Osage Orange
Osage orange, maclura, hedge-apple, bois d'arc, or 'tennis ball tree' (Maclura pomifera) is a member of the fig-mulberry family (Moraceae). Like other members of it family it has some rather strange traits. Osage orange was native to Texas and Oklahoma, approximately the home territory of the Osage people. Today it has now been widely planted far outside its natural range. Not everyone considers it to be a picturesque tree. The female tree can look somewhat like an orange tree with its orange-sized fruits. There are less messy species that are just as beautiful.
Osage orange has alternate ovate-lanceolate leaves, on zigzagging twigs. In the southern states its autumn folliage is a clear yellow. Although, specimens in Ontario, that I have seen, are not so colourful. A pair of stout thorns occur near each leaf-base. Osage orange is dioecious, as mulberries are. Male trees have racemes of staminate flowers. Female trees have pistillate flowers in little radial buttonballs. The buttonballs grow into greenish apple-sized compound fruits of 6 to 8 centimetres width. The fruit-ball is structured like a giant mulberry. The heavy fruits fall suddenly within a day, or so, in the autumn. The sap is full of latex, as is common in the figs and mulberries. Both the sap and fruit juice are somewhat distasteful, at least to humans. The bark is rough, reddish and convoluted. The Osage orange can grow to 18 metres tall. It tends to be a squat spreading apple-like tree.
Osage orange's large fruit is one of its most curious features. The seeds are often able to germinate even without pollination. Nevertheless, root suckering is the more common means of natural propagation. The large fruit is not eaten by many animals. The benefit of the strange fruit to the tree's dispersal is an enigma. (Possibly some now-extinct mammal was once its primary primary vector.) In Asia there is a related genus, Cudrania, that some taxonomists consider a synonym for Maclura. Some species in this genus can hybridise with the Osage orange. The well known Cudrania tricuspidata produces somewhat edible fruits. In this regard is is unlike the Osage orange.
In the nineteenth century 'hedge-apple' was planted by farmers as a type of spiny hedgerow barrier. When real barbwire was invented this tradition was discontinued. Still, Osage orange persists semi-wild even in southern Ontario. The heavy compound fruits can dent cars, or hurt heads, when they fall. The 'oranges' take a long time to rot away. Osage orange is more of a curio than an ornamental.
References
Barlow, Connie. 2000. The Ghosts of Evolution - nonsensical fruit, missing partners, and other ecological anachronisms. Basic Books. New York. viii - 291.
Flannery, Tim. 2001. The Eternal Frontier - an ecological history of North America and its peoples. Atlantic Monthly Press. New York. 1- 404.
Janzen, Daniel H., and Martin, Paul S. 1982. Neotropical Anachronisms: the fruits Gomphotheres ate. Science. Vol. 215, 19-27.
Cokinos, Christopher. 2000. Hope Is The Thing With Feathers - a personal chronicle of vanished birds. Jeremy P. Tarcher / Putnam. New York.
Invasive Species
D. Andrew White, 14, 09, 2009
'Invasive species' are plants of foreign origin that become naturalised in a new location. In the case of Ontario, the vast majority of these species come from Asia. Asia often gets a bad rep because of this. But actually, the same accusation could be made the other way around, Asia has many invasive species of American origin. The cause for the dominance of 'invasives' from Asia and Europe is that Eurasia has a range of climates similar to North America's. Eurasia is over twice as large as North America, hence it has over twice the number of species to share.
Invasive species often lack crucial natural controls, agents such as specialised insects, that keep their populations in check at home. Sometimes invasive species can push out native species. Japanese barberry (Berberis thunbergii) can smother-out other understory plants, as it has in parts of New England. The kudzu vine (Pueraria montana) is one of the worst of the smothering invasives. Luckily kudzu cannot grow in Ontario's cold clime. Naturalised Norway maple (Acer platanoides) is also suspected of reducing local biodiversity. Naturalised ailanthus (Ailanthus altissima) also seems to reduce understory diversity and to crowd out native seedlings. Sometimes there is no real solid evidence that the invasive does any real harm to the ecosystem to which it is introduced. European buckthorn (Rhamnus cathartica) does not seem to cause much damage. Buckthorn basically grows in the same kind of temporary habitat (fallow fields) as do the native hawthorns.
