Urban Trees

D. Andrew White, 01, 01, 2015

Arbor-Vitae / White Cedar

Northern white cedar, also called arbor-vitae, or simply 'cedar' (Thuja occidentalis), is not actually a cedar at all. It is a conifer in the Cupressaceae family. The name 'cedar' is one of many confusing European names inappropriately given to New World flora and fauna. Like the name of the American 'elk', the swamp 'cypress', the 'robin' thrush, and the 'sycamore' plane tree, the name 'cedar' is a misnomer. Apparently the pioneers were not very good at taxonomy. The real cedar (Cedrus) is an Old World member of the pine family. Arbor-vitae more closely resembles its relative the juniper than it does a pine.

Arbor-vitae has small leaves arranged in a decussate pattern with the laterals splayed outwards. The leaves are less pointed than are juniper leaves. Male and female cones are on the same tree, it is monoecious. The female cones are small, less than a centimetre long, with few scales and a few winged seeds. Unlike juniper, arbor-vitae does not have berry-like cones. The very compact branches form a dense upwardly pointed crown. An evergreen, the tree has a reddish cast to its green in the winter, and pleasing deeper green during the summer. The tree seldom exceeds 20 metres in height, and it often does not have a single bole. Forked trees are very common. It prefers sandy soils, well drained places and even rocky escarpments. The tree ranges from the eastern Boreal Forest in the north to as far south as Tennessee.

Arbor-vitae was probably named 'tree of life' for two reasons, (1) it is easy to clone by cuttings, and (2) the leaves were used as a cure for scurvy. Although the details were unknown to the early explorers, they tended to develop vitamin C deficiency in the winter, as their food stores were not nutritionally balanced. Arbor-vitae twigs contain significant amounts of vitamin C. The native Hurons in the St. Lawrence region informed Jacques Cartier of the medicinal value of arbor-vitae in 1535. So impressed was Cartier with arbor-vitae, that he took live specimens back to France. It became the first known New World tree species deliberately introduced to Europe.

Arbor-vitae is a very hardy tree, ideal for urban forestry in temperate regions. It can be grown as a full tree. It also takes well to trimming and can be sculpted into a tall hedge. It is not quite suitable for small hedges. Coppice sprouts do not easily form on headed stems. Therefore, it should never be trimmed so much as to bald it of greenery. To train it into a tight hedge, it should be trimmed lightly every year.

The ISA Species Rating: 66-75%.

Red Pine

red pine

Red pine ( Pinus resinosa ) is a pine of the southern parts of the eastern North American boreal forests. It is a pine with a symmetric crown that can reach up to 40 metres height, although seldom does it exceed 30 metres. It has thin needles (leaves) up to15 centimetres long. There are two leaves per bundle, and the evergreen leaves are retained for several years. The bark is scaly, but the twigs and non-furrowed parts of the bark are smooth and shiny, and reddish in colour. The pine cones are not very large, circa 6 to 8 centimetres in length.

Red pine is somewhat similar to Scots pine (P. sylvestris) and Austrian pine (P. nigra). Red pine leaves lack the bluish cast of Scots pine needles, and they are a little longer. The needles are less rigid and prickly than those of Austrian pine, and the crown is less dense. Red pine it is genetically closest to the ponderosa pine (P. ponderosa) of the Rockies. The ranges of the red and ponderosa pines do not nowadays overlap. However, their ranges were contiguous during the last ice age.

Red pine grows mostly in dryer soils than most other native pines. In sandy or stony upland areas it often occurs in association with eastern white pine (P. strobus) and jack pine (P. banksiana). Red pine does not extend as far north as the rugged, and stubby needled, Jack pine. The purest stands of red pine occur in the Great Lakes - St. Lawrence forest region.

Since red pine can have such a stately form, it is commonly planted as an urban tree. It is an elegant pine to plant for long lanes, and the wide lawns of industrial sites. In fact, being a boreal tree, it is has been widely planted in Sault Ste.-Marie and Thunder Bay. It is not as common in the south, but has been planted as far south as London Ontario. There are even plantation forests of red pine in Canada's 'deep south'. For those who adore the Canadian north, groves of red pine are a welcome sight.

