A cold grey windy day, marking almost the end of seed-gathering season. I pop out hastily to get the seed of the Wild Petunia (Ruellia humilis
), which was resolutely unripe a few days ago but has now turned brown and is ready to split open. I’ve been watching the Sky Blue Aster (Symphyotrichum oolentangiense
) which had closed damp flowerheads when last visited but now quite a few have opened into a small dandelion-like globes, waiting to be blown off by a puff of wind, or pinched off by me.
The Black Cohosh (Actaea racemosa
) which had its glorious flowering in September and October now has serried ranks of little seed capsules hanging from its arched stems. They’re still green, I’ll leave them a while longer.
The seed-gathering season is a long one. For me, it starts at the end of June when I collect the drying fruit of the Red Elderberry (Sambucus pubens
). I’m not sure whether I should have propagated them immediately. The instructions from Henry Kock indicate that I probably should have: he prescribes 60 days of warm stratification followed by a cold period of 120 days to break dormancy.
Kock is the author of Growing Trees from Seed – a practical guide to growing native trees, vines and shrubs
, a bible in the horticultural world. Before his premature death in 2005 at the age of 53, Kock was hugely influential as an interpretive horticulturalist for over two decades at the Guelph Arboretum, where he founded the Elm Recovery Project. (I am proud to say that I received one of those elms from the late Keith Squires, nurseryman extraordinaire, and some 20 years on, it is in full growth.)
Kock’s book, almost complete, was published posthumously thanks to three of his colleagues. Dipping into it, I find myself compelled to quote from his introduction:
“Covering many thousands of square miles, the Great Lakes bioregion is the ecological community of plants, animals and microorganisms encompassing the largest group of freshwater lakes in the world… The meeting place of three vast life zones – the boreal, mixed and deciduous forests (including prairies) - it contains a rich diversity of woody plants – trees, shrubs and vines – arising from the convergence and interaction of species from these three very different life zones.
“In addition, the birds migrating from as far away as South America – insectivores, seed-eaters and their avian predators – have also had a profound influence on the distribution and growth of the woody species in the Great Lakes region…
“Regrettably, it is one of the most heavily impacted bioregions in all of the Americas. It has been significantly fragmented by intensive human settlement; now, in some rural areas, the amount of coverage with native plants is less than 2 per cent.
“The disruption of the natural landscape by land clearing, paving and extensive planting of exotic (non-native) species has resulted in a climatic, hydrologic, vegetative and faunal imbalance that dramatically restricts the natural evolution of the region’s native species.
“Planting native tree, shrub and vine species to address this massive injustice to the land is a nearly sacred act.”
A vital reminder that the Great Lakes area is exceptional and that to engage in gardening and stewardship here is indeed a privilege - and a necessity.
So… undeterred by the prospect of a lengthy wait before I discover whether the germ of life still resides within my Red Elderberry seed, I rub off the desiccated remnants of fruit and place it in a bag with some handfuls of damp vermiculite.
It will spend two months on the windowsill for warm stratification and then migrate into the fridge where it will spend three months in cold stratification before it is brought out into warmth and spread in a pot under lights. Then, perhaps, there will be seedlings.
Stratification describes processes that mimic natural conditions in order to get seed to break dormancy. Many seeds native to our area are inhibited from germination until the conditions are right (for instance, they need to know that winter has been and gone). We can plant the seed outside where it gets real-world cues, or we can start the seed inside, away from hungry birds and mice and competing weeds, but still providing the triggers the seed will need.
A period of moist cold stratification in the fridge – from 30 days upward – will unlock dormancy for many species. Some require double dormancy – two winters in the real world, that can be mimicked by two periods in the fridge. My White Baneberry (Actaea pachypoda
) seed, bagged in moist vermiculite, has gone into the fridge for two months; it will come out in January, spend two months on a warm windowsill; and then back to the fridge for another two months before being potted and put outside and then, perhaps, there will be seedlings.
Not all native plants require stratification. Some are like annual vegetables, which, having only one season to complete the seed-to-seed cycle, are eager to germinate on exposure to moisture. To name a few natives that spring into action without cold treatment: Northern Sea Oats (Chasmanthium latifolium
), Bottlebrush Grass (Elymus hystrix
), Field Thistle (Cirsium discolor
), Obedient Plant (Physostegia virginiana
), Anise Hyssop (Agastache foeniculum
), Cardinal Flower (Lobelia cardinalis
), Butterfly Milkweed (Asclepias tuberosa
), Purple Coneflower (Echinacea purpureum
), Wild Bergamot Beebalm (Monarda fistulosa
For herbaceous plants (annuals and perennials which do not have a woody structure but die back into the ground each fall), I go to a couple of authorities to discover what treatment, if any, is needed. Prairie Moon Nursery
is one. The Ontario Rock Garden Society
is another. Sometimes they disagree and it’s a guessing game. Take notes of what you do so you know for the future if it worked.
Kock is the one for the woodies – and as entomologist Doug Tallamy has demonstrated, trees and shrubs are among the principal keystone species that are critical to the survival of lepidoptera (moths and butterflies), whose caterpillar abundance underpins the survival of bird populations. Here’s a link to the Northern Forests Ecoregion
. The Oak (Quercus
) genus can host (provide digestible foliage for) 445 caterpillar species; the Willow (Salix
), 395; in contrast, the top performing perennial is the Goldenrod (Solidago
I gather some Bladdernut (Staphylea trifolia
) seed. This is a pretty shrub that I trained as a tree but have now decided to let follow its inclination and develop into a thicket. That will provide better-protected nesting habitat, I think. It has fragrant bell-shaped white flowers buzzing with bees in early summer, and charming bladder-shaped seed pods in the fall.
We take a ladder to get at the higher-up pods. Indoors, as I extract the glossy round seed from the papery envelope, I check Kock to see what the treatment should be. I discover that the pods must be plucked from the shrub as they turn yellow, the seed peeled free and planted right away to obtain germination in the first spring. “Once the fruits have turned brown a deep dormancy sets in and delays germination to the second spring and even the third.”
Darn. Of course we took the brown pods. The seed goes into pots anyway, labelled and placed outside under protective netting. Another waiting game... Thank goodness for the easy germinators!
PS I supply seed to the North American Native Plant Society. You will be able to access it through the NANPS seed exchange
; the 2023/2024 list will be posted online soon. You have to be a member to contribute or order.