Native Seed Stratification Best Management Practices

Native Seed Intelligence

Many native seeds have the most amazing built-in mechanism that optimizes their potential for reproductive success, this mechanism is called "stratification". Typically, most native forbs (flowers) and sedges (grass-like plants) have this built-in protection. These seeds know when not to germinate and more importantly, when to germinate.  Think about it, most seed is produced during the spring and summer just after a plant has finished flowering.  If the seed germinated immediately it would need to grow up at the worst possible time of the year, midsummer when water is least available, light is scarce near the ground in a towering tallgrass prairie, and with only a half or a quarter of a growing season in poor conditions, they are likely to enter into winter as a small susceptible seedling. On the other hand, if the seed sits tight until the early spring and then germinates, it has optimal conditions of ample water, optimal light, and a full growing season. Interestingly enough, most native grasses do not have this adaptation. This could be because of many reasons such as higher drought tolerance or just different evolution.

How It Works

When the seeds recognize that they have gone through the cool and wet winter they know it's time to wake up and germinate. They need cold and wet to optimize germination rates.  Cold and dry or dry and warm keep them in a dormant state preserving them until the optimal conditions arise.  It is also difficult to trick them.  They will wait in these cool and moist conditions for a period of 30 - 90 days before germinating.  A shorter period will not work as well.

Stratification Best Practices

For both native seed mixes and seed by individual native species. 

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Best - Natural Area Installation

It is best to let nature take its course and install native seed between November 1st and January 31st to let the winter's natural cool and moist cycles wake them up in the spring.

Best - Sowing Seed Into Potted Plants

Sow seed directly into a sterile potting soil vessel such as a plug flat or plant pot and cover it with chicken wire to keep out the varmints. It is not recommended to seed native mixes into containers, only individual species. Place your seeded vessels in a shady place such as the north side of a building during the late fall or winter.  Again, let nature take its course over the winter.  Move the planted seeds into a sunny spot in the spring and keep them watered regularly and with any luck, your seeds will germinate like magic. 

Alternative Option - Spring Installation

Installing seed from spring to early summer (June 15th) will also produce good results.  The first spring you may see reduced forb and sedge germination because of the lack of the extended stratification. However, many of those seeds will sit dormant until the next spring to germinate at the optimal time.  You will still see germination of certain flowers and most grasses the first season and most other the second season. 

Alternative Option - Cheating The System Spring Installation

You can sow them in a slightly moist medium such as wetted sand or even a moist paper towel in a sealed plastic bag and place them in your refrigerator for a 30 - 90 day period to bypass this natural protection.  You only want to do this if you are trying to get a head start with a spring or early summer (before June 15th) installation or when growing potted plants from seed. It is not necessary if the seed is installed during the fall or the winter. Monitor the seeds during this period to ensure they do not germinate, become dry or become moldy.  If they germinate or become moldy, plant immediately or if they dry out remoisten the medium. Remember, this is sort of cheating the system and results may not be as favorable as the natural fall or winter installation or even the spring installation.