April 25, 2016 – Spring is an exciting season in the natural world! Spring warmth and rainfalls bring colour back to the southern Ontario countryside in April, as carpets of fresh green foliage sprout like magic out of the seemingly-barren earth. The spring flush of foliage and flowers in temperate forests is one of the natural world’s most spectacular landscape-wide displays – displays that you might be tempted to think would be lacking in a city ravine, only to be found up north. But nature has a fantastic memory when you give it a little space and leave it in peace – and even in southeastern Oakville, the ravine valleys of the urban creeks come alive during this vibrant time of year!
A walk in Joshua Creek in spring will reward you with far more than you would ever expect – carpets of “spring ephemerals” and spring flowers are not just present, but abundant, diverse, and vibrant in several areas of the creek valley nature sanctuaries south of Constance Dr./Aspen Forest Dr./Deer Run Ave. Even if you don’t have much of an eye for plants, it is hard to ignore the picturesque spring greenery that at this time of year.
“Spring ephemeral” is a loosely-defined term for a unique group of forest floor plants adapted to sprouting and (usually) flowering in early spring. Early spring is an advantageous time when the sun still reaches the forest floor, before the tall deciduous trees leaf-out and steal all the light. Spring ephemerals come in a variety of shapes, colours and sizes, and are some of the first important flowers available to support spring pollinators. The White Trillium, our provincial flower in Ontario (and the symbol emblazoned on most of our provincial documents) is perhaps the most famous of Ontario’s spring ephemeral flowers, and indeed, both the White Trillium (Trillium grandiflorum) and Red Trillium (Trillium erectum) can be found in Joshua Creek Valley without much difficulty. Species of spring flowers such as Yellow Trout Lily (Erythronium americanum) and Virginia Waterleaf (Hydrophyllum virginianum) may be much more numerous in this forest, but where they exist, there is nothing quite like a carpet of White Trilliums in bloom to really set the tone for spring in Ontario!
Many spring ephemerals are incredibly slow-growing. Plants like Mayapples, Trout Lilies, Trilliums, Blue Cohosh, Wild Leeks and others may take several years or more to grow from seed to flowering age, limited greatly by how much life-giving sunlight they can steal away for themselves each year. Species like the White Trillium and Wild Leek may take an especially long time – each could take around 7 years to grow from seed to flower, and around another decade to grow to true maturity! In this way, White Trilliums actually have a lifespan similar to that of humans – reaching maturity in their teens, and living for up to 70 years!
Many spring ephemerals are adapted to living with a thick layer of leaf litter, and rely on animal interactions (such as ant activity) to deposit the seeds in a place underground where they can sprout. This means that establishing a big, diverse carpet of spring ephemerals is a slow and challenging process, requiring specific conditions and a specialized ecosystem. This makes remnant communities of these species very valuable in places that have seen so much urbanization. Joshua Creek’s valley lands and their spring ephemerals are like a time capsule from a much earlier era, when spring flowers like this would have inundated Oakville from top to bottom, border to border. In places which have lost their forests – including deforested and altered sections of Joshua Creek further upstream – the spring ephemeral plant communities have been wiped out, and may not return for a long, long time.
Aside from the beautiful plant communities, spring brings another wave of activity to the Joshua’s creek valleys and natural lands. Migratory birds of all stripes and sizes flit about the trees, stocking up on insects, seeds, and whatever else they can find to fuel the next leg of their marathon flight journey. Migratory birds tend to make their biggest movements at night, where swarms of birds big enough to show up on national radars fly high in the sky for hundreds of kilometres, and even over the great lakes. But during the days in between major flights, when they return to the ground tired and hungry, they flock to natural corridors like Joshua Creek for protection, food and water.
Connected creek corridors with natural forest, swamp, marsh and shrub thicket habitats are life-saving rest stops that still allow the migratory birds to creep steadily northward, while also feeding and hiding from predators. With a sharp eye, a pair of binoculars, and keen ears, a budding naturalist can spot a plethora of colourful and songful northern species you would be hard-pressed to find here outside of migration season – species like the Hermit Thrush, Yellow-rumped Warbler, Black-throated Green Warbler and Ruby-crowned Kinglet are typically found further north (some much further north) during the summer, but pass through Oakville during migration. Other species, like the Winter Wren, Pine Warbler, Bank Swallow and Eastern Towhee were away for winter, but arrive in this region of southern Ontario in spring to set up shop for breeding season. To get to their ideal breeding habitats, many species must pass through our heavily-urbanized and deforested countryside, full of sterile gardens, roads and concrete. Even bird feeders are irrelevant for many of these species, as they are looking for nutritious insects and spiders rather than seeds. Small creeks like Joshua Creek are a much-needed safe haven for these species, full of necessary foods and shelter.
As you continue downstream, different habitats filter in and out – upland forest areas with Sugar Maples, American Beech and Eastern Hemlock fit into the mix, and lowland areas with Willows and Ash. A keen eye may notice that as the trees and habitats change, so too do the forest floor plants, with some areas devoid of spring flowers and others flush with them. In order to see many different types of plants, you have to visit many different types of habitats – and spring flowers are no exception! Keep an eye out for other interesting features – ferns are also popping up, uncurling their coiled fiddleheads from the forest floor. A dedicated observer may even notice that the bedrock exposed by the creek cutting into the ravine slope is grey rather than the rich red of the upper reaches of Sixteen Mile and Fourteen Mile creeks. Lower Joshua Creek is actually cut through a different bedrock altogether: the grey-coloured Georgian Bay shale formation, rather than the brick-red Queenston Shale. Joshua Creek is divided in half by these two bedrock types. In the middle above Upper Middle Rd. E., near where the two bedrock layers meet, horizontal pressures between bedrock layers have caused a ridge to form called the “Joshua’s Creek Pop-Up”, which is an unusual geologic feature for a region with little tectonic activity. However, the stars of the spring spring show could hardly be said to be the rocks – one could be forgiven for being distracted by all the spring plant and animal activity!
For a much-needed dose of spring green, and no matter what makes the biggest impression on you, Joshua Creek has more to offer than first meets the eye. Featuring a whole range of natural spaces from swamps lowland and upland forests, thickets and everything in between, Joshua creek is a real grab bag of different experiences, and some of its areas really shine in the spring.
Get out to Joshua Creek and experience the natural excitement of the spring rush! You’ll be amazed at what you can find hiding just a short way down in the valley.
Read more about Joshua Creek Challenges
All photos and text provided by ecologist, David d’Entremont.