Tapping maple trees to make maple syrup is more than simply drilling a hole, hammering in a spout, and hanging a bucket. In this article, I start with a discussion of why sap flows in trees because it is important to know if your tapping process is working well. I briefly discuss the types of spouts and tools. Then I dive into selecting the best trees, knowing when to tap, how many taps to put in each tree, and finally, how to drill the perfect taphole.
- Why sap flows in maple trees
- Maple spouts
- Tapping tools
- Number of taps per maple tree
- Bigger trees give more sap
- When to tap the trees
- Where to tap the trees
- Tapping the maple trees
- Old growth maple trees
This comprehensive guide will give you a solid background before you head out into the woods. There is nothing better than hands-on education in the field and I encourage you to watch your trees and their production closely. Try different equipment and different methods. Chat with other sugarmakers to learn from their experience. Most importantly, get out in the woods and have fun. Happy tapping.
Why Sap Flows in Maple Trees
Sap flows up and down maple trees due to different types of forces: pressure differentials within the tree, capillary action, cohesion, and gravity. The force of gravity pulls the sap down the tree when it is not frozen. Cohesion is the tendency for water molecules to stick to each other, so that one molecule gets pulled by its neighbors. Capillary action is the process that allows water molecules to seep through tight spaces, as it does between cells in a tree.
The pressure differential within a tree is where is gets fascinating. This force is driven by freeze and thaw cycles, and is the largest driver determining the volume of sap flow on a given day. Sap generally flows the most when nights are in the 20s and the days are in the 40s degrees Fahrenheit. It is that freeze – thaw cycle that acts as the pump to get the sap flowing up and down the tree, and eventually out the spout.
The cells of the maple tree contain some moisture and some gases. When the temperature drops below freezing at night, ice crystals form inside the cells which creates a rapid drop in humidity within the cell. The different humidity levels in adjacent cells then creates a pulling force that pulls sap molecules into the neighboring cells through capillary action. The new moisture freezes, and the cycle continues with the pulling force spreading throughout the entire tree. The result is lower pressure in the branches which pulls the sap up from the roots as the branches freeze.
The amount of sap that will be pulled into the tree branches depends on how this freezing process occurs. It is best if the temperatures drop relatively slowly and consistently. If there is a hard and fast freeze, then the sap will all be locked in the roots and it will not be able to move up into the trunk and branches.
Once the tree becomes loaded with sap, it freezes in location. We then wait for the next warm day for the tree to warm. Once the sap thaws, gravity will pull the sap back down the tree through the xylem cells. The sap generally starts out with a fast rush when it first thaws. The flow may then slow as the sap gets pulled horizontally through the cells. The flow will continue until most of the sap has flowed back down into the roots, waiting for the next freeze cycle to start the process again.
Maple Spouts
Over time, there have been countless styles of maple spouts. Each variation of spout, also known as spiles or taps, was designed to optimize the flow of sap, make a leak-proof seal, and connect to the bucket or tubing line. Spouts for buckets typically include a hook to hang the bucket.
Most spouts today are used to connect to tubing, and they generally fall into three categories: angled, straight, or stub and adapter. The angled spouts are the most common. They are often attached to a drop-line, or short piece of tubing, which makes them convenient to tap into the tree and connect to the tubing system. The straight spouts can also be tapped into the tree, and the tubing is attached after the spout is in the tree. The straight spouts are less expensive, but they are difficult to reseat if required after the tubing has been attached. The stub and adapter spouts come in two pieces. The adapter part is tapped into the tree while the stub is attached to the dropline. The upfront cost is a little higher for the two-piece spouts, but the annual cleaning cost and labor is somewhat reduced by leaving the stub parts on the drop lines and only replacing the adapters.
When selecting spouts, there are often many colors to choose. There can be advantages and drawbacks to any of them. For example, black spouts can thaw quicker in the sunshine which may help the sap to start flow earlier in the day. On the other hand, since black heats up more it could increase microbial growth as the season progresses.
