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Seed Mix

Creating a seed mix

Most tallgrass prairie seed mixes start with a 50:50 grass to forb ratio. Forbs include wildflowers and shrubs that behave like wildflowers, such as New Jersey Tea. A mix with too much grass seed becomes too dense for wildflowers to survive. However, a mix with too little grass does not contain enough fine fuel to burn properly. A 50:50 ratio gives enough wildflowers to cerate a diverse and showy habitat, and enough grass to carry fire.

The amount of seed (weight) depends on the site. The more competition you expect the prairie plants to have the more seed you will need. A typical rule of thumb is 10kg/hectare (10,000 square meters). This is a typical amount for broadcasting. If a seed drill is involved less seed can be used. Perhaps 7 kg/hectare.  Seed should always be cleaned, with awns and husks removed.  Doing so will allow for a lesser rate of seed to be used and greater germination can be achieved.

Another way to create a seed mix is to use a spreadsheet. For each species you assign a percentage of the total mix. Common species, such as Black-eyed Susan and Wild Bergamot can be given a higher percentage than rarer species, such as Butterfly Milkweed. You then must research
the amount of seed per gram. There are resources on the internet that can provide this information. Finally, you need to assign a value to the number of seeds per square meter that you would like. For example, 50 seeds per square meter multiplied by the number of square meters to be seeded (for example 10,000 square meters) is 500,000 seeds. Then you take the percentage of the mix for each species (for example 10% for Black eyed Susan). 10% of 500,000 is 50,000. Therefore, you need 50,000 Black-eyed Susan seeds. If you know the number of seeds per gram (in the case of Black-eyed Susan it is 3570) you divide the total seeds required by the seeds per gram to get the total weight required (50,000/3570 = 14 grams of Black-eyed Susan seed required). By doing this you can calculate more accurately the amount of seed for each species required. Otherwise you have to estimate by volume which is much less accurate, because seeds differ significantly in size.

Deciding on the species to use in the mix and the percentage of each depends on many variables:

One rule of thumb is that there are certain species that will perform the best initially. Generally, these species are lumped together as early successional, meaning they naturally show up first and then disappear or become much less common. Early succession prairie species include Black-eyed Susan, Wild Bergamot, Hoary Vervain, Showy tick-trefoil and Canada Wild Rye. The next species to appear are the mid successional species- such as Butterfly Milkweed, Round-headed Bush-clover, Big Bluestem and Indian Grass. The last species to appear are the most conservative species. These species are typically only found in prairie remnants and generally do not inhabit creations. Plants on this list are Pink Milkwort, Gatinger's Agalinis and White Fringed Prairie Orchid. A species mix with lots of early succession and some mid succession species will do the best. If appropriate the most conservative species can be added last. But research indicates that it may take a prairie at least 50 years to be ready for the conservative species.  

For more information on creating a seed mix refer to the book:

The Tallgrass Restoration Handbook for Prairies, Savannas and Woodlands

Edited by Stephen Packard and Cornelia F. Mutel