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louise0512

Pumice and Coco Coir, Discoloured Pumice, Haworthia Watering Questions

Louise (UK)
5 years ago

I'd really appreciate some advice from more experienced growers, as I'm feeling stuck and overwhelmed by the amount of conflicting information online.


I recently switched my collection of Haworthias to a 70% pumice (3mm approximate partial size) and 30% coconut coir mix, top dressed with a thin layer of pumice.


After the first watering, over the first 1-3 days I noticed that parts of the top layer of pumice turned a rusty orange colour. Initially I thought this was caused by 'hard' water and so switched to a high quality distilled water, but the same thing occurred, orange pumice.


The amount of orange has varied from plant to plant, but the result is similar when using tap, bottled, and distilled water; also when watering from the top, and when watering from the bottom (the plants do not sit in wet water trays and the excess water is wicked with a paper towel).


Has anyone encountered this problem before with pumice and coir? Could it be the coir (I used Canna Coco Professional Plus) reacting with the pumice, or just the pumice itself?


My biggest concern is if this reaction, and the mix, is going to cause problems for my plants, particularly over time. I'd also like to avoid water marks from mineral build up on the plants. Am I needlessly worrying or is it a cause for concern?


My other concern is the current drying time of the mix.


The room in which I grow my Haworthias is ventilated (an air purifier, with a fan, circulating the air 24 hours a day) and at a day temperature of approximately 20°C (68°F), a few degrees less during the night, with 50% humidity. They are set back from a south facing window (but daylight hours are low at this time of year).


I weighed the pots before watering, and it's currently taking 2 1/2 weeks for the mix to return to its start weight (I've only watered once).


My plants are still in active growth (in bloom, noticeable growth), hence why I'm watering in Winter (I'm located in the UK). As they are grown indoors in a room that is used often by myself, I can't put them into a winter rest by dropping the temperature.


Is the time it's taking for the mix to dry out a cause for concern? What is the ideal time for Haworthias that the mix should remain damp?


Given the conditions I expected it to dry much faster. Again, am I worrying unnecessarily or is it a cause for concern? How long is the ideal time for the mix to dry back to its start weight?


I can take a photo to upload later of the discoloured pumice (if requested).


I'd greatly appreciate any input regarding these issues. I've read an abundance of information online but can't find the answers to these questions.


Thank you in advance for any help!

Comments (23)

  • Chris (6a in MA)
    5 years ago
    last modified: 5 years ago

    I would not use coconut coir. I prefer CS soil mixed with pumice or perlite. Grit has to be 50% or more. Yellowing pumice indicates the mix is too water retentive. I learned this from Rina.

    Louise (UK) thanked Chris (6a in MA)
  • robinswfl
    5 years ago

    I have a number of Haworthia in pure pumice, most often in unglazed terra cotta pots, and I also have some Aloe plants in pure pumice, and those pup like crazy. But I am in Florida and it's warm all year. My plants are outside on a screened lanai 24/7 -- and the pumice DOES get dirty because of particles blowing through in the air, I suspect. But dirty -- not orange, as yours are....like DEEP off-white. Their mix is dry within 4-5 days. Two and a half weeks seems too long to me. It may depend on your pot type if you're using plastic or glazed ceramics.

    I agree with Chris, above, on the coconut coir. I'd eliminate it. I am not sure I would worry about the discoloration if the plant seems healthy. You might experiment with pure pumice on the Haws. I learned about that from someone here (I forget whom, unfortunately -- I think maybe Pagan). You can search by Pagan and "pumice" or "pure pumice" up top and see what appears. My Haws have done better in pure pumice than in any other mix I have tried, including those with Turface and grit. It requires watching and attention, but the plants seem their happiest and I get the most pups.

    Louise (UK) thanked robinswfl
  • Louise (UK)
    Original Author
    5 years ago

    Chris, thank you. Unfortunately the CS soils available in the UK, that I've seen, aren't very good, so I prefer not to use them. I also personally prefer not to use perlite. Discoloured pumice from water retention could explain it, as the mix is sadly far more water retentive than I was expecting; but do you know what causes the reaction to make it discolour? Is it trace minerals found in the pumice? There are no minerals in the water (high quality distilled), yet it still changes colour.


    robinswfl, thank you. I'm using plastic pots. I was going to make the switch to 100% pumice (I did a test on a pot of 100% pumice, without a plant, and found that it dried out after around a week), but after research, I have concerns then regarding fertilising. How do you fertilise your Haworthia? I would personally prefer to fertilise my haworthia using organic methods (vs mineral from synthetic sources composed by humans), using natural (plant sourced) products and beneficial microbes added to the coir. If I switch to pure pumice I'm unsure if it will be possible to use the organic method.

