My Banana Leaves are turning black

Discussion in 'Outdoor Tropicals' started by Yo_Jo, Jul 4, 2019.

  1. Yo_Jo

    Yo_Jo Member

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    I bought a banana plant from Costco for $20 about 2 months ago and I had dreams that it would turn my deck into a nice oasis but I have been chopping off blackening leaf after leaf. The leaves seem to start out in good condition but start to blacken after a week. Is this a problem of too much water, too little water, not enough sun or is this the same issue I am seeing on the Haskap Berry plant right next to it?

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    Last edited: Jul 4, 2019
  2. Sulev

    Sulev Active Member

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    Bananas like warm and moist weather and a spot that is exposed to full sun. Optimum temperature is ca 30°C (85°F to 90°F). Below 15°C their growth stops. They need plenty of water too, if your potting mix has good drainage, then it is impossible to water too much. Though, more than 2 inches per week is not necessary for such a small plant. I think that it is too chilly out there. Maybe something like heated propagation bench under the pot would help. Tropical plants may have root problems (may not obtain water and minerals from the soil), if the soil is too cold for them.
    Bananas are very sensitive to saltiness of soil. So keep this in mind, when fertilizing your musa - too much mineral fertilizer can kill the plant!
     
    Last edited: Jul 4, 2019
  3. Margot

    Margot Well-Known Member

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    I am not knowledgeable about growing banana plants here on the Lower Mainland and on Vancouver Island except to say many, many people do so successfully.

    Here is one example: Abbotsford goes bananas as plant bears fruit in hot summer
     
  4. Yo_Jo

    Yo_Jo Member

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    Thanks for the info Sulev and Margo (I want to grow one like Mr Flavelle did in his back yard). It's been a pretty on and off summer here in Vancouver with most people still wearing hoodies during the day - we call it a heat wave if it hits 30c for more than a few days over here.
    When we got it, I placed in into a planter with a mix of 3-1 potting soil/manure I used for growing veggies. After a month my wife has been fertilizing it with with the standard 15-15-15 mix every 2 weeks so if it only needs 2 inches of water per week perhaps the daily waterings are too much for it to handle.
     
  5. Margot

    Margot Well-Known Member

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    As I said, I'm no expert growing bananas but I can't help but wonder if you are over-fertilizing it. What do websites say about how to grow bananas (Musa)? Maybe you should review your cultural practices for clues about why the leaves are discolouring. Keep in mind too that you've only had it for 2 months so it is likely still adjusting from the ideal growing conditions it enjoyed before arriving at Costco to real life for it now on your deck.
     
  6. Sulev

    Sulev Active Member

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    Even in the same Vancouver Island, the microclimate varies considerably. The summer of the current year might be chillier than usual, and affect more those plants, that have unfavourable microclimate. At least according to the weather forecast info there is only 16...19ºC today (and similar was yesterday), that is pretty much lowest suitable temperature for banana plants. I am sure, that among those, who tried to grow bananas in the Vancouver area, there are plenty of those, who failed.
     
  7. Sulev

    Sulev Active Member

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    30ºC is optimum. Anything above 25ºC and below 35ºC is very ok for banana. But as at below 15ºC the growth stops, then even temperatures from 15 to 20ºC may cause lot of stress.
    Too frequent watering might be problem if your potting mix is not well drained. In their natural habitat bananas have frequent tropical rains. I think, it is best to avoid cold tap water.
     
  8. Yo_Jo

    Yo_Jo Member

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    I wanted to report back that after not watering it for 4 days the blackening seems to have slowed down. Since you mentioned that it only needs 2 inches of water per week I was most likely over watering that plant. Thanks.
     
  9. Tom Hulse

    Tom Hulse Active Member

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    Hi Yo Jo. :) What kind of potting mix did you you use? I see a lot of big bark chunks in there... bark & wood in the mix are not great for bananas. It limits nitrogen uptake, which they need a lot of. Your leaf pattern honestly looks like potassium (the "K" in NPK) deficiency, which bananas need a LOT of also. Nitrogen, phosphorus, and even other mineral deficiencies can severely limit how much K the plant can uptake from the soil. Cold temps can limit that uptake also, like Sulev mentioned.

    I would keep at it and expect to get better results within a month as the night temps warm up and your minerals in the manure become more available (was it composted manure?). I would consider switching to a very full spectrum water soluble fertilizer instead of just an NPK. Maybe roughly a schedule like water twice a week (or only as often as the plant really needs it) and fertilize half strength every week. You could plant some of those annuals right in the banana pot as a watering guide. After they become fully established, when they wilt tells you it's just past time to water.
     
  10. Yo_Jo

    Yo_Jo Member

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    Thanks for the reply Tom. Now that I am thinking about it, when we bought the banana plant we also got the gigantic bag of bark much soil from Costco so perhaps we did not use any soil/manure since that load was delivered a month after we bought the banana plant.
    I do have 40 litres of soil with chunky cow/horse manure in 4 to 1 mix (we used that for our vegetable patch) that I can throw on it. Would that help with the potassium? I also have some of the standard water soluble tomato or plant food fertilizer mix.
     
  11. Tom Hulse

    Tom Hulse Active Member

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    Ouch! That makes a lot more sense. That leaf patterning is exactly what I would expect trying to grow in straight bark mulch. "bark mulch soil" is kind of an oxymoron, since the whole purpose of mulch is to get plants to NOT grow their roots directly in it. That's how it keeps the weeds down while letting the larger plants reach below it into the non-mulch layer to thrive. Real soil is just the opposite.

    At this point you could either topdress with a soil/aged-compost mix and keep fertilizing lightly frequently, which should be fine; or it's early enough in the year where you could repot into a better soil. Repotting is really tempting, but it would set the plant back and may put you overall behind at the end of the year. I would probably only repot if the plant had a very full, tight root ball in there that could be just plunked into a bigger pot without disturbing it much. I use 50% aged chicken manure with a peat-based good-drainage soil mix to pot up bananas, Brugmansia, and many annuals in the spring. It's like nitrous for your plants. :)
     
  12. Yo_Jo

    Yo_Jo Member

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    If you think my banana plant's potassium is an issue what are your thoughts about adding wood ash to the soil? I am smoking a beef brisket and I am going to have several cup fulls of wood ash left over. A mixture of Apple, Cherry, and Mesquite?

    Will it help with the blackening leaves?

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