Introducing Long Point’s oak trees
The Long Point Basin has 8 species of oaks, distributed widely across many different ecosystems, from oak savannas (displayed in the rightmost photo) to swampy woodlands! These oaks are categorized into two major groups – red oaks and white oaks, with a few notable differences in the fruit structure and leaf morphology. For species in the white oak group, it takes one year for an acorn to fully mature, while red oak acorns require two years to mature. White oak acorns are sweet, and red oak acorns are bitter. All of Ontario’s species in the red oak group have pointed leaf lobes, whereas species of the white oak group have smooth leaf lobes. Black Oak (Quercus velutina), Northern Red Oak (Quercus rubra), and Northern Pin Oak (Quercus ellipsoidalis) are part of the red oak group, whereas White Oak (Q. alba), Bur Oak (Quercus macrocarpa), Swamp White Oak (Quercus bicolor), Chinquapin Oak (Quercus muehlenbergii) and Dwarf Chinquapin Oak (Quercus prinoides) are in the white oak group.
Black Oak description and habitat
Black Oak is a member of the red oak group – preferring to grow in oak woodland-savannas and dry oak-pine forests. It is a beautiful tree with a wide crown, growing >30m in fertile soils conditions, though often shorter in the sandy soils typical of oak savannas. It is rarely found in wetlands or other areas which experience periodic flooding. Strands of Black Oak occur in many areas of Ontario south of the Canadian Shield; the Long Point Basin, the Thames River Valley, Rondeau and Pelee in western Lake Erie, the Oak Ridges Moraine (near Lake Ontario), the Rice Lake Plains, and the AuSable (Pinery) Dunes along Lake Huron. Within the Long Point Basin, large populations can be observed at St Williams Conservation Reserve, Turkey Point, as well as Long Point Basin Land Trust’s Harlow Dune Nature Reserve and Trout Creek Nature Reserve.
In oak savannas, Black Oak most frequently grows alongside Red Oak, White Oak, Black Cherry (Prunus serotina), Red Pine (Pinus resinosa), and White Pine (Pinus strobus), with an understory with Chokecherry (Prunus virginiana), serviceberries (Amlanchier sp.), dogwoods (Cornus sp.), hazel (Corylus sp.), witch hazels (Hamamelis virginiana), New Jersey Tea (Ceanothus sp.) and Elderberry (Sambucus racemosa). The ground layer features a diverse herbaceous vegetation community including Bracken Fern (Pteridium aquilinum) and a wide variety of wildflowers, especially those of the Aster (Asteraceae) family, such as Woodland Sunflower (Helianthus divaricatus), and Large-leaved Wood Aster (Eurybia macrophylla). Black Oak also grows in more mesic (moist) habitats alongside Red Maple (Acer rubrum), and Sugar Maple (Acer saccharum), though it is typically less common than in oak woodland-savannas.
The foliage of Black Oak is usually around 10-20 cm in length, with 5-7 lobes, each with pointed bristle-like tips typical of the red oak group. Leaf morphology is strongly varies based on the position on the tree; leaves at the top of the canopy (receiving full sun) are smaller and have deeper lobes compared to those in the interior of the canopy. The foliage turns rusty orange or yellow in the autumn. Black Oak is often confused with Northern Red Oak, but they can be distinguished from each other using the following characteristics: 1) Black Oak has smaller acorns (~1.5 cm diameter, compared to 3 cm for Red Oak), 2) The bark of the Black Oak consists of dark-grey, square ridges, compared to Red Oak, which has smooth vertical ridges which often expose the inner bark, 3) The lobes of black oak leaves are typically much more deeply divided than Northern Red Oak leaves.
Black Oak is a very fire tolerant tree, in part due to naturally thick bark. An extensive and deep root system allows for the vigorous resprouting if the aboveground crown of the tree is killed. Fire tolerance allows Black Oak to thrive in oak savannas (and successfully outcompete other tree species), where understory fires are natural form of disturbance. If fires are suppressed, Black Oak struggles to compete against shade-tolerant trees, including maples and beeches characteristic of moist forests, as Black Oak cannot reproduce under heavy shade. This results in an ecosystem transformation from woodland-savanna to closed-canopy moist forest – a process termed mesophication. Restoration of these critical ecosystem functions, such as fire-induced disturbance, are highly important for the persistence of many wildlife species. In some areas of Norfolk, soils are too sandy for the development of moist mesic forests, allowing oak savannas to dominate in the long-term. Invasive species, including nuisance weeds (i.e., Garlic Mustard, Alliaria petiolata) and fungal pathogens are also a threat to the integrity of native oak savannas.
Ecological importance of Black Oak
Every autumn, Black Oak acorns are relished by wildlife, including squirrels (Sciuridae), deer (Odocoileus virginianus), turkeys (Meleagris gallopavo), grouse, Blue Jays (Cyanocitta cristata), and Black Bears (Ursus americanus). Oaks also support highly biodiverse insect community, including 534 species of lepidopterans (butterflies and moths). Black Oak is particularly associated with Edwards’ Hairstreak butterfly (Satyrium edwardsii), Scarlet Underwing (Catocala coccinata), Cryptic Dagger (Acronicta vinnula), Fawn Sallow (Agroperina ferruginea), Russet-spotted and Grote’ Pinion (Lithophane sp.). Black Oak can also host introduced pest species, such the Spongy Moth, which can (temporary) defoliate entire oak forests in under 2 months of feeding.
In consideration of the high ecological importance of the Black Oak tree, and their habitat, oak woodland-savannas, conservation actions have been implemented to ensure the continued vigour and integrity of these ecosystems. This includes acquisition of important high-quality habitat to prevent human-induced degradation, and land stewardship methods to remove invasive plant species. Long Point Basin Land Trust, and conservation partners such as the Nature Conservancy of Canada aspire to establish a large network of protected conservation lands, protecting the ecosystems of Norfolk County in the long-term.
Fun facts
- Black Oak savannas are globally rare ecosystems—and southern Ontario holds some of the best examples left in Canada!
- The roots of Black Oak stabilize loose sandy soils – a highly important ecosystem service in Norfolk County!
- Mycorrhizal fungi help Black Oaks absorb essential nutrients needed to survive and thrive in the sandy soils of the Long Point Basin.
- Black Oak trees support a vast food web—not just butterflies and moths, but also hundreds of species of beetles, including some that consume acorns, such as Nut Weevils (Curculionidae)
- Black Oak trees hybridize frequently with Northern Pin Oak in areas where they co-occur, making identification tricky!
Written by Matthew Palarchio, HBSc in Environmental Sciences, Western University.
All photos are provided by Matthew Palarchio
The species you’ve just read about—and the ecosystems they depend on—need our protection. Support the work of the Long Point Basin Land Trust and help preserve the wild spaces of the Long Point Basin: https://longpointlandtrust.ca/donate
To view a directory of all species featured on our website, visit: https://longpointlandtrust.ca/featured-species
