Quick answer
Sphagnum moss does not easily rot or decay due to its unique structure and composition. The cells of sphagnum moss contain compounds like sphagnan that resist microbial breakdown. Additionally, sphagnum moss creates acidic conditions that deter microorganisms from decomposing it. With proper care, sphagnum moss can survive for years without rotting.
What is sphagnum moss?
Sphagnum moss, also known as peat moss, is a type of bryophyte plant that grows in wet, nutrient-poor environments like bogs and fens. There are over 150 species of sphagnum moss, but the most common types used in horticulture are Sphagnum cristatum and Sphagnum subnitens.
Sphagnum moss consists of a dense mat of green, yellow, or red stems and branches with small, soft, spongy leaves. The leaves have large dead cells that can hold up to 20 times their weight in water. This ability makes sphagnum moss highly absorbent and moisture-retentive.
Sphagnum moss grows by spreading along the ground surface and stacking new growth on top of old growth. Over thousands of years, the mosses accumulate in wetlands and decompose very slowly into peat due to the buildup of phenolic compounds that resist decay.
Some key facts about sphagnum moss:
- Grows in wet, acidic, nutrient-poor environments
- Has green, yellow, or red stems with soft, spongy leaves
- Leaves contain specialized cells to retain moisture
- Slow to decompose, eventually forms peat
- Over 150 species, S. cristatum and S. subnitens most common
Why doesn’t sphagnum moss easily rot?
There are a few key reasons why sphagnum moss resists rotting and decay:
Cell structure
The cells in sphagnum moss leaves and stems have a unique structure. They contain:
- Pores – allows rapid water uptake
- Rigid cell walls – provide structural integrity
- Large central vacuole – stores water
This specialized cell structure allows sphagnum moss to absorb and retain exceptional amounts of water without breaking down.
Chemical composition
Sphagnum moss contains compounds that slow decomposition:
- Sphagnan – a pectin-like polymer that resists microbial breakdown
- Phenols – antioxidants that prevent oxidation reactions
- Waxes – coat cell walls and restrict microbial access
- Tannins – bind and precipitate proteins, inhibiting decay
These compounds make sphagnum moss unpalatable and indigestible for microbes like bacteria and fungi that normally cause plant matter to rot.
Acidic conditions
Sphagnum moss acids its environment through cation exchange. The moss swaps hydrogen ions (H+) for nutrients like calcium and magnesium. This releases the nutrients sphagnum needs to grow but creates acidic conditions with pH 3-4.5. Most microbes cannot survive in such acidic conditions, which slows decomposition. The mosses accumulate year after year in acidic bogs, resisting decay.
Does sphagnum moss last forever?
While sphagnum moss is remarkably resistant to rot, it does not last forever. Given enough time, sphagnum moss will fully decompose. However, complete decomposition can take thousands of years in bogs where anaerobic conditions persist.
In horticultural uses, sphagnum moss generally lasts 1-3 years before it starts to break down. With proper care, it can sometimes last up to 5 years before needing replacement.
Here are some factors that affect how long sphagnum moss survives before rotting:
Exposure to air
Sphagnum moss decomposes much more quickly when exposed to air. In permanently waterlogged bogs, decomposition happens anaerobically at very slow rates. But when kept moist in open air, aerobic microbes can colonize the moss and accelerate rotting.
Presence of nutrients
Sphagnum mosses have adapted to persist in extremely nutrient-poor conditions. But when nutrients like nitrogen and phosphorus become available from fertilizers or water, microbes are better able to decompose the moss.
Moisture levels
Sphagnum moss requires constant moisture to survive. If it completely dries out, the moss will die and start decomposing more rapidly when rewetted compared to moss kept consistently damp.
Warm temperatures
Microbial decomposition occurs faster in warm conditions compared to cool environments like bogs. Keeping sphagnum moss cool and shaded helps it survive longer before rotting.
Physical damage
When sphagnum moss gets crushed, torn, or loses its structural integrity, this allows microbes access to internal tissue to start breaking it down. Handling the moss carefully maintains its longevity.
So while sphagnum moss doesn’t easily rot, it will eventually break down depending on environmental conditions and how it is cared for.
How is sphagnum moss used in horticulture?
The unique properties of sphagnum moss make it useful for many horticultural applications. The primary uses are:
Potting mix ingredient
Sphagnum moss is commonly blended into soilless potting mixes at rates of 20-50%. It improves moisture retention, aeration, and structure of the potting mix.
Propagation medium
The ability to hold moisture makes sphagnum an excellent medium for propagating cuttings and starting seeds. It is ideal for orchids and many epiphytic plants.
