Is Salt Marsh Hay Good for Mulch?

If you’ve been gardening for a while, you’ve probably heard of salt marsh hay somewhere along the way. You may be wondering what salt hay even is, and is it good used as mulch? I use them from time to time and yes, they are good. However, there are a few not-happy things that you need to know.

Salt marsh hay is excellent for mulch. It serves as an effective weed suppressor, can help enrich the soil, and help offer frost protection. However, this hay is difficult to acquire, is typically expensive, and is debatably harmful to the environment, due to its harvests from sensitive coastlines.

Salt marsh hay can be a big help for gardens, but there are many people who aren’t even familiar with it. Here, I’ll be helping you understand what salt hay is exactly, and what you should keep in mind if you plan to use it. Without further ado, let’s go!

Is Salt Marsh Hay Good for Vegetable Gardens?

In general, it is common for salt marsh hay to be used as mulch for vegetables. It is often praised for its ability to smother unwanted weeds and helps provide soils with nutrients. Additionally, it can also help retain moisture and keeps a loose texture, making it easy for gardeners to use.

When I first heard about salt hay a few years back, I was afraid that if it was used as mulch, it could potentially leach off salt into the soil and poison plants.

But surprisingly, now I and lots of gardeners use salt marsh hay for their vegetable garden and even say they enjoy using it. Salt hay helps soils retain moisture, and is often rich in nutrients that can be helpful for plants. It is also easy to use and stays loose when used as mulch.

Their salty nature may be helpful to an extent as well. Thanks to its requirements for a saline environment, any seeds left on the marsh hay are much less likely to sprout. This would help prevent crops from competing with weeds and may be wonderful in a vegetable garden.

salt hay mulch

What is Salt Marsh Hay?

Salt marsh hay is a grass typically found in salt marshes. Growing up to 2 feet (0.61 m) tall, these grasses are composed of unique cells that prevent the plant from absorbing any salt. Once harvested, it then becomes salt hay, and was often used as mulch as far back as the colonial times of the US.

If you don’t know what marsh hay is, don’t worry.

Salt marshes are rich, low-growing ecosystems. Here, you can find a spindly, perennial grass named salt marsh hay (Also known simply as marsh hay, marsh grass or coastal hay). This grass typically grows up to 2 feet (0.61 m) high and contains cells that help the plant from absorbing the salts in the marsh.

Especially common in Northeastern regions of the US, it was a valuable asset in the colonial era. Townspeople once gathered this grass for many uses like animal bedding, feed and even mulch. Today, it’s not as commonly used, but after harvesting these grasses from the marshes, it is then turned into what we know as salt hay.

3 Benefits of Using Salt Marsh Hay in the Garden

The 3 main advantages in utilizing salt marsh hay in the garden are 1) its excellent weed suppressor ability, 2) it breaks down slowly and 3) it can be used as winter protection.

When it comes to the benefits of using marsh hay, there’s actually quite a few. Here are just some of the helpful uses of using salt marsh hay inside your garden.

1. Weed Suppressor

As mentioned earlier, unless your garden is a salty wetland, it’s unlikely for any seeds within the hay to sprout compared to the average run-of-the-mill hay containing many seeds.

If laid on soil in thick layers, this will help act as blockage and smother any weeds that do pop out. This should help prevent weeds from surviving, and salt hay even helps retain moisture, making it easier for both you and your plants to continue growing.

2. Breaks Down Slowly

Perhaps because of its marshy origin, salt marsh hay is said to rot much slower compared to other items such as straw or regular hay, which break down relatively quickly.

It does not need to be replaced as much, making it easier to use for longer periods of time. When it does break down, however, its nutritional value may be of use to your plants and even provide them with some nitrogen.

3. Can Be Used as Winter Protection

When winter comes, a thick layer of salt hay can be set down to help keep ground temperatures steady and prevent the soil from frost heaving and revealing tender roots.

With some chicken wire placed at the base, you can also pack salt hay directly around your plants. This will help provide tender shoots with both some heat insulation and protection against harsh winds, and you can worry less about stems snapping and branches breaking.

2 Downsides of Using Salt Marsh Hay

There are 2 major issues in using salt marsh hay for the garden. Due to salt marshes being on the verge of extinction, harvesting its natural grasses may be harmful to the ecosystem, making it rare and costly. Lastly, salt hay may also contain herbicide, which can potentially harm and kill plants.

The pros of using salt hay are plenty, but are there any situations you may find it’s better not to use it? Upon checking, there may be. Let’s go over this.

1. Salt Hay Can Be Damaging for the Environment

It’s unfortunate, but salt marshes are actually at risk of going into extinction. A professor of environmental health at UCLA has stated that many of the existing salt marshes, especially in California, are likely to disappear by the year 2100, with some of them already predicted to vanish in 2050.

