kumquat dropping leaves

stropharia(8b louisiana)February 11, 2011

My kumquat has been slowly defoliating from the bottom up. It's probably lost over 30 leaves by now. They are just falling off, still green; I've checked a couple times by gently pushing on the petioles, and the lowest couple leaves on many branches will fall off. I've seen this attributed to roots being too cold, but that seems unlikely in this case: I bring my plants inside when it freezes and kumquats are a bit cold-hardier than other citrus.

If anything, it seems to drop more leaves when it's inside. This suggests that it doesn't like it inside, possibly because it's not as humid as outside. I've suspected this and have tried misting the leaves, but it's messy with my current setup. I also have two lemons and an orange, and they don't mind it inside a bit. The kumquat and one of the lemons were recently transplanted into gritty mix, but the lemon (Meyer) got the rougher treatment, complete with some root pruning, and it's happy as can be. What gives?

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tapla (mid-MI z5b-6a)

Did you thoroughly check for insect issues - scale in particular, but mites, too?

Did you leave most of the old soil on the roots when you repotted?

Plants often defoliate with light changes - particularly when light levels diminish - a possible issue. Are there new buds emerging where old foliage was shed?


    Bookmark   February 11, 2011 at 5:58PM
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stropharia, When a plant drops GREEN leaves it is saying, "I am upset!" (The Horticultural Gospel according to Charlie Bingaman). That these leaves are on the lower branches suggests that the problem is not associated with some occurrence at the roots. If it is not internal, then it must be related to the (external) re-potting and/or the change from outside to inside. Another related spp., a Meyer lemon, similarly treated, did not display the same symptom.
I am left to conclude that the re-potted kumquat probably got too much water, maybe during the re-potting process.
I suggest that you give it every condition to allow the potting medium to dry out.

    Bookmark   February 12, 2011 at 5:50PM
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stropharia(8b louisiana)

Al, thanks for your advice. I've found no evidence of insects, damage or otherwise. I removed nearly all of the old soil, leaving behind only a few large (1"-3") chunks of bark that some roots were deeply embedded into, with the intention of removing them when I next prune the roots. There is a little new growth on the apical tips of many branches, but not as much as my lemons and orange, and none down where it is losing leaves.
I'm inclined to think it's probably the lowered amount of light from being indoors so much, perhaps combined with transplant and/or humidity stress. Since freezing temperatures should be gone for the season, I moved the kumquat back outside yesterday; it didn't drop any leaves overnight.

ronalawn, thanks for your reply. Why do you say that the dropping of lower leaves implies a lack of root problems?
Since the plant was potted into gritty mix, which is fast-draining and well-aerated, I sincerely doubt I've given it too much water. In fact, I watered it yesterday with Foliage Pro when I moved it back outside, because it had been probably ten days since last watering and it needed it.

    Bookmark   February 13, 2011 at 7:39PM
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tapla (mid-MI z5b-6a)

That there are buds emerging is a good sign. Some plants, especially those with fine roots, react poorly to having (almost) all the soil removed during a single repotting session, so my guess is, it would have been a drought response due to the plants inability to move enough water to the canopy; or it may have been light related. In either case, the mechanism that causes the foliage to be shed results mainly from decreased flow of a hormone/growth regulator (auxin) across the abscission zone at the base of the leaf petioles (stems) that is, in the end, attributable to insufficient water to carry on efficient photosynthesis.


    Bookmark   February 13, 2011 at 9:44PM
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stropharia(8b louisiana)

Very interesting, thanks for the physiological perspective. So a likely solution would be to ensure the root zone has water available and provide enough light for the plant to utilize the water?

    Bookmark   February 14, 2011 at 2:47PM
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tapla (mid-MI z5b-6a)

Sufficient water AND air in the root zone is what to shoot for. Think 'damp, not wet'. Try to keep the plant in bright light (but not direct sun) and out of wind until it resumes growing, then move it back into full sun over a period of several days.


    Bookmark   February 14, 2011 at 3:00PM
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