Rather unhealthy serissa

vtbonsaichief

Here’s a question for all you serissa growers. What’s wrong with my serissa? First off, some history. This particular plant was purchased at Mill Brooks bonsai in VT in the summer of ’03, and has been fairly healthy living in a smallish four inch container. Last year I repotted it into a large oval bonsai pot, mostly to allow more room for root growth. It took off and was doing great indoors. There was an invasion of thrips upon my apartment plants, but I nipped this in the butt, and they didn’t seem to bother my serissa terribly.

Later that year, I got a job working at a greenhouse, and my boss generously let me bring my serissa into the greenhouse. It started to really take off, and I was almost too busy to keep up with it. Sometime around august or so, I noticed it wasn’t doing as well as I thought it should, slower growth, no flowers, and I checked underneath the pot. White fuzzy masses were crawling everywhere, so I lifted the tree out of the pot and found a horrible infestation of root mealy bugs. I immediately washed off all the soil, squished every last one of them critters, and then had the greenhouse fumigated. I moved the serissa to another location, and repotted into a less glamorous, but more practical six inch plastic pot, using pro-mix, a standard growing medium that we grow all our plants in.

All thru the winter, this serissa grew slowly and seemed to recover. By March the roots had filled the pot enough to hold all the soil together, and I was waiting for the spring flush or growth. But again its top growth was slow and stunted, and I began to suspect and other infestation. It was those wretched root mealies again, and this time they were really bad, being in the interior root ball, which is basically a tangled cage of woody roots from which all the feeder roots originate. I washed all the soil off, assiduously squished all the bugs I could massacre and had the greenhouse sprayed. This time however, I used a systemic pesticide, and drenched the entire root ball for several minutes. To be thorough, I submerged the entire tree in water for about twenty minutes, in case any little critters escaped my attention on the aerial parts. Then I drenched the roots again in pesticide. Afterwards, I lightly washed the roots, repotted in promix, and water in. And just so that the bugs got the message, I put a diluted mix of the pesticide in the soil. I repotted in a much larger container to allow for maximum root growth and to minimize any heat stress from infrequent watering.

So here are the major issues: some leaves are turning yellow and then fall off. There is little top growth. From what I can tell root growth is slow and/or stalled.

She doesn’t look like she’s about to give up the ghost, but she’ still pretty stressed out. I’m pretty attuned to my tree and know what’s normal, so I know something is still up.

I’m wondering if I’ve missed some important factor, perhaps cultural.

Here are my theories:
1.The soil is wrong for growth of this species. As I mentioned I’m growing her in pro-mix, which is a very fertile, very light airy mix, and is peat based. There must be a dozen bonsai masters (and people who think they are masters) groaning in exasperation right now for my not using a more free draining mix. I’m well aware of the benefits of well draining soil media in bonsai, and indeed, for some of my other trees this is what I use. However, I find I need a more moisture retentive mix for certain species, if I am to keep them alive.

2.The only problem with this idea is that I took several dozen cuttings from my serissa mother, and have now several dozen four inch trees that are growing happily and healthy in pro mix. I’m skeptical of the mother suffering from lack of or too many soil nutrients.

3.Perhaps the moisture level is too high. In an effort to keep my serissa mealy free, I’ve taken to drenching to roots with water and allowing for only partial dry outs. This seems beneficial for the smaller daughters, but I’m not sure if this is helping the mother. I’ve let the mother’s soil dry out a few times (not completely of course) and it always seems to stress the plant more than I think normal. My understanding is that serissas prefer a moist soil medium, and do best out of full sun.


The siting of my tree is in a warm, but normally not too humid greenhouse, protected from full sun, but with the maximum of light. It is never allowed to become too dry, and again, it is never sopping swamp wet. I’ve kept soil disturbance to a minimum, and fertilize infrequently, and then only weakly. Is this some sort of virus?

Sorry for the doctorate length thesis upon why my serissa is sick. Maybe someone will bother to read it in full length. I’m really bored, so I’ve kept a detailed history of this tree.

So tell what I’m doing wrong.

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soonami

Peat based soils may work for rooting cuttings, but for bigger trees you really need to use a much freer draining soil that will fit the needs of the serissa. I have found mine that were rootted in a sandy mix did much better than the same generation rooted in a peat based compost mix.

But the yellowing and lack of vigor is not something I would worry about. Serissas are tempermental and will yellow or drop leaves when moved or watered improperly. The best for you to do is to make sure there are no more pests, and water only when needed.

Just a note, overwatering often causes yellowing and dropping of the leaves and a loss of vigor, so watch out for that

gregb

Serissa was never on my list of species to try for bonsai, then a friend gave me one as payment for dog-sitting. That was Dec. 2000 and I still have the tree and several of its suckers and cuttings from it. It lives outdoors most of the year, except when there's threat of frost. I accidentally left it outside last winter and the temperature went down to 22*; didn't even phase it.

It seems to me the problems that plague your tree are greenhouse based. It's summer now, try acclimating it to a semi shady spot outdoors; a place that gets a few hours of morning sun (east-facing) and shade in the afternoon. I also think you should be fertilizing full-strength according to the label of the brand of fertilizer you're using. The half-strength school of thought won't "get 'er done" as they say. It's worth a try since you say you now have several trees, try it with a cutting to start and see if there's any difference. Good luck!

vtbonsaichief

Yeah, so I'm currently drying her out right now. It'll be awhile before I go and transplant her into some other soil. Thanks for the input.

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PinkFloyd

I have several serissa. I, too, think that your problems are greenhouse related. Put it outside, and don't water it so much. Leaf drop is normal for them.


John lee