If you just got yourself some moss, you might have heard that moss loves moisture. But you might be wondering how that translates to how much you need to water it. Is natural rainfall enough? If not, how often and how much should you water your moss?
Moss should be kept moist with regular misting at least once every few weeks for established, drought tolerant moss and at most daily for newly transplanted moss less drought-tolerant moss. Frequency of waterings will depend on the temperature, humidity, moss type, and location of the moss.
I wish it were as simple as water moss X times per week with Y cups of water, but unfortunately, there are a number of variables that will impact how often you will need to water your moss. In this post, I’ll walk you through these variables so that you’ll be fully equipped to gauge exactly how much water your moss needs.
How Much Water Does Moss Need?
Moss thrives with moderate sunlight, moderate temperature, and plentiful water. You’ll typically find them growing in shady, moist areas rather than out in the open taking on the full intensity of the sun.
If you think about it, these conditions all point to water preservation. Moderate sunlight and temperature both limit water loss to evaporation. The shade cuts down the heat coming from sunlight. And obviously, plentiful water means there is more water.
Moss really likes water.
In fact, moss can absorb many times its weight in water. For sphagnum moss, it’s a factor of 20.
So why does moss need so much water?
Unlike most other plants, moss doesn’t have any roots. Instead it has root-like structures called rhizoids which only serve to anchor it to the substrate. Unlike roots, rhizoids don’t absorb any water or nutrients.
That’s one of the characteristics of non-vascular plants like moss and other bryophytes. They don’t have xylem or phloem (plant “veins”) to transport water and nutrients throughout the plant.
Instead, moss takes in water directly through its leaves through osmosis.
There are a few special features of moss leaves that allow them to do this:
- They don’t have cuticle, the waxy coat that covers leaves in other plants.
- This allows the leaves to absorb moisture directly
- They are usually composed of only a single layer of cells
- This enables the leaves to absorb water very quickly right at the site of photosynthesis
- They are very small and abundant
- This creates a large surface area for moss to absorb water
At the same time, these features also causes moss to lose a lot of water to evaporation:
- Without cuticle, there’s no protective coat that helps keep water from evaporating from the leaf surface
- A large leaf surface area means that moss will rapidly lose water to evaporation if not moistened
Bottom line is moss needs a lot of water because it has a high rate of water absorption and water loss.
So you’ll need to water it often to replenish the water it’s absorbed and the water it’s lost to evaporation. Even more so if it’s hotter where you are or your moss is out in the sun.
While moss does need plenty of water, it also shouldn’t be overwatered.
The leaves need exposure to the open air on occasion for the moss to take in CO2 for photosynthesis and O2 to perform respiration. If they’re constantly coated with a layer of water, it’s going to be really hard for them to get CO2 and O2.
That’s why moss is better watered during the daytime when it photosynthesizes the most. In addition to sunlight, water is one of the key ingredients to support photosynthesis.
At night is when moss reduces photosynthesis and increases respiration where it uses O2 to break down sugars to gain energy in the form of ATP.
Night is when moss mostly needs O2 and less water. The lower temperatures also means less water is lost to evaporation and there is less of a need for water to be supplied.
Another factor that impacts how much water moss will need is the species of moss. While moss in general needs plenty of water, different mosses will be more resistant to drought than others.
Here’s a handful of examples just to give you an idea:
Moss That Needs Frequent Watering
Sphagnum moss–a genus of over 380 species found mostly in peat bogs, forests, and moist tundras.
Carpet Moss–a genus of about 80 species found all over the world, but especially on moist, decaying logs. This type of moss is often used as a ground cover
Fern Moss–found near streams and moist shaded areas, such as forests, wetlands, swamps, and hillsides.
Moss That Is More Drought Tolerant
Bryum Moss–a genus of over 1000 species of moss commonly found in urban areas between cracks in the sidewalk and growing on rocks.
Pincushion Moss–found in drier climates like sandy savannas, sandstone cliffs, and clay banks along the roadside.
How to Water Moss
The key to watering moss is frequent misting.
Since moss doesn’t have any roots (just rhizoids that only attach the moss to the substrate), you don’t need to soak the soil or substrate like you would with other plants. Instead, you should be targeting the leaves where its leaves absorb moisture directly into their cells through osmosis.
Misting is the preferred method of watering moss because the small water droplets can evenly distribute themselves among the many tiny moss leaves. It’s a much better technique than pouring water directly onto the moss with a watering can.
As a general rule of thumb, the best time to water moss is during the morning. Water is mainly used to perform photosynthesis, which will primarily happen during the daytime. At night, it transitions mostly to respiration, where moss takes in O2 to break down sugars for energy.
For best results, used distilled water or rainwater to ensure there aren’t any chemicals (like chlorine and fluoride) or hard minerals (like calcium and magnesium) that will affect your moss. You can also pass tap water through a brita filter to pull out most chemicals or minerals from the water before using it to water your plant.
However, tap water is perfectly fine to use as long as your moss doesn’t seem to mind. If your tap water is widely believed to be safe to drink in your area, it’s probably fine to use it to water your moss.
As a reality check on how much you’re watering your moss, you should regularly check for any signs of dehydration, including shrinking and browning of the leaves. You can also touch it to feel if it’s dry or crispy.
