Floatation method for germinating Rhodophiala seeds

Started by Piotr, April 14, 2023, 11:44:09 AM

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Hi everyone,

I am new to this forum and my apologies if I am posting this in the wrong place.

I have read a lot about the floatation method for germinating seeds in the Topic of the Week, and I am currently using it to germinate some Rhodophiala bagnoldii seeds I ordered from Chile. I am based in the UK, so we have spring now. I got two packets, each was supposed to be around 30 seeds, but the one I opened had over 60 - and I would say almost 100% of them germinated. They still have not grown any leaves though. It has been a week since I put them in water, they started developing roots after maybe 2 days, but now some started dropping the roots, which float on the surface detached from the seeds. I have counted around 5 or 6 so far, but I am worried they will all do it and that will be the end of it.

Has anyone encountered this issue before with this method and Rhodophiala seeds? What did you do?

Thank you,



Hello Piotr,

Welcome to the forum, you have posted at the right spot.
Your pictures are very good and explain the problem very well. However, I have no idea what happens to your seed. The roots look healthy, even the detached ones. The only cause for this I can think of it mechanical. Can you exclude that a pet, a bird or a child is attracted to the floating seed and manipulating it in some way?
Another thing springs to mind. You write that the seed is from Chile, so you have to consider a hemisphere swap. Did you sow/float all the seed? A spring sowing might work in the UK with a long spring and relatively cool summer but you might have better results with an autumn sowing as Rhodophiala is winter growing. The seed should maintain viability if stored in a fridge.
I also think that you can plant all those seeds which have a root. No need to wait for the first leaf. That may navigate round the dropping root problem. 
Hope that helps,

Algarve, Portugal
350m elevation, frost free
Mediterranean Climate

David Pilling

Piotr - I am not an expert but I have grown Rhodophiala from seed. I would suggest that once the root appears you transfer the seed to growing media. It'll probably just drown in water.

There is a picture by me on the PBS wiki (https://www.pacificbulbsociety.org/pbswiki/index.php/Rhodophiala) which shows what germination should be like.

Just because the root detaches from the seed, I would not give up (although I would not be optimistic), take them and stick them in growing media.


Hi Uli,

Thank you.

No, they are in a secure position and there is no chance of any sort of disturbance, and if I move them I am careful. I placed them away from the window under a 15W LED lamp, and the jug holding water is enclosed in a large plastic ziplock bag. Maybe I should open the bag? The temperature is around 20oC during the day and slightly less at night where they are. I did not want to put them on the windowsill or even close to the window because there would be substantial temperature fluctuations (from around 14 at night to 28oC on a sunny day).

I used tap water, as others observed they had better results with tap water. I do live in a hard water area though - I suspect that might affect germination to some degree, but most likely would not cause root detachment, would it...?

Yes, I got two packets specifically to try one in the spring and one in the autumn. There were very mixed opinions regarding the best seed starting time in that discussion, so I wanted to see for myself.

I could maybe try planting some, but from what I read, most people observed that when they planted seeds with roots which did not have any leaves yet, they all died.

Have you tried that Uli?


Hi David,

Yes, I have seen that photo, thank you. Can you remember when you started them? As in was it spring or autumn, and did you store them prior to starting? Which species was that?

Maybe I should try transplanting some into soil, since there are so many, and then see what happens with the other half, left in water.

I used to live in Blackpool back in the day. Very windy there, isn't it

David Pilling

Piotr - I regret I know nothing more about the photo. In my time I have tried Rhodophiala bifida, but probably others. The Rhodophiala bifida is documented on the wiki:

"Seed was offered in BX 275. Alberto Castillo explained about the donation. Photograph by David Pilling shows a bulb on 13th August 2012 from seed sown on 6th June 2011. The seed germinated almost immediately at ambient (65 °F) temperature and the seedlings which were kept away from higher temperatures only became dormant at the start of August 2012."

On the wiki, the word *donation* is a link, where Alberto, says sow as soon as possible and keep growing as long as possible, along with the information it is an easy plant to grow.

I still have those bulbs, but they have not thrived, similarly commercial bulbs I bought have not flowered. My guess is that temperatures are not extreme enough here.

I have probably had other Rhodophiala species seed from the usual seed exchanges (SRGC/AGS).

All my seed growing has been done using damp kitchen towel in zip lock bags, as soon as a root appears I use tweezers and move the seed to growing medium. Always works.

In nature there will be general species that germinate in water. According to the wiki Rhodophiala bagnoldii grows in coastal deserts - maybe it waits for the rain.

There are general bulb species where you get a root, and then have to wait a year while it forms a little bulb, and then in year two, the leaf appears. But I don't think that is the situation here.

Yep, Blackpool is windy  :)  50MPH winds this week that did my Spring bulbs no good at all.


Hello again, Piotr,

I could maybe try planting some, but from what I read, most people observed that when they planted seeds with roots which did not have any leaves yet, they all died.

Have you tried that Uli?

