Do you have dried moss sitting in your home, waiting to spring back to life?
Moss can often revive from a dried, dormant state when rehydrated, given the right conditions. However, if it’s been heat-treated, chemically treated, or excessively dry for too long, revival may not be possible.
Whether you’re a moss hobbyist or you are thinking of growing orchids with live moss, understanding the resilience and revival capacity of these fascinating plants can transform your approach to growing them.
Let’s look at whether these seemingly hardy plants can bounce back from their dried state.
Is moss tolerant to desiccation?
Mosses are considered “poikilohydrous”. This means that they lack the ability to regulate the water content inside the plant in relation to the environment. For example, when the environment is dry they would fail to hold water inside the plant.
This shortcoming is compensated by their high water retention capacity. Depending on the species, Sphagnum moss for example can hold 16 to 26 times its dry weight in water by storing the water in its cells.
Their high water retention ability enables them to be rather tolerant to dehydration for a short period of time without physiological damage.
How long can moss tolerate desiccation?
When there is not enough moisture in the environment, moss does not die right away, they go brown and dormant. The length of the period for how long they can tolerate desiccation depends on the species of sphagnum moss. But, leaving the moss dry for 1-2 days should not kill it.
A study by Wagner and Titus (1984) shows that Sphagnum fallax, a hollow species, can recover after up to 5 days of dehydration and also can also survive for 10 days at low water levels, which is a higher capacity than Sphagnum nemoreum Scop, a hummock species.
Can dried sphagnum moss be revived when rehydrated?
If sphagnum moss can tolerate a bit of desiccation, does that mean we can bring dried moss back to life by rehydrating them?
If the moss is harvested from nature recently, you may be able to revive them by rehydrating them.
But if the moss you have comes from the store, it is virtually impossible to rehydrate them. This is because the dried sphagnum moss sold in compacted bricks in gardening supplies stores has been dehydrated for a long time before you buy them. Some may even been heat treated or chemically treated. There is no way that they can come back to life even though the moss is tolerant to desiccation for a while. “success” in reviving dried sphagnum moss.
If you have successfully revived dried moss, there are three possibilities:
1. The new growth could be mistaken for green algae, which has a dark green color – different from the bright green color of live sphagnum moss. Also, if your dried moss becomes green within a few months, it is most likely not live moss because the growth of moss from spores (seeds) is very long, taking at least 9 months. 2. It could just be a weed seedling. The bricks of dried sphagnum moss are full of seeds from other plants. If you use new sphagnum moss, it is common to get sprouts. Pay attention to the shape of the sprouts if they have smooth grass-like leaves rather than fuzzy leaves like moss. 3. Another possibility is that the new growth is indeed new moss because the dried moss from the store comes with spores which are fine dust-like seeds stored in brown-colored capsules. But again, it takes at least 9 months to grow from spores to moss.
Does dried moss have spores?
How do you know if your dried moss does come with spores?
Check if the moss has a tall, thin stalk structure supporting a little brown capsule (as in the picture). The capsule produces spores which are essentially seeds resembling fine dust that germinate if they land on a moist surface.
How can I grow sphagnum moss?
If your dried moss does not come with pods with spores, you can still propagate sphagnum moss asexually by using some starter live moss.
You can divide an existing clump of live moss and place the pieces into a container with a growing medium, such as peat, soil, or just a cloth. You can also trim the heads and transplant them into a new surface and they will start growing there.
The key is to provide enough and constant moisture (watering like 2 times a day) away from direct sunlight. The best is to use rainwater instead of tap water.
The ideal place to grow moss is in a shaded place with temperatures between 50 and 70 degrees Fahrenheit, protected from direct sunlight. It likes a very weak fertilizer. Too strong would kill the moss.
How long does sphagnum moss take to grow?
Spahgnum moss grows very slowly from spores. It could take at least 9 months to have some significant growth.
From cuttings, it can take a few weeks to grow longer. It grows between 0.75 to 4.75 inches per year.
To sum up, sphagnum moss can only tolerate around 5 days of complete desiccation. It is unlikely to revive the dried moss bought from the store because they have been dehydrated for a long time. Next time when you see some greenery showing on your moss, check if it is just algae or a weed seedling.
Tomáš Hájek & Eliška Vicherová (2013). Desiccation tolerance of Sphagnum revisited: A puzzle resolved. Plant Biology 16(4):765–773
Daniel J. Wagner and John E. Titus (1984). Comparative Desiccation Tolerance of Two Sphagnum Mosses. Oecologia, Vol. 62, No. 2 (1984), pp. 182-187.