  • rina_Ontario,Canada 5a
    5 years ago
    last modified: 5 years ago

    Discoloration possibly from coco coir. Another possible problem with it is that it could be containing too much salt. There are brands for sale that are well rinsed, but I do not know the name since I don't use coco coir. It is also more expensive.

    I also agree that watering every 2.5 weeks is too seldom, and especially in temps you mentioned. If your mix takes that long to dry up, it is not draining well. I believe it may be better to lower nighttime temps - you didn't really say, but mentioned 'few degrees' - can't tell how much that is.

    Pagan, ewwmayo, bikerdoc and many others grow fantastic looking haws (and many more rare and expensive ones) and I believe they use inorganic mixes. And they use fertilizers 'composed by humans' - you know exactly what you are giving your plant and how much of it. I actually fertilize very rarely, maybe 1-2x/yr.

    Louise (UK) thanked rina_Ontario,Canada 5a
  • Louise (UK)
    Original Author
    5 years ago
    last modified: 5 years ago

    rina_Ontario,Canada(5a), thank you. The coir I use is Canna Coco Professional Plus. I think it's one of the best quality coir available, but this is based on reviews not from personal experience as I have nothing to compare it to; but the manufacturer states 'washed in fresh water means no salts are present'. It has also been treated with Trichoderma.

    The night time temperature drops a little, but only by 2-3 °C, I can't be too specific as I've observed it varies, but all heating is switch off during the night.

    There are benefits to both organic and mineral growing. I know that many people prefer mineral growing for CS, but personally, if possible, I'd like to grow organically.

  • Nil13 usda:10a sunset:21 LA,CA (Mount Wash.)
    5 years ago
    last modified: 5 years ago

    I use ground coir for some things. I have a great local source that gets it in huge bricks and breaks it up into smaller bricks. They supply and orchid society so the quality is always high. I have been really happy with it. The staining is most likely from the coir. 30% sounds like too much though. Pumice is a really great growing medium and coir holds a lot of water. I don't think I'd want to have more than 15% coir.

    I typically use a gritty type mix for Haws, but I have had success with an orchid medium that is 2parts coconut husk chunks:1 part perlite. So there are alternatives to an all aggregate mix.

    Haworthia are cold season growers naturally, so mine grow fine outdoors even when the nights are in the high 30s- low 40sF.

  • Crenda 10A SW FL
    5 years ago

    Test the coir. Put it in water overnight and see if there is a color change to the water. (I haven't used any coir, so I don't know if it can 'bleed.')

    I've had perlite turn a brownish color from sun and rain. But as you can see in the pot on the left in this picture, it also get greenish from algae. It also looks much wetter than the other pot.


    And these look similar. It doesn't happen right away and these are in the Florida sun all day long.


    These are pots for propagation and I wouldn't be potting my specimens in this mix. This mix was c&s soil and perlite - which I have found it is way too water retentive for my conditions. Maybe these pictures help you nail down the problem.

  • rina_Ontario,Canada 5a
    5 years ago

    Lousie

    I was re-reading your post and have a question: you said you want ..."beneficial microbes added to the coir "...What exactly do you have in mind? And what kind of fertilizer do you want to use?

  • Nil13 usda:10a sunset:21 LA,CA (Mount Wash.)
    5 years ago

    If you steep coir in water you get dark brownish orange tea.

  • robinswfl
    5 years ago

    Louise, yes -- I do regularly fertilize the plants I have in pure pumice. I use Foliage Pro 9-3-6, which I learned about here at GardenWeb. There is also a popular Miracle Grow fertilizer with nutrients in the same proportion, and I use that too. I mix less than a teaspoon in a heavy gallon of water. When using a gritty mix or pure pumice, this drains out FAST.

    When I reread all the posts here, I wonder if maybe you have set some parameters for yourself and your plants that are either too difficult to achieve or unrealistic. Please understand -- I am not trying to be critical. We all try to "grow" in what we think are the best environments possible, and I know you are doing that too. And yet my experience, which continues even into this morning, is that the PLANT will tell me if it's the best environment in which to grow. I have gasterias THRIVING in soil-based mixes I would never DREAM of using--happened quite by accident. I also have Sansevierias struggling in a mix that works for 90% of my other Sans. To me, it's all about what the plants SHOW me they like the best.

  • mrsventure_5a
    5 years ago

    Louise, I use Canna Coco's coconut coir too, the compact brick form. I also mix it with pumice from Bonsai Jack and I add a bit of soil to that to provide nutrients.

    My pumice has never turned orange. I do water with rain water to minimise mineral deposits and optimise O2, so I am not sure if this makes a difference or not. But now I am definitely curious as to why your mixture is turning orange, that is so strange!

    Will be following.

  • Louise (UK)
    Original Author
    5 years ago
    last modified: 5 years ago

    Thank you to everyone who has replied, it's really appreciated!

