Pin Oak, Swamp Spanish Oak

The Pin Oak (Quercus palustris) is a popular park tree which originates from eastern North America. It belongs to the Oak genus (Quercus) in the Fagaceae family and is also known as the swamp Spanish Oak.

Pin Oaks are relatively small in comparison to other representatives of their genus, only growing up to 66 feet tall. Their globe shaped crown can grow between 33 and 66 feet wide, depending of the space available and pruning. This extremely fast growing tree is anchored into the soil by a combination of a tap and fibrous root system. Pin Oaks only live for around 150 years. Its special features include the red-brown color of its branch bark, its extremely straight trunk and its fantastic fall foliage.

The foliage of the Pin Oak is alternating and spirals on up to 2.36 inch long stalks around the branch. Typically for Oaks, the leaves are lobed and grow to around 6.23 inches long and 4.72 inches wide. The five to seven leaf lobes are bare and have a toothed margin. The scarlet fall foliage of the Pin Oak makes it a fabulous eye-catcher at the end of the year.

The flowers appear in May, together with the leaves. The yellow male flowers appear on the previous year’s wood and are catkin shaped, the female flowers of the monoecious plant are found in the leaf axils of the current year’s branches.

The 0.59 inch long and almost equally wide, striped acorns sit in bowl-shaped fruit cups (Cupula). Pin Oak acorns remain hanging on the tree over the winter and only drop in the fall of the following year.

In nature, the frost-hardy Pin Oak is not found in swamps, as its alternate name, swamp Spanish Oak, might suggest, rather in occasionally flooded river valleys. But the Pin Oak is also happy in gardens. Here, it prefers a sunny or, at the most, a semi-shady spot. Its light crown allows plenty of light through for under-planting.

The Pin Oak grows in moist to fresh and moderately dry soil. However, it does not tolerate droughts. A loamy to sandy-loamy soil which stores plenty of moisture is ideal. pH values from slightly acidic to slightly alkaline are best for the pin oak. However, it is not particularly fond of lime.

The ideal planting time for the Pin Oak is in the fall before the first frost. Dig a planting hole which is twice the size of the tree’s root stock. Water the root ball thoroughly for a few hours before planting the tree. Loosen the soil well in the planting hole and mix in some foliage compost. After planting, the young tree must be well silted up. A supporting post protects the tree with a fibrous root system from falling over in the first year.

It is important to give the Pin Oak plenty of water, particularly when it is freshly planted. The soil should be kept constantly moist in order to activate root growth. The foliage, which drops in the fall, can be reused as fertilizer for the oak. Note: Do not leave Oak foliage lying on the soil, as the high tannin content inhibits the growth of neighboring plants and grass.

The Pin Oak does not require pruning in the outdoors. As a globe cut tree or hedge it requires regular pruning maintenance, whereby the excess and diagonal growing branches are removed. The Pin Oak generally tolerates pruning, however it thrives most beautifully if it is left in peace.

Its manageable height makes the Pin Oak ideal for avenues. It can be planted in small groups or as a solitary tree. With tall trunks and globe crowns, Pin Oaks decorate front yards and path edges and are impressive with their stunning fall foliage in orange-red. The dwarf specimens can even be grown in containers on the terrace. The Pin Oak enjoys limited popularity in the timber industry, even though it is well suited to furniture construction.

The dwarf specimens of Quercus palustris are particularly relevant for gardens. The densely branched varieties ‘Green Dwarf’, ‘Isabel’ and ‘Swamp Pygmy’ grow to a maximum of 10 feet tall and develop a 7 feet wide crown. In contrast to the natural variants, the bred specimens have slower growth.

If you wish to propagate the Oak from acorns, place the fruit in water overnight. Then plant the acorn in potting substrate and place in a bright, warm spot. Water it regularly. The small Pin Oak will be ready for planting in the following year.

The Oak processionary moth (Warning! Keep your distance!), Oak gall wasp and Green Oak leaf roller are pests which specifically target Oaks. An infestation can be recognized from holes bitten in the leaves and the white webs. The pests should be immediately treated with nettle stock or a chemical pesticide, as the damaged leaves are at increased risk from mildew and tinder fungi.