The ISA Species Rating: 70%.

Scots Pine

Scots (Pinus sylvestris) is a handsome European pine. Scots pine is native to Eurasia’s boreal forest. It becomes less frequent in the larch and fir dominated taiga of eastern Siberia. The cones of Scots pine open after wildfires. The preferential habitat for seedlings is, in fact, in burnt-over areas. Though, it is somewhat less reliant on fire that jack pine. In the north it is a boreal forest species, and to the south it is more of a montane tree. It really was common in the Scottish Western Highlands, until a few centuries ago.

Scots pine has greyish-green needles that come in bundles of two. These leaves are fairly thick, stiff and somewhat curved. These needles are shorter than those of the red pine. The cones are rounded, with blunt spines on their scales. The bark of younger stems is fairly smooth, reddish and papery. This loose papery bark can rattle or ‘hum’ during a strong wind. Older bark is fissured and a pale reddish brown. The trunks are often fairly contorted. And old trees may have markedly lopsided crowns.

Scots pine was once very popular as an urban tree in North America. It is a very hardy pine, and is not easily killed by the abuses of urban milieux. Nowadays native species are in favour with urban foresters, at least in Canada. In south-eastern Canada, the preferred native species is red pine. Partly this is a prejudice against 'alien' species.

Scots pine has been widely planted in Ontario, but it has not naturalised to any great extent. In the York Regional Forests near Aurora there has been extensive afforestation. Several of these tracts of sandy over-exploited farmland have been reforested with sundry species of pine. I have investigated several of these tracts and found that there is very little new growth of either Scots or jack pine. The white pines, which are the minority canopy tree in most places, are the main under-storey seedlings. Apparently the Scots and jack pine do not grow well in areas that have not actually been burnt-over by bona fide wildfires. The eastern white pine is much more able to sprout in clearings than are either of the upland pines.

The ISA Species Rating: 53%.

Jack Pine

Jack pine, ‘jack’, black Jack, grey, or scrub pine (Pinus banksiana), is a pine of the eastern boreal forest. It has short paired needles, roughly an inch long. The cones are smallish, tight scaled and rotund, with a curved axis. The tree often has a contorted crown, and it can be rather picturesque. It seldom grows more than thirty metres tall. It is a fairly slow growing tree.

Jack and lodgepole pine are Canada’s northern-most species of pines. Jack pine’s northern subspecies has cones that open properly only with the heat of wildfires. Its habitat is mostly the dry uplands, where summer wildfires are common. Southern subspecies rely less completely on fire, as their cones can open without extreme heat. Jack pine is most common in the uplands, while black spruce dominates the bottomlands.

Jack pine, lodgepole and Virginia ‘scrub’ pines are all very similar looking trees. These kinds of pine may actually be the same species, or at least close subspecies. They get their pejorative names from the low value of their timber. These pines also tend to occur on poor ‘accursed’ soils. Nevertheless, they are an important source of pulp and paper.

Lodgepole pine: Jack pine can hybridise with the lodgepole pine (P. contorta) of the Rockies. The lodgepole pine has wide variation within it. The coastal subspecies of lodgepole pine can be even more contorted than Jack pine. The montane version is straighter, but still not an excellent source of lumber. The lodgepole pine is also well adapted to wildfires.

Virginia pine: Jack pine has a close relative in the Appalachian Mountains. Virginia pine (P. virginiana) is very similar to the jack pine. Indeed ‘jack pine’ is one of its common names. It is also adapted to wildfire, very much like jack pine is. The jack and Virginia pines do not nowadays overlap in their natural range.

Oddly, jack pine does very well in southern Ontario. In the Highland Creek and Don River watersheds they have been planted, and they are doing quite well. It is a somewhat wild looking tree. But it can be planted as an ‘urban’ tree.

The ISA Species Rating: 53%.

