Here’s What Happens if You Don’t Trim Ornamental Grasses

If you have ornamental grass, you might not have realized that you need to trim it now and then to ensure it remains as healthy and aesthetically pleasing as possible. However, it is essential to cut it back. So, what happens if you don’t trim your ornamental grass?

If you don’t trim ornamental grasses, they will likely look messy, giving the space an unorganized look. Parts of the grass will be brown, and other parts will grow green, which can look odd. The old growth might prevent new growth from coming in, and rotting is more likely to occur.

Eager to learn more about trimming ornamental grasses? Stick around to find out everything you need to know!

How Often Should You Trim Your Ornamental Grasses?

You should trim your ornamental grasses once in spring or fall for the best results. It will grow and flourish during the summer, so there’s no need to cut it during this season. 

You might be tempted to trim it back every few weeks or months, but that’s unnecessary and may even cause harm by damaging the healthy parts of the plant. Once you stick to trimming the grass once per year, you shouldn’t run into any issues.

This Is What Happens if You Don’t Trim Ornamental Grasses

It Will Look Messy

Failing to trim your ornamental grass will make it look unappealing, especially if it’s a deciduous variety. 

As you may know, many deciduous ornamental grasses turn brown during fall and winter. So during spring (right before the new green growth starts), it’s essential to cut back this brown growth to ensure the grass is uniform once the green colors come in from the bottom.

You certainly don’t want the bottom of the ornamental grass to be green while the rest is brown, so cutting it back avoids this issue. 

Old Growth Might Prevent New Growth From Flourishing

If you don’t trim your ornamental grass during spring, it might prevent new growth from coming in correctly. Cutting everything back allows space for new plant growth and development so that nothing can get in the way.

It’s like any other plant that needs pruning every year. Most plants need to be pruned back in spring because their old growth prevents new growth (like flowers, branches, and leaves) from coming through. Ornamental grass is similar in that regard. 

Although failing to trim it might not prevent new growth entirely, it certainly won’t make the natural process any easier.

Rotting May Occur

You must also consider the chance of rotting when thinking about trimming your ornamental grasses. If you leave old brown grass to continue growing into the summer, it might begin to rot at the top, which will look highly unappealing.

On top of that, it can damage the ornamental grass, so you want to avoid rotting at all costs. The rotting may fall off eventually, but it’s always best to get ahead by trimming the ornamental grass before it gets to that point.

While trimming is important for maintaining your ornamental grass and keeping it from rotting, there are other things that are important if you want healthy and thriving ornamental grass. For example, keeping the soil well-drained ensures the grass remains healthy and prevents the chances of root rot and other diseases.

How To Trim Ornamental Grasses

You now know that trimming ornamental grasses is essential for health, growth, and maintenance. However, the exact way you cut the grass depends on its type. There are two main types of ornamental grasses: deciduous and evergreen.

Below, I’ll discuss the best way to trim these ornamental grasses.

Trimming Deciduous Ornamental Grass

Deciduous ornamental grass does not remain green throughout the year. This grass type usually turns brown for half of the year. Unlike other deciduous plants, many deciduous ornamental grasses retain foliage and flowers throughout the year. The main thing that changes is the color.

Examples of deciduous ornamental grasses include:

  • Miscanthus
  • Feather reed
  • Mexican feather grass

Although you can use the term ‘trimming,’ it’s more like ‘cutting’ when it comes to deciduous ornamental grass because you usually need to remove a large chunk of the plant. Here is how to trim (or cut) deciduous ornamental grass:

  1. Ensure it’s the right time of year. Spring is the best time to cut back warm-season ornamental grass, so make sure it’s not too early. Later winter is also a suitable time.
  2. Grab the bottom of the grass plant with your hand. Doing this will secure it so that you can cut it more easily.
  3. Cut the entire grass plant from a few inches above the ground. Use your other hand to do this. Make sure you cut right across. At this point, most of the ornamental grass should be gone, with just a little growth left at the bottom.
  4. Throw the old grass away and wait for new growth to come in. You’ll likely have cut a lot of grass off, so it might be good to place it in a compost bin if you have one. You should notice fresh new growth in the coming weeks and months. 

Repeat this process once annually to ensure your deciduous ornamental grass stays in the best condition. There’s no need to repeat it more than once a year, as this will likely cause more harm than good.