In the long run of things, all continental flora are the result of natural invasions. North America's plants are basically a mixture of species of South American and Eurasian origin. Natural cross-diasporas have been gradually mixing species for millions of years. However, human activity, since 1492, has vastly accelerated this mixing process. Often these diasporas are very imbalanced, with natural control agents not following their hosts to the new worlds. Sometimes the native flora are unprepared for introduced diseases. Dutch elm disease, chestnut blight, sudden oak death, emerald ash borer, and Asian longhorned beetle, are only a few examples. More infamous are the current bio-introductions that are human diseases: HIV, SARS, West Nile virus, avian influenza virus, swine flu, and other globe-trotting micro-organisms.
Are Invasives always Bad?
It is always good to consider critiques of any bold claim, and ‘invasion biology’ is no exception. It has often been claimed that invasive organisms cause harm to native ecosystems. They displace native niche holders, or even actively exterminate native species. However, this belief has become something of a cliché. One horticultural writer, David Theodoropoulos, rose to the challenge and questioned the widely held belief that ‘aliens’ are always ‘bad’.
Using mostly examples from botany, Theodoropoulos questions the assumption of the badness of aliens. Certainly it is questionable whether loosestrife (Lythrum salicaria ) causes any real harm to New World wetlands. The saltcedar (Tamarix gallica) seems to fit right in with native plants in many places. Prickly pears (Opuntia spp.) are a nuisance to cattlemen and shepherds - in Eurasia and Australia. But there is not a lot of evidence that they bother the native animals or plants very much. Even the notorious caulerpa seaweed (Caulerpa taxifolia ) does not seem to be as harmful as some have claimed. Starting as an aquarium escapee, the seaweed has spread widely through the Mediterranean Sea. It does not always result in decreased native flora and fauna. Indeed, there is some evidence that native fauna populations are higher in caulerpa-beds than in the neighbouring beds of seagrass.
Now one may take issue with the overriding counter-claim that alien are usually beneficial. One would be hard pressed to claim that invasive fungi such as chestnut blight, or elm wilt, are good things everywhere. Nor could one claim that feral dogs, cane toads, or zebra mussels, cause no harm whatsoever. (Theodoropoulos might over-state his case sometimes.) But as is often the case, the truth is sometimes in the middle. Certainly alien species should not be introduced willy-nilly. This is especially true when the species is a pathogen. Still, for all that, an explicit critique of invasive alarmism has long been overdue.
References
Harrington, R.A., Kujawski, R, and Ryan, H.D. 2003. Invasive Plants and the Green Industry. Journal of Arboriculture. 29(1): 42-48.
Theodoropoulos, D. 2003. Invasion biology: Critique of a pseudoscience. Avvar Books, Blythe, California.
Ontario's Vegetation Zones
In Ontario there are three main forest zones - plus small outliers of prairie and forest-steppe. There have been many attempts to formalize the vegetation zones of the world. ‘Hardiness Zones’ schemes, such as the USDA system, take mostly the minimum annual temperatures to demarcate growing conditions. These fail to demarcate differences in rainfall. Hence, deserts and steppes fail to show up properly. Yet they are excellent guides for garden plants – that are watered and tended by humans. Growing season, measured in days per year, is a very useful tool. But the system is biased towards crops. One fairly workable system has been the “Life Zone” system developed by L.R. Holderidge. In this system average annual precipitation and ‘bio-temperature’ are considered important factors. ‘Bio-temperature’ is the average annual temperature above 0o Celsius - only the non-dormant seasons are counted. The Life Zone subdivisions correspond fairly closely to the older vegetation classification schemes. Alpine coniferous forests, for example, do resemble boreal forests in yearly rainfall, bio-temperature and in their vegetation. The few discrepencies that occur in the Life Zone system can be easily corrected with additional qualifiers. The tables below shows some of the vegetation and Life Zone parameters that occur within Ontario.
