by Ray Allen
When to Plant Your Wildflower Garden
Plant In Spring, Summer or Fall
Planting In Mild-winter Areas
Planting In Areas With Killing Frost
Many people like to say "Nature plants wildflowers in the fall." and that is basically true. All season long, flowers in the wild are blooming, then "going to seed", which means dropping their seeds to propagate their individual species. For example, a very successful species such as Black-eyed Susan blooms in midsummer, and then drops a large number of seeds from each dying flower in late summer. If weather cooperates, these seeds may sprout before winter. If it is dry and hostile for the seeds, they will simply lay there through the winter and sprout in spring.
Fall Planting Advantage: Earlier bloom.
Your site may determine the time of year you plant. If it is a flat site, you can plant any time you like. If it's at all steeply sloped, you should probably choose spring. This is because fall-planted seed is subject to "washouts", since it has to lie there all through late fall and winter, while spring-planted seed has only to wait until it sprouts. The dangers to fall planting on a slope are obvious.
If you decide to plant in fall, wait until after killing frost. The timing is roughly the same as when tulip bulbs are planted late enough to be sure your seeds will not sprout before winter. The point is to wait until the soil is so chilled that seed cannot sprout, but stays dormant until warming soil and moisture trigger germination in spring.
A great advantage of fall planting is that the weather in fall is usually more predictable than spring. Chances are that in fall you won't be delayed by rains or be locked to a tight time period when your seed must go in. Simply choose your site, prepare your ground and sow your seed before the ground freezes. There's definitely less time pressure on the gardener in fall than in spring.
One disadvantage of fall planting is that you have no idea how much weed seed may be in the soil in your cleared area. However, with fall planting, your flower seed at least has a level playing field with any weed seed that's there. In spring, the weed seeds have some advantage, since they've been there through the winter, all ready to sprout.
If you're like most meadow gardeners, once you clear your ground by tilling or any other method, you'll want to sow your seed immediately thereafter - if possible on the same day, surely the one after. You can't till the area one weekend and seed the next. Here's the reason. The minute you open the ground, you turn up weed seeds that are in all soil. If you wait before putting in your flower seed, those weed seeds have an important "jump" on the flowers, and they may become quickly dominant over the flower seed as your meadow area grows. By putting the flower seed in quickly, you at least give your flowers a "level playing field" with the grasses and weeds that are sure to grow up with them. Remember when you created a vegetable garden by clearing an area? Weeds popped up quickly, and you immediately pulled them. In this case, no one is going to pull the seedlings that appear after your seeding, at least for awhile. Some of those seedlings are going to be weeds you didn't plant. Don't be foolish enough to think some weeds aren't going to be there; they are.
Spring Planting Advantage: A chance to remove the weeds.
The idea is to clear the ground, do not sow seed, but instead begin immediately to encourage weed growth as quickly as you can. This means watering if it's dry, and watching closely. After about two weeks, you'll see green seedlings popping up, and you'll know at least the early germinating seed population of your soil. Wait as long as you can (this usually depends on weather and how early you got started). Once you have a good idea of what you're dealing with, you're ready to kill those young weeds and spread your flower seed.
There are several ways to proceed. Many use a herbicide like Round-Up. Others have been known to lay wet newspaper on the weeds to smother them, but this is not surefire and takes longer. At this point, you must resist heavy raking or tilling again, because if you do, you'll turn up fresh weed seeds which will begin their sprouting process, starting the whole cycle over again. In other words, at this point, you must kill the weed seedlings you see, but NOT disturb the soil again.
Once your soil is clear, sow your wildflower seed and it will grow in what is probably the most weed-free situation possible. Nothing is perfect, and of course, over time, weeds and grasses will invade. But this method gives your flower meadow the best possible start. Obviously, there are several disadvantages. First, it takes time. Second, it usually requires more watering once your flowers sprout, since you're farther along into the season, and spring moisture has subsided. Thirdly, bloom is delayed, compared to when it would have begun if you had seeded when you first cleared the ground. But if you're serious about installing the best ever meadow, all this is worth it.
Certain flowers and certain seasons:
Another consideration about annuals: If you plant in fall in cold-winter areas, you may lose the more tender species to late spring frosts after they germinate. Cosmos is one species that is susceptible to spring-kill, but favorites like red poppy and cornflower are tough "half-hardy annuals", and aren't fazed by a few spring frosts.
Ray Allen 11/18/02; updated 10/18/03, 2/18/04, 4/15/05