Some spouts have built-in check valves that prevent the sap from flowing back into the tree as the pressure inside the tree drops. This can help prevent tap holes from contamination with microbes which slows the process of the tap hole sealing back up. Check valve spouts are generally not recommended if you do not use a vacuum system because the valve resists the initial flow of the sap.
There are two sizes to be concerned with when selecting a spout. One is the size of the tap hole required. Matching the drill bit size to the spout is critical to minimize leaks. The second size to consider is the end of the spout that connects to the tubing. Most spouts are designed for 3/16” or 5/16” tubing systems. The smaller tubing is typically used in systems that implement natural vacuum as opposed to powered vacuum pumps.
Overall, there are many options to consider when it comes to maple spouts. The type of spout for your maple sugaring operation is an important consideration. Each has its pros and cons. It often comes down to personal preference when selecting the one that is right for you.
Tapping Tools
The tapping drill bit is critical. It must be exactly the right size. Some spouts specify a 19/64” bit, so you would not want to use a 5/16” bit because it is 1/64" too big. The tapping bits designed for maple trees have more cutting edges than standard wood bits; they are sharp and fast. The tapping bit is one tool you do not want to scrimp on, so make the investment and do not grab that old rusty drill bit out of your toolbox. The drill bits only last so long, so keep an eye on how well it cuts and plan to replace it as soon as it shows any sign of degradation. This likely means replacement every couple thousand tapholes.
Battery-operated drills are typically used for tapping maple trees. Do not use the old-school hand-crank drills. The problem with those is that it is impossible to drill a perfectly round hole because they wobble. It is imperative to have a round hole, so you need to be able to drill straight in and straight out. Make sure that the drill bit is centered in the drill chuck. A small misalignment could mean a day’s worth of oval holes that will tend to leak. There are tools that can be attached to your drill to help guide the bit and keep it from wobbling. Those can be expensive and heavy, but might be worth it if you are having trouble getting nice round holes.
You will also need a small hammer or mallet. Let me stress small. You also want a light hammer, so aluminum or wood can be a good option. When tapping in spouts, you need to be careful that you do not hammer too hard because that can split the tree which will create leaks. Some tapping hammers are sold with claws for scraping the bark away from the tap hole. I do not recommend doing that. That bark is the tree’s protection and the last thing we need to do is damage it.
Depending on how high up the tree you tap, you may need a spout removal tool which is essentially a rod with a notch in it for prying out the taps at the end of the season. These are generally only required when tapping on snow shoes with a few feet of snow. Once the snow melts in the spring you find the spout way up above your head in a place that you cannot reach. It has been many years since I remember that much snow, and I have never needed a spout removal tool.
Number of Taps per Maple Tree
The Vermont Current Use and the Organic guidelines allow for increasing numbers of taps based on the diameter of the tree. According to the guidelines, trees 9” or 10" to 15” can have one tap, trees 15” to 21” can have two taps, and trees over 21” diameter can have three taps. As recently as the 1970s, up to four taps were allowed. I’ve personally never put more than two taps per tree. I was horrified to once see seven or eight buckets hanging on one tree. Don't be greedy.
When I first started tapping, I put in either one or two taps depending on the size of the tree. I also tapped trees down to the minimum diameter. It just seemed like I should, since the tubing was running right past and I didn’t want to miss out on the sap. However, years ago I attended a class put on by UVM’s Proctor Maple Research Center, and I realized that my tapping process had room for improvement. My top two take-aways from lecture: only put one tap per tree if you are using vacuum and only tap trees that are at least 12” in diameter.
I recommend putting only one tap per tree. The reason is that with vacuum the sap gets pulled from quite a bit of the tree circumference. Think of the negative pressure pulling out the taphole and all of the same anywhere nearby being pulled out. When there are multiple taps on the same tree, each tap tries to pull sap from overlapping areas on the tree. You might get more sap from two taps, but you won’t get double the amount.
