Trilliums, Deer and Why Balance Matters

Come spring, the woods transform into a carpet of wildflowers. Tiny star shaped May flowers, little purple wood violets, the yellow of adder's tongue.

Our woods at Bondi Village Resort are carpeted with them.

And trilliums. Being in Ontario, we're particularly fond of the Trillium, which is our Provincial flower.

thanks to Bondi guest Mary Jaekl for this lovely photo!

The blooming time is brief -- limited to the month of May -- but while they are out, the woods turn white - and pink, and red - with their signature 3-petals.

We've all heard the admonishment, 'don't pick the trilliums.' Don't dig them up, either. Enjoy them where they belong instead. These plants are more vulnerable than people might imagine. They do not transplant well, often dying in the process. They take 5 to 7 years to grow enough to begin seed production. They are not cultivated in nurseries -- any you see for sale have been harvested in the wild, causing habitat destruction and putting pressure on the species. So it is best to just let them be.

They possess a number of unique features. One example is that these are plants whose seeds are spread through myrmecochory, or ant-mediated dispersal, which is effective in increasing the plant's ability to outcross, but ineffective in bringing the plant very far. As you can imagine, ants don't drag seeds over mountain ranges as a general rule. Yellow-jacket wasps and harvestmen spiders (which are better known as Daddy Long-legs, and aren't true spiders) also help with the seed dispersal of the trillium. Again, this is a short-haul system of transportation. Which led ecologists to question how it and similar plants were able to survive glaciation events during, oh, say an ice age.

And that is where deer enter the picture. For better, or for worse. The height of the trilliums is an effective index of how intense foraging by deer is in a particular area. Deer love the taste of trilliums. Given a choice, they will select a trillium over any other available browse. Which is perhaps not great news if you are a trillium quietly blooming in a secluded patch of forest. In the course of normal browsing, deer munch up the larger flowers, leaving shorter ones behind. Scientists, who are a crafty bunch, use this information to assess deer density and its effect on understory growth in general.

When foraging intensity increases, individuals become shorter each growing season due to the reduction in energy reserves from less photosynthetic production. One study determined that the ideal deer density, based on trilliums (T. grandiflorum in the study, which leans towards the Latin names) as an indicator of overall understory health, is 4 to 6 animals per square kilometer. This is based on a 12 to 14 cm stem height as an acceptable healthy height.

In practice, deer densities as high as 30 deer per square kilometers are known to occur in restricted or fractured habitat where natural control mechanisms such as wolves and other predators are lacking. Such densities, if maintained over more than a few years, can be very damaging to the understory and lead to extinction of some local understory plant populations.

It is important that Nature be able to do her work, and keep populations in a proper balance.

It's not all bad news for the trilliums, though. The same deer that munch the big blossoms also contribute to the survival of the species, by carrying away the seeds. An ant may carry a seed only about a metre, but a whitetail deer will prance off through the forest like Bambi on caffeine for about a kilometre before, well, before planting the seed shall we say.

Everything has a balance, and Nature is better at it than we are, it seems.  We all need to learn to tread lightly on the planet.