Black Spruce

Black spruce, bog spruce or swamp spruce (Picea mariana) is not generally an urban tree. Although, for some reason, a significant number of private home owners have planted the tree in and around Toronto. Likewise, the very similar red spruce has also been planted in the Toronto region. Often these spruce have been transplanted from a cottage or farm 'up north'. Black spruce is a short needled (leaved) conifer with small rounded cones. Black spruce needles have high concentrations of terpines and phenolic compounds. To most browsing animals the needles are distasteful. Generally this tree does not exceed 18 metres height. The crown becomes irregular with age, the lower branches thinning to leave a knob-like cluster at the crown pinnacle.

Black spruce is a true boreal forest species. The tamarack is the only 'tree' to grows further north in Canada. In the eastern side of the taiga, at the tree-line, the slow-growing, centuries old black spruce may be only a few metres tall. In places the taiga thins out into tundra quite abruptly. In most places, patches of forest follow sheltered valleys into the surrounding tundra. Black spruce in this region have such a short growing season that they do not produce viable cones. Instead they clone themselves by layering, the lower branches drooped upon the ground take root.

Black spruce prefers moist boggy areas. It is not uncommon for bottomlands to be nearly pure black spruce stands, while the uplands between are dominated by jack pine (Pinus banksiana). Black spruce bush can appear to be endless, where it is common. Strangely, black spruce also occurs in isolated patches in the bogs of southern Ontario, Michigan and Minnesota. It is possible that these isolated refuges are leftovers from the last glacial retreat. As the boreal forest migrated north, some black spruce remained in bogs, while temperate forest encircled in around them.

Black spruce is very similar to red spruce (Picea rubens). Red spruce grows from the Canadian maritimes south to the peaks of the Appalachian mountains. Probably a few tens of millennia ago red and black spruce were the same species. Generally, red spruce tends to be neater in crown form than black spruce. The twigs are slightly different in colour and texture. There are however, natural hybrids and intermediate forms where the ranges of the two species overlap.

Siberia and boreal Canada have, or once had, many animals in common, beaver, mammoth, moose, caribou, musk ox, grisly bear, and timber wolf. One might expect that such a widespread tree as black spruce should also occur in the Old World. Actually a different set of spruce species occur west of the Rockies, which differ from those in Siberia, which differ from those of Scandinavia. The same trend is true for the tamarack (larch) species, the pines and many of the willows. Although, a few shrubby species, such as the common juniper, are almost circumpolar. Asian and North American plant species in general are not as closely related as are the animal species.

Black spruce does not generally do well in southern cities. Homeowners tend to find that these conifers become 'ratty' with age. Actually, these urban spruce often have more 'perfect' crowns than their wild counterparts. Nevertheless, if a black spruce is planted in the deep south, it will eventually die of water stress or disease. Its crown will tend to become unappealing with age. Relative to most other urban trees, black spruce is not handsome. In summary, it is not an ideal urban tree.

The ISA Species Rating: 58%.


Yellow-poplar or the tulip-tree (Lirodendron tulipifera) is a peculiar member of the magnolia family. This beautiful tree can be very tall, up to 50 metres or more in height. The bole is usually very straight, with hard furrowed bark. The bisexual flowers are very much like tulips in form and size, but they are greenish-yellow, and not exceptionally noticeable. Since the flowers tend to be high in older trees, they are not always easy to observe. The seeds are winged capsules that are arranged on a tight cone. The leaves are peculiar also. They have four to six pointed lobes, with no terminal lobe. The leaves are emarginate, they end in a 'fork'. In the autumn these leaves can turn a splendid bright-yellow.

American tulip-trees are related to the tulip-tree of China (L. chinense). Although, the Asiatic species is much smaller. Tulip-trees grow naturally on rich moist bottomland soils. If planted, the tulip-tree can survive in less hospitable habitats, including urban yards. It is a tree of the Carolinian forests, and is much more common in the forests of the eastern U.S.A.. It does grow wild in the deepest south of Ontario. In Canada's few remaining old-growth deciduous forests (eg. Spring Water and Rondeau Conservation Areas), the tulip-trees tower above their neighbours.

