This rugged tree is native to a large part of the United States, from Maine to Florida and westward to Minnesota and Texas. It grows up to 70 feet tall and its canopy can grow just as wide, which makes it a valued shade tree. The tree has a long lifespan; some specimens live up to 300 years old. Swamp oaks hold up great in areas prone to heavy winds. In young trees, the peeling bark is especially attractive. The bark becomes deeply ridged and dark brown in older trees. A distinguishing feature of its acorns is that they grow on thin stalks up to four inches long.
Light
Swamp white oak is best grown in full sun, but it tolerates partial sun.
Soil
Provided that the soil is acidic and has a high mineral content, the tree can grow in wide range of soils, from clay to loam and sand. In its natural habitat, the tree grows in water-saturated soil, hence its name. However, this is not a prerequisite. Swamp white oak also grows well in well-drained soil or in soil with occasional flooding and saturation. The tree’s ability to survive in water-saturated soil, which means low oxygen levels, makes it also suitable for locations with heavily compacted soil, as it is often found in urban areas, as long as the acidity requirement is met.
Water
While swamp oak prefers consistent moisture, it can withstand dry periods. A newly planted tree, on the other hand, should be watered regularly—as much as weekly—in the absence of rain for the first two summers until it is well established.
Temperature and Humidity
As a native tree to a wide climate range, swamp white oak is tolerant of hot weather as well as subzero winters.
Fertilizer
Other than amending the soil with plenty of organic matter before planting a new tree, the best regular fertilization you can give an established oak tree is to let its leaves on the ground in the fall, as they add nutrients to the soil when they decompose. If a soil test indicates poor soil, add a slow-release fertilizer in early spring so it’s available to the tree as the weather warms up and the oak starts growing in spurts. The recommended N-P-K ratio for oaks is 12-4-8 (12% nitrogen, 4% phosphorus, and 8% potassium). Do not fertilize late in the growing season, as it will lead to extra foliage growth and make the tree more susceptible to winter injury.
Types of Swamp White Oak
There are two cultivars of note:
American Dream® Swamp white oak is a cultivar with a broadly pyramidal shape and dense foliage. Its leaves are deep green, thick, and glossy and change to yellow brown in the fall. The cultivar has good resistance to anthracnose and powdery mildew. Beacon® ‘Bonnie and Mike’ Swamp white oak has a narrow columnar shape. Its branches grow upright instead of spreading, which makes it suitable for urban settings. The foliage turns yellow in the fall.
Pruning
Swamp white oak does not naturally form a leader and as the tree grows, its branches tend to droop. If you do not like this natural shape, or the low branches and wide canopy creates clearance issues, you will need to prune the young tree to a central leader, and also prune the lower branches.
Propagating Swamp White Oak
It is possible to grow swamp white oak from acorns but getting the timing right can be challenging. You need to wait for a tree to drop its acorns naturally, and then collect them promptly, as they dry out within three to four days after they drop and become unviable. In light of this, it is recommended to purchase a seedling or young tree from a nursery. Swamp white oaks in containers can be planted any time between spring and fall.
Common Pests & Plant Diseases
Swamp white oak is susceptible to anthracnose, canker, powdery mildew, shoestring root rot, and oak wilt. The tree can also get leaf spot, which is common to appear on oaks late in the season and is merely an aesthetic issue that won’t kill the tree. Leaf blister, a fungal disease that looks like little bumps on the leaves, can defoliate a tree.
Common Problems With Swamp White Oak
When a swamp white oak shows signs of chlorosis, the underlying cause is alkaline soil, which makes nutrients unavailable to the tree. This can occur suddenly even to a mature tree after a new structure has been erected nearby. The culprit in this case is concrete or limestone, which increases the pH of the soil and makes it alkaline. To avoid this, do not plant a swamp white oak near building structures. Or, if the tree is already there, add organic materials to the soil to reduce soil pH: peat moss, rotted manure, or rotted leaf compost, which the tree produces itself every fall.
