March native gardening
Each year the pollinator garden in Laurel’s Sweitzer Park can be thinned.
Courtesy of Jimmy Rogers

This time of year, gardeners of all stripes open their calendars and almanacs to figure when to sow seed, when to cut stems and when to plant tender plants. If you have native plants entering their second spring, there’s another activity to consider: thinning.

Traditional American gardens position plants at least a foot apart, so that they will only touch when they reach their mature size. In functional native gardens, designers favor denser plantings to crowd out weeds and increase diversity. As these designs mature, some plants will begin to spread more than others. Most of the time this is OK. For instance, you may want to see black-eyed Susans (Rudbeckia hirta) fill out along the sidewalk, both wowing passers-by in the summer and suppressing winter weeds with their basal florets. However, an overzealous wild bergamot (Monarda fistulosa) spreading into that same bed might intimidate pedestrians with its 5-foot-tall stalks.

Thinning enables beautiful gardens to remain gardens instead of gradually morphing back into natural landscapes. Those landscapes are also beautiful, but plants growing beyond convenient borders or crowding out other plants can prove inconvenient or unaesthetic to the humans who share close quarters with them. Additionally, regular thinning will give you an opportunity to open a plant library for friends and neighbors to take some of your most vigorous plants back home to their own gardens.

First, let us define some terms. Native gardeners often use the word thinning to mean a reduction in density of either individual plants or the density of the garden as a whole. When a plant has grown more densely than is practical, gardeners split or divide these plants and move them somewhere else, which is called transplanting. When new plants start coming up from a mother plant, either by seed or from runners, these are called volunteers, and they too can be transplanted. Here in the Mid-Atlantic, our climate allows for native transplanting during most of the year, even in the winter. You need only refrain from transplanting when the ground is frozen.

Human interest drives all of this thinning, splitting and transplanting; the plants don’t need us to move or divide them. Always consider the wait and see option, as your garden may reorganize itself in ways you will appreciate. However, when we put plants into garden beds, we are creating an artificial situation and need to step in occasionally to ensure they meet our needs.


When you find a volunteer popping up in an inconvenient place, first choose a new home for your bonus plant. Consider these options:

  • Fill in any bare soil or empty spots with lower-growing plants.
  • Partner plants that bloom early with plants that bloom late.
  • Position lower-growing plants along pathways and next to late-growing tall plants.
  • Arrange a bed with different flower shapes and colors.

To remove the plant, grab a small shovel or trowel and imagine a circle surrounding the plant’s leaves. Double the width of that circle and place the tip of your shovel anywhere along the edge. With the blade pointing straight down, cut into the soil. This technique will avoid slicing as many roots as possible.

Once you have made your first cut, lean back and lever the dirt up a little bit. If the soil is rich and very wet, the plant may come right out. If the soil won’t yet release the plant with a gentle tug, remove your shovel and place it 90 degrees around the circle from your first cut (15 minutes on a clock). Make another vertical slice and lean back again. See how far you can lift the soil. I often find that young plants will come out after the second cut. If the soil detaches 

from the ground, then you have completed the first step. If not, keep working your way around the circle until you’ve fully excavated the plant.

Leave some soil attached to the plant, as it has already established a web of tiny roots that take up water and nutrients. However, if you consistently remove a lot of soil when you uproot volunteers, you’ll end up with a lot of holes in your garden. Most of the soil won’t yet be full of roots, so you can crumble or even smack the soil back into the hole. Press the remaining soil back in or fill the whole in with another plant that would go better in that spot.

Your uprooted volunteer can now be planted again, ideally that same day. For very small plants, first try what I call the crevice method. Make a first vertical cut and wedge open the soil just enough to slip in all the roots, then reseal the crevice, putting good pressure on the roots. If you need more space, excavate more soil the same way you did for uprooting and plant into the hole. With either method, you’ll want the plant to be exactly as deep in the soil as it was before transplanting. Some plants have an obvious color difference between the top of the roots and the bottom of the stem. Others are harder to tell, so take note before uprooting. Make sure all of the roots end up packed in soil and press down firmly with your hands to either side of the plant.

Transplanting will leave air pockets in the ground, so the last step is to water in your volunteer.  Watering for a count of 10 seconds will flood those air pockets, hydrate the plant and settle the soil around the roots.


If a plant is mature, consider splitting it. Some plants are organized into lots of little plants (sometimes called offsets or pups) that are loosely connected. After uprooting, force them apart by hand with gentle pressure at the underground connection points. These can now each be planted singly or be grouped together for a fuller look.

If a plant doesn’t form obvious offsets, then it will need to be divided more forcefully. After uprooting a plant, always check if it can be ripped in half, ideally keeping clean vertical sections of the plant intact (stem connected to roots). For a large or tough plant, make a clean strike with a shovel along the vertical plane. After being planted, the divided portions will grow back into a more uniform shape.

A mature garden generates a mountain of volunteers and potential divisions, so offer up free plants to your community. Neighbors and friends are more likely to start a native garden if they receive some starter plants. Plus, every time you see your plants in another’s garden, you will be reminded of your unique connection.