Winter Experiment Results

adenium1949April 24, 2013

Hello all,
Here are my results (so far) of growing seedlings over our UK winter period using both light and heat. The light units are T5 HO fluorescents and heat from a propagator base. The lights were in use for 15 hours each day since 25th October last year when the seedlings were emerging. The propagator base provided a minimum of 80 degrees 24/7. The two plants I am illustrating are representative of this first batch. Several other batches were sown later. I want to see if it is possible to get from seed to flower in one year so extending the growing period is a must. It also provided interest in an otherwise dull period for adeniums. Both of these plants stand 14 inches tall from the base of the 3 inch pots. As you can see the result was a "swings and roundabouts" affair. There was plenty of growth but at the expense of other characteristics, namely the caudex development.
Here is the first example. Here there is otherwise healthy growth but an insignificant effort for a caudex. I would expect a plant of this size grown normally to look much more mature and not like a giant seedling.

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Here is the second plant. You can see that there is no caudex development at all. I have obviously not pinched the plants as I believe that doing so to a seedling delays flowering to some extent, although it may have provided benefits in caudex development. I wonder if lack of caudex will prevent or delay flowering. I also wonder if I should have changed the tubes for a different spectrum at some stage. Well, there you have it, you win some you lose some, but whatever happens it was interesting, and they have the summer to adjust, so if you are interested I will post subsequent developments.
Happy growing,
Brian UK.

    Bookmark   April 24, 2013 at 2:44PM
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Good, we can compare notes :) i'm growing in zone 7b/8a Croatia, foggy and cloudy edge of capital city.

First off, your seedlings could have a genetic predisposition to grow this way, i've had a number of such cases, even with arabicums. But more likely in my opinion is that your fertiliser is too high in nitrogen, causing more green growth than caudex enlargement. What is your npk ratio? Also, i've noticed that adeniums kept in a heavier or "dustier" medium tend to elongate, while those in a gritty coarse medium develop a thich caudex, when both are fed the same. Out of all of my seedlings, those i left in a cactus mix/perlite (as control vs a gritty mix) fared the absolute worst over the winter, they are thin and rather pathetic.. I'll attach pics of what i mean later when i get home, just today i repotted some excellent examples.

    Bookmark   April 24, 2013 at 2:48PM
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Wow, that is some growth! Lovely plant. I had mine under lights for 6 hrs a day and I think all I achieved is keeping them alive. These seedlings in the pic are anything between 6 and 8 months old. Some that are really small are 8 months believe it or not. I'm putting them in the greenhouse during warm days now, hopefully they will start putting on growth now. You have done a super job with that one. I'm wearing L plates with these plants
Regards Averil uk

    Bookmark   April 24, 2013 at 2:52PM
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Brian, is the second pic an obesum?

    Bookmark   April 24, 2013 at 2:53PM
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Hi Averil,
They are both obesum hybrids from Mr. Ko seeds.

Hi Teyo, Looking forward to corresponding with you in Croatia.

Thanks both of you.

    Bookmark   April 24, 2013 at 3:02PM
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The second one I wouldn't have recognised the leaves as obesum. Although they haven't come out as you hoped, I'm fascinated they have grown so fast annd it's always exciting to watch how they go on Eh? the pic I have here is of 3 plants "born" on 21 June last year....not very big as you can see ha ha

    Bookmark   April 24, 2013 at 3:09PM
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greenclaws UKzone8a

What an interesting experiment Brian. It will be good if you would post follow ups of their progress. A couple of questions if I may....
Were the lights placed close to the seedlings when they emerged and moved slowly higher as they grew or were they fixed at a set distance above all the time? Just curious as they seem to have been drawn to the light source.
Did you feed them at all?
The caudex growth has really suffered IMO and I agree, they do indeed look like giant seedlings! With your proven track record of getting DR's to flower here in the UK, it will be exciting to see if these will be held back by their current stature and lack of girth. Please do tell us what happens with them.
Gill, UK.

    Bookmark   April 24, 2013 at 3:54PM
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Adenium1949, WOW, that is some impressive growth on those!!! Very interesting! I kept mine under T5's during the winter for somewhere between 12-14 hours a day but they were about 6 months old or so by the time they went under lights. My lights had "growth" bulbs in them, not "flowering" bulbs so I think our lights may be similar?

Teyo has a good point - what was your fertilizer? Also, the seeds may just be programmed to do that...

I was told it's good to keep them going at least their first winter anyways and not let them go dormant. I think I can safely say that ALL of us want to be kept updated on your progress!

I believe my tallest, without branching on its own is around 9 inches, but many of mine branched on their own without pinching. I actually didn't know about pinching until fairly recently, so some of mine I decided to prune back the center stalk.

Averil, you deserve kudos for those little darlin's, no L plates for you!!!

    Bookmark   April 24, 2013 at 4:06PM
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Hello all,
Many thanks for your responses, I will try to answer them all together if I may.
The lights were positioned at 4 inches above the sprouts initially and maintained at that distance as they grew. I was a little concerned at the recommended distance fearing they may be cooked but the tubes run very cool in practice.
The growing medium (Miracle grow plus perlite) contained slow release fertiliser already. Perhaps Miracle Grow was a good name. I subsequently gave very dilute azalea feed with a ratio of 6-4-6 plus micronutrients, again as an experiment. I think adeniums are often over-fertilised and was deliberately mean with the amounts. As plants get bigger I deliberately underpot as I feel the plants are less prone to rot inthe smaller amount of compost and dry quicker if the weather turns nasty. This strategy works for me but of course may not be appropriate in other climates.
Plants raised during a UK summer are usually far to small to spend the winter dormant IMO. Again this may not apply in other regions. We all have to find what works in our own situation and not try to copy too closely what is written.
I mentioned before that I made further sowings at intervals. These later seedlings have received less heat and are shorter but better proportioned. I think I may delay sowing untill early January next time, but a lot can change before then! (including keeping better notes).

