Hi all! I have a medium sized terrarium that I keep on my coffee table. It's in a closed glass container and has 4-5 different types of moss, and a succulent (a jade, I think). I put it together about a week ago, and noticed today that there's mold growing in there (the white, fluffy, fuzzy stuff that usually grows on rotting vegetation). However, it only seems to be growing on the one moss (I don't know its name, but it looks like a fern), and is starting to latch on to the other moss around it. I just can't believe how fast this spread. The succulent is unaffected. Does anyone know why this happened? Is there something wrong with the one moss, or is it just too humid in there? I only spritzed it once, lightly, after arranging the terrarium to help the moss spring up. Any help is appreciated!

Hi redwhite, Welcome to All Things Plants!

It sounds like your terrarium needs a bit of aeration. Can you remove the lid for @ 24 hours or so, or perhaps leave the lid ajar for awhile to see if allowing the moisture to escape makes a difference? I've had terrariums of different shapes and sized for many years and the ones I've had trouble with mold or fungus growing were because I had not removed the lids in awhile and too much moisture built up inside the terrarium. I've learned to remove the lids once in awhile if moisture begins to fog up the glass and sometimes I just push the lid aside a tad and leave it for a few weeks to allow for more air circulation. Do you water the plants in your glass terrarium? If it's completely closed it won't need water very often if at all. Closed terrariums are very humid environments and it may be the moss just needs more fresh air than it's receiving.

I'm really surprised your succulent (jade) is surviving in a closed terrarium; I'd think terrarium conditions would be entirely too moist for succulent type plants.

I hope others will pop in here with suggestions and advice. Meanwhile ... again,

Lin

plantladylin:

I only watered it once so far, just a very light spritz with a water bottle to help the moss spring up. I put the lid back on after but noticed that droplets remained on the succulent, so I kept the lid off overnight. I've been removing the lid about an hour a day to make sure there's not a lot of moisture buildup.

In retrospect, I wish I would have used a mini fern instead of the succulent for the very reason you mentioned, but so far it looks great. But because of all the mold I think I'm going to have to take it out anyway. I'm just wondering if I'll need to scrap all this moss and start over.

Thank you!

I wonder if the mold/fungus could be in the soil; I've heard of bagged potting mix containing mold spores. I know that mold thrives on moisture so if you could take the lid off of the terrarium and perhaps have a fan circulating air, maybe the mold would die on its own. I'd probably break down the terrarium and build it anew with fresh soil and wash the soil from the roots of any of the current plants in case spores are attached to them which would just cause a new growth of the mold.

I did a site search for terrariums and came up with one article and a few different threads where terrariums were discussed. I don't have time to go through them right now as I need to finish cooking our dinner but if you have time you might find some useful information regarding terrariums. http://garden.org/search/index...

I agree with plantladylin that the situation calls for more air.
Did you use bagged soil or soil from a garden bed or flower pot?
Dig you buy the mosses or dig them from the wild?
Do you know the botanical names of the plants?
Some photos would help also.

plantladylin: It didn't occur to me that it could be in the soil! I used a bagged potting mix that I had sitting around for a few months. I used the fern-like moss in another terrarium and there's nothing wrong with it, but I used a different soil in that one. I'm going to take your advice and wash off what I can and start over with a new potting mix. But now I worry because I used that soil in a few other plants I repotted over the weekend (all succulents). Also, when I rework the terrarium I'm going to switch out the succulent with a fern. Thank you so much for your insight!

greene: I bought the moss and the soil. The moss wasn't named by the seller, but I believe it was two different kinds of fern moss, a couple big chunks of reindeer moss, a moss I'm unfamiliar with, and some black lichen. When I rework the terrarium I'm going to keep this one uncovered now and then.

Thank you both so much!

Hi Redwhite! Welcome to ATP!

Terrariums can be a bit difficult to get "balanced." And I agree with everything Lin has said, in particular about the soil... I use Miracle Gro potting soil for starting seeds and had a really strange white mold stuff this year that has never shown up before. The first step I would take is opening your terrarium up to the air for a good while... and yes, you may just need to start over, sad to say ; save what you can and replant.