Ontario's Vegetation zones, as they were circa 1850
Tallgrass PrairieWarm Temperate outliers in Cool Temperate Region (Moist Forest & 'Steppe' outliers): Outliers of steppe grassland, occur near Windsor-Essex. Patches of tallgrass can occur on sandy, or poor, soils in the 'Great Lake Plains'. Black oak, bur oak and white pine 'forest-steppe' can accompany this grassland. The soil is mostly Gleysolic, in the Ontario portion. |
Hardiness Zones: 6 Bio-tempurature: 10-10.5oC Precipitation: c 600 mm/yr Growing Season: c220 days/yr | Oak SavannahCool Temperate Region (Moist Forest): Savannah-like forests can occur on poor soils or rocky alvars. These parklands are most common along the lower Great Lakes. These forests are 'parklands' of black oak, bur oak and white pine, with a tallgrass under-storey. Most soils are sandy and Gleysolic. |
Hardiness Zones: 5 Bio-tempurature: 9-10oC Precipitation: 600-800 mm/yr Growing Season: 210-220 days/yr |
Carolinian Broadleaf ForestCool Temperate Region (Moist Forest): The forest trees included sugar maple, American beech, red oak, white oak, white ash and other broadleaf trees. Sweet chestnut, tulip-tree, buttonwood-plane and pepperridge-tupelo trees occur in the far south. Predomiantly loamy Luvisolic and sandy Gleysolic soils. |
Hardiness Zones: 5-6 Bio-tempurature: 9-10.5oC Precipitation: 600-1200 mm/yr Growing Season: 200-220 days/yr |
Laurentian Mixed ForestCool Temperate & Boreal Region transition (Moist Forest): The dry upland forests have stands of tall white pine, eastern hemlock, red oak and sugar maple. White spruce, red maple, and tamarack are common in wetter areas. The mixed forest becomes more conifer dominated in its northern edges. Soils grade from Luvisols, to Brunisols to Podzols. |
Hardiness Zones: 4 Bio-tempurature: 7-9oC Precipitation: 800-1200 mm/yr Growing Season: 180-200 days/yr |
Boreal ForestBoreal Forest Region (Moist & Wet Forest): In wet areas black spruce and tamarack are dominant. Jack pine and red pine occur in the drier uplands. Moorland or 'muskeg' is common in the poorly drained areas. The drier uplands are prone to wildfire. Brunisolic soils dominate to the west, Podzolic soils occur in the east, with more Organic muskeg soils towards the far north. |
Hardiness Zones: 2-3 Bio-tempurature: 3-7oC Precipitation: 600-1200 mm/yr Growing Season: 100-180 days/yr |
Vegetation can influence the development of the soil. Factors that help to determine the kind of vegetation include the drainage patterns of an area and its climate. As to the specific species composition of a ‘flora’, this is often determined by the contingencies of prehistory. Nevertheless, different parts of the world that have similar climates also have similar kinds of 'vegetation'. The species (flora) are quite different, but the types of plants (vegetation) look very similar. Conifers tend to the cold climates and alpine zones, deciduous forests occur in the temperate zones, and broadleaf-evergreen forests occur in the tropics. Grasslands occur where the rainfall is insufficient for trees, and savannahs occur in the in-between zones.
Much of the original vegetation of Ontario has been disturbed by human activities. The disturbance is greater in the south, but it does also extend to the boreal forest and beyond. The outliers of forest-steppe in Ontario are the most disturbed of all. Most of these forests have been long ago cleared to make way for farmland.
References
Daniel, T.W., Helms, J.A. and Baker, F.S. 1979. Principles of Silviculture. 2nd Edition. McGraw-Hill Book Company. New York. pp 15-36.
Holderidge, L.R. 1967. Life Zone Ecology. Tropical Science Center. San Jose. Costa Rica.
Lugo, A.E., Brown, S.L. Dodson, R. Smith T.S. and Shugart H.H. 1999. The Holdridge life zones of the conterminous United States in relation to ecosystem mapping. Journal of Biogeography. 26, 1025–1038.