Yes, I normally do not wait until I get a leaflet on floating seed. I keep thinking that the seed would use up all its stored energy germinating in water which does not contain any nutrients whereas in suitable substrate there would be nutrients available. I have lost some seedlings in the process of transplanting but this may have other causes like sciaridae flies for example. They are much more aggressive here in Portugal than they used to be in my former greenhouse in Germany. 
Another thing: I now think that there is a myth about papery Amaryllid seed being short lived. It is the fleshy green round type of Amaryllid which cannot be stored. The papery black seed can certainly be stored in appropriate conditions for several months without losing viability. If you consider the natural habitat and climate where most of papery seed bearing Amaryllid species come from, their seed must be able to survive the dry season following seed set. Fleshy seed bearers flower before the autumn rain starts and their fast ripening seed falls to the ground with the onset of winter rain, at least more or less. 
I am writing this because water flotation is not mandatory for papery seed. I only use it for seed which was stored for longer than might be good. If your seed puts out roots within days of floating this means two things: firstly the quality is very good (may I ask if it is from Chileflora?) and secondly it is from a desert plant which has to hurry to get a plantlet big enough before the moisture from the rain is gone for a possibly long time. Seed of desert bulbs must be able to survive for longer by the nature of its habitat.
If I have fresh seed from my own plants I sow directly in substrate and cover with a thin layer of white sand to deter my sciaridae. Excellent results.
I took the attached picture this morning. It shows seedlings of different ages, all planted after root formation but not leafing with the water flotation method. All of this seed was stored for more than 8 months at least prior to floating. The longest time from floating to root forming was in Cyrtanthus montanus with up to two weeks. 
The next candidate for flotation is seed of Pamianthe peruviana which was given to me but I do not know how old it is.

Algarve, Portugal
350m elevation, frost free
Mediterranean Climate


So far as I recall, I have used this only for Agapanthus and had very close to 100% success - there were a LOT of seeds.

Float the seed and wait for a root of 3-4-5mm long and then transfer to a damp sandy compost. Make a tiny hole in the compost with something like a cocktail stick and drop the root of the germinated seed into the hole, the seed sitting on top of the compost.

Job done.



I would offer another possibility:
The roots that you see 'floating' (or sinking,) may not have "detached from the seed," as you state, but may have only separated from the papery sheath during the float. Or, in other words, they've outgrown the sheath, and thus discarded it.
The roots portion in this case would still be attached to the newly germinated seed.  Lacking any leaf development yet, the seedling is now looking just like only a root segment, without the sheath.  Does this seem like a possibility?

Using the float method for hippeastrum (a Rhodophialala relative,) I've noticed when floated awhile, the root (and the very small seed portion it protruded from) may look like only a long root segment.  I saw this as I transplanted  several hippeastrum to a seed flat ladt week.  Some looked like just long roots that had separated from the sheath.  I think they'll  transplant succesfully.  I treated them like all the others seedling starts when transplanting.   I have never waited for leaves to appear during the float, but maybe others do.

I agree with Uli that not all paper seeds need to be floated, at least in hippeastrum species and hybrids.  I also use it when the seed is older.  I had some one-year-old Hipps seeds floating last week, with very good germination.  I like science projects, and floating certainly seems like one....

I also agree with CG100's post that when floating seed and I see a 3mm root the seedling probably needs soil, as he stated.  I transplant by poking a hole and laying the root vertical into the hole, with the sheath laying on top of the soil/sand.  Because the sheath is generally perpendicular to the new root, this works.  I give a hole a little squish to firm the soilaround tge root, and then sift a fine dust of planting medium over the seeds. I give them light so when the first leaves poke through, they have light.  They all seem to make it.

With hippeastrum, floating seems to add a step.   If your germination rate is as good in a moist seed flat, and you have the lights and warmth and shelf space, you can skip the transplanting step required by floating.  Also, the floating method produces the long single 'water root' vs. the soil germination method that produces the more normal roots in soil.  This may be a cause of loss or a seedling growth delay as the seedling transitions from water root to soil.  It seems that the seedlings don't seem to have a preference of one method over the other, though.

If I float them to long, I begin to see the finer hairs of what I assume are water molds attaching to the root and sheaths, and I figure that can't be good-so it's time to get them out!

Again, my experience is with Hippeastrum seed- both species and hybrids.  The others on this thread have more experience with Rhodophiala seed floating. 

I just started another float (because I don't have the shelf space just now for another seed flat.)  That picture attached.
Member: : Pacific Bulb Society


Hi everyone,

Thank you for your replies.

I did plant around 20 of them into soil yesterday morning as I had some other things to plant so I just went ahead with it. They had actually started developing leaves at that stage. Today I can see that they have not stopped growing, as all seed cases were flat on the soil surface at the time of planting and today they moved quite a bit. Also the ones with visible first leaves, which were maybe 3 mm, are now taller, so yes, they are definitely in a hurry.

Yes, Ken, I observed yesterday that the seemingly detached 'roots' turned green on one side and started developing a leaf. Who knew! I thought they were getting ready to die. But I left those in water together with the rest to see what they would do.

