Wild Herbs to Seed on a Hill in Caledon
Answered by: Conrad Richter
Question from: David Holahan
Posted on: May 21, 2008

I have worked for your customer above for 20 years.

They have an area on the hill behind there house in Caledon that was devastated by grubs, and drought last year. It is next to 200 acres of forest, and it has NO shade, on sandy soil.

She now has the bright idea of growing wildflowers in this area, which is 45,000 sq ft.

By my calculations, based on a maximum coverage of 4oz per 450 sq ft, which I read somewhere, I figure she has enough for 7,312 sq ft.

Do you agree? Your thoughts about the feasibility of this idea? Better ways to do it?

First, it is important to know that seeding wildflowers in any large area always comes with some risk of failure. The main problems are:

1) Germination conditions are uncontrolled so germination rates are usually much lower than when the same seeds are grown in a controlled environment such as a seedflat. Even dandelion seeds sown outdoors can fail completely if conditions turn unfavourable.

2) Even if germination and seedling establishment is successful, there is no guarantee that the introduced plants will compete successfully with the plants already in the area, or be able to resist pests and diseases that are present in the area.

Despite the best advice, there is always an element of luck in these projects. Sometimes it takes more than one try to get it right.

So with that said, I will comment on the specifics of your project. You client ordered Magnus echinacea, New England aster, red yarrow, heartsease and ox-eye daisy. All of these will grow in sandy soil and full sun. And they are all hardy in your area of Ontario. All are perennial except for heartsease which is biennial.

For biennials to persist beyond their second year they must set seed, and those seeds must find a way to get established in crowded conditions among the grasses and other plants present. I would say that of the five herbs chosen, hearstease will die out after the second or third year because it is not a particularly aggressive grower and will likely get crowded out. It will provide some colour initially, but that’s all. In contrast, sweet william, another biennial, has shown itself to be a very effective competitor on our farm in Goodwood where it has persisted for over 10 years in conditions similar to yours (dry sandy soil, full sun). It is always a delight to find beautiful patches of brilliant red and purple sweet williams growing in the gassy meadows on our farm.

The perennials should work in your area, but one can never be sure until you try. If after the initial sowing a few plants die out it is sometimes possible to reseed over the area with other plants. It make take several sowings to gradually "fill up" the area with the desired colours.

You have about 600 grams of seeds to work with. Using the seed densities found in the Herb Growing Infobase (in the Richters InfoCentre area of our website), I calculate that you have about 1.4 million seeds. Over the 45,000 square foot area, that’s only 30 seeds per square foot. The germination rate in outdoor field conditions will easily be less than 50%, maybe as low as 10%; so that gives you only 3 plants per square foot. That is not enough to crowd out the weeds and grasses that will come up. (Of course, the area must be prepared for seeding first by plowing and disking the weeds out). I would like to see at least 100 seeds per square foot. And would make up the difference by adding more species to the mix, such as the sweet williams I mentioned already and other herbs such as St. John’s wort, black eyed susan, soapwort, blue flax, and evening primrose.

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