It’s time to tap those maple trees

Cooking sap with a small commercial type evaporator. iGrow photo

By David Graper
SDSU Extension Horticulture Specialist

Warming late winter weather means that the sap is beginning to flow in our maple trees around the region. In fact, trees were tapped at McCrory Gardens on February 9th this year and the sugar maples had sap dripping out of the spiles just a couple days later, with the above normal temperatures this week. Warm days and chilly nights support the best sap flow – ideally a nice sunny day that reaches the mid-40’s followed by a night down in the mid-20’s is about ideal. Under those conditions a single spile might yield 2 to 3 gallons of sap in a single day. Typically our main sugaring season is going to be from about the second to fourth week of March, depending on where you live. The northern part of South Dakota or southern North Dakota would normally start later in March while southern South Dakota would normally be the first part of March.

If you go to the website and click on a station location near where you live, you can see what the climactic averages are for your area. Scrolling down the list for Brookings, it shows that by about the first week of March, temperatures are generally getting up into the low thirties during the day while going down into the teens each night. Those night temperatures are still a bit too cold for good sap flow. By the middle of March though, day temperatures are reaching the upper thirties with overnight lows in the 20° + range – usually a good sign that sap should be flowing. However, one really has to pay attention to the weather because those average or “normal” temperatures seldom really occur. In fact, at McCrory Gardens we have gotten very good sap flow during warm spells in February. Unfortunately the weather usually turns colder again, shutting down sap flow until it warms up again in March. So, it is probably a good idea to get your trees tapped as soon as you can so you don’t miss out on any of that precious sap for the short time it is available to us in the sugaring hobby or business.

Canada is the world leader in maple syrup production, making 80% of the sweet treat. But, generally anywhere along the northern tier of states the right climate exists to successfully produce syrup from several maple species. Dr. Peter Schaefer, began experimenting in his home yard, tapping silver maple trees about ten years ago and found that he could be quite successful. A few years later, I tried making syrup from trees in my yard, but really only had boxelder (A. negundo), another maple that produces a clear sap, can also be used to make a tasty syrup, similar to the syrup that is made from sugar maple.

We have now been collecting sap to make maple syrup from the maples at McCrory Gardens for several years. Last year we also experimented with Norway maples (A. platanoides) which also seemed to work equally well. Its sap was also clear when collected in the late winter to early spring despite the fact that if you break a leaf during the summer, it has a milky sap. We have also tapped some larger Amur maples (A. ginnala) and some hybrid maples, and they all seemed to produce a similar sap and syrup when boiled down. Sugar content did vary some between the species but the point is that you can probably tap any of the maple trees you might have in your yard, providing the trunk diameter is at least 12” or greater.

All of these maples have similar seeds, called samaras. The actual seed is attached to a flat wing-like structure. When the seeds are mature, they fall from the tree and spin or helicopter to the ground. Seeds of sugar maples and boxelders mature in the fall, but some of the samaras may still be attached to the tree in the winter, which aids in identifying whether or not it is a maple.

Silver maples are a very common tree in many communities in eastern South Dakota. They are easy to grow and get large very quickly. Their leaves have the typical maple leaf shape but are much more deeply dissected and have a silvery underside. Another good identifying characteristic is that the leaves are frequently attacked by the maple bladder gall mite. This minute pest causes little green to reddish bumps to develop on the undersides of the leaves. It does not harm the tree but is a good characteristic to help identify silver maples. Silver maple seeds mature in the spring and are generally fall off the tree by early June. The bark is gray-brown and will often form elongated plates that curve outwards with age. Silver maples are also planted in shelterbelts. They have soft, brittle wood so they can be prone to storm damage.

It turns out that there are other species of maple that can be used that can be found growing here in South Dakota, such as Amur Maple (Acer ginnala) and some of the hybrid maples, usually a cross between silver maple and red maple. In order to be tapped trees need to be at least 10-12” in diameter at about 4 feet above ground. Larger trees can even have a second tap or spile installed to collect even more sap.

Boxelder trees are also fast-growing trees with rather brittle wood. They can be found growing across the state, but are not often planted because they are generally not considered as ornamental or attractive as other species of maples. They are also very sensitive to certain types of broadleaf herbicides, such as 2,4-D, showing significant leaf damage from nearby applications. The leaves of boxelders are quite different from the other maples in that they are pinnately compound, meaning that they have three leaflets per leaf instead of the larger, lobed leaves of the other maples. The bark is gray-brown and with age develops fairly thick, irregular ridges. Boxelders are also known for producing lots of suckers at the base of the tree.

Sugar maples may be found in some people’s yards, mostly along the far, eastern and southeastern parts of the state. This is the tree that provides us with the vibrant fall color that makes maple forests farther east so colorful in autumn. The bark is gray-brown with occasional patches of white. Unlike silver maples, sugar maples have very hard wood and a much slower growth rate.

Before starting to make maple syrup, you need to have access to some of the maple trees mentioned in this article. If you don’t have many maples in your yard, check your neighbor’s yard. Perhaps they would be willing to help you out in allowing you to tap their trees and maybe even help in boiling down the sap later on for a share of the syrup. Note that just two large silver maples (18” diameter) will produce enough sap to make a gallon of syrup.