Tulip-trees are a good urban choice for eastern North America's warm temperate region. Variegated and fastigiate varieties have been discovered, and propagated by horticulturalists. However, they are a questionable choice for any place much further north than Burlington Ontario. Although, many tulip-trees have been grown successfully in the greater Toronto area. They also do very well in British Columbia's deep south. Tulip-trees should be planted with caution. They are best planted in warmer regions. In northern towns un-seasonal frosts, or very cold winters, could kill these trees. Also, tall older trees are prone to wind and lightning damage. If you must plant a tulip-tree, remember it can eventually become a towering giant.

The ISA Species Rating: 77%.


Katsura trees are the 'latest thing' in urban forestry. Katsura (Cercidiphyllum japonicum) are members of the Cercidiphyllaceae family. They are stately trees with tall crowns that can reach up to 30 metres or more in height. Lower branches tend to be retained, thus the crown, if not pruned, droops down to the ground. The leaves are heart-shaped (cordate), with tiny rounded teeth. Often leaves are arranged in a decussate fashion, opposite pairs, each at right angles to the set before. Some twigs, or sections within a twig, have a spiral-alternate leaf arrangement. Overall in shape and size, the leaves have an aspen-like appearance. Spring budding leaves are often quite reddish. In the summer the leaf-stocks retain this reddish tinge. These leaves turn a beautiful yellow in the autumn before they fall. The flowers are small and simple reddish-brown affairs. They are dioecious, male and female flowers are on separate trees. These plants are wind pollinated.

In structure the flowers and pod-like fruits are primitive like those of magnolias. Even the vascular anatomy of the xylem is rather primitive for an angiosperm. Botanists suspect that the flowers, fruit and wood of katsura are similar to those of the earliest angiosperms. However, the katsura is actually not in the magnoliid clade. Genetic studies show them to be a side-branch of the rosids. Still, Katsura is a 'living fossil'. Cercidiphyllaceae have declined since their heyday in the Mesozoic. Now there is only one Cercidiphyllum species, the katsura. These trees grow wild in both Japan and China. Natural stands of katsura are rare, especially in China. Nevertheless, the Shaanxi forest has a significant grove of katsura.

Katsura is fairly hardy if planted in good soil. In temperate climates, except in dry regions or in places too far north, katsura thrives. It is not a planter-box tree, nor is it ideal for roadside planting. It is most suitable as a tree for wide open lawns. Katsura's hardiness is in the middle range. As one has no prejudice against 'foreign' trees, katsura is an excellent and exotic choice.

The ISA Species Rating: 73%.

Weeping, Peking or Matsudana Willow

Weeping willow (Salix babylonica) is a tree of Asiatic origin that was introduced to Europe centuries ago. It is a large willow that can reach at least 25 metres in height. Newer twigs droop, but older stems stiffen as the wood grows, and ascend skyward. Thus overall, the young twigs are pendulous, the branches lean slightly upward, and the trunk nearly erect. Its leaves are narrow and lance shaped. The leaves fall very late in the autumn, and they are not very colourful. Weeping willow is monoecious, a single tree has both male and female flowers. Like the poplars, to which willows are related, pollination is by wind.

Peking willow, Beijing willow or Matsudana willow (Salix matsudana) is very similar to weeping willow. The Peking willow is not as 'weepy' as the weeping willow. Indeed botanists are now inclined to believe that Peking willow is merely a subspecies of the weeping willow. In fact, the Peking willow may be closely related to the ancestor of the weeping willow. The weeping willow would then be an ancient cultivar of this willow long ago selected for its weepiness. One cultivar of Peking willow called Tortuosa, Dragon's claw, or Corkscrew willow has very contorted twigs and leaves. This Corkscrew cultivar is becoming popular in its own right as an urban tree.

