Mosses are at their best when leaves are fully hydrated. The nuances of the shades of their verdant color vary among bryophyte types from neon chartreuse to brilliant emerald to deep, dark, almost black, depths of greens. Many bryophytes dramatically change appearance from their moist to dry states. However, other mosses and liverworts may look similar with the naked eye in both dry and wet conditions. Since mosses absorb moisture quickly, this transformation can occur right before your eyes. The green chorophyll becomes more intense while robustness and size of the leaves increases as they unfurl when re-moistened.

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  • Moisture is essential for the reproductive cycle of mosses. In the gametophytic stage, mosses have sex. The male sperm swims to the female egg for fertilization. In vegetative reproduction, the little gemmae get splashed out of cups to form their own new plants using water as a vehicle for dispersal.

  • Without a cuticle, and with only one cell layer, these non-vascular plants absorb primarily through their leaves. In addition, external water movement occurs with the substrate surface through a series of capillaries. Certain bryophytes have specialized transport cells. These cells (hapoid and leptoid) could be compared to the internal systems (xylem and phloem) of vascular plants. Polytrichums have rigid stems and possess these internal water transportation qualities similar to more complex plants.

  • Mosses can absorb water like a sponge but some only a little at a time while others, like Sphagnums, can absorb up from 20-30 times their weight. The absorptive properties of mosses allow extensive colonies to provide water filtration slowing down the rush of stormwater and giving it a chance to reach the soil. Mosses can reduce the impact of flash-flooding or heavy rainstorms as erosion control plants.

  • Although some mosses like to be really wet consistently, others may prefer to dry out. A considerable number of mosses will not tolerate constantly “wet feet.” In contrast, aquatic mosses can actually live under water. Fontinalis was recently found to be growing at 1000 ft depths in Yellowstone Lake near a geo-thermal vent.

  • Mosses absorb moisture and nutrients through their leaves. In other words, they drink rainwater and eat dust particles. Their entire sustenance is derived through this simple diet.

  • Although all mosses require some moisture to survive, needs can be met through living in microclimates that provide moisture niches. Crevices, cracks, nooks and crannies are desirable micro-habitats.

  • Mosses have botanical mechanisms for tolerating dormant, dry states. Some types even need to dry out between periods of heavy moisture.

  • In arid habitats, bryophytes and other cryptogams form what are called “biological soil crusts.” During intense and sudden downpours, they absorb water and hold the soil in place preventing or reducing  erosion.

  • Since mosses can absorb water so easily through their leaves, correspondingly contaminants in the water particles including pollutants or undesirable amounts of minerals, could affect mosses either in natural settings or gardens. However, in this moss gardener’s experience, supplemental watering, from typical urban sources with their array of chemicals, has NEVER harmed any of my moss installations.

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4 Responses to “Moisture and Mosses”

  1. 1

    Hey Marc,
    Rarely does Leucobryum fall apart as you have described. It sounds more like two Sphagnum colonies (cradles) sandwiched together. Sphagnum species have tendrils (strands) that are only loosely connected. It falls apart easily. I recommended that you cut strands into smaller pieces and distribute across your terrarium substrate — soil or pebbles. Leucobryum colonies can be crumbled up and scattered around as well. If you do have Leucobryum, then beware. It is the only species that I’ve ever had mold happen on when planted in a terrarium. On another note: You might enjoy visiting the Web site my friend, Annette Launer. She lives in Germany, too. She captures incredible images of mosses in her nature treks including Sphagnum and Leucobryum. Happy Winter Solstice! Mossin’ Annie
    http://bryophyta.blog.de/2014/02/12/gully-cover-17749469/

  2. 2
    Marc

    Hallo Annie,

    I live in Germany and would like to try keeping some moss in my garden an in a terrarium. I searched everywhere for a supplier with little succes (I wish you had a store in Germany too!). Recently I found a moss cradle at my garden store, it was called only “moss” but looks like some cushion moss type (I’m not sure if it could be Leucobryum glaucum) It was sold in two layers attached to each other, one facing up and the other one facing down, and it was moist.

    As I came home trying to spread my cushions on a surface they started falling apart, Is it normal? Could it be rotten? I tried submerging one in water to see if it carried insects in it, but it almost dissolved in the water, leaving me with many single strands in the hand and light brown water. I tried misting another, carefully laid on pebbles, and it does get greener but still…

    I have purchased one or two cushions of mystery-moss (maybe also Leucobryum) before from other sources but they were either completely wet and alive or completely dry and dormant, none of them falled apart.

    What should I do with the unstable cushions? Do they have a chance to survive or will they only rot and even grow moldy?

    Thank you in advance for your help

  3. 3

    Mosses make a great choices as terrarium plants. You are smart to realize that selecting the “right” bryophyte should be based upon the humidity/moisture of the intended environment. YES, there are many mosses that will thrive in a “moist” terrarium. In particular, I’ve had success with Thuidium, Climacium, Mnium, Atrichum undulatum, Bryoandersonia, Hypnum, Entodon and Brotherella to name a few. It your terrarium stays soggy, then I’d recommend using Sphagnum. Although I like using Leucobryum “pincushions” for its light green contrast or shape, I’ve found that it does not survive in the long run. Other mosses to avoid in WET terrariums are certain types of SUN mosses that need to dry out like Ceratodon or Bryum.

    FYI — Don’t be fooled by suppliers that don’t know the differences between moss types and their environmental requirements. I’m amazed that marketers promote FROG moss. Frogs would like to live amongst all types of bryophytes — mosses and liverworts, maybe even hornworts. When I investigated what frog moss might be, I discovered photos of bryophytes that were not actually the types cited by even a scientific name. The photo was of another bryophyte not the one cited. Beware of uninformed suppliers that do not know what they are selling.

    Good luck with your terrarium project. I was just admiring a trio of terrariums in my own living room. Placed in a South-facing window, these containers bead up with moisture each morning. It’s been over two months since the last misting. Occasionally, I give them a breath of fresh air by removing the lid and rehydrating as needed.

    Go Green With Moss!
    Mossin’ Annie

  4. 4
    Frank

    I have a terrarium that has a very moist soil location that I would like to grow moss. Is there a particular variety that grows in a wet environment?


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