While it's not necessary for the health of the trees, the task does make the trees more beautiful — and luckily, it is very easy to do at home.
Tips to Make Your Own Trees Dazzling:
Determine if your trees would benefit from cleaning. Whitespire birches are good candidates because they have naturally white stems and don't have any peeling bark or heavy ridges that could be damaged by scrubbing. Poplars may also be good candidates. Younger trees won't need cleaning because algae and dirt tend to build up over many years. You may need to clean older trees every two or three years to maintain the white look.
Wait for the right conditions. If you have other plants under your birch trees, you'll want to wait until the foliage dies back in late fall so you don't damage the other plant material with your feet while scrubbing the limbs of the tree. We were fortunate this year to have a warm spell in early November, so the task was a pleasant one.
Be gentle. Don't use rough scrubbers on tree limbs as you may damage the bark and invite pests or diseases to infect the tree. Soft sponges, loofahs, and old T-shirts work well. Try not to remove any lichens that are growing on the trees as these are beneficial plants in the community.
Moisten, scrub, and rinse. Cleaning the trees is as easy as moistening down the limbs, scrubbing them gently with a sponge and a bucket of warm water, and rinsing the algae and dirt off. You can add the tiniest drop of dish soap to your bucket of water, but plain water can work as well. Try not to scrub the dark areas of the branches where the limbs were removed too much so they remain dark in contrast to the white bark.