Dark spots on Monstera deliciosa

Discussion in 'Indoor and Greenhouse Plants' started by Mani, Jun 21, 2020.

  1. Mani

    Mani Active Member

    Messages:
    211
    Likes Received:
    38
    Location:
    London
    Any ideas why these have formed?

    Thank you!
     

    Attached Files:

  2. Tom Hulse

    Tom Hulse Active Member 10 Years

    Messages:
    361
    Likes Received:
    35
    Location:
    Marysville, WA USA
    Hi Mani, any chance we could see a photo of the whole plant? With a plant as strong and healthy and hardy as a Monstera, bacterial spotting or leaf die-off is usually too little water, too much water, or not enough light; or some combination of those three. Does the plant ever sit in water for long after you water it? How often do you water it? Do you ever fertilize, and if so, what do you use and at what frequency and concentration? How far from a window is it, and what is the window oreintation?
     
    Mani likes this.
  3. Mani

    Mani Active Member

    Messages:
    211
    Likes Received:
    38
    Location:
    London
    Here is a full length view.

    I let it drain each time i water. I've only watered twice so far and have let it dry before watering thoroughly. It's about two feet from a glazed West facing window so is in indirect good light.

    It has been doing well or so I thought.

    The soil mix looks very peat based. The soil is still moist from watering 5 days ago.
     

    Attached Files:

  4. Tom Hulse

    Tom Hulse Active Member 10 Years

    Messages:
    361
    Likes Received:
    35
    Location:
    Marysville, WA USA
    That's helpful, thanks! Your pot is too small for the amount of leaf mass and the speed this plant wishes to grow. It's not getting enough nutrients (and maybe water), so it is just starting to abandon some of the older smaller leaves so it can keep growing up. A too-small pot is theoretically ok only if you are absolutely perfect on watering and supplying most of your nutrients not thru the soil but from outside fertilizer. That potting soil looks like mostly coco coir with chips, and perhaps some organic matter too, but I can't really tell from the photos. Overall it's still a very nicely grown plant, good job. Time to repot! :)
     
    Mani likes this.
  5. Mani

    Mani Active Member

    Messages:
    211
    Likes Received:
    38
    Location:
    London
    Oh ok, thanks for that! It's a brand new plant - I thought it would last a while in that pot. Glad I asked the question now!

    What soil mix do you recommend. From research I have seen that a 60/40 mix of coconut coir (60) and perlite/worm castings (40) is good.

    Your thoughts?
     
  6. Tom Hulse

    Tom Hulse Active Member 10 Years

    Messages:
    361
    Likes Received:
    35
    Location:
    Marysville, WA USA
    Perlite and worm castings could not be more different, so I'm not sure what the breakdown of those two is. Are they both 20% for a total of 40% of the mix? That may be ok if the coir was very coarse with with chips. If it is the fine coir, then the perlite (or pumice) should be in the range of 1/3 of the total mix.

    Many, many mixes will work great. My personal favorite for this kind of plant is 2 parts blonde peat (or 1 peat + 1 ground coir), 1 part perlite, 1 pumice, 1 aged compost, 1 worm castings. So that is basically saying 1/3 (water-retention+structure), 1/3 drainage, 1/3 fertility. To this I add several types of organic amendments (like kelp meal) and a couple types of lime for pH adjustment. You can get these type of mixes premade at hydroponics stores or make them yourself for much cheaper.

    Btw, since this is a new-to-you plant, that leaf spotting is probably also related to the change in conditions from wholesaler's perfect greenhouse with perfect fertilization (which allows a smaller pot) to your relatively drier, less-humid house with more average care. This change is another reason why it can't support as many leaves.
     
  7. Mani

    Mani Active Member

    Messages:
    211
    Likes Received:
    38
    Location:
    London
    Thanks! Yes, about 20% each of Perlite and worm castings.

    What pH should I be looking for for a Monstera? Is that the same for most houseplants? What pH testing kit do you use, if any? Sorry for so many questions!
     
  8. Tom Hulse

    Tom Hulse Active Member 10 Years

    Messages:
    361
    Likes Received:
    35
    Location:
    Marysville, WA USA
    A pH range of roughly 5.5-7 is what I shoot for with these, perhaps around 6.0 might be my goal for a Monstera at that age. They do well in well-draining peat-based substrates (which makes it a little easier to keep the pH down). I use a basic pH pen I got from Amazon, can't remember the brand but I think it was around $30 USD/$41 CAD/£24. However these will grow well in almost any decent houseplant soil, without any pH testing.
     
    Mani likes this.

Share This Page