At a glance:
- Soil needs: Not picky about soil type or pH, but prefers slightly acidic. Can tolerate poorly-drained/waterlogged soils, as well as extremely acidic soils.
- Water needs: Thrives in moist conditions. Needs regular waterings when young, but can be drought-tolerant when established.
- Sun needs: Full sun to partial shade, tolerating as little as 2-6 hours of direct sunlight per day.
- Size needs: Medium. At full size, up to 30-70 feet tall, with a spread of 40-60 feet.
- Growth rate: Medium. 1.5 to 3 feet per year.
- Tolerates Black Walnut: Yes, this tree can be planted near Black Walnut.
- Wildlife value: Extremely high. Birch (Betula) is the fourth-best genus for supporting insects, behind only oaks, willows, and cherries/plums.
A bit more…
The river birch, or Betula nigra, is one of the most useful trees for restoration of riparian habitat (riverbanks and creek banks) in the Eastern USA. In fact, you may notice that trees which thrive in riparian zones tend to be a bit over-represented on my website. That is largely because it’s what I personally need the most. My property has a creek running through it, and the surrounding forest can be a bit swampy. These are the parts of the land which need the most attention, so I find myself concentrating more on trees that work in these areas.
But this need is not unique to me. These zones are struggling mightily nation-wide. Two recent epidemics have nearly wiped out two massive forest species: Dutch elm disease killing the American elm, and the emerald ash borer attacking the white ash. These two together are responsible for the deaths of hundreds of millions of ash and elm trees. And those are two of the most important trees in North American riparian habitats! To compound the disappearance of these crucial trees from the landscape, creeks and streams are also the most easily overrun by aggressive invasive plants, as they serve as super-highways for seeds. Riparian habitats need our help now more than ever!
Like any tree that thrives in riparian habitats, the river birch can tolerate poorly-drained soils and periodic flooding. However, unlike some others, it can tolerate very acidic soils. This makes it useful for habitat reclamation in areas where strip mining has occurred, which brings sulfur to the surface and thereby acidifies soils. Another trait which makes Betula nigra well suited to riparian restoration is its tolerance to road salt. While strip mining may make soils highly contaminated locally, road salt is a very widespread problem affecting creeks and streams all over the country. Quite a few of our native trees are very sensitive to road salt, which can damage and weaken them. It is important that if your riparian habitat receives runoff from salted roads, you plant trees which can tolerate it. The river birch is one such tree.
On to details about the tree itself. The river birch is a handsome tree which certainly adds charm to the landscape. It often develops multiple primary trunks — typically three. It also has a peely/papery bark, like other birches, but its a bit darker than the paper birches which are more iconic. Despite these charms, some people consider it a “messy” tree. This is for two reasons. First, it produces a lot of pollen, and its primarily wind-pollinated, which means that pollen gets spread around easily. Some people don’t like seeing this pollen end up on their driveways and windshields. Second, it sheds a lot of twigs, year-round. If the tree is above a side-walk or walkway, this may necessitate periodic cleanings. However, none of these seem like a big deal to me, especially if you are discerning about where you plant it. The same traits that people often consider messy are traits which contribute greatly to a healthy forest floor!
As a kid, I was more familiar with the black birch. It is common in the Smokies, where I spent a lot of time. This is the tree that is most typically used to make birch beer, and breaking small twigs to sniff that familiar root beer scent was a common childhood past time. But while river birch trees aren’t the typical source for birch beer, they can be used to make it. In fact, their sap can be used as a sweetener in general, similar to maple trees.
In terms of the ecological value to planting a river birch: it is very high. In terms of number of Lepidoptera (butterflies and moths — key pollinators and the key food source for birds rearing their young) it supports, it is behind only oaks, willows, and prunus (cherries/plums). In the northeast, it hosts 411 species from that genus alone. And some of the butterflies and moths that it supports are among the coolest you could hope to bring to your yard. This includes the morning cloak butterfly (Nymphalis antiopa), the bright green luna moth (Actias luna), and the massive polyphemus moths and cecropia moths (Antheraea polyphemus and Hyalophora cecropia). Lots of birds eat its seeds too, including goldfinches, titmice, cardinals, and more. Due to its ability to thrive in a habitat which is gravely under threat while simultaneously supporting a massive number of insects and birds, the river birch is a fantastic choice if you have anywhere with moist or wet soil.