Not only would the loss of these wetlands be a heavy impact, harvesting its grasses may sometimes be problematic. These grasses often provide a safe habitat for different lifeforms like mollusks, crustaceans, and even birds, and when salt hay is harvested, these organisms’ homes and birds’ nests could be harmed in the process.

With all of these factors combined, and salt marshes becoming rare, it’ll especially be harder for us to find this. With salt marshes dwindling and harvest proving to be difficult, it can be pretty pricey. This can be difficult for you if you’re trying to be environment friendly, or just make local purchases.

salt hay mulch

2. It May Contain Herbicide

As helpful as it is in the garden, it’s very common for hay to be treated with herbicides to help control and kill off weeds while the hay is being grown.

If you purchase any coastal hay treated with herbicides, it’s likely that once the hay is soaked by rain or heavy watering, the remaining herbicide on it may leach off into your soil. This could potentially poison your crops and maybe even kill them. Some unfortunate cases can even lead to the death of entire gardens, everywhere the herbicide laced hay was used.

Where Can I Find Salt Hay?

Salt hay may be found online or at local garden centers. Since it is less likely to be found in areas far from the coast, salt marsh hay can be expensive. Grasses may be collected from the beach, but this is not recommended. Local farmers should be consulted for other sources.

First, check in with local plant nurseries or even ask some farmers. If they’re unable to provide you with any, you can simply ask if they have any other connections and continue following the thread of sources.

If physical stores are completely void of it, run a quick check online. But this hay can already be expensive and combined with shipping fees, prices might be higher than you’d like.

Some folks do harvest their own salt hay by collecting them off the beach, but this is risky. Depending on your area, this may not be allowed and could do more harm than good. Find what works best for you, but try to do so without going against any regulations or harming any natural habitats.

How to Use Salt Marsh Hay as Mulch

For salt marsh hay to be used as mulch successfully, it is recommended to first verify sources and confirm the hay is indeed salt hay, and confirm it is free of herbicides. After evaluation, the hay can be used in 2-3 inch layers, ensuring plants are not smothered in the process.

If you plan to use this in your garden, there are a few things I recommend doing to make sure everything goes smoothly.

1. Make Sure It’s Actually Salt Hay

Before proceeding with a purchase, be sure to ask where the grass was actually gathered. Everyday grasses by roadsides and pastures are sometimes simply cut and sold as “marsh hay”, often containing weeds. To be safe, make sure you’re actually buying salt hay!

2. Check for Herbicides

In the meantime, confirm that the marsh hay is free of herbicides. You can actually test your hay at home as well to see if it has any persistent herbicides, and I highly suggest doing so before actually using it.

The test is as simple as soaking your new mulch in water, and using it to water test plants with. If plants are dying or showing signs of stress, this could mean the hay contains herbicide, and must not be used.

How to test your straw and hay mulch for herbicide that could harm your garden

3. Place Layers of Salt Hay on Soil

After carefully clearing your soil of any pests or weeds, lay your new mulch out all over the surface. Take care not to cover any of the plants. For younger plants, you may first break up or trim the hay into smaller chunks to avoid smothering.

You can use as much of the hay as you like. Many folks find it best to layer at least 2-3 inches or more of the marsh hay on top of their soil to both effectively suppress weeds and help retain moisture.

If you purchase a bale of salt hay, the size may vary depending on your sources, but 1 bale should cover at least over 1800 square feet (167.23 m²). Try to purchase this as early as you can in the year, and you’ll have plenty of this marsh hay to use within the garden.


What alternatives are there for salt hay?

Some good mulch alternatives I’ve heard other people use are Mainely Mulch and seaweed. These two would make great replacements, and can be found more easily than marsh hay.

Mainely Mulch is a pre-engineered blend of both hay and straw and claims to be a good substitute for salt hay. Seaweed may be avoided out of fear of it leaching salt into soil, but if cleaned, it shouldn’t contain nearly as much salt, and is quite high in nutrients.

What’s the difference between hay and straw?

Although these two words are used interchangeably, hay and straw are two separate things. Straw is yellow and hollow at the center, and is usually what is leftover after grain harvests. It’s often used as bedding for animals but is not used as feed because of its lack of nutrition.

Hay, however, is harvested by cutting down plant life like alfalfa or grass, and then dried for preservation. Because of its higher nutritional value, hay is what is used to feed animals. Both of these are commonly used as mulch but have very different features.


Using salt marsh hay as mulch has multiple benefits such as suppressing weeds, enriching garden soils, and helping to provide winter protection. While these are especially helpful in gardens, salt hay is frequently difficult to find.

Even if salt hay can be located, this mulching material can be very expensive. Using it may also not be environmentally friendly, as grasses are harvested from sensitive coastal habitats and may be harmful for the environment.


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