When to Divide Ornamental Grasses: A Simple Guide to Keeping Your Garden Beautiful

Ornamental grasses can greatly enhance the aesthetics of a garden with their graceful foliage and unique textures. To ensure their health and longevity, it’s important to know when to divide ornamental grasses. Dividing ornamental grasses is typically done in late winter or early spring, just before new growth emerges and during the dormant period. This timing minimizes stress on the plants and allows them to establish and grow vigorously in the upcoming season.

The process involves carefully digging up the clump, dividing it into smaller sections, and replanting them at the same depth as they were before. Proper timing and technique are essential for maintaining the vitality and beauty of ornamental grasses in your landscape. Dividing ornamental grasses might sound like a daunting task, but fear not; this guide will walk you through it step by step.

The Ideal Time for Division

Spring Division

Spring is a splendid time to divide your ornamental grasses. Here’s why:

Advantages of Spring Division:

• Spring’s mild weather provides the perfect conditions for plant recovery.
• Dividing before the growing season allows plants to establish themselves.
• It’s easier to see the plant’s structure before new growth obscures it.

Ideal Conditions for Spring Division:

• Choose a day when the soil is workable but not waterlogged.
• Aim for a day with mild temperatures, ideally before the grass starts actively growing.

Examples of Grasses Suited for Spring Division:

• Feather Reed Grass (Calamagrostis x acutiflora)
• Blue Oat Grass (Helictotrichon sempervirens)
• Pampas Grass (Cortaderia selloana)

Fall Division

Fall is also a great time for division. Here’s why you might choose this season:

Benefits of Fall Division:

• Cooler temperatures reduce stress on the transplants.
• Divisions have time to establish their root systems before winter.
• You can see the plant’s structure clearly after the growing season.

Conditions and Considerations for Fall Division:

• Aim for a day with mild temperatures, ideally before the first frost.
• Water your grasses well in late summer to prepare them for division.
• Choose a location with good drainage to prevent waterlogging.

Examples of Grasses Suitable for Fall Division:

• Maiden Grass (Miscanthus sinensis)
• Fountain Grass (Pennisetum alopecuroides)

Signs that Division is Needed

Before you dive into dividing your ornamental grasses, it’s crucial to recognize the signs that it’s time for this operation.

Overcrowding and Loss of Vigor

Indications of Overcrowding:

• The grass’s center becomes dense and dead, while the outer edges thrive.
• The grass looks less vigorous, with fewer and thinner blades.

How Overcrowding Affects Health:

• Overcrowded grasses compete for resources like nutrients and water.
• This competition weakens the grass, making it more susceptible to diseases.

Declining Aesthetic Appearance

Changes in Appearance Signaling Division:

• Your once-elegant grass now looks messy and unkempt.
• Flowering becomes sparse, and the overall shape is no longer attractive.

Impact on the Garden or Landscape:

• Neglected ornamental grasses can detract from the beauty of your garden.
• Well-maintained grasses enhance the overall aesthetic appeal of your landscape.

Steps to Divide Ornamental Grasses

Now that you know when to divide your grasses let’s get into the nitty-gritty of how to do it.

Pre-Division Preparations

Gathering Necessary Tools and Materials:

• You’ll need a sharp spade or shovel, pruners, and a tarp or old sheet to catch divisions.
• If the grass is particularly tough, consider using a saw or even a reciprocating saw.

Choosing the Right Location for the Divisions:

• Decide where you’ll transplant the divisions. Have this spot prepared in advance.

Division Process

Step-by-Step Guide to Dividing Ornamental Grasses:

• Start by clearing away dead foliage and cutting the grass back to about one-third of its height.
• Use your spade or shovel to dig around the grass in a circle, about a foot or more from the center.
• Lift the grass clump out of the ground.
• Depending on the size of the grass, you might need to use pruners or a saw to divide the clump into sections.
• Plant the divisions in the prepared spot, making sure they’re at the same depth as they were before.

Tips for Minimizing Stress on the Plants:

• Water the divisions well after transplanting to help them settle into their new home.
• Mulch around the transplants to conserve moisture and control weeds.
• Fertilize sparingly; too much can shock the newly divided grass.

Post-Division Care

Transplanting Divisions:

• Give each division plenty of space in its new location to allow for growth.
• Water the transplants regularly, especially during dry spells.
• Monitor them for any signs of stress or disease.

Watering, Mulching, and Fertilizing Recommendations:

• Keep the soil around your divisions consistently moist for the first few weeks.
• Apply a layer of mulch to help retain moisture and suppress weeds.
• Fertilize with a balanced, slow-release fertilizer in the spring, but avoid over-fertilizing.

Special Considerations

Warm-Season vs. Cool-Season Grasses

Understanding the difference between these two types of grasses can help you determine the best time for division.

Differences in Division Timing:

• Warm-season grasses, like Maiden Grass, are best divided in late winter or early spring before new growth.
• Cool-season grasses, such as Feather Reed Grass, are typically divided in early spring.

Varieties Within Each Category:

• Keep in mind that there are many varieties of both warm-season and cool-season grasses, each with its unique needs.

