Rheum nobile/alexandrae

[Philippe]

One month later, with some warmer days in between, particularly in the last 2 weeks, the Rheum nobile show quite steady growth now.
Here the last pics from today:










The first three are always the same as last times ( I think each time put in the same ordrer in the previous posts), and the last one is new to the update.
Again some difference between it and the first other three. A different collection, but it looks like it isn't going to be R.alexandrae this time, the leaf blade is quite different. But I find this bright green strange, in regard to the more reddish colour of the others.
We'll maybe see what it will be later.

The bigger leaves on the strongest plant ( the third one) are about to reach already the 5 cms length mark. I suspect the summer growth will reserve surprises in the next weeks.

[ebbie]

This Rheum alexandre is from AGS seed in 2010. I hope it will bloom next year. It's been hardly any problems. But I think Rheum nobile is more difficult.

[Philippe]

Time again for a little look at the Rheum nobile in the garden.







The first one is the weakest one. It didn't grow that well I find. Things started right untill late June, when warmth and drought came together to give us one of the "prettiest" summer of the last decade. Maybe this plant in particular didn't appreciate the weather, and choose not to grow further?

The second one is already a stronger plant, situated just 1 meter away from the first one.  This is reassuring as it means Rheum nobile can reasonnably still cope with what was a too warm and too dry summer here, a thing we hopefully should not have every year.

The third gave the greatest hopes of the season. It might be because of its position above a dyke in which runs a streamlet, providing sufficient air and perhaps also soil humidity, but it's the prettiest one. The biggest leaves were about 10cms long.

I am really sad to say that I have lost the 6 individually potted seedlings that grew on again at the season's beginning. I suspect that at this vulnerable stage the warmth combinated to too much watering in the propagation bed, and not enough air movement because of almost constant shading brought them later to die in July. These were sadly 6 true Rheum nobile as far as I could see from the leaf.
All the rest that had been planted in the garden last year or so will be R.alexandrae. From diverse sources. A shame that one can make the mistake on such an inimitable species when collecting seeds in the wild ( apart from the very different habit of the plant, I guess R.nobile wouldn't grow happily where R.alexandrae grows).

Next update next year then, with good news I hope!

[johnw]

Amazing Philippe.  You put us all to shame, these are very healthy Rheums.

johnw - another brilliant day to 22c

[cohan]

Searching for information on particular plants, I often end up referred to SRGC pages- of course, who is growing some of these odd plants if not SRGC members?
I happen to have R alexandrae seed now, just wondering if it needs any special germination treatment? Still web searching, but hadn't found anything yet... and it sounds like if I get seedlings, they are not too fusssy, but want to be moist?

[Lesley Cox]

Definitely, R. nobile is more difficult to grow (I've lost all of mine in their 2nd year) and, according to Harry Jans, IMPOSSIBLE to flower in cultivation. I guess Phillipe may be the closest any of us has gone to that amazing event.

Most Rheum seeds seem very quick and easy to germinate and most seem OK to grow on but a few present more difficulties. I didn't get any germination from R. tartaricum and only a couple of seedlings from alexandrae. R. nobile germinates well - 100% - but the problems start after that. Of course it is a wet scree plant rather than a boggy plant like some. My most favourite of all is the tiny R. delavayi, just about 15cms high in flower and making little tight mats of 3-5cms wide foliage, deeply veined and reddish. It always comes through rather late for me after winter dormancy and I always fear I've lost it. Only had seed a couple of times and not recently. I think it too, doesn't like a bog but prefers a moist but very well drained place. Mine has been in a raised bed for most of its life, but currently still in its moving pot. Compare its size with the little "juliana" type primrose beside it.

[Lori S.]

Your R. delavayi is charming, Lesley.  I hope mine look like that one day.
Rheum rhizostachyum has survived here as well.  Here it is in seed:



(P.S.  Ignore the big weed in the upper left corner of the photo... was supposed to be Saussurea napalensis but turned out to be some meter-tall Picris(?).   I was just waiting to see the flowers, towards an ID before I yanked it out.  )

[ebbie]

cohan, Rheum alexandre also germinates fairly quickly and does not require cold stratification. The substrate should be slightly moist, but not wet! In the second year you should they can plant outdoors. Give them a cool and bright place. For me, they suffer in the summer under the heat. Your temperatures are likely to be better.

 Lesley and Lori, what interesting plants are your Rheum!

[Lesley Cox]

Yours is gorgeous Lori. I don't know that name at all. I think there are a number of quite dwarf rheums which are very attractive but not at all common - or generally available, unfortunately. I once had R. ribes of which there is a super photo in the Phillipa and Rix "Perennials" book. It didn't stay with me long enough to flower though and can't be got here in NZ. And R. spiciforme was quite happy with me for several years and did flower for two, then vanished one winter, or rather, didn't reappear in the spring so maybe rotted.

[cohan]

Thanks for the input, ebbie and Lesley! How wet does alexandrae need to be once in ground?