Weeping willows are very popular as large yard trees in urban and rural homesteads alike. Willows grow best in moist soil, weeping willow is best not planted in places that are too dry. These willows are known for shedding dying branches, although the degree to which they do this is not greatly different from other fast-growing trees. Older willows often develop burl galls, and other wood deformities. Heartwood rot is not uncommon, consequently older trees are often hollow. As they age adventitious shoots sprout up around the root collar, and epicormic twigs sprout out of the trunk. The wood is not very strong, and wind and glaze storms often break the weaker branches. However, these annoyances can be overlooked, because the willow has many positive features. Old weeping willows can be magnificent due to the shear girth of their trunks. Many weeping willows are now over the century mark. These old trees can have trunks over a metre in width. The scaffold branches of these old willows can extend outward, almost horizontally. Some of the mature weeping willows almost approach the white oak in their handsomeness of form.

The ISA Species Rating: 40-54% (Corkscrew form considered 54%).

European Beech

European beech, hêtre, or fau (Fagus sylvatica) is a member of the beech-oak family. It has simple stiff leaves arranged alternately and opposite. The leaves have prominent veins, the margins are wavy, and they are typically less than 10 centimetres long. The buds are very pointed. Male and female flowers are separate, but on the same tree. The male flowers are in small round clusters, the whole cluster on a long stock. The female flowers are usually single or in pairs, on short stocks. The flowers are wind pollinated. The fruit is a small tetragonal nut, set in a bristly involucre, like a little chestnut. The bark of the beech is smooth, even on old trees, and is a dark grey. This forest tree can grow up to 40 metres tall.

European beech is somewhat similar to the American beech (F. grandifolia). However, the European beech has smaller leaves and darker bark. The European beech also has a greater number of horticultural varieties. Most of the varieties of American beech are regional races (sub-species) of purely natural origin.

Copper or Purpurea beech is a variety of European beech found in Switzerland in 1680. It has very dark purplish leaves. To some degree if self-crossed these beech breed true. The offspring of inbred Purpurea also have purplish leaves. Although, the leaves of these offspring vary from dark purple, to dark green, to a muddy green-brown. (Some of these colour variants are widely considered downright ugly.)

Swat Magret is a form of Purpurea beech with a beautiful leaf colouration. It was discovered in Germany in 1895. This cultivar is propagated by graft cloning.

Weeping or Pendula beech is a cultivar with a marked decumbence. The branches droop downward, but the main trunk, because of wood tension, is roughly vertical. Often these stems are 'trained' in the nursery, to straighten them.

Dawyck beech or Fastigiate beech was discovered in Scotland in 1860. It has very erect branches, resulting in a very narrow vertical crown form. It is best propagated as a graft cultivar.

Fernleaf beech or Aspleniifolia beech is a graft cultivar which has leaves with highly indented lobes, looking something like fern leaves. (One could also say that they look like oak leaves.) These cultivars do not breed true. The form is an unstable mutation. Its leaves easily revert back to the wild type. Coppice sprouts, and even damaged twigs, can sprout normal looking beech leaves.

Fau de Verzy or tortillard is a very tortuous strain of 'corkscrew beech'. Several hundred of these tortillards grow around the Chapel of Saint Basil near Reims France. They have existed since the sixth century A.D. Some of the tortillard seeds grow true to variety, others resemble normal beech. The variety may be a mutant, or a viral induced deformity.

Most of the European beech planted in the Americas are ornamental cultivars and varieties. European beech is a little more tolerant of urban conditions than is our native beech. However, some of the ornamental beech variants are rather sensitive to urban stresses. Often ornamental cultivars tend to more sensitive than wild trees. In the colder northern regions or in the dry prairie regions, these ornamental beech have some problems coping with urban stresses.

The ISA Species Rating: 77-89%.

End Note: The 'Southern Beech' or the Nothofagus species, are not actually a kind of beech at all. They are a genus not closely related to beech trees. They do look vaguely like beech trees in seed and leaf-form. Most of the ornamental species available in Canadian nurseries originate in South America. They are somewhat winter hardy, but not generally hardy enough for Ontario.

