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I'm planning to tap a maple tree in my yard this year and have hand carved a spile from a small piece of cherry I had in the garage. Most online materials I've found recommend drilling a hole 5/16" - 7/16" depending on the spile size. In this case the spile diameter is around 1/2" and I'd rather not thin it down any more.

My question is, will the 1/2" diameter hole significantly increase the risk of injury to the tree or is this still within the realm of what would be considered a reasonable size that a healthy tree can sustain?

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  • As nice as the hand carved spile looks and feels, I took Ecnerwal's advice on a second tree and thought I'd share it here. I used 1/4" polyethylene tubing (this is quality food grade stuff normally used for water filtration systems) and wrapped a bit of plumbers tape around it to snugg it into a 1/4" tap hole. Works great and so far is outperforming the larger wooden spile. Total cost: $0.10
    – Eaten by a Grue
    Commented Mar 9, 2015 at 21:21
  • The commercial spiles are 20-40 cents in bulk - a little more in small quantities as opposed to 100 at a time.
    – Ecnerwal
    Commented Mar 9, 2015 at 23:00

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All tap holes injure maple trees.

Extensive research into spile-hole damage (with an eye to reducing it, and preserving productivity) is precisely what has driven the downsizing of spiles. Few producers (essentially no serious ones) use even the 7/16 size currently. The area of damaged wood (which cannot produce sap in the future, until the tree has overgrown it with adequate thickness of new wood to support a new spile hole) is significantly less with a smaller hole, and the amount of sap collected is substantially the same regardless of hole size.

In this particular study, comparing 5/16 and 7/16 spiles, the 5/16 spile had only 59% of the damaged area as the 7/16 spile (for gravity - i.e. bucket or bag collection, as opposed to under vacuum where it was generally less, but not as much less.)

http://www.uvm.edu/~pmrc/smallspout.pdf

More recent research also indicates that using a new (washing, boiling, alcohol or even autoclaving do not suffice - new) spile each year increases sap yields, as there is some type of EXTREMELY persistent biofilm that resist all the mentioned treatments and lead to the tree blocking off the hole early. As such, purchasing a 10-pack of modern small spiles and using, then discarding, one each year for 10 years would be both kinder to your tree and more productive for your sap collection than using your hand-carved spile.

Mentioned in this page (as unpublished and personal communication - I have also had the above specifics that don't work confirmed in personal communication with Dr. Perkins, who stated that they had, in fact tried all of them without success):

http://www.uvm.edu/~pmrc/check-valve.pdf

Also, don't overdrill the depth, for the same reason:

https://www.uvm.edu/~pmrc/wilmot_deep.pdf

This shows a nice visual of a taphole and a section of tree above the taphole (taphole damage extends above and below the actual taphole for some distance)

https://www.uvm.edu/~pmrc/wilmot_taphole.pdf

This image from northernwoodlands.org shows a board with a visible taphole and several visible stains (the tapered dark areas.) You can see that a good deal of new white wood has grown over the two stains to the left of the hole as the tree continued to grow. Even the stain with the hole has been grown over, but it was some years (and tree-growth rings) later than the other two. As a general guide, you never want to tap directly above or below a visible old tap hole. taphole in board from northernwoodlands

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  • In addition, you are supposed to stagger your tapping years on each tree, and give it a chance to rest and rebuild. Tapping a maple every year will eventually kill it. Also, there are two maples that are suitable for tapping, the sugar maple (identified by it's brilliant sunset orange foliage in the fall), and the black maple. Other maples make very inferior syrup.
    – Escoce
    Commented Mar 10, 2015 at 15:57
  • @Escoce that is not supported by research or practice. Guidelines and practices are based on tapping every year, and so long as the minimum size of tree and number of taps are observed, tapping every year has no detrimental effects. Other than a potential need to boil off more water as they make less concentrated sap, there's no issue with using other maple varieties, either; many producers do so quite successfully.
    – Ecnerwal
    Commented Mar 10, 2015 at 17:00
  • That's true, but other maples produce lower grades of syrup, that's where those lower grades come from, due to the extra cooking as you explained.
    – Escoce
    Commented Mar 10, 2015 at 17:09
  • There is no direct correlation between grade and tree species - the same tree will produce different grades over the course of a season's production, and operator skill and equipment used also affect grading (which is primarily based on color, not flavor or inherent quality, other than egregious off-flavors.)
    – Ecnerwal
    Commented Mar 10, 2015 at 17:44

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