    I've removed all my plants from the coir and pumice mix. There were root problems but fortunately no rot. I plan to repot them into pure pumice, but I'm concerned that the pumice I have isn't drying fast enough.

    I weighed a pot of pure pumice, watered without a plant and these were the results:

    55 grams, 28/11, (Start weight)

    72 grams, 28/11, +17 (Distilled water from top, wicked with a paper towel)

    -

    66 grams, 30/11, -6 (2 days after watering)

    62 grams, 01/12, -10 (3 days after watering)

    60 grams, 02/12, -12 (4 days after watering)

    58 grams, 03/12, -14 (5 days after watering)

    58 grams, 04/12, -14 (6 days after watering)

    56 grams, 05/12, -16 (7 days after watering)

    56 grams, 06/12, -16 (8 days after watering)

    55 grams, 07/12, -17 (9 days after watering. Start weight)

    The majority of the water had evaporated by day 5 (and over half by day 3), but it was 9 days before the pot returned to it's start weight. I know that the results will be slightly different with a plant, but am I being paranoid or is this still taking too long to dry?

  • Karen S. (7b, NYC)
    5 years ago
    last modified: 5 years ago

    Don't know why this has become so complicated. I grow multiple Haworthias in crappy old C&S mix w/ lots of Pumice (sometimes Perlite) & they do fine.

    To me you are really overthinking this.

    Perhaps you don't know this, but Haws benefit greatly from a fair amount of neglect. They do not do well when fussed over.


  • Louise (UK)
    Original Author
    5 years ago

    Karen Sternberg, given how soggy and damaged the roots were in the coir and pumice mix (if I had left them any longer, I'm certain they would have rotted), I don't think I'm worrying unnecessarily.

  • Karen S. (7b, NYC)
    5 years ago

    Sorry, that's not what I meant, but rather about how long it takes for the pumice to dry.

    Just grow them on the dry side, whatever mix you end up using. Always better to err on the drier side w/ these.

  • Louise (UK)
    Original Author
    5 years ago

    Chris, thank you. I agree, I think the 3mm particle size is the reason for the water retention.


    I purchased it based on this recommendation: http://www.haworthia.com/growing-medium/


    Unfortunately it's very difficult to source pumice in the UK. Do you think the drying times I calculated above will be too long?

  • rina_Ontario,Canada 5a
    5 years ago

    It isn't easy to find pumice where I am, so I use perlite. Works as good, it is less $ and most important - easy to find. I know some don't like it since it is very light - but it works. And could be covered with a thin layer of grit that will keep it from floating.

  • Louise (UK)
    Original Author
    5 years ago

    Thank you for the suggestions, but before I purchase any other medium I'd really like to know if the drying times I've calculated with the pumice are definitely going to be detrimental. Is it not possible to say for certain?

  • robinswfl
    5 years ago

    I think the drying times that you calculated with the pumice will be detrimental only if you water the plant/pumice while it is still wet. Beyond that, I think you may be over-thinking this and over-worrying.

    I get 1/8" pumice from General Pumice Products here in the U.S. I just sifted and washed a bucketful over the weekend. It is drying in big oil pans outside -- and right now, it's really cold here in SW Florida. I don't think it will be fully dry until Thursday, and that will be 5 days. Chris is right -- use unglazed terra cotta pots if you can. Even with pumice, they will remain lightweight. Haworthias in pumice shouldn't need to be watered more than once a week, unless you live in hot southern Florida in the summer. Even then, mine only get watered about every 5 days. You don't HAVE TO water a Haw the very minute its mix is dry. You can wait a day or so and it will be fine.

    Louise (UK) thanked robinswfl
  • Louise (UK)
    Original Author
    5 years ago

    robinswfl, thank you! This will be the third time (in two months) that I've re-potted my Haworthias due to soggy mix (the first was a supposed specialised succulent mix), so sadly, I agree, I am over-thinking and over-worrying; but I feel that it's necessary. I don't want to get it wrong a third time, and I don't think some of the plants will survive another incorrect mix.

    Given the drying time of the pumice, would watering every 2 weeks be appropriate?

    Thanks again.

  • Pluto1415 (6a/b, NE Ohio)
    5 years ago
    Louise,. don't forget that once the plants start growing they will use that water. so just because it takes x number of days when empty does not mean it will remain the same with a plant. I am still pretty new to succulents and I've read a lot here. One thing I have learned is that plants don't like schedules. I have things that appear to be the same size plant in the same size pot and one will be home dry in 4 days, one will take over a week, it depends on each individual plant for me.
  • Nil13 usda:10a sunset:21 LA,CA (Mount Wash.)
    5 years ago

    Now if the plain pumice turns brown, that's probably diatoms which are a type of algae.

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