Northern Catalpa

Northern catalpa ( Catalpa speciosa ) is a member of the Bignoniaceae family. It is native to the Carolinian forest west of the Mississippi and south of the Great Lakes. It is a strangely tropical looking tree. The leaves are large and cordate (heart-shaped), and alternately arranged. The leaves remain greenish, or turn brown-yellow, in the late autumn. Leaf fall is so late that it is practically wintertime. The flower is tubular and asymmetric, and it is white with thin yellow and purple longitudinal stripes. The spectacular trumpet-vine like flower blooms spangle the tree after the leaves have unfurled. Each seedpod is about three decimetres long, but only about a centimetre thick. Superficially the catalpa seedpod looks like a bean-pod. However, it contains numerous paper-thin samara or winged-seeds. In late autumn the splitting pod releases the windborne samara, like a milkweed pod. The bark is rough and dark. Branches are often craggy and irregular in form, a wonderful tree form. A mature tree can reach over 30 metres in height.

Catalpa is a genus of relatively few species. There are a few catalpa species in Asia, and two in the Americas. Southern catalpa (C. bignonioides) occurs in the southern Appalachians. Several cultivars of this southern catalpa are grown commercially. Most relatives of the catalpa are in other genera, and most occur in the warm-temperate to tropic regions. And many, like the trumpet-vines (Bignonia spp.), are not even trees. One interesting warm-temperate species is the desertwillow (Chilopsis linearis) of Mexico and the southwest USA. Desertwillow is much like catalpa but has long willow-like leaves.

Northern catalpa has been planted as an ornamental quite far north of its natural range. It can even survive as far north as Ottawa. However, it often has a degree of crown dieback in Canada. It does not always do well in the north. Like many other forest trees, it cannot tolerate extremes of drought stress, soil compaction and other urban stresses. Its late falling leaves and large seedpods make for extra autumn-cleanup work. It is sensitive to canker fungus, and its leaves are often infested by sphinx moth caterpillars. It is an interesting tree, but a bit of a liability in Canada.

The ISA Species Rating: 49%.

Black Walnut & Walnuts

female walnut flowers

Black walnuts (Juglans nigra) are members of the Juglandaceae or 'walnut family'. They are trees of moderate growth rate that can reach, eventually, up to 50 metres in height. They have long pinnately compound leaves. The whole row of leaflets may be up to a half metre in length, like the leaves of an ailanthus. These leaves have a distinctly tarry texture, and they are bitter tasting. Twigs are large budded, stout, and have a spiralled leaf arrangement. The handsome bark is dark and deeply furrowed. The wood is durable and very dark. The monoecious trees are both male and female. The male flowers are long catkins. The red-purple plumed female flowers have a single ovule. This ovule develops into a large rough shelled nut with a thick greasy husk.

Black walnuts are best known for their thick shelled nuts. These walnuts are hard to crack, but their 'meat' is very delicious. These nuts are relished by squirrels, which cache great numbers of them in the ground. A portion of these buried treasures are 'forgotten', misplaced, or deemed surplus, by their rodent vectors, hence squirrels aid in the propagation of walnuts in the wild. To a limited extent black walnuts have been cultivated commercially as nut-trees. Although, they are not so commonly cultivated for their nuts as are European walnuts (Juglans regia). (European walnuts have thinner shells which are more easily cracked.) Black walnuts are natives of the Carolinian forests from southern Ontario to Texas. These walnuts grow in moist bottomlands and the older primeval forests of the east.

Butternut (Juglans cinerea) is a species of walnut that was once common in the Carolinian Forest Region. It has pale bark and more elongated nuts. In recent years an introduced disease, the butternut canker fungus, has afflicted these trees. The disease can be fatal. Indeed, butternut is considered to be at some risk of extinction. Oddly, certain trees in the American Midwest were noticed to be semi-resistant to the fungus. These trees have recently been recognised as hybrids of the Japanese walnut (J. ailantifolia). The hybrids are called ‘buartnuts’ (Juglans x bixbyi). Apparently, the garden-grown walnut has been hybridising with the wild butternut for a few decades. Luckily native butternuts still outnumber Japanese walnuts and buartnuts. On a speculative note, the Japanese walnut may prove useful as a source of canker-resistant genes. Genetic engineering may be able to help save the butternut from extinction.