Yes, I agree that floatation adds another step, but I do not start hundreds of seeds so I do not mind moving them from water to soil. Also, I was able to select the strongest ones to go in the pot. I have never grown a bulb from seed so I am trying different things to see what happens. Normally if I grow other plants from seed I do what David does, and as soon as I can see a root they go into soil. Or I just sow straight in soil. But this is new and exciting 😊

Yes, Uli, these are from Chileflora. They say on their website that this species is restocked in November, and since it is April now, I thought it might be a good idea to try some now, as I suppose this is roughly the time when they would be germinating if they were back in Chile. I will probably try the other packet in the autumn, maybe half in water and half in soil, to see if there is a difference in how they behave then.

To be honest I thought only a few would germinate, at best, not ALL of them. I assumed the seed would be old or poor quality, especially that they never replied to a single email at Chileflora. I was actually prepared not to receive my order at all.

You have some good looking Hippeastrum seedlings Uli. Do you ever have issues with Stagonospora in your Hippeastrums?

David, do you grow them outside? I have a Rhodophiala bifida 'Hill Country Red' from RarePlants (UK). They say they grow theirs under glass, where they flower regularly, but apparently tried outdoors and they survived. What do you mean by saying 'not extreme enough'? Summers not hot enough or winters too mild? Do you have a photo of what they look like now?

Below is a photo of the 'detached roots' yesterday

David Pilling

Quote from: Piotr on April 16, 2023, 05:52:46 AMDavid, do you grow them outside?  What do you mean by saying 'not extreme enough'? Summers not hot enough or winters too mild? Do you have a photo of what they look like now?

I don't grow r. bifida outside. They're in pots, it is just not convenient to put them outside. By not extreme enough, I mean Summers are too cool, Winters too warm. I don't have a photo, they grow long thin insignificant leaves, which seem to come and go in no particular seasonal pattern.

With bulbs one normally gets a big outpouring of growth at the start of the growing season - for me with Rhodophiala bifida that does not happen. It as if they tick over, growing the minimum to stay alive.

I can grow a lot here, but there are some plants for which the climate is not right. I am not bothered enough to play with getting them warmer in the greenhouse, I doubt there is enough heat even then.

One of the UK seed companies had a phase of selling a transparent concoction in which seeds could be grown. Orchid growers have various sorts of growing medium agar agar (not a typo).

The word "soil" is fraught with danger for the seedlings - sterile soil, well draining soil...


Ah, I see what you mean David. Maybe they are overcrowded? That is what RarePlants advise on their website, apparently if grown in pots they have a tendency to split up rather then flower. But I do not know. I am only just starting with this genus. And I have mine in a not too large pot (only one bulb).

My apologies, I should have expressed myself more clearly perhaps. I tend to use "soil" and "potting mix" interchangeably, which is not quite correct is it. I did use a soil based potting mix though (1 part) and horticultural sand (2 parts), plus some pumice and charcoal. The potting mix is meant to be sterilized but could potentially pick up all sorts during storage. I did not pour boiling water over it or bake it prior to planting the seedlings. I believe in them ;) 

I used agar to grow bacteria cultures and plants in vitro as a student back in the day. But this is maybe a bit much for growing plants at home as a hobby :) 


Hello Piotr,

This is a most interesting thread! 
Stagonospora is not really my problem with Amaryllids. The most annoying pest I have here in Portugal is Narcissus fly. I have never seen them but I find the empty, rotting bulbs. Some genera seem to be less affected, like Amaryllids belladonna and Nerine but Hippeastrum, Zephyranthes and Habranthus, Sternbergia and the larger Narcissus themselves are affected to the point of disappearing entirely. Growing in shade does not help. 
The second pest are voles. I have to grow valuable bulbs in pots. Hippeastrum and Iridaceae like species gladiolus, Ixia, Babiana are particularly vulnerable. And Lilium, of course.

Chileflora is notorious for their bad or non existing communication with customers, there were rumors that they had closed down but it is good to know that they are still there. I have grown some very good plants like Alstroemerias from their seed. The quality of their seed has always been very good.

If you are just starting to grow bulbs from seed: are you familiar with the WIKI? Here is a link to a very good article https://www.pacificbulbsociety.org/pbswiki/files/00_others/McGary_bulbs_from_seed.pdf
I have also written one for the Bulb Garden which I can let you have. (Need your email address) I can only recommend to raise bulbs from seed, it is so rewarding. Nothing more exciting than the first flower from a batch of your own seedlings.
If you read several articles on this subject you will see that many ways lead to success which means that you will eventually find your own best way, this applies to the seed substrate as well. And then it is worthwhile sharing your experience because there is always something new to discover for others.

Bye for now 

Algarve, Portugal
350m elevation, frost free
Mediterranean Climate

David Pilling

I got a private communication about Rhodophiala bifida, it said "They sport contractile roots and dwindle when at the pot bottom". Better planted in the landscape.


One think I do and find it improves germination is to use a small amount of hydrogen peroxide in the water.  about 0.5%.

Santa Barbara