A Gardening Journal
Today in the Garden of a Lifetime: Blue-leaved Cow Parsnip in Bloom
- Published: June 06 2016
When cow parsley enters its bloom cycle, progress is dramatic day by day. Just over a week ago, only the main flowerhead was fully in bud; the side heads were sheathed and still nestled amid the foliage.
Now, all heads are extended and, with the main umbel leading the way, flowers and seeds are maturing by the hundreds.
Below, a portion of both the main head (at the top) and one of the side heads below. The uniformity of flower maturation is startling: Every flower at the top seems to have been pollinated, and is maturing to seeds.
Similarly, every flower in the younger umbel seems to have opened at once.
With the pressure to survive mounting generation by generation, it's likely that the prevalence of deleterious attributes will decrease, whereas those that are beneficial, not harmful, will increase. So there is likely to be an advantage for any plant that produces a large amount of flowers simultaneously, especially when they are as small as these. One flower—or even a hundred—might be less noticeable to pollinators.
These massive umbels of Heracleum antasiaticum might benefit simply by being such a large landing pad for pollinators that want to take a break from flying. Who knows but that the umbel serves as a meeting spot, a village square for the six-legged set. As everybody stops by, checks out everyone else, takes a stroll, pauses for a chat, snack, or even a snooze, all kinds of pollination could be happening as a result, simply, of all of that foot traffic. And what if some visitors were herbivores, and would be delighted to eat the flowers? If hundreds of flowers are present, it might be more likely that some would escape predation.
There is also an advantage when all of those flowers have matured to seeds. It just takes one to germinate and grow so it doesn't matter if hundreds of others were eaten or landed on the road instead of the ground. For a short-lived perennial such as this, when survival depends on successful production of viable seeds, more is better.
This blue-leaved species of cow parsnip, Heracleum antasiaticum, can take several years to mature. Here's a look at this plant last year, which was its third season of displaying foliage alone. Here's a look at this plant just over a week ago, when it was in bud.
Here's how to grow Heracleum lanatum, which is the rare perennial species in this genus of plants that are monocarpic, meaning that they usually flower just once before dying. Its foliage is huge as well, but in the more usual mid-green, and with cow parsnip's typical jagged edges. It matures to slightly larger than H. antasiaticum: four to five feet high and wide. Its hardiness, culture, and handling are similar.
Here's how to grow the giant of the genus, the biennial Heracleum sosnowskyi. Its hardiness, culture, and handling are similar. It can be two to five times the size of H. lanatum, and needs careful siting and handling to keep in control: As with nearly-as-large Heracleum mantegazzianum, all parts of H. sosnowskyi can cause a severe contact dermatitis. Plus, both are self-seeders, and can proliferate into a dangerous infestation if allowed to escape from the garden.