I don't know the current 'rules' but I was taught to add a layer of charcoal under the soil. I think it was supposed to keep things smelling clean and fresh.

Greene, that is so right -- I haven't actually had a terrarium in quite a while but as I recall charcoal was part of the system.

Yo, that's 'horticultural charcoal' by the way, not charcoal briquettes.

http://homeguides.sfgate.com/r...

I've got a layer of activated charcoal on all the terrariums. It's usually a layer of rocks for drainage, a thin layer of charcoal, and then the soil. It looks like I'll have to change the soil and start over.

Thank you all for all of your help!

In the past I've used pebbles (rinsed thoroughly) for the bottom layer, then a thin layer of horticultural charcoal, then my potting medium. I once used a very old cookie sheet and baked the soil in the oven for a few minutes (something I read should be done to kill any pathogens in the soil) but I only did it that one time because it smelled up the kitchen. I only keep two terrariums nowadays, a 10 gallon rectangular aquarium and an old 85 gal. hexagonal aquarium but I didn't use the pebbles or charcoal in either. Moisture builds up quickly in enclosed glass or plastic containers but I haven't had issues with mold because I open or remove the lids on occasion, leaving them off for a few days to allow for air circulation and to give the soil time to dry out a bit.

Some older photos of my two current terrariums:


And, my glass container plantings from a few years ago :

Lin, your photos brought back a lot of memories for me -- it's been quite a few years now, but I once had a lot of different containers planted too! I still have a big glass jug like in the front of the last picture (now empty, however). I planted it in a horizontal position, I think it came with a little stand that held it that way; I must have had a LOT more patience in my younger days! And I have a ponytail palm plant growing in the sunroom that's now about 5' tall, but when I bought it many years ago it was so little I was considering putting it into a terrarium... pretty funny when I think about that.

Sandy, I don't have the big heavy 5 gallon glass jug anymore ... at one time I had two of them planted as terrariums (I cheated and had a glass company cut a hole in the back side for easy planting.) The first jug got broken back in the late 1970's and the second one I dropped and broke about 4 years ago. I certainly had a LOT more patience in my younger years than I do now.

I have a couple of the Ponytail Palm (Beaucarnea recurvata) I saw a beauty planted in someones yard a couple of years ago and keep saying that I'm going to plant one of mine in the ground but still haven't done it!

plantladylin: Those are beautiful terrariums!

I just built my terrarium three days ago. And the issue that I'm having is similar to the one that was stated above. I have read all the comments and I have taken my lid off of my terrarium. I got all the products for the terrarium online through Amazon as a starter kit. I'll leave my lid off for a few days but the question that I have is should I remove the fuzzy Stringy mold from inside the terrarium with a stick?

Been up to my eyeballs in work lately; I just revisited this thread.
About baking the soil and having it stink up the kitchen...I suggest getting a toaster over and use it outside to 'bake' the soil to sterilize it. Yard sales and thrift stores usually have a few toaster ovens for sale. The same toaster oven can be used for other non-food things like clay or 'shrinky dinks' and other creative stuff you don't care to breathe inside the house.

Pinkrose, you might want to let the Amazon seller know about the mold. They may make a $$ adjustment for you or at least learn to be more careful what they put together in a package.

Hi Pinkrose, to All Things Plants from me too!

Leaving the lid off of your lovely terrarium will help dry out the soil and yes, I'd try to remove as much as that stringy mold as is possible without damaging the plants. If you aren't up to completely emptying, cleaning and replanting your terrarium I'd say leave the lid off for a week or more to let the soil completely dry out and see if perhaps that takes care of the problem.

At one time I had a couple of terrariums that look very similar to yours and moisture would build up so quickly that I never had to water and I still had to remove the lids for days or a week at a time to allow air circulation and to let it dry out.

Here's some information you might want to read regarding mold in terrariums: http://www.stormthecastle.com/...

lin, I love,love all your terrariums, you think outside the box. Thanks for all the ideas you have now given me