Some of the basic equipment needed includes a drill, taps – known as spiles, some collecting containers, storage containers, filters and something to boil the sap in – preferably a flat, large pan, a thermometer and finally some containers to store the finished syrup. Probably the easiest way to get started is to go online and search for maple syrup supplies and order a starter kit that will have everything you need to start out tapping a few trees. A hydrometer to assist in determining when you have fully cooked down your sap to syrup might also be a good investment, but you can also determine that by using the thermometer. A digital thermometer that can read temperatures up to about 250° F work well. A starter kit is a good place to begin so that you get a feel for the process and find out if you want to get into this hobby in a bigger way.

Install the spiles in the trees before typical sap flow begins, that means by the end of February or early March for most people but watch the weather forcast! Spiles come in two sizes, designed to be installed in either a 5/16” or 7/16” hole that you will drill into the tree about 1 1/2 to 2” deep. Wrap some tape around the drill bit to indicate the depth you want. An ordinary drill bit will work fine. Angle the hole up slightly so that sap will easily flow out of the hole. Remove any wood chips from the hole by blowing in it or use a small piece of wire to get them out. Position the spile in the hole so that it is pointing up the right way, which will vary depending on the type of spile you are using, but generally you will see the tip open on the top where the sap will flow out. The spiles designed to be hooked to a small collection tube should be positioned so that this one points downward. Carefully tap the spile into the tree until it is snugly seated in the hole. The spiles are tapered so that they will go in easily but become tight in the hole as you tap them in farther. If you tap them in too far, you might split the wood, causing a poor seal.

Attach the bucket to the spile, either by hanging it from the spile or by inserting the tube into it. A good method that we have found when tapping trees at McCrory Gardens is to purchase inexpensive 5-gallon plastic buckets with covers. Drill a hole, large enough to accept the tube near the top of the bucket, and insert the tube through the hole. Try to position the tap in the tree at the right height above the ground so that the bucket can be set on the ground. It is important to keep the collection buckets covered so that bird droppings, twigs, rain, snow and other debris do not get into the sap. Weigh down the bucket with a rock or brick to keep the wind from tipping it over. The more traditional metal or plastic 2-gallon buckets can also be used equipped with the large hook that hangs down below the spile. There are also other systems that use heavy-duty plastic bags and an aluminum frame that attaches to another type of spile. You can even use a clean milk jug to collect the sap. Just cut a hole in the jug near the top large enough to allow it to fit over the spile. You may want to also support the jug with some twine or wire so that it does not fall off the spile when it is full of sap. We now prefer using the larger 5-gallon buckets because we do not have to worry about emptying them as frequently – a good producing tree can yield one to three gallons of sap in a good day. But as much as five gallons of sap from one tap can be collected in one day from some boxelder trees, so a smaller container might need to be emptied more than once per day to gather all the sap.

Weather considerations

Since wind is almost a constant in South Dakota, after installing the spiles wait until the weather warms up to install the collection buckets so they do not blow away. Daytime temperatures need to get above freezing, preferably above 40° to get the sap flowing. Nighttime temperatures must drop below freezing, preferably down to about 25° F to get maximal flow. Wait until the weather forecast looks like these conditions will exist before you put out your collection containers. Often one or two trees start flowing in a yard before the rest and can be used as indicator trees. Keep an eye on them, to see when sap starts to drip out of the spiles and know when collection containers should be installed on the rest of your trees.

Sap storage

Since it takes between 35 and 45 gallons of sap to make a gallon of syrup, you probably will want to store your sap until you have a larger amount to boil down to make at least a quart of syrup. However, fresh sap can really only be stored for about a week at 40°F before bacteria will start to grow in it, turning it cloudy. It will likely still be ok to use since it will be boiled for such an extended length of time but it may change the flavor. It was often thought that the sugar content of maples other than the sugar maple was too low, making their use for maple syrup impractical. We have found the sugar content of silver maples to be about 3%, which is similar to that of the sugar maple which can range from 2 to 5%. Boxelders sap has a similar sugar content making all three species suitable for syrup production.

Collected sap can be stored up to a week or so at 40°F but it should be processed as quickly as possible for best quality. It generally takes 35 to 45 gallons of sap to make a gallon of syrup. That means in order to make a gallon of syrup, the other 34 to 44 gallons of sap needs to be boiled off as steam. Cooking the sap down to syrup usually needs to be done outside so that the steam can escape. If you were to do it inside your home, you would have all that steam condensing on the walls, ceiling and other parts of your home which would not be good.

As the sap is boiled, it will change from a clear liquid, looking pretty much like water, to a more amber colored, thicker liquid as it gets closer to being syrup. During this process the sugar content goes from 1 to 2% up to 67% when it is syrup. The sap should be boiled vigorously to evaporate the water as quickly as possible. The temperature should be monitored as the sap boils down. When the temperature of the boiling sap reaches approximately 219°F, it would then also be considered at the syrup stage. As the temperature rises, it becomes more likely to boil over, so you need to watch it closely. Once the boiling process is complete, it should be filtered to remove any contaminants, cooled and bottled.

Making maple syrup can be a fun and rewarding activity. It is easy to do and can make a tasty treat for your family to enjoy. If you own a shelterbelt and have access to a larger number of trees, it could even become an additional source of income for your family. Dr. Peter Schaefer and I have been presenting workshops this spring on making maple syrup and will also be doing research on the awareness and feasibility of maple syrup production in South Dakota and the region over the next year. For more information on maple syrup production see: