White fungus in mulch

Keeping Mushrooms From Growing in Your Mulch

Although mulch is a good thing, too much mulch creates a very wet environment which is favorable for mushroom growth. Mulch has many different natural benefits when used around plants and trees: it keeps the ground moist, holds in nutrients, keeps weeds from growing, and adds an aesthetic appeal. Traditionally, mulch is made from wood, but can also be comprised of other things like synthetics, rubber, stone, and other recycled materials. Although they do not harm plants, mushrooms in mulch can be unsightly.

Mulch in Moderation

There are times when you can actually have too much of a good thing. While having a layer of mulch around your plants, flowers, vegetable beds, and trees is a good thing, you can overdo it. Too much mulch around your plants can actually have a suffocating effect, where the roots will not get the nutrition they need.

Tip: Install raised beds for greater control over soil conditions.

Use Compost

Mushrooms thrive in wood or bark mulch. To avoid excessive mushroom growth, use organic compost instead of mulch. Since the materials in organic compost are already broken down, there’s not as much decaying material for mushrooms to feed on.

Tip: Although some mushrooms are edible, never eat a mushroom unless you are certain it is edible.

Prune Branches

Mushrooms like dark, shady places. If your trees are overhanging a lot, or the flowers and shrubs are causing some shade to cover the mulch, mushrooms can being to propagate. Prune your trees, shrubs, flowers, and other plants to keep them from overhanging or causing too much shade.

Rake Mulch

Use a rake and mix the mulch up. Move it around and loosen it up to let the mulch dry out and to create room for the plants to breathe.

Replace Mulch

Once the mulch begins to rot and deteriorate, it is time to get rid of it. Four things that mushrooms love are dense cover, a shady area, moist ground, and rotting vegetation, so removing these things will give you have a better chance of keeping your mulch free of mushrooms. If mushrooms have started growing, remove the entire mulch bed. Pick out the mushrooms and turn the soil. Then, add a new layer of two to three inches of fresh mulch.

Add Fungicide

As a last resort to getting rid of the mushrooms in your mulch, you can apply some fungicide. A general purpose fungicide will work well enough. However, if you want to keep the harsh chemicals out of your garden, use two tablespoons of baking soda per one gallon of water. Lime will also work well in getting rid of the mushrooms. Mushrooms like soil that is acidic, and the lime will sweeten the soil to get rid of them. The only problem is that this could have adverse effects on the other plants because of the change in the soil composition. It is better to use other methods first before using chemical remedies.

Why are there so many mushrooms in my mulch and grass?! We’ve heard this question A LOT this year and the short answer is; its been really wet and rainy! While harmless to plants, mushrooms can be an ugly addition to your flower bed; if eaten by a curious child or pet, it could make them sick.

The good news is that there are several ways to get rid of these unsightly additions. The experts at Hively have put together a list of the most effective ways to combat mushrooms appearing in your mulch beds. Follow the advice below to win back your beds!


Mushrooms need a wet environment to thrive. Using a rake and mixing up your mulch will loosen up the mulch a bit and provide a better opportunity for it to dry out, as well as break up any existing mushroom colonies.


If your mulch beds are under a tree, consider trimming back the tree’s branches, allowing sunlight to reach the mulch bed. This will help dry out the mulch and make it more difficult for mushrooms to grow.


Mushrooms feast on deteriorating vegetation, so your old mulch is the perfect meal for them. If it’s been a while since you’ve mulched, it may be wise to remove the old mulch and any mushrooms you see. You can then turn the soil and add a new layer of fresh mulch, removing any potential food for new mushroom growth.


There are a few treatment options if you find yourself in a fight against mushrooms in your mulch. The most common treatment option is adding a general purpose fungicide. If the plants in your mulch bed enjoy a more neutral soil, you could add lime to your existing soil since mushrooms prefer more acidity.

Leave Them

If it seems that no matter what you do your mulch bed is destined to house mushrooms, you can embrace them. As long as you don’t have artillery fungus (clusters of tiny, cup-shaped fungus with black “eggs” inside), you can leave the mushrooms in your garden without worry. We’ve even seen some creative gardening ideas that incorporate gnomes and other decorations that complement the look.

If you need help trimming larger trees, revamping your mulch beds, or any other larger project that may need an experienced touch, give Hively a call at 717-292-5696 and we’d be happy to help!

White Mold: Is It Dangerous & How to Remove It

By: John Ward
Published: January 16, 2019, Updated: January 31, 2020

Mold is a naturally occurring fungi, much like mushrooms and yeast. Hundreds of species of mold can be found in both indoor and outdoor environments. While many of these species are perfectly safe, others can be hazardous to your health, especially when they grow inside your home.

While most people tend to focus on black mold, also known as Stachybotrys, only a few are concerned about white mold growing within a building or home. However, white mold can also be very dangerous and should be dealt with as soon as possible.

In this article, we will outline the best ways to identify white mold in your home and remove it safely.

What is white mold?

White resembles many other molds and thrives in wet or musty environments. Many homeowners don’t realize that they have a white mold problem because of its colour, which makes it difficult to detect. It can grow on plants, fabric, food and other organic materials like drywall, wood and carpeting. This makes it a threat not only to your health, but to the structural safety of your home.

What does white mold look like?

White molds can either remain white or change to green, black, grey, or practically any other colour over time.

white mold on door

When they first develop, white molds are very hard to detect since the spores are so tiny that they can only be seen under a microscope. Once colonies form, however, white molds appear as spots on a surface. They can be flaky, powdery, stringy or filmy at first glance. They can also resemble mildew, which is the early stages of mold. However, mildew is relatively harmless when compared to white mold, which can grow not just on surfaces but also deep within organic materials.

Here are a few of the most commonly found molds beside white mold:

  1. Aspergillus is a genus composed of 100 different mold species from all different climates. These molds are generally black in colour and toxic.
  2. Cladosporium molds are olive green or blackish-brown in colour. They can be found indoors and outdoors–most commonly on living or dead plant materials.
  3. Penicillium molds are greenish-white in colour and most often found growing on bread and other food. They can be used in the production of cheese and are famous for being the main ingredient in penicillin-based antibiotics.

Pictures of white mold

What is the difference between white mold and black mold?

Black mold (Stachybotrys chartarum) is one of the most well known mold species because it’s the most harmful of all the molds found in indoor environments. It is typically greenish-black in colour, which makes it easy to distinguish, especially when found growing in areas of high moisture. Black mold is considered highly toxic mold and poses terrible health risks.

black mold and mycelium growth

On the other hand, white mold is a powdery, stringy, flakey, or filmy substance that can change colour or remain white, making it difficult to identify. Generally speaking, white molds present less health risks than black mold.

How to differentiate between white mold and efflorescence?

White mold and efflorescence look a lot alike. In fact, they’re so similar that people often mistake one for the other. Both are white in colour and found on walls and other building materials. Understanding what both substances are and how they form will help you to determine which one is making an appearance in your home.


So what is efflorescence? Simply put, efflorescence is salt deposits commonly found on concrete and brick. It develops when water evaporates from concrete or brick, and leaves behind a salty residue on the surface of the material. However, efflorescence causes only cosmetic damage and will not threaten the structural safety of your home. Likewise it also doesn’t pose any risk to your health.

Mold or Efflorescence? It’s one of the most commonly misidentified anomalies. Most people believe this is mold.

Tips for distinguishing between white mold and efflorescence:

  • Efflorescence dissolves in water–mold does not
  • Efflorescence is typically found on concrete and brick while mold grows on organic materials like wood and drywall
  • White mold is a living organism (fungus) while efflorescence is simply salt deposits
  • Efflorescence is not harmful. It won’t make you sick, but white mold will.
  • White mold gives off a distinctive odour while efflorescence not.

What causes white mold?

Like other molds, white mold grows due to high moisture levels combined with the presence of a food source, and the right temperature. Common food sources for white mold include wood, drywall, carpeting, laminate, insulation and any other organic, carbon-rich material.

The best temperatures in which mold grows is between 2 and 40 degrees Celsius.

white mold growth on joist

As white mold spreads, it eats away at the material it is growing on. If this happens to be drywall or wooden beams, white mold can lead to both cosmetic and structural damage of your home.

Where can you find white mold in your house?

White mold can grow practically anywhere in your home, as long as the three conditions listed above (moisture, food source, temperature) are met. That said, some areas of your home are more likely to foster mold growth than others.

Here are the seven of the most common places we find white mold growing in homes:

  • White mold in basements: Have you ever noticed that your basement tends to be cooler than any other room in your house? While this can provide much needed comfort in the hot summer months, it can also be promoting mold growth. Here’s how. When warm outside air comes into contact with the cold basement walls, it condenses, creating moisture droplets on the walls. If this moisture isn’t dried promptly, mold will soon start to grow on your basement walls.
    Dampness from the soil outside can also bring in extra moisture to the basement, creating a wet and humid environment perfect for mold growth. And because basements often lack proper ventilation (and are prone to flooding), they make a great breeding ground for white mold.
    Ways to tell if you have a mold in your basement are a earthy or musty smell, condensation on the walls, bubbling paint or wallpaper, and discoloration on walls, ceilings, carpets, or furniture. If you notice something that looks like efflorescence, examine it closely and remember the tips we gave you on distinguishing between white mold and efflorescence. White mold will look white, cottony, flakey, and stringy and grows on organic materials.
  • White mold in attics: Attics contain plenty of food sources for mold including wood and insulation. As such, roof leaks from rainfall or melting snow, condensation resulting from temperature fluctuations, and/or leaky pipes can give mold the moisture it needs to thrive in attics.
  • White mold in crawl spaces: Crawl spaces are typically very tight spaces that are difficult to dry once moisture makes its way inside. Several reasons why mold tends to grow in crawl spaces are leaking pipes and plumbing, high humidity due to poor ventilation, and foundation cracks that allow water and moisture to enter. For all these reasons, many people question the practicality and necessity of crawl spaces.
  • White mold on carpets: As most of us know, wet carpets are very difficult to dry, especially when we’re talking not just about a small spill, but a large leak or flood. This is when bacteria and mold have the opportunity to thrive. It is important to avoid carpeting your home below ground level or in rooms that are prone to spills, high humidity, and flooding (e.g. basements, kitchens, bathrooms and laundry rooms). Luckily, moldy carpets are fairly easy to recognize as they will give off a strong musty odor and cause allergic reactions. Try to clean and dry wet carpets promptly in order to avoid mold spreading to the subfloor. If this happens, you will likely have to remove and replace your entire flooring system.
  • White mold on wood: Unfortunately, white mold loves wood, which means that your hardwood floors, furniture, cupboards and structural components of your home (beams, joists, etc.) are at risk. If you’ve had a recent moisture intrusion, keep an eye out for the most common sign of white mold on wood: discoloration in the form of white spots or blotches.
  • White mold on plants and plant soil: White mold that grows on plants or vegetation is referred to as Sclerotinia. Because mold spores can become airborne easily, it is important to control the problem right away.
    There are several signs of mold growing on plants. Water-stained spots will appear at the root even though the remaining part of the plant will look healthy. The plant may be wilting and discolored at the root. Or, there may be brown lesions on the plant and, from these lesions, a dense white cottony patch will form.
    White mold can also appear on and spread through plant soil. Overwatering a plant, poor drainage, and old soil can promote mold growth. The best mold prevention for plants is not to overwater them, to remove weeds that carry diseases, to use fresh soil, and if possible to remove all crop residue after harvesting. Mold spores survive winter conditions so it is best to deal with the problem as soon as you see it.
  • White mold in your car: Even though your car isn’t technically your home, it is still one of the more common places we have found white mold. The truth is that moisture can easily make its way into your car, whether through the air conditioner, a poorly sealed window, door or sunroof, a spill, or simply an open window. Once mold has started growing inside your car, it can quickly spread onto upholstery, carpeting, and seats–ultimately destroying your vehicle. And if mold has gotten inside your car’s air conditioner, it will circulate through the air and expose you to potentially toxic mold spores. The best indication that your car has mold is white spots or an earthy odour.

Is white mold dangerous?

While mildew and similar types of mold are less of a danger and more of a hindrance, white mold is a health hazard. Inhalation of white mold spores, especially over a long period of time, can cause mold-induced asthma, allergic fungal sinusitis, allergic bronchopulmonary aspergillosis (danger for those with asthma or cystic fibrosis), and hypersensitivity pneumonitis.

Let’s look at the health effect of mold in greater detail:

  1. Allergenic molds cause allergies as well as asthma. When you come into contact with these types of molds, your respiratory system flares up. Around 20-30 % of individuals have a allergic reaction to mold that can lead to rhinitis, otherwise known as hay fever. Minor reactions are congestion, rash, and itchy eyes to very severe reactions of swelling, difficulty breathing vomiting, diarrhea, vomiting, and mental confusion.
  2. Pathogenic molds are able to cause more serious diseases. For people that have weak immune systems, these types of molds can severely affect the person’s already compromised health. Minor reactions are skin irritation, nail infections, and athlete’s foot while severe reactions are life-threatening infections of organs.
  3. Toxigenic molds release substances called mycotoxins, which are extremely harmful to humans. Pathways of exposure to these molds include ingestion, inhalation and direct contact (touch). Depending on the individual, the duration of exposure, and the pathway of exposure, reactions to toxic molds can range from irritation to lifelong illness. Some of these deadly illnesses are hormone disorders, liver damage, nervous system disorders, and cancer.

Most white molds tend to be allergenic or pathogenic. However, regardless of the type of mold you find growing in your home, you should always consult qualified professionals about how to remove the mold toxin from your home safely and effectively.

How to identify white mold?

Most of the time, you can identify white mold by examining its colour, texture, and odour. If it is fluffy, white, slimy and carries a specific musty odour, it’s likely white mold. Meanwhile, black or olive green discoloration will most likely be black mold.

white fluffy mold

However, mold doesn’t always grow in plain sight, which is why it is important to get your home tested for mold as soon as you suspect a problem.

How to remove white mold?

While some types of mold and mildew are easy to remove with household products like vinegar, white mold is much more difficult (and dangerous) to remove on your own. It may have penetrated deep below the surface of the contaminated material or it may be growing in places you aren’t even aware of.

Furthermore, do-it-yourself mold removal always puts you at risk of spreading the contamination and exposing yourself to toxic mold, which can lead to serious health effects. Furthermore, most people do not possess the equipment or know-how to remove toxic mold safely and effectively.

Whatever you do, don’t let mold grow in your house for a long time. Contact a certified mold removal expert to explore all remediation strategies and help you pick the one that’s best for you.

Due to its changing appearance and tendency to grow in areas of high moisture (much like black mold), white mold is not the easiest to recognize unless you are a trained and experienced mold professional. Furthermore, properly identifying white mold is only part of the problem. The other part includes finding the moisture problem that’s causing the mold growth and cleaning up the contamination effectively. For this, it is always better to rely on a reputable mold remediation company.


Mushrooms are the visible structures of the unseen fungi growing in our landscapes. Think of mushrooms as the flowers and fruits of the fungi world. The mushrooms these fungi produce may cause a concern depending on where they are growing. Mushrooms and other fungal growths can be unsightly and are a concern since some may be toxic to children. They can be found growing in mulch, turf and landscape beds.

There are many types of mushrooms and other types of fungal growth including puffballs, stinkhorns and others. Slime molds, though not a fungus, can appear as a slimy, oily or powdery growth on lawns, mulches or wood. To see pictures of each, click on the links in the previous two sentences.

Unfortunately, it is almost impossible to prevent mushrooms and similar organisms from growing. Many fungi get their energy from decomposing dead organic matter. They are actually a part of the natural recycling process. There are no chemicals that effectively kill all the fungi that cause mushrooms. You can remove the mushroom, but you must remove the fungus to keep the mushrooms from returning. To remove the fungus, you will need to remove the organic matter upon which it is growing.

Control of Mushrooms

There are several possible sources of food for fungi:

  • Buried wood, roots or other organic matter. Dig up and remove the source.
  • Thatch under lawns. De-thatching and aerating the lawn may reduce mushrooms.
  • Mulch, especially mulch that is too thick. (Greater than 3 to 4 inches in depth).
  • Piles of leaves, logs and limbs. Remove them if you need to discourage mushroom growth.

Even if you remove the food source, the mushrooms may still continue to grow. Removing the food should help to some extent. Mulches can be removed, properly composted and used again.

Some mulches are more prone to producing mushrooms and other fungal growth. Proper mulch selection, application and care can reduce mushroom problems.

  • Bark chips from mature, old pine or cypress trees decay more slowly and are less prone to mushroom problems than chips from other types of trees. However, this is only true of chips from old, mature trees. Chips from young pine or cypress trees do not have this advantage.
  • Wood or bark mulches from hardwood trees can be more prone to fungal problems than bark mulches from old pine or cypress trees. Composting these mulches before use will help reduce the chance of producing mushrooms.
  • Mulches from bark or wood products should be composted for at least 6 months before being used as mulch. Add a nitrogen source to the mulch and keep the mulch moist and turned during composting
  • Do not allow mulches to get dry. This leads to an increase in fungal activity. Then when the mulch gets wet again, mushrooms appear. Apply mulches 2 inches deep and wet the mulch well at application. Keep the mulch moist but not overly wet.
  • Finer textured wood or bark mulches can be more prone to problems. Use coarser textured mulches and/or apply mulches in a thinner layer.

Mushrooms that grow at the base of trees (also called conks) are usually an indication that the interior of the tree is decaying. This can indicate that a tree is at risk to fall. If you see mushrooms (or conks) attached to tree limbs or roots, contact a certified arborist to evaluate the tree to see if has become a hazard.

Another fungal problem we see in mulch piles involves hydrophobic fungi. When mulch is applied too deeply or is piled up in areas, the mulch can be infested by these fungi that waterproof the mulch. Water will then no longer able to penetrate the mulch and the plant roots can dry out and die – even though the plants are being watered. This is especially a problem with woody mulches that are applied too deeply. Dig into affected mulches and you will notice that they are dusty dry. To prevent problems, do not apply these mulches more than 2 inches deep.

In addition, mulch piled against the base of trees can lead to tree damage and death. Pull mulches slightly away from the trunks of all trees and shrubs.

Once you begin seeing mushrooms, it may be best to just ignore or remove the mushrooms you can see and wait for the fungus to quit producing more mushrooms. This can take a while depending on the fungus, weather, etc. These fungal fruiting structures are often short-lived but interesting to watch. Try to ‘enjoy’ your landscape oddity until it runs its course.

Some information taken from Control of Nuisance and Detrimental Molds (Fungi) in Mulches and Composts from Ohio State University

Mushrooms in my Mulch

As is so typical in mid- to late summer, prolonged rainy weather has left most of us looking at soils and garden beds that range from wet to waterlogged. After an extended period of daily or almost-daily rainfall, we typically see mushrooms popping up everywhere.

The vast majority of fungi do not cause plant disease and are actually beneficial. Some fungi help protect plants from organisms that would otherwise damage plants. Fungi kill nematodes and insects in the soil that might attack plants’ roots, for instance. There are even fungi that help protect plant roots from pathogenic fungi.

Some fungi actually enter into mutually beneficial relationships with plant roots. The fungi attach to or even grow into small feeder roots. Then, in exchange for carbohydrates provided by the plant, these fungi help the roots more efficiently absorb water and minerals from the soil, greatly benefiting the plant partner.

These fungi are called mycorrhiza, which means “fungus root.” Humans have a similar symbiotic relationship with the billions of bacteria that live in our guts.

A large group of fungi called saprophytes is critical to the health of our landscapes. Saprophytic fungi eat and digest (decay) dead organic matter. These fungi help keep dead organic matter from building up in nature.

For the gardener, they are vital in the process of turning organic matter into compost. When you incorporate organic matter into the soil of a bed, it is the saprophytic fungi that help break it down into vital humus and release the nutrients contained in the organic matter.

These fungi decay organic debris in the lawn — grass clippings and dead leaves would otherwise accumulate and choke out the grass.

But, after a generous period of rainfall, many of these fungi make their presence known by sending up mushrooms — lots and lots of mushrooms.

The fruiting bodies of fungi grow on wood chips, shredded bark, and other mulches, and the resulting mushrooms may look unsightly but are mostly harmless. Fungi help break down dead organic matter, providing nutrients for plants. The mushrooms they grow emit spores that spread the fungi to new areas.

How Do I Get Rid of the Fungus?

Unfortunately, it is almost impossible to prevent mushrooms and similar organisms from growing. Many fungi get their energy from decomposing dead organic matter. They are actually a part of the natural recycling process.

• Step away from the buffet!
Lawn mushrooms feast on damp, decaying organic stuff – think grass clippings, doggie-doo, old mulch, and rotting tree stumps. Removing these food sources means mushrooms will wither and die. So have those stumps ground up, ditch the decomposing mulch, rake up mown grass and scoop that poop!

• Dry it up!
Mushrooms thrive in moist environments and are often a sign of over-irrigation or poor drainage. While you can’t control how much rain pours down, do practice deep, infrequent lawn watering. Your grass will develop an extensive root system and mushrooms will disappear as your soil dries out. De-thatching your lawn and aerating compacted soil in the spring or fall allows for better airflow, which helps drainage.

• Here comes the sun!
Because mushrooms dig the shade, trim excess branches so more sunlight gets into those areas.

• Fertilizing is fun!

Applying nitrogen fertilizer helps eliminate mushrooms by speeding up the decomposition of organic materials. Don’t use slow-release or water-soluble formulations, though.

• Chop ‘em down, pull them out!
You can remove mushrooms as you spot them, but if the food source is still around, those toadstools will keep popping up. Cutting them down will help prevent their spores from spreading to new spots in your yard, and will also make sure your dog or child doesn’t chow down on them.

• Let ‘em be!
They’re not especially pretty, but mushrooms do help your garden. They transform organic material into nutrients for your yard and help your soil retain moisture. Plus, according to Irish legends describing fairies dancing on ‘fairy ring’ toadstools, some mushrooms bring good luck to the household. So feel free to surround your mushrooms with garden gnomes and other decorations so people will think you have a fairy-friendly backyard!

Why are there so many mushrooms coming up in my yard and garden, and what can I do about them?

The most important thing to understand about mushrooms is that they are simply the above-ground fruiting bodies of fungi that live in the soil. The vast majority of fungal mass is below ground where it goes unseen and unnoticed until mushrooms emerge. The vast majority of fungi are beneficial. They are decomposers that break down dead and decaying organic matter such a stumps, old roots, or leaves. Most mushrooms do not damage lawns or gardens; they are simply an unsightly nuisance.

Mushrooms only grow when environmental conditions are just right. Prolonged periods of wet, humid weather, such as we have had over the past few weeks, cause fungi to send up fruiting structures. Fungi disperse to new areas via windblown spores. When the spores land in a suitable location they develop into new fungi which will grow mushrooms given enough time.

Mushrooms will go away on their own once the weather dries out. Keep in mind that although these fruiting bodies have disappeared, the fungal mycelia is still growing in the soil. The fungus will continue to grow and persist as long as there is plenty of organic matter to feed upon. Mushrooms will emerge again as soon as the growing conditions are right, which may not be for another year. If you are unwilling to wait for mushrooms to go away on their own, you can remove them by hand or with the lawn mower. Although removing the mushrooms themselves does nothing to affect the fungi in the soil, it will reduce the number of spores released into the environment and the number of new mushrooms in different areas of the lawn and garden. Fungicides are generally not recommended because they are largely ineffective and mushrooms aren’t damaging anyway.

It’s also worth mentioning that many mushrooms are poisonous. Never eat an unknown mushroom unless you are absolutely confident of your identification skills. If you do decide to try eating wild mushrooms, be very cautious and only eat a small amount initially. Even mushrooms that are purportedly edible can make some people very ill.

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Common Mulch Fungus: Does Mulch Cause Fungus And Can It Be Treated

Most gardeners take advantage of organic mulch, such as bark chips, leaf mulch or compost, which is attractive in the landscape, healthy for growing plants, and beneficial to the soil. But sometimes organic mulch and fungus go hand in hand. In fact, various fungi are natural components of this rich, organic environment.

Does Mulch Cause Fungus?

Mulch doesn’t directly cause fungus, but when certain conditions are present, mulch and fungus work together in a symbiotic relationship; fungi are living organisms that develop as part of the natural decomposition process.

Many types of fungi help break down woody tissues and other types survive by consuming bacteria in the mulch. Either way, fungus is beneficial so no mulch fungus treatment is necessary in most cases. As the fungi speeds decomposition, the decomposed mulch improves soil fertility by making nutrients more available to other plants. Decomposed mulch also increases the soil’s water retention capabilities.

Types of Fungus in Mulch

Both molds and fungus are a normal part of the decomposition process. Here is some of the most common mulch fungus seen in the landscape:

Mushrooms are a common, familiar type of fungus. You may see mushrooms in a variety of colors and in sizes ranging from tiny puffballs measuring less than an inch to varieties that attain heights of several inches. Stinkhorns are commonly seen in mulch.

Some people think mushrooms are a nuisance, but they aren’t harmful in most regards. However, while some mushrooms are safe to eat, many are highly toxic – even deadly. If this is a concern, or if you have curious children or pets, rake or mow the mushrooms and dispose of them safely.

Slime Mold

Slime molds, also known as “dog vomit,” tend to be nuisances, but their growth is usually confined to small areas in damp mulch or old, rotting logs. Slime mold is easily recognized by its bright pink, orange or yellow color.

As mulch fungus, treatment of slime mold involves raking the surface of the mulch frequently to prevent growth. You can also remove the slimy substance with a rake, then dispose of it away from your yard. Otherwise, let the mold complete its natural lifespan and it will dry out, turn brown and become a powdery, white mass that is easily blasted with a garden hose.

Bird’s Nest Fungus

Bird’s nest fungi looks exactly like their name suggests -tiny bird nests complete with eggs in the center. Each “nest” measures up to ¼ inch in diameter, growing in small clumps usually limited to a few inches. This interesting little fungus is harmless and nontoxic.

Artillery Fungus

Artillery fungus resembles a tiny cup with one black egg in the center. Artillery fungus is named for its sticky spores that burst and can be windblown considerable heights and distances.

Although this fungus grows in mulch, it is also attracted to light-colored surfaces, including cars or houses. The spores, which resemble specks of tar, can be difficult to remove. Other than its annoying, unsightly qualities, it isn’t harmful to plants, pets or people.

There is no known cure for artillery fungus. If this fungus is a problem in your area, avoid using wood mulch adjacent to buildings. If mulch is already in place, rake it often to keep it dry and aerated. Large chunks of bark are less inviting than shredded mulch or small pieces.

Fungi in Mulches and Composts

Wood chip/bark mulches and composts can be a source for several interesting fungi including artillery fungus, slime molds, bird’s nest fungi, stinkhorns and mushrooms. These fungi often raise questions from home gardeners, particularly after rainy weather. Wood, bark and composts, as organic matter, naturally decompose over time. Bacteria and fungi are involved in this decomposition process deriving their energy for growth from these carbon-based compounds. These fungi are natural components of the mulch environment, are not harmful to landscape plants, and no known health hazards are associated with them unless they are eaten. They are usually found from April through October, following rainy weather.