Orchid potting
Sphagnum moss is often used to pot orchids. It allows air circulation to the roots while retaining moisture between waterings.
Wound dressing
Sphagnum moss can absorb exudates and stimulate healing when applied to tree wounds. The antiseptic properties help protect against pathogens.
Carnivorous plant soil
Many carnivorous plants like Venus flytraps and pitcher plants grow best in a sphagnum moss-based soil mix.
Container planting
Sphagnum moss mixed into potting soil helps increase moisture retention for plants grown in containers.
Hanging baskets
The lightweight nature of dried sphagnum makes it ideal for planting hanging baskets. It improves moisture retention while not adding heavy weight.
Storing bulbs and rhizomes
Packing dormant bulbs in slightly moist sphagnum moss helps provide the right amount of moisture to keep them healthy.
Tips for using sphagnum moss
When using sphagnum moss in horticulture, follow these tips for best results:
- Look for sphagnum labeled for horticultural use, which has been properly cleaned.
- Rinse the moss with clean water before using to remove any debris.
- Wear gloves when handling dried sphagnum moss to avoid inhaling dust.
- Mix into potting soil at approximately 1 part moss to 2 parts soil.
- For epiphytes, use long-fibered sphagnum moss.
- Soak dried moss before use – it expands up to 20 times when rehydrated.
- Shred and incorporate rehydrated moss into potting mixes using your hands.
- Use moistened moss to pack around propagate cuttings and seeds.
- Store dried excess moss in sealed plastic bags or containers.
- Replace old sphagnum moss every 1-3 years as it starts to break down.
Following proper care and handling guidelines will help sphagnum moss last as long as possible in horticultural settings before rotting.
Can you use peat moss instead of sphagnum moss?
Peat moss, also called sphagnum peat moss, is partially decomposed sphagnum moss harvested from peat bogs. The two materials are often used interchangeably in horticulture. However, there are some key differences:
| Characteristic | Sphagnum Moss | Peat Moss |
|---|---|---|
| Decomposition | Undecomposed live moss | Partially decomposed dead moss |
| Color | Green, yellow, red | Dark brown |
| Texture | Coarse fibers | Fine particles |
| Absorbency | Holds up to 20X its weight | Holds up to 10X its weight |
| Acidity | Living moss still acidifies | Not acidic |
| Cost | More expensive | Less expensive |
The main considerations when choosing between sphagnum moss vs. peat moss are:
– Sphagnum moss is more absorbent and acidic, better for carnivorous plants.
– Peat moss is cheaper, better for improving soil structure and moisture retention.
– Sphagnum moss lasts longer before decomposing compared to peat.
Either can be used successfully as a soil amendment. Peat moss is a more economical choice for general gardening. For specialized uses like orchid growing, sphagnum moss is preferable.
Can you reuse sphagnum moss?
Sphagnum moss has a relatively short lifespan and starts decomposing after 1-3 years of use. Once moss has begun to break down, it is not recommended to reuse it.
Rotting moss loses its beneficial properties:
– Decomposing moss has poorer moisture retention and acidity.
– Old moss has less structural integrity and cannot properly anchor plant roots.
– Decaying moss releases nutrients that can burn plant roots and cuttings.
– Decomposition causes shrinkage, so rehydrated moss does not expand as much.
However, sphagnum moss can be reused in limited circumstances:
– When slightly starting to decompose but still holding shape.
– For outdoor garden beds where plants can grow into and anchor into the moss. Avoid potting mixes.
– As a mulch layer in flower beds to retain moisture and suppress weeds.
– Possible to blend with new sphagnum moss at a 1:4 ratio of old to new.
When reusing old sphagnum moss, pasteurize it first by soaking in water heated to 160°F (71°C) for at least 30 minutes. This kills pathogens like bacteria, fungi, and nematodes.
Poke around the moss and look for any rotted, blackened areas which need removal. Then rinse thoroughly before reuse in horticulture. Replace any reused moss at the first signs of poor plant growth.
Conclusion
Sphagnum moss possesses unique properties that allow it to resist rotting and decay for years, unlike most plant materials. The structural composition of sphagnum leaves and stems, retention of moisture, acidic conditions, and inhibition of microbial growth all contribute to sphagnum’s longevity. While sphagnum moss will eventually decompose when conditions favor decay, proper horticultural use allows the moss to persist for 1-5 years on average before needing replacement. With good care, sphagnum moss can provide growers with an effective and sustainable substrate for propagating and growing many types of plants.