Seed is best gathered in the area where it’s to be grown. A plant grown from local seed will be genetically programmed to grow in sync with the environmental cues of the location from which the seed originates.

This means it will be attuned to the hours of daylight and weather conditions of – in the case of seed from Return of the Native - points north of the GTA and south of the Canadian Shield. It will be more efficient at marshalling its resources – emerging in spring, putting in its growth spurt, producing seed and moving into dormancy at the best times. It will also be more likely to resist local pests and diseases. Which is not to say it won't grow for you elsewhere in Ontario or Eastern Canada. And if you save your seed or encourage self-seeding, after a few generations the plants will have fine-tuned their adaptation to your conditions. 

Seed falls into two main categories:
---Warm germinators are like the annual vegetable seeds with which most gardeners are familiar. Sow outside in spring, or start inside earlier for setting out when frost is no longer expected. Because annuals have only one year to fulfill their destiny, they usually germinate fast and readily. And quite a few perennials do the same. Don’t start these too early because unless you have a good setup with growlights and a fan, they will get weak and spindly for lack of light. Four or six weeks ahead of the last frost (which comes around May 28 in Huronia) is soon enough.
---Cold germinators. In this category are most of our native trees, shrubs and perennials which are quite particular about how and when they will germinate. In Ontario, the seeds of many native plants need to be exposed to winter before they will break dormancy. This is known as stratification, or ‘cold treatment.’

You can achieve this by seeding outside in the fall, either directly into the ground or in pots placed outside; or by seeding into pots and placing them outside in late winter, generally some time in February. Or you can simulate winter in the fridge (not the freezer), with seed either sown into pots or placed in plastic bags filled with a moist medium - a soil mix, or a soilless mix, or vermiculite. Moisture is essential. With some exceptions, seeds sitting ‘dry’ in the fridge will remain dormant. Unless otherwise indicated, 60 days’ cold treatment suffices. If in doubt, provide cold treatment for your native seed, it will not harm it.

Sometimes, stratification is not enough and scarification is needed to get germination going. Scarification means penetration of a very hard seed coat. There are a variety of possible methods. My favourite is to use a pair of nail clipperrs to nick larger seed. You can also rub between two pieces of sandpaper or plunge the seed into boiling water and let it soak for 24 gours.

Research continues into the secrets of unlocking dormancy in the more difficult native plants. Some need to be sown as soon as they are harvested and do not store well. Some prefer their cold treatment to include oscillating temperatures (more easily provided by seeding outside), others take two, or even three years to germinate. Some like to be covered, some need exposure to light. Some need an acidic treatment similar to what happens in the digestive tract of a bird or other creature, still others need exposure to fire. But the plants on the ROTN seed list are reasonably straighforward and predictable.

Here are a couple of websites with more information about germination requirements.
North American Native Plant Society 
Ontario Rock Garden and Hardy Plant Society
These are helpful videos from Robert Pavlis of Garden Fundamentals:
Small seed 
Scarification