It’s a little different for buckets, since the volume of sap removed is only about half of what it is with vacuum. Bucket taps won’t compete with each other and you would likely get twice as much sap with two buckets.
Even more important to me than the productivity is the tree health. I want my operation to be sustainable for future generations. One tap vs. two taps means half the number of holes in a tree. That just has to be better for the maple tree in the long run. Less damage to the tree increases the odds of good productivity in future years. For number of taps per tree, I highly recommend only one.
Bigger Trees Give More Sap
Not tapping trees that were 10” or 11” in diameter was tough for me. Those trees seemed to be in their prime and ready to pump out sap, so I was hesitant to bypass them. However, there is data indicating that sap yield increases with the size of the tree. In general, bigger trees have bigger crowns so that makes sense. Of course I had to prove it to myself. I measured the circumference of 200 trees, found the average tree size per line feeding into the collection tank and then measured the flow from the 20 lines on three different days.
The normalized data clearly show that bigger trees produced more sap. Armed with this knowledge, I now pass right by the smaller trees that aren’t 12” in diameter yet; I know their time will come.
When to Tap the Trees
Historically in Vermont, we tapped on Town Meeting Day, which is the first Tuesday of March. As climate has changed, most sugarmakers now tap in February. Some even tap in the fall and make their first syrup in December. However, the fall sap is usually not as sweet as spring sap. Tapping in the fall is usually done because there are physically just so many trees to get tapped that folks need to start that early. One issue with fall tapping is that tap holes naturally seal over in 6-8 weeks after tapping due to the natural microbial growth that occurs. To keep the holes productive for the six months that the tap may be in the tree, large operations often use check-valve spouts as well as 24/7 vacuum to keep the tap holes as sanitary as possible.
Whenever possible, I prefer to tap on days above freezing. It makes for a more pleasant day in the woods, but more importantly it ensures that the tree is not frozen. When trees are frozen it increases the risk of cracking when the spout is inserted. And cracks create leaks. It is a bonus if the sap is starting to run when you are tapping. The flow of sap helps to flush the taphole and gives you that instant satisfaction as you see the sweet sap start flowing.
Where to Tap the Trees
When selecting the location on a tree, it is critical to stay away from previous tap holes. This is because each hole in the tree creates a column of “brown wood” in the tree that does not conduct sap. The brown wood extends up to a foot and a half above and below each taphole. If you tap brown wood, there will be little to no sap produced from the taphole. You should stay at least 4” to the side and 8” above or below old tap holes. I like to find the previous year’s hole and always move to the right looking for a suitable tapping location. This works well to find previous tap holes which can sometimes be difficult to see.
If you have a vacuum system, you can tap below the lateral lines. This is counter-intuitive, but it is true. The vacuum will pull the sap right up to the laterals with no problem. This essentially doubles the tappable zone on the tree making it far easier to avoid old tap holes. When tapping below the laterals, the tubing connected to the spout should point down with the dropline looping back up to the lateral. This loop of sap will offer you a location to monitor for leaks throughout the season.
Do not tap over your head. When you do that, it is tough to drill a perfectly round taphole and can lead to leaks. It is much better to be at a comfortable position where you can hold your drill with two hands. Be careful about tapping too low. In that case, a large snowfall could cover your taps or buckets which can lead to frozen sap that does not thaw during the days and impedes sap flow.
You may have heard that tapping over a big root or under a large branch will yield more sap. There is no data to support that. You may have heard that you should always tap a particular side of the tree. This is not true. South facing tapholes may produce more sap in some years, but north facing tapholes will be more productive in other years. This is dictated by the weather patterns of the season as well as any micro-climates within your sugarbush. If you decide to always tap over a big root on the south side of the tree, you will quickly find that part of the tree becomes so covered with brown wood that it will no longer be productive. It is best to evenly spread the tapholes around the tree from year to year. This is healthier for the tree, and in the long run you will yield more sap.
