On a short leash, self-sowers can add to the garden

I have come to the conclusion that you are either a gardener who loves self-sowers or one who detests them. It is as black and white as anything can be in the garden.

Self-sowing annuals and tender perennials — those plants that seed around the garden all on their own — can create a new layer in a garden, taking advantage of gaps in the garden to create moments of color, texture and interest. But not all self-sowers are welcome, and the list of the good and bad varies not just between hardiness zones, but also between gardens, based on soil, moisture, exposure and any number of other factors.

The key to a good relationship with self-sowers is finding a handful that do what you want them to, which usually means that they offer excellent interest and spread nicely without being aggressive or invasive.

And it’s that last bit that’s the issue for a lot of gardeners. Having had a bad experience with one self-sower, many gardeners lose interest in entertaining any others in the future.

I’d hate to be without Verbena bonariensis, the tall-stemmed annual with a lollipop purple flower, but clearly there are plenty of gardeners who detest it based on the looks on their faces when I mention it.

Relying on self-sowers sounds like a good way to avoid some work in the garden, but that’s not the case. In fact, a good way to look at it is like planting in reverse. When you look at an area of the garden in need of plants, you figure out how many you need in that spot and then plant them. With self-sowers, you need to look at an area and decide what needs to come out. It’s less expensive than buying new plants, but no less work.

Left to their own devices, self-sowers can overtake an area, outcompeting perennials and eventually each other and look rather messy. So it’s important to edit out many — most, actually — of the self-sowers that do show up.

This can be done by using a hoe to remove them early on, or they can be removed by hand, which works better when they are closer to plants you want to keep. Another method to consider is judicious mulching in fall, leaving areas where you want seeds to take open and mulching areas where you don’t want them. This, of course, requires a good knowledge and previous observation of the self-sowers in your garden.

The seeds of annual breadseed poppies (Papaver somniferum) will always germinate in clumps with dozens of seedlings, none of which will amount to much if they are all left. Judicious removal of most of them is called for, and should be done without a tinge of guilt.

I admit to letting some self-sowers run a bit rampant. Virginia bluebells (TMertensia virginica) fill several garden beds at this time of year. But I can enjoy their blooms and lop off the foliage immediately after to clear space for perennials to get some light.

It’s an additional job at a busy time in the garden, but it’s worth it, and I bet even the gardeners who dislike self-sowers couldn’t argue with that.