Lesley- delavayi is very charming for sure- I've seen pics before, and it is very desirable
Lori- another cool species- how tall is that one? Was that from Czech seed?

[Philippe]

Hi Cohan

Just came upon this thread again. Nothing to update with R.nobile though. R.alexandrae seems to enjoy a very moist soil, with good/reasonable drainage however. Some plants grow nearby a streamlet in the alpine garden. Not directly at the water, but maybe 1 meter away, and not really much higher than the water level. Of course there is no water in the ground at this place, but the soil never never dries out.
So I guess they really love a generous water supply throughout the growth period.
And the fact that the plants look thirsty as soon as the sun is too strong for a few days, coupled with warm temperatures, is a clue to what their favourite diet is: moist/quite fresh/quite cloudy
However they are strong plants in the general climate here, and they don't get the same care as R.nobile, by far not!

[Lori S.]

Rheum rhizostachyum is smallish but not near so small as R. delavayi appears to be.  The leaves have gotten to about 20 cm max so far (usually only 3-4  leaves present).  It's bloomed in 2 consecutive seasons now, with flower stems elongating this past season to about 25 cm in seed. 
I grew it from seed in 2010, so I don't have a great deal of history with it!  Seeds were from V. Holubec, collected in 2006 in Tajikistan, Yazgulem Range, Pamir, at 3800m in gneiss scree, and described as "caespitose perennial plant; 2 ovate ground leaves, 15 cm long, flowering spikes 15cm long, red prominent fruits". 

As was said, I found too that Rheum delavayi, R. rhizostachyum and R. alexandrae germinated at room temperature within a few days, without needing stratification.  I grew R. alexandrae years ago, not in rock garden conditions, and didn't get it to flowering.  Perhaps it would have a better chance now that I probably have more suitable places to plant it.

I have Phillips and Rix's "Perennials" too, Lesley, and used to make long lists of what I hoped to get from the photos there!  Rheum ribes would be one of those!

Enviable results, Ebbie, and especially, Philippe!

[ebbie]

R.alexandrae seems to enjoy a very moist soil, with good/reasonable drainage however. Some plants grow nearby a streamlet in the alpine garden. Not directly at the water, but maybe 1 meter away, and not really much higher than the water level. Of course there is no water in the ground at this place, but the soil never never dries out.
So I guess they really love a generous water supply throughout the growth period.
And the fact that the plants look thirsty as soon as the sun is too strong for a few days, coupled with warm temperatures, is a clue to what their favourite diet is: moist/quite fresh/quite cloudy

Yes Philippe, I agree. For me, the plants are located next to a small garden pond. I think that the humidity in the air is important, too. On the other hand, the root at a plant that was too close to the pond, rotted away.

I am curious if my plants this year will come to blossom.

[cohan]

Thanks for the additional details, Lori, Philippe and Ebbie. If I get more than one seedling, I'll probably try a couple of different spots. I don't have any ponds or streams, but I do have below grade areas between ridges of rock garden and berm, north sides of those raised areas that stay cool and more or less moist, so it will probably be a spot like that- not right at the bottom where it may be too heavy, but a bit above where the soil should stay cool and moist.
The issue of plants wilting is interesting to me- I have a few species that wilt on any slightly warm, sunny day, even with moisture still in the soil, and some humidity in the air...yet they are not full shade plants, I think. I'm gradually trying to move them to spots where the roots and crown are cool and shaded (again, north slopes, or behind rocks/wood)..

[Philippe]

First update 2014

All 3 true Rheum nobile are still here, despite the last-not-really-winter.
It's funny to see how every June 2014 Rheum looks almost perfectly similar to what it looked in the update of  June 2013: same number, disposition and proportions of leaves. Everything nearly the same, but the plants are only on the whole bigger.

First one is still smallish, as it did last year. It produced so far 3 to 4 new leaves, but they are small, not more than 3/4cm. It might stay a weaker plant for ever, and I wouldn't be surprised not seing it come again in one of the next springs.



Second one becomes an interesting plant, with the central nerves getting white and larger now, as does the stem. The leaf shown in the pic is about 8/9cm now.



The last produced 3 big leaves already this spring, reaching 8/9 cm here too. As last year still the most promising of all 3.



I don't dare to say that the last 2 rheums are on the way to get adult, and have passed what should be the hardest and most dangerous part of their childhood, but if there is no critical event  meanwhile ( a very very bad winter/summer, or deadly damages on the roots by rodents), they are "teenagers" now, and seem to be able to cope with the normal climate here, and I want them to flower in some years.
Every other not happy ending story is not allowed, it's gone too far now

I just wonder how do the flowering plants behave. I think Rheum alexandrae is not really self fertile, and the first time I could harvest seeds on it was when 2 different plants flowered at the same time last year.
I hope Rheum nobile sees things a bit different, then it would be more than providential if 2 of the 3 cultivated plantswould come to flower at the same time. If they ever get to that stage of course.
I didn't see seeds in lists these last 2 years. The best would be to have, of course, euh let's say...about 15/20 Rheum nobile on different stages in the rock bed