Tapping the Maple Tree
Now you found last year’s taphole and picked out this year’s location to avoid brown wood. Your maple drill bit is sharp and the drill is fully charged. It is a sunny day in the woods and you can feel spring coming. Finally, it is time to tap.
The taphole should be 1.5” to 2” deep to get into the sap conducting wood. Deeper holes do not produce more sap. The hole can be horizontal to the ground or at a slight incline up into the tree. Having a slight incline helps to avoid pools of sap that could freeze and push the tap out of the hole. Make sure you are on stable footing and hold the drill with two hands. You want to drill straight in and straight out quickly and in one smooth motion. This should give you a hole with nice clean edges. Do not ream out the taphole because you will end up with an oval hole. The taphole must be round; otherwise, it will leak.
Once the hole is drilled, you need to clear any wood shavings out of the hole. If the sap happens to be running, that will help flush the taphole. Do not blow in the hole because that only introduces bacteria into the hole that you are trying to keep sanitary. Twigs work well, but make sure the twig is clean and do not chew on it for a while and then stick into a fresh taphole.
Check the color of the wood shavings. They should be a nice light color. If they are darker brown, then you hit non-conductive ‘brown wood’. Do not be tempted to drill a new hole. That would add a new wound to the tree, and you would be creating a massive leak that would most likely give you troubles in your system. It is best to go ahead and put in the spout. You will most likely still get some sap. Hitting brown wood is frustrating but it does drive you to be even more selective with where to tap the next tree. Consider it one of the hard lessons you will learn in your maple sugaring adventure.
You need to be careful when you tap in the spout. You do not want to split the tree because that will create a leak in the system. Frozen wood splits easier which is why I like to tap on warmer days. Wood can still split even when warm, so you need to tap the spout gently. I may seem odd, but you need to listen to the sound of the hammer on the spout. The sound will change once the spout is seated properly. When I tap in the spouts, I listen for a knick-knick-knick-knock sound. That ends up being my mantra as I spend the day tapping. Once I hear the ‘knock’ I know I am good and I stop. Depending on your spouts and hammer you may have different sounds, but there will be a change when the spout is fully seated.
Now you can hang your bucket or make sure that tubing is all connected and move on to the next. Start looking for old tap holes as you approach your next tree and you’ll be well on your way to finding the perfect taphole location for the next spout.
Old Growth Maple Trees
While hiking in the Northeast Kingdom of Vermont a while back, I came across a handful of old growth maple trees that were nearly five feet in diameter. Talk about standing out in the crowd! Since maples can live to 400 years old, I have no doubt that these trees were thriving when Vermont became the 14th state in 1791. They may have lost some branches and the centers are rotting out, but they are strong and standing tall.
Note the five foot long walking stick for scale!
Old growth trees are not common here in Vermont. By the late 1800’s, Vermont was mostly denuded of trees to clear the land for sheep and to provide lumber, charcoal for the iron industry, firewood, and pulp for paper. Only about 20% of our trees were left uncut and those were up in the high elevations. The sheep were eventually replaced by cows. The forests have come back and they now make up about 80% of our landscape. Finding old growth trees in relatively good health is rare and I feel privileged that I found these majestic maples and was able to sit in their presence.
I wondered if these big trees had ever been tapped for making maple syrup. There are signs of past sugaring throughout the woods in this general area but nothing near the trees that I could see. Based on the roughly 20 million sap buckets that were hung on maples in 1800s, I tend to think these beautiful trees have been tapped at some point in their long history.
It’s All About the Trees
Maple syrup is entirely dependent on the maple trees. I hope that the trees in my sugarbush will be tapped for decades and maybe even centuries more. I want to leave them healthy for future generations. To that end, I only put one tap hole in each tree. I’m also not tapping the little trees – or the really big trees. A maple tree like I visited recently with a diameter of 55” is off the charts. And once they’re that old, I think they deserve a break. They’ve earned it.