Here’s a summary of the differences between warm-season and cool-season grasses:

Aspect	Warm-Season Grasses	Cool-Season Grasses
Optimal Division Time	Late Winter to Early Spring	Early Spring
Examples	Maiden Grass (Miscanthus)	Feather Reed Grass (Calamagrostis)
Division Frequency	Typically less frequent	May require more frequent division
Division Process	Generally straightforward	Similar division process, but potentially smaller divisions
Challenges	None in particular	Larger grasses may be more challenging
Fertilization	Balanced, slow-release fertilizer in spring	Similar approach in early spring
Overall Size	Can range from small to large	Tend to be smaller in size

Ornamental Grass Size

The size of your ornamental grass can influence the frequency of division and the division process.

How Size Influences Division Frequency:

• Smaller grasses may need division less frequently than larger ones.
• Large grasses can be more challenging to divide due to their size and weight.

Managing Smaller and Larger Grasses:

• Smaller grasses can be divided with ease using the steps outlined earlier.
• Larger grasses may require more effort and possibly the help of a friend.

Common Mistakes to Avoid

Here are some common pitfalls to steer clear of when dividing ornamental grasses:

• Dividing at the Wrong Time: Timing is everything; make sure you choose the right season for your specific grass type.
• Neglecting Pre-Division Preparations: Gathering the right tools and preparing the transplant location can make the process smoother.
• Planting Too Deep: Keep the divisions at the same depth as they were before to prevent rot.
• Overwatering: While newly transplanted divisions need moisture, overwatering can lead to root rot.
• Over-Fertilizing: Excessive fertilizer can stress the plants; use it sparingly.

Can you divide ornamental grasses in the spring?

Yes, you can divide ornamental grasses in the spring, and it’s actually one of the preferred times to do so for many varieties. Dividing ornamental grasses in the spring is beneficial for several reasons:

1. Mild Weather: Spring provides relatively mild and consistent temperatures, which are ideal for plant recovery after division.
2. Pre-Growth Season: Dividing before the active growing season allows the newly divided sections of grass to establish themselves before the peak of growth.
3. Clear Plant Structure: Early spring offers a clear view of the plant’s structure before new growth starts to obscure it. This makes it easier to see where and how to divide.

When dividing in the spring, be sure to choose a day when the soil is workable but not waterlogged. Aim for mild temperatures, ideally before the grasses start actively growing. It’s also important to provide proper care to the transplants, including adequate watering, mulching, and monitoring for signs of stress.

Keep in mind that the best time for dividing ornamental grasses may vary depending on the specific grass species, and local climate conditions.

Can you divide warm-season ornamental grasses in the fall?

Dividing warm-season ornamental grasses in the fall is generally not recommended because it goes against their natural growth cycle. Warm-season grasses typically thrive during the warmer months of spring and summer, and they tend to go dormant or slow down their growth as the cooler fall weather sets in. Dividing them in the fall, when they are preparing for dormancy, can be stressful for the plants and may reduce their ability to establish new roots before winter.

The best times to divide warm-season ornamental grasses are typically in late winter to early spring, just before or as new growth begins. This timing allows the divided sections to establish themselves during the active growing season and better prepares them for winter.

If you must divide warm-season grasses in the fall due to specific circumstances, it’s essential to take extra care, provide adequate water, and monitor the transplants closely to minimize stress and increase their chances of survival. However, spring remains the preferred season for dividing warm-season ornamental grasses.

What happens if you don’t cut back ornamental grasses

If you don’t cut back ornamental grasses, several things can happen over time:

1. Overcrowding: Ornamental grasses can become overcrowded, with older growth overshadowing newer shoots. This can lead to a less attractive appearance and reduced air circulation, potentially creating a haven for pests and diseases.
2. Drooping and Flopping: As grasses grow taller and their foliage becomes denser, they may start to droop or flop over. This can make them appear unkempt and diminish their visual appeal.
3. Loss of Aesthetic Value: The natural beauty and form of ornamental grasses can diminish without proper pruning. Instead of their characteristic upright and graceful appearance, they may become messy and chaotic in appearance.
4. Decreased Vigor: Over time, grasses that aren’t cut back may become less vigorous, resulting in reduced growth and overall health.
5. Seed Production: Some grasses will produce seeds if left untrimmed. While this can be desirable for some gardeners, it can also lead to unwanted self-seeding and potentially invasive growth in the garden.
6. Winter Interest: Certain ornamental grasses can provide visual interest during the winter months, with their dried foliage and seed heads creating appealing textures and colors. By not cutting them back, you can enjoy this aspect of their beauty.

In summary, while some gardeners appreciate the winter interest and more natural appearance of uncut ornamental grasses, neglecting to trim them can result in reduced aesthetics, overcrowding, and potential health issues over time. Pruning tall ornamental grasses at the appropriate times can help maintain their vitality and visual appeal.

FAQ

Conclusion

Dividing ornamental grasses doesn’t have to be intimidating. Knowing when and how to do it can breathe new life into your garden, keeping it vibrant and beautiful year after year.

The best time to divide ornamental grasses is late winter or early spring, just as new growth emerges. This gives the divided plants the entire growing season to establish themselves.

So, keep an eye on your grasses, follow the steps outlined here, and enjoy the swaying beauty they bring to your outdoor space. Happy gardening!