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Euonymus atropurpureus open capsule with exposed arils, Oakville, Ontario
 

Arboriculture - Part 3

Seed Collection

by Catherine Kavassalis <c.kavassalis@gmail.com>
February, 2008

The light of dawn is barely visible in the east as a vehicle skirts down back roads, doubling back and changing directions to evade watching eyes. Why the subterfuge? It is harvest time and the seed collector must reach her prized trees before bird, beast or rival collector find the treasure.

I admit that I had never given much thought to how tree growers and nurseries acquired their seed. But last fall, I was offered the opportunity to attend a workshop on seed collection and my eyes were opened to this curious but serious business. This workshop was organized by the Ministry of Ontario Natural Resources (OMNR) and the Forest Gene Conservation Association (FGCA) to train collectors to gather high quality source-identified seeds. This highly regulated seed collection system will help ensure the sustainability of our native species while improving planting success.

While most gardeners are familiar with plant hardiness zones, which reflect minimum winter temperatures, seed collection zones are more sophisticated. Temperature, rainfall, soil, light, pests and disease are all factors that can affect whether a plant will survive and reproduce in any given area. Over time, this produces adaptive variations within the genes of a given species. This genetic diversity increases the ability of this species to survive over time. Ontario is divided into 38 seed collection zones defined by a combination of climatic and geopolitical data. Certified seed collectors carefully identify the location from which seeds are gathered so they can be distributed to appropriate growing zones. Detailed records about harvested trees are also maintained to allow growers to trace the most productive seed sources for subsequent plantings.

Collectors carefully watch and protect favourite sources. For instance, canker-free butternut (Juglans cinerea L.) is a rare find and the nuts are highly coveted. The price per kilogram of seed is dependent on ease of acquisition, rarity and demand. Many trees do not produce significant annual seed crops, like the red pines (Pinus resinosa) which produce at three to seven year intervals. Collectors must monitor a stand of trees over time to forecast the crop potential. By observing flowering, weather, insect activity, and fruit set, seed collectors gauge whether a tree will be worth the picking effort. Slicing open fruits (a cutting test) is advised to ensure viable seeds are developing. Seed cases do not guarantee healthy seed, or any seed for that matter, is inside. Acorns that retain their caps or float in water are generally not viable. Certified collectors will always test a portion of fruits from a particular tree before committing to the harvest. Once collectors have identified a good potential seed source, they will watch and wait for the perfect time to pick their prize - or steal it ...

… from squirrels. Squirrels are expert harvesters of many varieties of fruit including the uncommon cone-like samaras of our native Tulip tree (Liriodendron tulipifera). As squirrels usually locate their caches in the same places year after year and may amass bushels in a given season, they are a considered a good potential source of free labour. Of course hand-picking using ladders or lifts or whipping crowns with bamboo canes and raking fallen fruit from tarps can work just as well. Timing is everything. Too soon and the seed will not mature properly. Too late and the crop may be lost to disease, insects, birds and or animals.

Though seasonal work, seed collectors can extend their income by collecting from a range of species. While most fruit are harvested in fall, sycamore can be collected through winter, silver maple in late spring, red osier dogwood in summer. The 100 or more woody plants native to Ontario provide a range of picking opportunities.

Fruits come in great variety. The arils of yews, legumes (pods) of locusts, samaras of ash, drupes of dogwood, pomes of pear, and catkins of birch, each require different collection techniques and storage, before shipping to growers. The catkins of white birch (Betula papyrifera) must be hand-picked into burlap bags to avoid shattering the fragile female fruit or inadvertently gathering male catkins. Fleshy fruit must be shipped quickly in plastic lined bags to storage facilities so that seed can be promptly extracted from the pulp. Storage facilities can then process and keep seeds for many years. Such stores of high-quality source identified seeds are important repositories for growers.

As consumers, we should always ask our nurseries or growers if their stock is from zone appropriate seed. Planting native source-identified stock preserves local adapted gene pools and ensures good tree growth. In this way, we can do our part to preserve and restore Ontario’s natural environment.
 

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May toads nestle in your flower beds and help you tend your beauties in the spring.

 

 

Resources and References:

Information on seed collection

General information about seeds

Misc.

 

 

 

 

 

 

 

 
Copyright © 2008 Catherine Kavassalis
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