Juglans is both an Eurasian and American genus. The greatest number of species occur in the Americas, especially in South America. It is probable that the Juglans genus originated in South America. Many species of walnut live in the Andes Mountains, and whole forests in associations in Central America can be dominated by various Juglans and oak species. J. australia of the southern Andes and J. neotropica of the northern Andes are examples of New World walnuts. These species have fairly large nuts, but mostly they are valued as lumber trees, and the nut-husks are used for making dye.

Black walnuts are fairly disease tolerant and can live, if planted, in soils dryer than their natural habitat. Black walnut is sometimes planted as an urban ornamental. Usually the city milieu most favourable are spacious yards, with plenty of surrounding tree cover. The large husked nuts fall mostly in the autumn, but squirrels knock some down in mid-summer. These nuts (4-5 cm wide) are large enough to hurt if they fall on one's head. Furthermore, the wood of walnuts is durable, but old dead branches have a tendency to break and fall. The trees also seem to have some proneness to lightning strikes. The roots of walnuts exude a substance called juglone. Juglone is s an example of an allelopathic agent. This allelopath inhibits the growth of other plants. Consequently, turf grass, flowers and other plants do not thrive when planted under walnut trees. Because of the large nuts, weak wood, and the juglone, walnuts do pose some problems as ornamental trees. Black walnuts are not a good choice for small yards, near traffic lanes, near walkways or near gardens.

The ISA Species Rating: 67% (considered 'poor' as an ornamental).


Kerr, Pat. 2008. Keeping the historic Butternut alive in Canada. Tree Service Canada. 2(1): 15.

Ross-Davis, A., Huang, Z. McKenna, J., Ostry, M. and Woeste, K. 2008. Morphological and molecular methods to identify butternut (Juglans cinerea) and butternut hybrids: relevance to butternut conservation. Tree Physiology. 28: 1127-1133.

Shagbark & Hickories

Hickory (Carya spp.) is a genus of trees and shrubs in the walnut family (Juglandaceae). The hickory leaf is compound like a walnut. Typically there are 5 to 9 leaflets per leaf. In the autumn the leaves, of most species, turn yellow to golden-brown. Male flowers are arranged on catkins several centimetres long. Female flower catkins are short, and often tuft-like. The fruit is generally a smallish (1-3 cm) nut, which is much like a petit walnut. It has a smooth husk and shell. In the autumn the husk splits at the flower-end into 3 or 4 longitudinal segments. Hickory nuts are collected and cached by squirrels. Squirrels act as hickory nut planters, as they do not dig-up every nut that they bury. The bark is very tough and hard. This results in either a very smooth bark, or a deeply fissured rough shagbark. The wood is very hard and dense, but it is also flexible. They have deep tap-roots when mature. Most hickories are forest trees which require quality soils. Many species can attain 45 metres in height, eventually.

The name 'hickory' is an Amerindian word. The hickory has left a deep imprint in North American traditions. Hickories were important for their edible nuts. The flexible and strong hickory wood was used to make hunting bows. It is also an excellent firewood. Not long ago farmers had a tradition of leaving hickory trees standing as 'nut-trees' when they cleared forests for farmland. In southern Ontario many of the old nut-trees remained even until the early 1970s. Older rural school yards often had, or have now, a few hickories left standing. Children would collect the nuts on their lunch break.

Eleven hickory species occur in North America, and two occur in southern China. Some species can hybridise with each other, even in the wild. Hickories grow wild from the Carolinian forest south to northern Mexico. The genus is mostly American, and may have originated in the Americas. Some species of note include:

Shagbark (Carya ovata) is a Carolinian forest species. It grows north as far as Ottawa. It prefers rich upland forests. The thick husked nut is small, and hard to crack, but it is quite edible. While the young bark is smooth and hard, the mature bark breaks up into shaggy plates - 'shagbark'. The leaf generally has only five (5) leaflets, the terminal three are the largest.

Bitternut (C. cordiformis) is a Carolinian species. It grows as far north as Ottawa. Its nut has a thin husk and a thin shell. The nut is very bitter. It has 7 to 11 leaflets per leaf. The bark is quite smooth, tight and shallow fissured, even on old trees.