Brian UK

    Bookmark   April 25, 2013 at 11:24AM
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Brian, thank you sharing your Experiment Results. We are learing from one another.

    Bookmark   April 25, 2013 at 11:32AM
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ladylotus(Z3/4 ND)

I really love experimenting and was surprised at the amount of growth in absence of a bigger root/caudex system. I think I would have done the same with two more plants and tried pinching them to see what results you had with them...would the caudex have formed?...would they have bloomed at the same or withing a short time.

I am really going to enjoy watching for your follow-up posts. I think I will give a few experiments on my seedlings a whirl next winter. Great information! I will be very curious to see if you get bloom this summer from yours.

Thank you for sharing your experiment.

    Bookmark   April 25, 2013 at 9:19PM
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Thanks Marie and Ladylotus,
I think experimentation is important, you never know what may turn up, and then it can be shared. I went for growth and got that, now I'm going for blooms. The plants are now acclimatising to the real sun so we will see what happens. If we all share info then our geographical location will not be a barrier to growing these amazing plants, at least thats the theory.
Happy growing,
Brian UK.

    Bookmark   April 26, 2013 at 2:57AM
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Hey Brian, what kind of watering frequency did these plants get? I know that caudiciforms evolved their characteristic caudex for water storage purposes. So if these kids got a lot of water on top of supplemental heat and light, they might have just skipped the caudex formation bit of their programming since they didn't need it.

I wonder if that process can be switched back on if you were to withhold water now or maybe the caudex only forms when the seedlings are very young (probably because in nature, the seeds fall off the plant and germinate at the time of year when there is little rainfall).

This experiment is brilliant, btw. I hope it flowers like the devil too!


    Bookmark   April 26, 2013 at 7:00AM
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Hello Pagan,
The plants were only watered when the soil was quite dry on the surface and the pots felt light. At the moment I'm tending to think that the heat was the main factor, as subsequent sowings under lights and heat are better proportioned but in this later case they received less heat but same conditions otherwise. Perhaps one thing we can learn is that size does not equal maturity? Anyway they are being given every oportunity to show what they can do, so here's hoping.

Brian UK.

    Bookmark   April 26, 2013 at 7:45AM
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This has been quite enjoyable reading through your notes, Brian. Also, everyone's comments.
I agree that experimentation, trial and error are very important for each of us. Not only do we live in different climates, but what we can provide for growing conditions and such are also very diverse.
Your two seedlings shown definitely have very healthy foliage. The spacing between the leaf nodes is greater, possibly due to so much terminal growth.
The other may be that when they flower the stem may not be strong enough to hold the flowers weight, if it should have a large double or triple flower.
Either way it will be interesting to see if you get some blooms this summer.
I hope that you do.
I have found here (Canada, West Coast) that for me it seems the best time of year for starting the adenium seeds is Jan/Feb..
I had started some in Oct a couple years ago and some in Jan/Feb of the following year. For the extra effort and cost of keeping them going over the winter was not really necessary.
I had a bunch under grow lights this past winter and some just left on the window sill in southern exposure.

I have kept atleast 8 seedlings all from the same seed lot just to see when they do flower what the differences will be for flower color, form, etc. The growth in caudex, height has been quite different with most.
Thanks for sharing your photo's Brian and averil.

    Bookmark   April 27, 2013 at 10:34AM
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Loveplants2 8b Virginia Beach, Virginia

Great experiment... Thanks for all of the great information !

Looking forward to watching your follow up pics as well !!

Great job!!

Take care,


    Bookmark   April 27, 2013 at 11:51AM
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i forgot i promised pics with my above comment
here are some seedlings that were sown in the last half of august last year. by the first half of october it got too cold to keep them outside, and from then until now they were inside on a windowsill, with little direct sunlight (also we had very very few sunny days because my area is very prone to fog). they were fertilized through the winter,but with a low N fertilizer.

this is while repotting, they are all very similar in size, this one had a caudex diameter of 4 cm, and the overall height of the plant from ground level to the top is 13 cm

    Bookmark   April 29, 2013 at 10:05AM
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kodom087 z9a

Great reading on everyone's post in this thread!


    Bookmark   April 29, 2013 at 11:35AM
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Wow Teyo, I love them...they are so cute.

    Bookmark   April 29, 2013 at 2:34PM
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ladylotus(Z3/4 ND)


You really got a lot of root growth and your caudex is so stout for only 8 months. Did you pinch your seedlings back or just leave them be with only adding a low Nitrogen fertilizer? Very nice group of seedlings.

    Bookmark   April 29, 2013 at 6:44PM
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Hi Marie and Ladylotus, thank you for your comments.
Ladylotus, no they weren't pinched back, i'm of a opinion that pinching makes young plants uglier,and try to avoid it whenever possible. i'm specifically targeting getting them fat and strong without unnecessary elongation of stems (which would later probably have trouble carrying flowers!).
i used a low N fertilizer, and they were in a very gritty mix that i think forced a caudex building response in them. this is all still experimental though!

    Bookmark   April 30, 2013 at 9:43AM
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