Average breast height, which is a forestry measurement, is 4 1⁄2 ft (1.4 m) from ground level. Wrap a fabric measuring tape around the trunk at this height, and note the tree’s circumference.  If the ground is sloped, measure 4 1⁄2 ft (1.4 m) from ground level on the uphill side, mark the spot, then do the same on the downhill side. The average breast height is the midpoint between the uphill and downhill measurements. For a trunk that forks at a height less than 4 1⁄2 ft (1.4 m), measure the circumference just below the fork. To find the diameter, divide the circumference by pi, or approximately 3.14. Then find the radius by dividing the diameter by 2. For example, if the circumference is 154 in (390 cm), the diameter is approximately 49 in (120 cm), and the radius is about 24 1⁄2 in (62 cm). For tree species with thick bark, such as black oak, subtract 1 in (2.5 cm) from the radius measurement. Subtract 1⁄4 in (0.64 cm) for species with thin bark, such as birch. If you’re not sure and just want a rough estimate, subtract 1⁄2 in (1.3 cm) from the radius. Including the bark would add extra girth and throw off your measurements. Check around the tree in question for dead or fallen trees of the same species. If you find one with visible rings, measure the radius and count the rings. Then divide the radius by the number of rings to find the average ring width.  Suppose there’s a nearby stump with a radius of 25 in (64 cm), and you count 125 rings. The average ring width would be 1⁄5 in (0.51 cm). Growth rates vary by tree species and environmental conditions. The living tree you’re measuring probably grew at a rate similar to a tree of the same species that grew nearby. You’ll plug your ring width measurement or, if there are no nearby stumps, an average growth rate into an equation to estimate the tree’s age. Even if you have the average ring width, you can also use the average growth rate to estimate the age, then compare the results of the 2 methods. If you can’t find any nearby stumps or felled trees, search online for the average growth rate for the species of the tree you’re measuring. Including your location in your search terms could yield more accurate results.  For example, oak, ash, beech, and sycamore trees grow about 1⁄2 to 3⁄4 in (1.3 to 1.9 cm) in circumference per year. If you don’t know the species, plug both 1⁄2 in (1.3 cm) and 3⁄4 in (1.9 cm) into your equation to guess an age rage. For a more accurate estimate, factor in the tree’s location. In open conditions, growth rates are usually greater, or 3⁄4 to 1 in (1.9 to 2.5 cm) per year. Growth tends to be slower in urban locations and crowded forests. Be sure to check how the growth rate is calculated. Many sources base growth rates on how much the tree’s girth, or circumference, grows per year. However, you might find rates based on the average ring width of the radius. If you used a nearby stump to calculate the average ring width, divide the radius of the living tree in question by the average ring width.  Say that, excluding the bark, your tree has a radius of about 24 in (60.96 cm). Using a nearby tree stump of the same species, you calculated an average ring width of 0.20 in (0.508 cm). Divide 24 (or 60.96) by 0.20 (or 0.508) to come up with an estimated age of 120 years. If you found the average annual growth rate based on girth, or circumference, divide your tree’s circumference by the growth rate. Suppose your tree’s circumference is 154 in (391.16 cm), and its growth rate is between 0.75 and 1 in (1.905 and 2.54 cm) per year. Divide 154 (or 391.16) by 0.75 (or 1.905), then divide 154 (or 391.16) by 1 (or 2.54). Your estimated age range would be between 154 and 205 years old.

Summary: Measure the tree’s circumference at breast height. Find the trunk’s diameter and radius. Subtract 1⁄4 to 1 in (0.64 to 2.54 cm) to account for the bark. Use nearby fallen trees to calculate an average ring width. Look up the species’ average growth rate, if necessary. Divide the radius by the average ring width. Divide the circumference by the average annual growth rate.


In some instances, it might be best to install the yarn bomb during daylight hours. Other times, you might find it more beneficial to install it at night, when few others are around to interfere.  Yarn bombing during the day will likely make it impossible to remain anonymous, but if secrecy is not important to you, the daylight will make it much easier to see. If you want to remain anonymous, you will need to pick a time of day when very few people are likely to be around. Usually, this means installing the yarn bomb at night. Aside from your yarn artwork and installation tools, you may also need to bring a few helpers with you.  You will need to bring a yarn needle, matching yarn, and scissors to actually install a crocheted or knitted piece. If you are latch hooking or cross stitching, bring the tools you would usually use to create a piece of this nature. Take your diagram, as well, so that you can check your work against it as you move through the installation. You should also bring along a ladder if you need to reach tall places and a flashlight if you are working at night. Even if you think you can install the yarn bomb on your own, it is a wise idea to bring at least one friend with you if you are doing the work in the evening or at night. Use your diagram as a guide as you wrap each piece of yarn artwork around the appropriate part of the object. Hold each piece in place with safety pins until all of the pieces are in their correct position. If you are cross stitching, latch hooking, or wrapping, you won't have any previously created pieces to wrap around the work. Instead, you will need to use the object itself as your canvas and create the entire work on scene. Use additional yarn and a large yarn needle to stitch all the seams together, holding the yarn bomb in place more securely. Once everything is in place, you can remove the safety pins previously responsible for holding the pieces together. Use a simple stitch to make the process as easy and quick as possible. For instance, a whip stitch is usually a good choice. It is crucial that you do not cause any damage to anyone's property while installing your yarn bomb. Aside from man-made property, like benches and signs, you should also avoid damaging the plants and animals living in the area.
Summary: Go during the best time of day. Bring everything you might need. Wrap each piece around the object. Sew seams to install the yarn bomb. Never cause any property damage.