So, you’ve planted and carefully nurtured your perennial herbs, and they’ve finally reached the size you had in mind when you started them.
Or maybe they’ve gotten just a little bigger than that. Or a lot bigger… It may be time to divide them.
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Why Divide Plants?
Dividing provides you with free new plants to set in new locations, or to sell, swap, or give away to neighbors. It also keeps your perennials from spreading so aggressively that they choke each other out or fill in all the spaces you meant to keep for annual herbs.
Perhaps most importantly, it keeps your plants healthy. If you leave certain perennial herbs undivided too long, they may grow woody or leggy, or may begin to die out in the middle. Division will keep them fresh and growing.
10 Herbs That Benefit From Division
Many perennials thrive best when they’re divided frequently. Gardeners don’t all agree about which these plants are.
Clumping herbs grow in ever-thicker clusters of plants which can be easily divided by taking out shovelfuls here and there. Most gardeners agree that these need to be divided.
Woody or shrubby herbs are single plants that get overgrown. Some master gardeners say not to divide shrubby plants. But I’ve divided my sage and lavender successfully, and some master gardeners recommend doing this.
Step-by-step instructions for each method follow the list of plants.
1. Chives (Allium schoenoprasum) –Rodale’s recommends dividing established clumps every 3 years. I divide mine more often than that, largely to stop them from taking over the garden.
2. Echinacea also called coneflower (Echinacea angustifolia), spreads aggressively in densely matted root clumps. I’ve found that it takes some aggressive shovel-jumping to divide this, but despite the rough handling, the divisions are almost impossible to kill.
3. Lavender (Lavandula spp) is a woody shrub which I’ve found useful to divide regularly.
4. Lemon balm (Melissa officinalis) is a soft clumping herb that spreads rapidly by runners. It’s very easy to divide.
5. Marjoram (Origanum majorana) grows in tall soft clumps which spread rapidly and are easy to divide.
6. Mint (Mentha spp) is a soft clumping herb that spreads rapidly by runners. It’s very easy to divide.
7. Oregano (Origanum vulgare) grows in tall soft clumps which spread rapidly and are easy to divide.
8. Thyme (Thymus vulgaris) is a low-matted herb that grows in expanding clumps. The foliage will trail out beyond the range of the roots. Push the tops back so you can see where the roots are before dividing.
9. Sage (Salvia officinalis) is a woody shrub which I’ve found useful to divide regularly.
10. Tarragon (Artemisia dracunculus) is a small soft shrubby plant that should be divided every 2-3 years. Some master gardeners warn that the roots are fragile and should be carefully cut apart with a knife, not jumped on with a shovel, at least when the plants are small.
When Should I Divide My Herb Plants?
If plants are overflowing the space you designated for them, or if they’re getting dead in the center, then they need to be divided.
Some master gardeners recommend dividing perennial herbs every 3 years. I dig out large clumps of my thyme, oregano, chives, mint, and echinacea every year, and lift out and replant some of my existing plants.
Herbs should be divided when they are not in bloom or in their most vigorous growth. I divide most of my plants in early to mid-spring, though I’ve done occasional fall divisions.
The Pennsylvania State Extension says that in areas where spring is late and short it’s best to divide plants in September, 4-6 weeks before the ground freezes.
Step-by-Step Guide To Dividing Plants
1. Check Soil Moisture
Don’t divide plants if the soil is too wet to work–if you can squeeze water out of a clump of dirt. If the soil is dry–if a squeezed fistful of soil crumbles into dust rather than sticking together–water your herbs well 24-48 hours before you divide them.
2. Dig Around The Drip Line of Your Plants
Dig straight down all the way around, and then stick your shovel in at an angle to cut underneath the plant. Pull the whole plant free from the soil.
3. Divide Your Plant
Soft clumping plants like thyme can sometimes be pulled apart with your hands. For tough-rooted plants like echinacea, you’ll probably need to use a shovel, and you may have to jump on it.
4. Trim The Divisions
Trim off and discard any dead or damaged roots.
Set your plant divisions into pots, or into the ground, at the same depth as when you took them out. Tamp the soil down around them gently but firmly.
6. Water Them In
Water your plants well after replanting
Dividing perennial herbs takes some energy and attention, but it multiplies the number of your plants while also extending their productive lives.
Enjoy expanding your own plantings, and maybe also cultivating the goodwill of your neighbors by sharing plants with them.