Frangipani stem rot

A New Zealand gardener is having trouble with her potted frangipani. I am posting my reply separately as other gardeners may have had a similar problem:

I live in Auckland NZ. I have white frangipani over 1.5m tall in a large pot. It last flowered about 4 years ago which was it’s first year in the pot. Now we are getting good leaf growth and new stems in the summer but the new stems rot in the winter and we have to cut them off.

There are several reasons why new growth on frangipanis can rot in winter – (1) water-logging of the mixture while the tree is dormant. (2) Lack of nutrients, such as potassium, which strengthens cell walls as well as promoting flowering. Have you given the tree any fertiliser? (3) Its position in winter is too cold for a tropical tree.

Remedies for (1) and (2): If your tree has been in the pot for 4 years, it is quite possible the roots have blocked the drainage hole/s, and that is causing the softer, new growth to rot when the tree is not using the moisture in the pot. Or, perhaps the holes have become blocked if the pot is in direct contact with the ground. Frangipanis form lots of roots and they must have good drainage.

As their roots are rather brittle, if you can’t remove the root ball from the pot easily, lie the pot on its side and hose out the potting mixture. Then carefully re-pot it into a larger pot with fresh potting mix that contains some complete fertiliser, and gently water it to settle the mix around the roots. If you can’t find a larger pot for the tree, trim the longest roots (so that they will have to grow about 5 cm to fill the pot) and re-pot in fresh mix in the same pot. Sit the pot on some pieces of tile so that the drainage holes remain clear of the soil.

Remedy for (3): Even the white frangipani (which is the hardiest) will not do well if temperatures are too low or they are in windy positions. When growing frangipanis in temperate zones, on the north side of a wall is a good position for them. A brick or concrete wall is best because the wall absorbs heat during the day and releases it slowly at night, keeping the air around the tree slightly warmer.

5 thoughts on “Frangipani stem rot

  1. Thank you so much Lyn. One of the smaller branches bent before I got your reply. Should I cut it off or support it so there is not a 90 degree bend? I also assumed a weak tea seasol solution is a dash of seasol in a watering can full of water? Sorry English is my second language.
    Also I do have the option of putting it back in a pot and keeping it indoors in a sunny spot over winter? Is that better again? I’m in Brisbane. Thank you most sincerely. Best regards, Reggie

    The bent branch needs removing on the branch side of the thickening (collar) where the branch begins. The seaweed ‘tea’ should be an amber colour if the instructions on the container do not specify the amount to add to a watering can. I would not disturb the plants again by moving them back into a pot. Brisbane weather is quite suitable for frangipanis. – Lyn

  2. I have two large frangipanis which were very happy in a large pot. I decided they were too large and found a lovely sunny, well-drained spot for them. We did have a heatwave after I transferred them into the garden. I watered them but didn’t overdo it. I didn’t split them up but planted them into the ground together. Although they look joined, I am pretty certain they are two distinct plants.
    Plant 1 was always the larger of the two and used to flower prolifically. After transplanting, and although it arguably got the better position, the leaves did not grow further and remain very small. There were a few flowers but they were very small or died very quickly. The branches and stem are now starting to feel soft and a little wrinkly.
    Plant 2, although it is much more shaded, couldn’t be happier. Big leaves, beautiful flowers.
    Could you please suggest a treatment plan?

    From the photos you sent Reggie, it looks as though the large plant may have suffered root damage during transplanting, and the remaining roots are not enough to support good growth for such a large plant. This is a common problem when transplanting large frangipanis as the roots are brittle and easily broken.
    The other possibility is collar rot. I notice the mulch is right up against the trunk. This keeps the base of the trunk constantly damp and encourages fungal or bacterial infection of the trunk. Mulch should always be kept at least a hand width from all trunks or stems. I would scrape the mulch back ASAP. Then spray the foliage of the weak tree with a very weak tea solution of liquid seaweed fertiliser. – Lyn

  3. I have 5 frangipanis, three of which have not had any leaves this year. One is an old tree, which also has fungi growing on it (white flower) that was about 2.5 metres tall, and a few years old and simply beautiful last season, another in another garden (pink flower) and one in a pot (white flower). The base of the plants seem okay, but the end branches are a brown colour inside instead of the milky. Is there any way to fix the problem as I would particuarly like to keep the big one rather than start again. Would a harsh pruning help, and if so, what is the best way to do it. Thank you
    Sharyn, it sounds to me that these tropical trees are not getting the warmth they need, either because they are not getting enough sunlight or your winter temperatures are too low. The white frangipani is the hardiest, while the pink requires warmer conditions. Or, the fact the trees are only receiving Seasol. As the company says, “It is not, by definition, a fertiliser (as it contains only marginal nitrogen and phosphorus levels)”. It’s a health treatment, but can’t replace an annual light application of complete organic fertiliser.
    Regarding pruning, frangipani trees do not require regular pruning. If a branch is inconveniently placed, it can be removed during winter while the tree is dormant. Frangipani trees will bleed sap if pruned during a growth period. Do not shorten branches of frangipani trees, or dieback will occur. On all trees and shrubs, a thickening of the stem forms where the new branch begins to grow. This is called the ‘collar’, or ‘wrinkle’. On frangipani trees, remove the entire branch, cutting through the branch at the outer edge of the collar. If you remove the branch flush with the trunk, scar tissue that forms will damage the phloem layer that transports carbohydrates in plants.

  4. I commented a replay after a NZ gardeners but hers was in pot, mine old tree in ground, very high but lims rotting. Do I give it a severe cut down?
    You can, Judy, if you follow the instructions here about pruning to the outside of the ‘collar’ at the base of the branch and don’t just cut off the rotted parts. – Lyn

  5. I have a 1 metre high frangipani in a pot and would like to re-pot into a bigger pot. The pot I would like to use is a wine barrel which has been cut in 1/2. Would this be suitable for it, and when would be the right time to transfer the plant. I have another frangiapani tree which on some branches have become soft at the tip, and then some are hollow. What should I do. Thanking you for your advise Gianna
    Hi Gianna. Late winter is the best time to repot frangipani. You haven’t said what size barrel you have and they come in a variety of sizes. Potting mix will go sour if a plant is too small for the roots to use it within 12 months. When potting on, the pot should only be at most twice the diameter of the existing pot. You can transfer your tree into a larger pot and sit it on bricks inside the barrel until it gets large enough to go directly into the barrel. When you do replant it in the barrel, make sure that there are lots of holes around the base of the barrel as frangipanis will rot if drainage is poor. This may be the problem with the other plant, Gianna, or it may be getting too much shade. Repot that one into a slightly larger pot with a free draining potting mix, and keep it in a sunny, warm position. – Lyn

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