The March Garden Divide – What to Do Now (and What to Wait On)

March is a great time to divide many popular plants, but whether you should depends on your climate and the weather conditions. So let's take a look at potential plants to divide in March, and when it is better to wait until later in the season, or longer.

The top plants to divide in March are herbaceous perennials and ornamental grasses. It is a perfect moment for many gardeners as they are about to start growing again for the new season. However, for those still experiencing winter frosts, snow, and storms, it is not so opportune, and you may do more harm than good dividing plants this month.

Here we deep-dive into when to divide plants in early spring, and the best candidates that you may have in your garden. To prevent any mistakes, we reveal the zones where you should wait and the plants not to divide this month.

Plants You Can Divide in March: What to Do Now

1. Summer and Fall-Flowering Perennials

If the ground is workable, not frozen or waterlogged, a long list of summer and fall-flowering perennials can be divided in March. Lifting and dividing perennials every few years helps to keep clumps vigorous and continue to put on the best displays.

Over the years, clumps can get congested, and the flowering is affected. Dividing not only rejuvenates them, but also gives you more plants to add to your backyard ideas.

You can divide lots of the best perennials in early spring, including aster, sedum, bee balm, hardy geranium, monarda, salvia, black-eyed Susan, and many more.

When it comes to how to divide plants, smaller clumps can be dug up and divided by hand. Larger ones may need a sharp knife or two sturdy garden forks (such as this steel spading fork at Lowe’s) inserted back-to-back to lever the clump apart.

2. Foliage Plants

The importance of foliage plants cannot be underestimated, as they offer glorious color, sculptural foliage, and texture to any flower bed or container.

Many of the most popular foliage plants can be divided in March. Just like flowering perennials, congested clumps can suffer from bare centers or smaller foliage, which can be solved by lifting, dividing, and transplanting. Also, if a clump has got too big for its space, it can be divided into smaller sections.

The likes of hostas, hardy ferns, bergenia, brunnera, and lamb’s ears (if you want more plants with silver foliage) are suitable for dividing in early spring.

The job is best done on a dry, cloudy day, rather than a hot, sunny day, and care must be given to keep newly-planted divisions well-watered to get them established. A soil moisture meter (available at Amazon) can help you determine when to water divisions to ensure they put down strong roots.

3. Cool-Season Ornamental Grasses

Perfect for height, movement, and interest throughout the winter, ornamental grasses come in a wide variety, with specimens suitable for anything from screening to pots. When you grow ornamental grasses, they need to be divided every 3-4 years to prevent congestion, which can affect vigor and lead to dead centers.

Cool-season ornamental grasses such as carex, calamagrostis, festuca, hakonechloa, schizachyrium, and stipa can be divided just as they start growing in early spring to rejuvenate clumps, and give you new ones for free.

As the time to cut back ornamental grasses also lands in late winter or early spring, you can either prune and divide at the same time, or divide plants a little later, though any new growth should be an inch or two when lifted, split, and replanted.

Ornamental grasses can be split with a sharp spade or a hori-hori knife. The clumps can get very large, so it may take some work to dig up and divide an older one. It is recommended to wear gloves when working with grasses, as the blades can cause nasty cuts.

You can get a Japanese hori-hori garden knife at Amazon with a serrated blade that is ideal for sawing through tough roots.

4. Ground Cover Plants

Ground cover plants are vitally important but often underrated. The benefits of ground cover plants go far beyond smothering weeds and preventing soil erosion. There are lots of flowering ground cover plants that can make colorful carpets, and evergreen ground cover plants to bring year-round interest to often trickier spots with shade or slopes.

If you have extra areas to fill, you can propagate fast-growing ground cover plants by division rather than spending money on new ones. Or, if any of your existing plants are looking sparse, dividing them can revitalize clumps and give you new plants.

Popular ground cover plants like ajuga, creeping thyme, lamium, monkey grass, ground cover sedums, and more can be divided into sections in March and replanted straight away to get down roots before temperatures rise for summer.

When lifting and transplanting, adding bone meal into the planting hole and mixing it into the surrounding soil helps the new clumps to develop roots quickly. You can get a bag of organic bone meal at Burpee, which is ideal for new plants.

Plants You Should Not Divide in March – When to Wait

1. Anything When the Ground Is Frozen

The simple truth is that you don’t want to lift and divide any plants during frozen winter weather. It means the task isn’t suitable for colder US hardiness zones, particularly zones 3 or 4, in March, where it may be a job for April, or even May.

Depending on the weather, gardeners in zones 5 or 6 may be able to divide plants in the second half of March; otherwise, wait until next month if the ground remains frozen this month.

The dangers of dividing plants in freezing weather are that it stresses the plant, and roots can get damaged in extreme cold. If the ground is frozen or freezing temperatures are forecast, wait until the conditions get more suitable and the weather improves.

2. Spring-Blooming Perennials

Perennials are divided in spring or fall. A good motto to remember is that summer and fall-flowering perennials are better for spring division, and those that bloom in spring are better for fall.

Dividing spring-flowering perennials in March disrupts their natural life cycle, disturbing them just when they should be putting their energy into blooming. You’ll lose out on flowers for that season – is it worth it?

Instead, if you grow peonies, bleeding heart, irises, lilies, phlox, astilbe, or any other spring bloomers, don’t touch them in early spring.

Hold fire, and divide the plants after flowering, in early fall. This gives new clumps a lot of time to bed down roots ahead of winter, and they can flower come next spring.

3. Tender Plants

Any tender or borderline hardy plants in your yard shouldn’t be divided until at least after the risk of frost has ended. March is too early in many US hardiness zones to lift and divide plants, if the conditions are still too cold then leave it until late spring, usually April or May.

Wait until the soil has warmed in late spring to lift and divide the likes of cannas, agapanthus, red hot poker, dahlias, or alstroemeria. Dividing and planting them too soon can result in plants getting damaged by freezing weather, or rotting in cold, wet soil.

4. Warm-Season Ornamental Grasses

Cool-season ornamental grasses can be divided in March, but you do want to wait with warm-season grasses.

These types of grasses start growing later than cool-season ones, starting in late spring as opposed to early spring – hence the slight delay in lifting and dividing them, as you still want to do it just as they start growing.

If you have panicum, pennisetum, blood grass, pampas grass, or miscanthus varieties, these warm-season grasses should be divided in late April or early May once they just start growing for the new season.

As well as plants to divide in March, there are other key seasonal tasks to add to any spring gardening checklist.

Pruning is an important job, as many trees, shrubs, and perennials need trimming before they start growing again when the temperatures rise. You can see our guides to plants to prune in spring and trees to prune in March for detailed guidance on lots of plants that may need some attention this month.

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Tools for Dividing Plants