Shotgun or artillery fungus (Sphaerobolus), although not considered to be pathogenic to living plants, can be a problem in other ways. While it decays or breaks down the mulch, it also produces fruiting structures that resemble tiny cream colored or orange-brown cups that hold a spore mass resembling a tiny black egg. As the cup-like structure absorbs water, pressure is built up and eventually the cell inverts and bursts with such force that the spore masses are propelled as high as 6 feet and distances of 12 feet or more, toward light or light surfaces. These spores stick to surfaces such as cars, siding or leaves and resemble small tar spots. Once it sticks in place, the spore mass is very difficult to remove without damaging the surface to which it is attached. If removed, it leaves a stain. A few of these spots are barely noticeable, but as they accumulate, they may become very unsightly on houses or cars. Also, sanding or scraping the spores and letting them fall back onto the mulch will re-inoculate the mulch.

Moist, rotting mulch appears to be an ideal situation for artillery fungus, especially foundation mulches located on the cool, north sides of houses. To minimize artillery fungus, avoid highly susceptible mulches containing wood and shredded blends of bark and mostly wood from large commercial piles. A four-year study, “Artillery Fungus Sporulation on 27 Different Mulches”, conducted by Pennsylvania State University, showed wood pieces and shredded blends of bark and wood that absorbed moisture supported significantly greater levels of artillery fungus sporulation than large, hard, dry pieces of pure bark, such as pine bark nuggets. Almost all wood/bark mulches will eventually support artillery fungus over time (3-4 yrs), and should be replaced or covered with a fresh layer of mulch.

To date there are no known ways to manage the artillery fungus other than to avoid using wood chips/ bark mulches next to buildings. Where wood mulch already exists, frequent disturbance by raking the mulch surface may help keep it dry and less inviting.

Slime molds, although not really a fungus are normally a temporary nuisance confined to small areas. In addition to mulches and composts, slime molds are often found on old well-rotted logs, where they can find the moisture and bacteria required for survival. Slime molds or “dog vomit” fungus are brightly colored (yellow, orange, etc.) slimy masses that are several inches to more than a foot across that feed on bacteria growing in the mulch. These molds dry out and turn brown, eventually appearing as a white, powdery mass. If their appearance is offensive, discard the slime mold in a compost pile, household garbage, or a spot in the yard away from existing mulch.

Bird’s nest fungi resemble tiny gray to brown bird’s nests up to 1/4 inch in diameter with eggs. These fungi may grow in large areas of mulch, but they are not a problem. The “eggs” or structures of the fungus splash out of the nest when hit by a raindrop. These structures occasionally stick to surfaces, but they are easily removed and do not leave a stain. These naturally occurring fungi decompose organic matter and do not need to be removed.

Other fungi found on mulches include stinkhorns and mushrooms. The cap of the stink horn gives off a very unpleasant odor. Stinkhorns produce a sticky spore mass on their tip which has an odor of dung, or other things that attract flies. The flies land on the stinkhorn and in doing so collect the spore mass on their legs and carry it to other areas.

Mushrooms are fleshy, spore-bearing fruiting bodies of fungi typically produced above ground and reproduce by airborne spores. Mushrooms come in various colors, shapes, and sizes ranging from less than an inch to several inches tall. Some are soft and fleshy and disappear soon after they emerge; others may remain in mulch for a few days, weeks, or an entire growing season. Mushrooms may be poisonous if eaten and should be removed if small children have access to the mulched area. Note that some people use the term “toadstool” to describe poisonous mushrooms. There is no reliable control for nuisance fungi other than to frequently disturb the mulch by raking the surface to dry out the area so it will be less inviting.

Written by: Tina Smith
Revised: 09/2011

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