When does one plant wildflower seeds?
The short answer to the above question, if you’d like to stop reading now, is this: In my 20-plus years of gardening in Truckee, the statistically most successful time to plant wildflower seeds is within a few days of the snow melting. For the methods and reasons, you’ll have to wade through the rest of this article.
Many believe that throwing out “wildflower seed” is an inexpensive and maintenance free method of planting a riot of color in the garden. After all, wild plants grow and bloom every year in all sorts of conditions. What people do not realize is that out of millions of seeds produced by wild plants, few ever germinate and fewer still ever make it to flowering.
As gardeners, we usually enjoy better odds than those offered by Mother Nature. We improve all the variables in large and small ways to increase our chances of success. In order to germinate and thrive, seeds and the resulting plants need water, decent soil with nutrients, air and, of course, sunlight.
In Truckee we have irregular rains and snows, nutrient poor, ground-up rock and rock-flour soils, very dry air and plenty of intense sunlight.
You are certainly welcome to simply throw seed onto a sunny slope and see if it will grow. If you did so in early April this year, I expect you will have a fairly good show of color this summer.
Most of our indigenous plants disperse their seeds in the late summer and fall. The soil is warm from a season of sunshine and we begin to see a few storms. If the seeds fall in the right spot and the storms are regular enough, seeds may germinate and establish a reasonable root system before winter. If, as often happens, the fall storms yield to a long Indian summer and early winter drought, then many of the young seedlings may dry up and die.
I have had excellent results seeding in the fall and I’ve had poor, always depending on the weather. In spring, the days are lengthening, the temperatures are rising, the soils are moist and the snows are melting, releasing additional water into the ground for weeks or months. Seeds planted in spring are almost guaranteed to receive April and May rain and snow showers.
Meadows are created over thousands of years by a wide range of species in locations with the only decent soils around. As the meadow plants grow, die and compost, the soils get better and better. A large part of the soil improvement is due to the grasses that make up 60 to 80 percent of most meadows. Clovers and other legumes are also responsible for the improvements.
Most of us are granted pretty lousy soil. Look at how few plants occupy a given area of land. When planting wildflowers, you can put in as much effort as you would for a new lawn or, like many, you simply improve the circumstances a little to increase your chances of success. By raking in a light layer of mature compost, you are adding beneficial composting microbes to the soil. You are also incorporating humus, the mineralized result of composted organic material that helps soil form structure, retain water and nutrients and generally support life.
By mixing seed with a compost before broadcasting it, you end up with a much more even distribution of the seed than you would trying to spread just the seed by hand. The greater seed-to-soil contact will result in higher rates of germination. The seeds should be just at the surface or less than one eighth of an inch below. Walking over or rolling the area after sowing the seed is beneficial provided the soil is not actually wet. Do not ever work or disturb soggy soil. It destroys many of the properties that allow it to support plants.
Mulching the area with a very light layer of straw or pine needles (pine-straw) after seeding, will provide some shade, slow wind and shatter rain drops. The mulch lessens the need for supplemental watering. By placing a few, or many, softball sized rocks around over the straw you will help keep it from blowing away. Additionally, the rocks both retain heat and shade the ground. Seedlings often emerge and grow more quickly around rocks. Wildflower “mats” work because they offer a moisture retaining medium and a loose mulch but they are also many times more expensive than seed, compost and pine needles for a given area.
Once the seeds are in, do not let them dry-out. Even an hour of hot sun or drying wind as the roots are emerging from the seed can kill and there is no second chance with germination. That is one of the reasons earlier planting can be advantageous. On the other hand, in warmer temperatures, seeds germinate faster. I often tell clients to simulate occasional afternoon thundershowers if we aren’t having any naturally. As the seedlings grow, water less and less frequently.
You want the deeper roots to keep following the water as it occurs only lower and lower in the ground. Later in the summer, the wildflowers will bloom longer if they are again given occasional water.
I usually use an organic fertilizer when seeding. Many of the newer “bio-active” fertilizers work by inoculating the soil with beneficial microbes and then feeding them. The plants slowly receive their nutrients as a bi-product of microbial activity. Plants are healthier and the soil is more productive. Organic fertilizer is best added at the time of seeding so that new roots can form beneficial associations from the start.
Eric Larusson is a co-owner of the Villager Nursery with over 30 years of mountain gardening experiments under his trowel. He holds degrees in molecular biology and horticulture and is one of the instructors for the Mountain Gardening Class Series offered at the Villager Nursery spring through fall.