousands of taps to install who are concerned about missing early sap flows can consider increasing the size of their trained tapping crews. A larger crew can accomplish more tapping over a shorter window of opportunity, versus tapping when trees are too frozen and risk splitting the bark.
Preserving sapwood
Each tap hole that is drilled into a maple tree will result in the formation of a vertical stain column in the sapwood that is made naturally by the tree as a wound response. Researchers refer to this stain column as non-conductive wood, that is, sapwood that no longer conducts sap through it. Stain columns act as plugs to sap flow.
Photo 1 & 2. Left photo, two parallel stain columns of non-conductive sapwood and corresponding tap holes. Right photo, two models of stain columns, or sap plugs, represent the approximate volume of good sapwood that is permanently removed from future sap flow.
Each tap hole generates approximately 20 to 30 cubic inches of non-conductive wood within the sapwood. Small drill bits (5\16th or 19/64th inch) will generate significantly less non-conductive wood than larger old-fashion tapping bits (7/16t h inch). Tapping crews must visualise under the bark where these stain columns are, to avoid drilling into stained wood that will not conduct sap.
When are sap plugs formed? As sap collection is finished for the year and the trees begin growth in spring, the trees block any leaking sap from wounds by plugging up surrounding fibre cells and cell tissue that conducts sap near the damage. Trees can stop leaking sap similar to our ability to stop the flow of blood from minor injuries. The stain column enables the tree to maintain internal sap pressure during spring and summer to enable the canopy to form unhindered.
Photo 3 & 4. Non-conductive wood forms a little deeper than the depth of the drill bit. Limiting tap hole depth to no more than 2 inches helps reduce the stain column and less risk of drilling into an old deeper stain column having off-flavour sap. Right photo, stain columns become buried deeper into the trunk with annual growth. The healthier the tree, the faster new sapwood will accumulate over top of old tap holes.
Photo 5. The tapping area on each maple tree should occupy approximately 30 to 36 inches (75 – 90 cm) of trunk above the lateral sap line, for all trees having attained the minimum tapping diameter of 10+ inches (26+ cm) at chest height. This pictured tap with drop line is placed at the upper most location to show height, but could be placed anywhere in the tapping area, utilizing all sides of the tree. In a healthy sugar bush, this will ensure all non-conductive wood is spread out adequately, to always have clear sapwood for future tapping.
Measuring syrup density
Accurately measuring the density of finished maple syrup has received considerable attention recently in the international maple syrup industry. Ensuring that maple syrup has reached the minimum allowable density of 66 ⁰Brix will produce quality syrup and will also significantly reduce the occurrence of spoilage mould contaminating syrup. Syrup density lower than 66 ⁰Brix provides more available water for spoilage organisms to germinate and grow in syrup, particularly where hot packing practices are not adequately killing spoilage moulds during bottling.
All devices that are used to measure syrup density should be calibrated where possible, or tested for accuracy, before each batch of syrup is processed. Density instruments include thermometers, digital and handheld refractometers, hydrotherms and hydrometers. Start the processing season by re-reading the operating instructions to be confident you are using the instrument properly, calibrating properly and making corrections for temperature when required.
The following is the procedure for zero-setting and verifying a Misco density reader. Calibration procedures may vary for other brands of digital readers. Always refer to the operators manual for proper use and care.
Photo 6 & 7. Portable electronic refractometers are calibrated at the factory, however will need to be reset to zero prior to each batch of syrup to maintain accurate density readings. Zero-setting the unit is simple and quick. You need distilled water, preferably lab-grade tissue paper that won’t scratch the glass sample dish, new plastic hollow stir sticks or thin straws, verification fluid of known density, e.g. ACER 66 ⁰Brix verification fluid, and finally, the operators instruction manual.
Photo 8 & 9. Thoroughly wash and clean the sample dish with distilled water to remove all traces of sugar from previous syrup samples. Places 2 or 3 drops of distilled water onto the sample dish. Toggle the Menu button until the display shows ‘Set Zero?’. Press ‘Go’ to set the sample of distilled water to a density of zero, clean off the water sample.
Photo 10 & 11. To verify that the unit has been zeroed and will measure syrup density accurately, place 2 or 3 drops of known verification liquid in the sample dish and measure the density at room temperature. The known density of the verification liquid (+/- 0.1 at 20 ⁰C) should appear on the display when measured, in this example 66.0 ⁰Brix. If not, repeat washing with distilled water, repeat zero-set, then verify again. If the density is still inaccurate, the instrument may need to be returned to the manufacturer for factory-recalibration.
Growing sugar maple seedlings
Seeds of native sugar maples can be collected and germinated into seedlings quite easily. It is best to collect seeds from nearby healthy maple trees in the fall and plant the resulting seedlings locally to help preserve the natural genetic resources of local forests.
Photo 12 & 13. Dry seeds collected in the fall can be stored cool and dry in labelled containers. Early March is a good time to stratify sugar maple seeds before spring planting time. Maple seeds will not germinate unless they receive an adequate cold treatment while in a moistened conditioned. Right photo, each seed is a mini-tree in a neat little package, waiting for an opportunity to grow.
Photo 14 & 15. To break seed dormancy, soak the dry seeds in clean water for 24 hours at room temperature, then drain the excess water.
Photo 16 & 17. Place the moistened seeds onto a wet paper towel in a container. A few holes in the lid will allow some air circulation to reduce the incidence of mould. Place the container in a refrigerator, garage or shed that will remain at approximately 0 to 3 ⁰C for a period of six to eight weeks. Avoid freezing the moist seeds.
The cold treatment will ‘stratify’ the seeds, that is, will overcome dormancy to allow the seeds to germinate in soil and grow into seedlings. Watch the seeds to see when the tiny white root appears. Place seed in potting soil when the root is about 1/4 inch long about one inch deep, taking care not to damage the delicate root. Not all seeds will germinate. Keep the soil moist and the new seedlings will emerge after a few days. Place in shaded light.
Alternatively, sugar maple seeds can be stratified naturally outdoors by planting the seeds directly into tilled garden soil about one inch deep. A layer of shredded leaf mulch approximately 1 inch thick will insulate the seeds from extreme winter cold, help maintain soil moisture and improve seed survival to germination the following spring.
Keep in mind that new sugar maple seedlings and young sugar maple trees are not adapted to full sun and windy exposed areas. Shade and shelter are needed when starting sugar maple trees from seed.