Pecan (C. illinoensis) is a hickory native from the southern Mississippi basin, to east Texas, and south to Matamoros Mexico. It is not winter hardy in Canada. It is the most famous hickory. The large (3-6 cm) edible nuts are harvested commercially. It has 9 to 17 leaflets per compound leaf. The mature bark has scaley ridges.

Hickory is a handsome shade tree. Even the bare winter tree is interesting, with its twisting branches and twigs. It is difficult to transplant. (It should not be snatched from the wild.) Hickory is a slow growing genus of trees, it is not a shade tree for the impatient homeowner. It can be somewhat finicky as it should be planted in high quality soil. Once established it is hardy. Although not widely available in nurseries, hickory is well worth obtaining. Hickory generally requires full sunlight, it should not be planted in the shade.

The ISA Species Rating: 64-74%.

Esculent Fig

Strange as it may seem, the esculent fig (Ficus carica) can grow in Canada. At least, it can be cultivated in the southern parts of Ontario and British Columbia. This kind of fig is a small plant, three metres high at most. It has palmate leaves with rounded lobes, like those of a mulberry. The stem contains latex that is somewhat toxic, like the mulberry to which it is related. The compound fruits are unusual, the flower-head is so concave that the florets actually face each other. The flower-head therefore forms a vase-shaped inside-out fruit. Like many other Ficus species, it does not have an exact fruiting season.

Figs are normally fertilised by wasps. These wasps actually lay their eggs inside the fruit, where the larvae eat a portion of the seeds. So yes, there are usually a few dead wasps and eggs inside of figs. However the Ficus carica does not actually require fertilisation to set seed. So, don’t worry too much - if you are squeamish about eating insects. (Unless you eat wild figs.)

There are many species of figs, especially in the tropics. The F. carica comes from the eastern Mediterranean. It can be cultivated in cooler climates if it is sheltered from deep-cold and un-seasonal frosts. Planting it near walls, protected from the wind, is sometimes efficacious. Greenhouses, even unheated ones, work well. It takes some skill to prune the shrub such that it produces an ample supply of fruit. In Ontario, it is difficult to get it to fruit properly outdoors.

Weeping Fig

Weeping figs or Benjamin figs (Ficus benjamina) are actual trees – and not mere shrubs. In the wilds of Indonesia, Thailand, Malaysia and northeastern Australia the plant is one of the strangler figs. It twines up other trees until it reaches the sunny upper canopy, after which it becomes a fairly large tree. Grown indoors it lacks this option. Indeed, in Canada it is basically a smallish houseplant. In its pre-strangler phase it is an under-storey tree. It is therefore pre-adapted to becoming a shade-tolerant houseplant. Only very old trees, twenty or so years old, are too big for most houses, but they can be cut back – i.e. pruned severely. If pruned every so often, it can thrive indoors for decades on end.

Weeping fig is one of the most popular indoor ‘trees’. It has small pointed glossy leaves that turn a pretty yellow before they are shed. It is basically an evergreen, but it does have a noticeable biannual leaf shedding. Old leaves fall as the new leaves fill-out. As a house plant it can bear fruit, though these figs are quite small (6-9 mm). Without fig-wasps to pollinate it, the seeds remain sterile. These fig trees actually like full sunlight, as long as they are well watered. Moving it outdoors in the summer can speed-up its growth. Perhaps obviously, it should be taken indoors before winter’s first frost. In the winter it needs less water. It is best to start the plant in fairly acidic potting soil. Sometimes ordinary tap water is more alkaline than is ideal for the plant.


Mikolajski, Andrew. 2007. Growing fruit trees and shrubs. Marabout.

Morency, Pierre. 1989, L'Oeil Américain - histoires naturelles du Nouveau Monde. Boréal / Seuil. Québec. 276-288.

Sternberg, Guy and Wilson, Jim. 1995. Landscaping with Native Trees. Chapters Publishing Ltd. Shelburne, Vermont.

Trudge, Collin. 2005. The Tree. Three Rivers Press. New York.

Web page designed by D. Andrew White M.Sc. ©
anno domini 2014