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I have some poincianas in pots that I started from seeds back in early July. In the summer, I kept them outdoors on the balcony and they mostly did quite fine, although later in August, some of the leaves on the lower branches would turn yellow with some areas remaining green, giving the impression of spots. The yellowed leaves also stopped opening up with the sun. I did a little research and discovered that poincianas generally prefer drier soil, so I reduced the amount of water they get.

Once the weather started to cool, I brought them indoors and put them in a bright and sunny spot. I have been trying to keep them very dry (watering lightly every 2 or 3 weeks), and while plants seem to be growing new leaves (although slower than in the summer), I'm still seeing lower leaves turning mostly yellow and then falling off.

How should I be watering these plants? I'm concerned about under-watering, but it seems that almost any amount of water lately is over-watering and causing leaves to turn yellow and fall. To be honest, they're not obviously wilted from lack of water, but they're still rather small (they are between 5 and 5.5 inches tall) so I was worried that too little water and they'd die and not recover. How can I safely water them without killing them?

The yellowed leaves are mostly on the right here, though you can see that one stem on the left side of the image is developing some yellowed leaves as well, closer to the trunk. The progression of yellowing always starts near the trunk and moves towards the tip. Yellowed leaves mostly on the right side of this image

Close-up of yellowed leaves. enter image description here

Another angle. enter image description here

FrustratedWithFormsDesigner
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1 Answers1

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One problem I see is that the pots are way too big for the size of the plant. When there is a larger mass of soil that the plant has yet to root into the soil will stay damper longer.

I suggest down potting one into a six inch diameter pot. If you can get one that is narrow and deeper that would help too. That style of pot is more suited for your plants which want to be trees.

If you are providing good light you may have to repot late next year. You will know the time is right when the soil at the top has roots in it and it dries out quickly.

At that time pop it out make and take a look. Are the roots going around the exterior of the root ball? If they are cut them and scarify the root ball with a sharp knife and a series of thin vertical cuts. Repot one size up and repeat as required.

kevinskio
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  • Is moving a plant to another smaller pot a good idea? I've never tried it. I suppose I could do it with the plant pictured here, it is all alone in its pot. The other two plants share a pot, might be trickier if their roots are tangled. I originally started off with almost 10 seeds, and only two large spare pots, so I figured I could put 5 in each pot. These three were the only ones that sprouted. – FrustratedWithFormsDesigner Nov 18 '15 at 19:09
  • I think I'll pop them out and see if their bottoms are damp. I don't have spare pots, but would it be safe to just remove the lower lawyer of soil if it's perpetually damp and the roots haven't reached it yet? – FrustratedWithFormsDesigner Nov 18 '15 at 19:09
  • @FrustratedWithFormsDesigner sure, pop them out, whether there is one seedling or three or four they will spend the next few years growing roots due to the imbalance in pot size to root ball. They plants should be 'snug' in their pots with a little room to grow roots. You need smaller pots! – kevinskio Nov 18 '15 at 19:11
  • Ok, so I took your advice and re-potted the single plant into a smaller pot. Its roots had actually already started to circle the large pot! I separated it from most of the soil and put it into a 6-inch pot I found with some loosely packed dry soil (very dry - all my potting soil has dried out to the point where the water just sits on the surface for a few minutes before soaking in!) and watered it lightly, with a little plant food. Hopefully, the shock won't kill it and having roots closer together will help it absorb what water it does get - the bottom of the large pot was dry... – FrustratedWithFormsDesigner Nov 21 '15 at 16:24
  • ...but there *was* dampness closer to the middle of the large pot, near where the roots were. The two plants sharing a pot don't seem to be yellowing as much - I may repot them later when I get more 6-inch pots, but I don't think they were as urgent as the single plant. – FrustratedWithFormsDesigner Nov 21 '15 at 16:26
  • This morning some leaves were still turning yellow and others (green ones) were looking shrivelled! It's both under-watered and over-watered at the same time! :( I gave a little water on the surface near shallow roots, but I fear this plant may have been too far gone to be saved. I'll have to get some smaller pots if I'm going to try to save the other two. – FrustratedWithFormsDesigner Nov 25 '15 at 17:29
  • Don't give up hope. Trees are remarkably resilient. Try more light, less water and patience – kevinskio Nov 25 '15 at 18:41
  • Heh, well light is harder to control than I'd like. I do have a "plant light" that I'm using on some potted hot peppers that are indoors over winter. I nudged the poinciana closer to it, we'll see how it does (I do have doubts that it's as effective as advertised). The leaves on all three plants haven't opened for several days, but I think that might be due to the mostly overcast weather we've been having for a while. – FrustratedWithFormsDesigner Nov 26 '15 at 15:01
  • It's been a few weeks and they all seem to have recovered from being re-potted separately into smaller containers. They all went through a bit of a period of being under-watered as they were still turning yellow. Then just as some leaves started to curl up and dry I started watering a little bit every day. They've mostly recovered now, and are getting light watering once per week. Poincianas seem rather tricky and fussy to take care of! – FrustratedWithFormsDesigner Dec 22 '15 at 02:08
  • Follow-up: Only one from that first set of plants survived, but I think most of them survived that first winter. A second plant that was started a year or two later has also survived this long. As a final note, it seems these things can go dormant in the winter. Leaves all die off by late December, and start growing again in early March. The plant is still alive and needs to be lightly watered 1-2x/week as long as there are green buds. – FrustratedWithFormsDesigner Apr 27 '18 at 21:16
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    Conclusion: if you like a challenging houseplant, the Poinciana is for you! – FrustratedWithFormsDesigner Apr 27 '18 at 21:17