iGrow Gardening: Harvesting maple syrup in South Dakota

Flat pan with 3 channels for sap flow. iGrow photo

By David Graper
SDSU Extension Horticulture Specialist
and Peter Schaefer
SDSU Professor of Forestry (retired)

As the weather warms in learly spring sap begins to flow in maple trees. For many people that live in the northeastern part of the United States, that means that maple syrup season has arrived. However, producing maple syrup is not well known in this part of the country. Most people think that you need sugar maple trees (Acer saccharum) to make it worthwhile. But in fact, other species of maples also can be used. Silver maple (A. saccharinum), red maple (A. rubrum), Norway maple (A. platanoides) which is sometimes confused with red maple because of the burgundy-red leaves that some cultivars produce, and even boxelder trees (A. negundo), actually another type of maple, can also be used to make a tasty syrup, very similar to the syrup that is made from sugar maple. Canada is the world leader in the production of maple syrup, making 80% of the sweet treat. But really anywhere along the northern tier of states the right climate exists to successfully have various types of maples produce enough sap for syrup production.

Peter Schaefer, SDSU Professor of Forestry (retired), began experimenting in his home yard, tapping silver maple trees about 10 years ago and found that he could be quite successful. David Graper has also made syrup from his yard but used boxelder, also known as Manitoba maple, as his source of sap. Trees need to be at least 10-12” in diameter at about 4 feet above the ground to be tapped. Larger trees can even have a second tap or spile installed to collect even more sap.

Before starting to make maple syrup, you need to have access to some of the maple trees mentioned above. Silver maples are a very common tree in many communities in eastern South Dakota. They are easy to grow and get large very quickly. They have the typical maple leaf shape, but the leaves 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 surface of the leaves. It does not harm the tree but is a good characteristic to aid in identifying silver maples. The bark is gray-brown and will often form elongated plates that curve outward with age. Silver maples were also frequently planted in shelterbelts. It does have soft, brittle wood so it is often prone to storm damage.

Sugar maples may be found in some people’s yards, mostly along the far, eastern and southeastern part 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 maple, sugar maple has very hard wood and a much slower growth rate.

Boxelder trees are also fast-growing trees with rather brittle wood. It can be found growing across the state but is not often planted because it is not usually as ornamental or attractive as other species of maples. They are also very sensitive to certain types of broadleaf herbicides, like 2,4-D and Banvel, showing significant leaf damage if an application is made nearby at the wrong time. The leaves of boxelder 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 develops fairly thick ridges with age. Boxelders are also known for producing lots of suckers at the base of the tree.

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

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.

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’s 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 it can also determine that by using the thermometer. A digital thermometer that can read temperatures up to about 250° will 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 or not.

Spiles should be installed in the trees before typical sap flow begins, that means for most people by the end of February or in early March. 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 the right way up, which will vary depending on the type of spile you are using, but generally you will see the tip of the spile, where the sap will flow out will be open on the top. The spiles designed to be hooked to a small collection tube should be positioned so that the tube will be pointed 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 in 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 things do not get into the sap. Weigh the bucket down with a rock or brick to keep it from tipping over in the wind. The more traditional metal or plastic 2-gallon buckets can also be used with the spiles that are 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 trees, so a smaller container might need to be emptied more than once per day to gather all the sap.

Since wind is almost a constant in South Dakota, just install the spiles but 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 sap flowing. Nighttime temperatures should drop down below freezing, preferably down to about 25° 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 before the other trees in a yard. These can used as an indicator tree. Keep an eye on that tree, checking to see if sap starts to drip out of the spiles to know that the rest of the collection containers should be installed on the other trees.

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. It was often thought that the sugar content of maples other than sugar maple was too low, making using them for maple syrup impractical, but we have found that the sugar content of silver maple to be about 3%, similar to that of sugar maple which can range from 2 to 5%, depending upon the time of year. Boxelder sap has a similar sugar content so that all of these are really suitable for making syrup.

Converting your maple sap into syrup is the most difficult part of the process because it takes lots of time, and you will need to do this outside your home. If you had 40 gallons of sap collected you would not want 39 gallons of water, converted to slightly sweet steam, added to the inside of your home. It could lead to disastrous results. So, typically the sap is boiled down outdoors, often over a wood fire. Small amounts of sap can be cooked down over a propane fired turkey fryer but a flat, wide pan will provide a much larger surface area to create more steam to remove the excess water more rapidly. Flat, steam-table pans work well, old turkey roaster pans or ordinary kettles can be used too.

Something as simple as a fire ring in your backyard can be used or a structure out of concrete blocks to support the pans and allow a place to build the fire beneath the pans can be constructed. Containing the fire beneath the pans to concentrate the heat will create a more efficient system and need less wood to evaporate off the excess water.

Try to keep the pan or pans of sap boiling rapidly. Avoid adding an excess of cold sap to a pan that is rapidly boiling or you will then have to wait for it to heat up again to start evolving more steam. Try just trickling in a bit at a time or use two or three pans – the first to act as a warming pan, the second to boil the sap initially then moving the sap into the final pan to finish boiling off the majority of the excess water.

As the water is boiled off, the color of the boiling sap will gradually get darker. The temperature of the boiling sap will also slowly rise from near the typical boiling point of water finally reaching the boiling point of syrup which is 7.1° above the temperature of boiling water or about 219°. Be careful as you get close to the final temperature because the sap is more likely to boil up. The bubbles created will also become lighter in color and larger in size as you approach the end point. If you exceed the 219° temperature, there is a good chance that it will boil over and burn. It is a good idea to stop at about 218° and then finish the syrup over a stove or turkey fryer where you have more control of the process than over an open fire.

Once the final temperature is reached, it is ready for filtering and can be poured into storage bottles. There are special filters used in filtering the syrup. The minute particles, sometimes called “sugar sand” are so fine that they will pass through ordinary filters, like a coffee filter. It would be better to invest in a filter made specifically for filtering the syrup. You can also allow the syrup to sit for several days in a closed container, allowing the fine particles to settle out to the bottom. Then pour off the clear syrup on top. Ordinary pint jars may be used for storage, but plastic maple syrup bottles may also be purchased for this purpose as well. The syrup should be at least 180° before you put it into the storage container to assure that the syrup will store well.