Trimming Evergreen Ornamental Grass

Trimming evergreen ornamental grass is much simpler because you don’t need to cut away large chunks. In fact, you usually don’t need to cut anything.

The best way to trim and maintain ornamental grass is to run your fingers through it to let all the loose pieces of grass fall off. You’d be surprised how much can come off by doing this, so it’s certainly worth it! 

Like with deciduous ornamental grass, it’s best to trim evergreen ornamental grass during spring. There’s generally no need to cut any pieces of the grass away unless you can clearly see dead or brown growth that won’t come off by using your fingers. In that case, don’t be afraid to cut off the dead or browning pieces.

So, as you can tell, evergreen ornamental grass requires less maintenance than deciduous grass.

Why Spring Is Often the Best Time To Trim Ornamental Grass

You might be wondering why you must wait until spring to trim your ornamental grass, and there are different reasons why it’s the best time. For example, trimming in spring allows new growth to come in more easily. 

However, that is only if the grass is warm-season. If it’s a cool-season plant, it’s best to trim it in the fall.

Many ornamental grasses are warm-season. So in the sections below, I’ll discuss why you should aim to trim your ornamental grass in spring rather than any other season.

It Allows Healthy New Growth To Come In

During spring, your warm season ornamental grass will grow more quickly again as it comes out of dormancy. 

So, trimming the old grass at this point is best because you’re doing it right when growth is starting to pick up. If you cut the grass too soon (i.e., in winter), new grass is less likely to come in, and if it does, it won’t be as vibrant and healthy as it would be in spring and summer.

The extra sunlight during spring assists with photosynthesis and encourages new healthy grass to come in. That’s because most deciduous plants and grasses shut off photosynthesis entirely during the colder months. 

All of this makes spring the best time to trim your ornamental grass.

The Grass Will Start To Gain More Strength in Spring

As spring approaches, ornamental grasses become stronger due to higher levels of photosynthesis. They use photosynthesis by exchanging things like sunlight and water for oxygen, giving them plenty of energy to thrive.

Since this doesn’t happen so much during winter, there’s no need to do any trimming (especially when it comes to deciduous ornamental grasses) at that time. If you wait until spring, the grass will have more strength to support new growth.

You Won’t Risk Cutting Away Healthy Growth

Sometimes, you might want to wait until summer to trim your ornamental grass. But in that case, it might be too late because you’ll already notice new growth coming in from the bottom.

If you try to trim or cut the grass at this point, you’ll risk cutting off healthy growth that’s already started to come in, and this can stunt the development of the ornamental grass for the rest of the year. Cutting off healthy grass will likely make it grow slower, which is precisely what you want to avoid.

However, trimming it during spring won’t be an issue because the new healthy growth shouldn’t have started to come in yet. So, there’s no chance you’ll accidentally cut off new healthy growth.

Transplanting Ornamental Grasses

While trimming or cutting ornamental grass is necessary, it might not always be enough to maintain your plants. Occasionally, ornamental grass can grow too big and become slightly invasive. In that case, trimming and cutting the grass isn’t enough.

Since these grasses spread through their roots, you need to get to the roots to control spreading. It’s best to transplant ornamental grass during spring at the same time as you would trim it. If it’s a cool season ornamental, do it during the fall.

Below is a guide on transplanting ornamental grass, which requires more work than trimming.

How To Transplant Ornamental Grass

Examine the Ornamental Grass

Firstly, it’s essential to examine the ornamental grass to see how big it has grown and whether or not it’s even worth it to transplant. If there is still plenty of space around it, it might not be worth digging up the roots and replanting them. But if it’s growing into other plants or causing other problems, you should transplant the roots.

Prune the Ornamental Grass

Before transplanting the ornamental grass roots, prune the ornamental grass to make the process easier and more efficient. That way, you can easily dig around it and pick it up without anything getting in the way.

Once you’ve trimmed away everything you need, you can move on to the next step.

Cut Around the Entire Grass Plant and Remove It From the Soil

Next, you’ll need to dig around the ornamental grass plant using a shovel. Make sure you dig deep enough to ensure it’s easy to get to the roots. Cut in a circle around the ornamental grass; once the circle is complete, you should be able to remove the roots from the soil.

