Although many wildflowers do fine in marginal soil with low-nitrogen content, performance for most wildflowers is best in well-drained, composted, garden loam. Simply put, the better the soil, the better the display of flowers.
At high altitudes, soils reach their extremes and are inherently more fragile, more alkaline or more acidic and more deprived of organic matter than soil in more moderate climes. Top soil is often non-existent, or subject to rapid degradation because of severe wind and intense sun. We encourage gardeners to build up and care for soil by:
Adding organic matter. We continually obtain the best yields in our gardens after focusing upon feeding first our soil and secondly the plants growing in it. Feed soil with copious amounts of fully decomposed compost. Be aware that overly fresh manure and other undigested organic matter may take too long to decompose in cold, spring soil, aggravating already acidic pH levels and lowering nitrogen levels. If necessary, add overly fresh manure as early in the fall as possible.
Adding nutrients. The optimum method for building a supply of available nutrients in garden soil is to add organic soil aids each spring. Organic soil aids decompose slowly over the years thereby preventing overdose damage. The necessary macro- and micronutrients are assured. Testing and fine-tuning for specific nutrients becomes unnecessary. Balance between nitrogen and phosphorous is preserved when both are added at the same time at recommended amounts.
Add mycorrhizal and bacterial inoculants. Seeds Trust offers Soil Aids to stimulate plant growth and to fix atmospheric nitrogen into plant available nutrients. The mycorrhizal inoculants will help plant roots absorb water and scavenge for nutrients.
Testing soil pH. An unbalanced soil pH can bind nutrients into garden soil and prevent them from being made available to plants. A test for soil pH (acidity or alkalinity) is fast, simple, accurate and inexpensive. We test our garden beds each spring with the Lamotte pH test kit.
Minimizing tillage. Proper tillage increases the biological activity in the soil and leads to rapid breakdown of organic matter in soil. We try to minimize turning or mixing the different levels of soil.
Many wildflowers, once established, are drought-resistant. However, it is mandatory to keep soil moist 3-4 weeks while germination takes place. Seeds must be kept moist during the fragile stage when they swell with water until the time when new little roots have grown deep enough to find soil moisture. Important: do NOT let the seeds dry out! This may require watering 2 to 4 times each day. Sunny, hot, windy days and sandy soil conditions may require a short watering, as often as every hour. (Most automatic sprinkler systems can be adjusted to this demand.) After wildflowers have been established, water less frequently but consistently to prolong season-long blossoming.
Divide the area to be planted into a number of equal areas. (We draw lines in the soil with sticks.) Divide the seeds equally and place in separate bags. Using one bag for each area will prevent under-seeding some areas or over-seeding and running out before every area is planted. Lightly rake seeds so they are covered with approximately ½" of soil; or mulch with straw or compost. Note: we have seen no distinct germination advantage using expensive hydro-seeding techniques in areas that can be watered.
Weeds should be "managed" rather than "eradicated". Before rushing out to destroy every weed in sight, remember that weeds can help prevent erosion and help keep soil moist. Certain weeds provide habitat for beneficial insects. Pulled and left on the ground or moved to a compost pile, they become an important source of organic matter.
Minimize weeds in wildflower gardens by minimizing or preventing soil disturbance. Anytime soil is opened, tilled or turned it becomes vulnerable to invasion from new plants. Plants most often to appear first are what botanists call "pioneers". Unfortunately, most of the rest of us know them as the most troublesome weeds including thistle, mustard and mullein.
Rushing to plant wildflower seeds in the spring before weeds emerge is not always a successful strategy. If weed seed is in the soil (some varieties can be dormant for up to seven years), weeds can successfully out-compete wildflowers. Ideally, weeds should be controlled before wildflowers sprout; newly sprouted weeds and wildflowers are difficult to distinguish. We suggest when planting a newly disturbed area, waiting until the first crop of weeds has come up and been removed before sowing wildflower seeds. In some cases, we have seen a second and even a third crop of weeds that needed to be removed. Densely planted wildflowers in an established garden will help prevent the germination of new weed seeds blown or washed into the garden.