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maria_c_gw

Using perlite as drainage material

maria_c
11 years ago

Hi all,
Brought home a peace lilly yesterday. It was in a plastic pot, with a white decorative pot around it, which had some space for drainage (i.e. the plastic pot sat a bit higher in the white pot.) I checked it to see if it was root bound when I got home. It appeared to have very little soil and mostly roots. However, it's winter, and I know it can shock a plant...so I decided to leave it alone.

Today, I bought some little rocks and thought...maybe I should just give it an extra drainage layer and add some perlite for moisture (our house is very dry!). So I took it out of the pot, pressed on the root ball to loosen the roots, and filled the bottom of the pot with perlite and rocks and placed it back in. I put a bit of perlite on the top as well.

My main concerns is that the plant won't have enough soil now, or the perlite on the bottom will cause too much moisture. Has anyone else placed perlite on the bottom of their containers?

I really don't want to do a complete repot until spring. So I'm hoping I didn't totally shock the plant and will have to get some potting mix/new pot/etc. to save it...That being said, it's not looking any different now--but I just did all of this about 1 hour ago. So who knows!

Comments (10)

  • tommyr_gw Zone 6
    11 years ago

    Perlite aids in drainage, peace lilies like a consistently moist soil. I'd do 2 parts potting mix to one perlite.

  • greenman28 NorCal 7b/8a
    11 years ago

    Maria,
    I would remove the rocks and Perlite immediately.
    Different layers of material actually create drainage problems, particularly
    when fine particulate mixes are sitting on top of a gravel/pebble/perlite layer.

    When adding Perlite to container mixes, you'd want about 70 percent Perlite to *improve* drainage.
    Perlite will reduce the overall water-holding capacity of a mix, which theoretically allows a mix
    to dry out sooner; but the actual drainage characteristics won't change signficantly until Perlite
    is the majority of the mix.


    Josh

  • pirate_girl
    11 years ago

    It's got to be mixed together, the perlite into the mix. Just placed below doesn't do anything, sounds like it might, but it doesn't, sorry.

  • maria_c
    Original Author
    11 years ago

    ok, thanks everyone. I might leave it...for a while, unless it starts to look bad. I can't really do anything to the plant unless I want to completely repot it--so I'd have to go out and buy a different pot. It's just too rootbound to evenly mix its soil with anything. Hopefully I can leave it be for a month or 2 and when it starts to warm up outside, I can just repot it in a larger pot.

    It is odd though...I've had really good success with the layering technique. Most of my plants I do a consistent mix of soil and perlite and then put rock/perlite on the bottom (with a coffee filter under that) to aid drainage. Most of my other plants thrive with this mixture. But it may well be because they are not plants that need high moisture or as much water?

  • maria_c
    Original Author
    11 years ago

    Also, someone on another forum said I should never use drainage layers, and only wicks. Any ideas about this? What type of material is good for a wick. What should it's placement look like?

  • pirate_girl
    11 years ago

    I have access to pumice, so I use that in my mixes, but I also use perlite if I can't use pumice for some reason.

    I do use some wicks to ensure complete drainage on certain plants. Wicks can be made from knitting yarn like one would use to knit or crochet baby clothes, washable synthetic. No natural fibers, which would rot over time.

  • dsws
    11 years ago

    I did perlite/rocks on the bottom with the previous plants I had. I gave them away when I moved several years ago, but they thrived for as long as I had them.

    As I understand it, the choice of potting medium is far more important than whether there's a layer of rocks and/or perlite under it. We usually think of soil as being made of particles. Water thinks of soil as being made of pores.

    Water has surface tension: in effect, the surface of the water tries to pull itself flat. To let air into a small pore, the surface has to bend very sharply. It doesn't like that. So small pores will stay full of water.

    Roots need oxygen.

    Roots metabolize sugar made in the leaves (or stems, if the plant's stem is green), using oxygen from the air to burn it, same as we animals do. Roots also do the heavy lifting, literally. Water is heavy, and roots do the metabolic work necessary to lift it to the leaves.

    Oxygen doesn't diffuse fast enough through water to support much metabolism more than a tiny distance from air. So roots need air very close to their cells. Roots adapted to living in water get their air via a tissue called aerenchyma. It makes the roots brittle, but at least it keeps them alive. Roots not adapted to living in water, don't. They die if the soil is soaked.

    So you need to have a connected network of large pores throughout the soil. If you do, it doesn't matter whether there's a layer of perlite underneath or not: the roots will get air. If you really, really don't, it also doesn't matter whether there's a layer of perlite underneath or not: the roots will drown. It's only when there's barely enough pore space that a wick will make it enough and a layer of perlite (clogged with small particles from the potting medium above) will make it not enough.

  • shayfish
    11 years ago

    Peace Lily is actually a plant that is okay with being repotted in the winter. I just split up one of mine and one of the repots started to flower almost immediately.

  • maria_c
    Original Author
    11 years ago

    Hmm. In that case, maybe I should just suck it up and repot. Also, I guess I'll ask this here too. Can I do some sort of mix with spahgnum moss instead of peat moss? Would this be too absorbant/wet for the lilly if I did a mix of spahgnum, perlite, and possibly bark? Do I really need peat in there?
    (Trying to put this spahgnum moss to use...!)

  • tapla (mid-Michigan, USDA z5b-6a)
    11 years ago

    Your moss won't go bad - save it for air layers and emergency treatments. For now, directing your energy toward what is required to keep your plants' root systems healthy is energy well spent. Roots are the heart of the plant, and a healthy root system is prerequisite to a healthy plant.

    I'd also look for ways to avoid repotting now, if possible. Recovery will be very slow, and the impact of repotting will be a plant weakened for an extended period while day length and photo-intensity slowly increases.

    Al