At the same time, you should also be aware of the possibility you could be overwatering your moss. It can be hard to tell the difference between overwatered and underwatered moss, but some signs include:
- Mold growth
- Muddy soil/soaking wet substrate
- Yellowing/browning of the leaves
- You’ve been watering your moss often
If you see any indication of your moss not responding well to your watering schedule, that’s a good sign that you should revisit how much water you’re giving your moss.
If you do need to make adjustments, a good rule of thumb is to make slight adjustments as opposed to making a drastic correction (i.e. suddenly deciding to soak your moss in water 24/7 after “discovering” your moss is underwatered, which is a mistake I’ve made before).
How Often Should You Water Moss?
How often you should water your moss depends on the type of moss you have, where you are growing it, and if it’s been recently transplanted.
I can’t see what type of moss you have and I can’t cover the individual watering requirements for all 10,000+ species of moss.
But generally speaking, most mosses will prefer to have plenty of water (for the reasons I covered above). Some species will just need a little more or a little less than others.
Mosses can be divided into two major groups:
- Acrocarpous–slower and more upright growth. Unbranched branches
- Pleurocarpous–faster and more sprawling growth. Freely branching branches
Acrocarpous mosses will need less water than pleurocarpous mosses due to its slow growth and can be found in rocky, drier habitats. But this still means it will need to be watered anywhere from once a day to once every few weeks depending on how recently it was transplanted.
Pleurocarpous mosses will need more water to support its faster growth and are often found in forests and bogs. Ideally, they should be watered once or more per day and should not be allowed to dry out.
To come up with some actual watering schedules, we first need to fill in the other two variables: where your moss is being grown and if it’s been recently transplanted
Moss Grown In a Terrarium
Of all growing locations, moss grown in a terrarium needs the least watering of all. You might not even need to water it at all if the conditions are right.
If you’re wondering how that works, I explain the details of how a terrarium works in this article.
But the basic concept is that in a closed terrarium, water cycles throughout the container in a closed loop, providing a constant supply of water and high humidity. It’s essentially an entire self-contained ecosystem in a bottle.
If water never escapes, there’s no need to replenish the water levels with consistent, repeated misting. In fact, it’s actually easy to overwater a terrarium by adding too much water.
Signs of overwatering a terrarium include mold growth, foul odors, and thick condensation visible through the entire day.
The only time you would need to add some water to the terrarium would be if there wasn’t enough water added to begin with. In this case, you wouldn’t see any condensation on the container at any time throughout the day.
Moss Grown Indoors
Unlike moss grown in a terrarium, moss grown indoors (and outdoors to a greater extent) will be exposed to the open air, where it will lose moisture to evaporation.
What this means for you is that you will need to mist your moss consistently to replenish any lost water. For indoor moss, this usually means about a couple of times per week.
Ideally, you should keep the humidity high with a humidifier or a nearby tray of water. This will help reduce the rate of evaporation.
The benefit of growing moss indoors compared to outdoors is that it won’t be exposed to the elements, namely strong winds and full sun. You also have more control over the light levels, temperature, and humidity.
The shelter from wind and sun means that less water will be lost to evaporation and less need for more frequent watering compared to growing it outdoors.
The downside of growing moss indoors is that it won’t create “natural” conditions for your moss. It’s going to miss out on things like seasonal and daily temperature fluctuations, rainfall, condensation, gentle breezes, and fresh air.
Moss Grown Outdoors
Moss grown outdoors is going to need the most water of all. Especially if it’s being exposed to full sun and winds.
In most cases, you should expect to mist your moss anywhere from once a week to once a day depending on the type of moss and your specific environment.
Ideally moss should be planted somewhere where there’s shade and some shelter from the wind. This will help prevent moss from losing moisture too quickly.
Fortunately, being outside does have the benefit of getting occasional rainfall. If your moss is locally sourced, it also benefits from being in it’s natural environment. Best case scenario, you can leave it to its own devices and it will take care of itself once fully established.
Speaking of establishment, let’s also cover how transplant recency impacts your moss’s water needs.
Recently Transplanted Moss
Recently transplanted moss will need time for their rhizomes to attach to their substrate and to acclimate to their new environment. Your moss will need extra energy to make these adaptations.
These conditions put your moss in a position where it really needs water, but is least capable of absorbing it from what’s available.
In most cases, recently transplanted moss will need to be watered daily for a few months. Afterwards, the watering frequency can be gradually reduced to once a week once the moss has established itself.
The exact frequency can be adjusted if you notice your moss showing any signs of over or underwatering.
Established moss has fully acclimated to its new climate and its rhizomes have anchored the moss to the substrate.
At this point, you can consider your moss to be in “maintenance mode”. It’s fully established and has reached its full potential in terms of ability to take in water and nutrients.
It doesn’t need as much water since it doesn’t need to adapt to a new environment. It also doesn’t need to support rhizoid growth to grab onto a new substrate.
Moss at this stage will only need to be watered once every few weeks for more drought-tolerant mosses and once every few days (maybe less) for moss that prefers more water.
You may even be able to rely on natural rainfall to do all your watering depending on the season. However, it may still need to be watered during hot and dry seasons to avoid repeated cycles of drying out.
Hope that gives you enough info to come up with a watering schedule that works for you and your moss!