Pull the grass up to assist you if you have difficulty digging the roots up.

Divide the Grass Into Sections

Once the roots are exposed, split them up to create smaller sections. That will allow you to replant the roots in different garden areas, ensuring each plant is small enough. The smaller you want the ornamental grass plants to be, the more root sections you’ll need.

You can use different tools to split the roots, but an ax is one of the most valuable things. If that’s not an option, a shovel is a decent alternative. Ensure each section you cut has enough healthy roots to promote new growth. Once you’ve divided the roots into your desired number of units, move to the next step.

Replant the Grass Wherever You Want

You can place the roots wherever you want. Some can be beside each other, while others are across the garden. If you don’t want to use every section, the best thing to do is dispose of the unwanted ones. 

Make sure each one you plant has enough space around it, as the root systems will grow throughout the year. 

To replant the smaller sections of grass, dig holes in the soil and place the roots in them. Then, all you need to do is cover them with more soil and let them grow. Now is also an excellent time to give the ornamental grass plants water, especially if the heat starts picking up after the cold winter.

Repeat Whenever the Grass Plants Grow Too Wide

Although it’s essential to repeat the trimming process annually, it’s not always necessary to replant each year. You only need to replant your ornamental grasses when they become too big to manage or if they interfere with other plants.

If the ornamental grasses are growing and spreading extremely quickly and you don’t want to replant each year, consider using more permanent means (like root barriers) to handle the issue. Although root barriers are usually used for trees, they can be used for all kinds of plants, including ornamental grasses.

Controlling the Spread of Invasive Ornamental Grass

Trimming is one form of vital maintenance, and replanting is another (less critical) form of care. However, you can also add barriers to prevent the ornamental roots from spreading. Thankfully, this method is generally unnecessary, but if your grass is particularly invasive and getting in the way of other plants, it’s an excellent option to consider.

Unfortunately, it’s not as simple as adding barriers on top of the soil and calling it a day. Instead, you’ll need to dig trenches around the ornamental grass and place a viable barrier material inside these trenches.

Examples of materials you can use as a barrier include:

  • HDPE (High-Density Polyethylene) is often used as a tree root barrier.
  • Polypropylene.
  • Bamboo.

The barrier must be waterproof and long-lasting. There’s no point in using something that will disintegrate or rot within a year, so make sure you pick something appropriate.

An example is this Bamboo Shield, available on Amazon. It’s 25 feet (7.6 m) long, so there’s plenty of material to use. Plus, it holds up well in different climates.

Here is a brief guide on how to control the spread of ornamental grass roots:

  1. Examine the area before beginning. This allows you to see where you need to dig the trenches. 
  2. Start digging. Dig trenches around the ornamental grass, ensuring they’re deep enough to reach the roots. How deep you must go will depend on how deep the roots are. Most ornamental grasses have deep roots between 13 and 18 inches (33 and 46 cm), so the trench should be within this range.
  3. Measure the trenches and barrier material. You’ll want the material to be the right size, so measure accurately. 
  4. Place the barrier into the trenches. Ensure the barriers go down all the way so that they can stop the roots from spreading further.
  5. Fill in the gaps with soil. Once the barriers are in, fill the gaps and press the soil to ensure everything remains in place.

It’s also vital to ensure the barrier from the soil is visible to the naked eye. That way, you’ll know precisely where the border is if you ever need to remove it. It also ensures the roots can’t grow over the barrier. It only needs to come up a few inches.

You Must Trim Ornamental Grass After Installing Barriers

You might think it’s unnecessary to continue trimming your ornamental grass each year if you’ve added root barriers, but that’s not the case. Root barriers simply block the roots from being able to spread, so the grass will still have new growth that needs to be cut after winter.

After installing root barriers, the trimming and cutting processes are the same, so you can follow the steps earlier in the article.


Trimming ornamental grass is vital if you want everything to remain healthy and aesthetically pleasing. It will look messy and uneven if you don’t trim it once annually. Some parts may also begin to rot eventually.

The trimming method you use will depend on the type of ornamental grass. With deciduous varieties, it’s best to cut off much of the brown grass to allow fresh, green grass to come through. With evergreen varieties, it’s usually enough to simply run your fingers through to remove dead parts.

Alexander Picot

Alexander Picot is the principal creator of, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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