Tuberous Pelargonium

David Victor
Fri, 27 Aug 2004 07:44:30 PDT
Dear all,

It was very pleasant to me to find some replies on this subject in my mail 
box this morning, so thank all of you that have shown interest.

Mary Sue said

>Dirk Wallace sent me seed of my first tuberous one, Pelargonium
>incrassatum.......... I loved the foliage, but when it finally bloomed I 
>found it dazzling.

This is the most glamorous of all of these plants and certainly catches 
everyones eyes when it is flowering. One of my plants had 15 inflorescences 
in flower at one time this year, with twenty or thirty flowers on each.  An 
absolute sphere of dazzling pink flower.  However, I do believe many of the 
others are equally (and perhaps even more) beautiful, but in a quieter way.

>I haven't done as well growing the others I have tried. Partly I've never
>been sure about when to water. And I didn't know on transplanting how deep
>to plant them so David's remarks about cultivation were helpful too.

Once they are a couple of years old, I find they are fairly easy to keep 
for some years.  Unless it is below freezing outside, I open the greenhouse 
for the daylight hours in winter, to keep humidity as low as possible.  Out 
in the South African deserts it can get cold at times!  I do find light a 
useful resource, especially in our northern latitudes with very short day 
length in winter.  I find daylight fluorescent tubes, low to the bench work 
very well.

>The other one he sent me was P. echinatum which I also grew from Silverhill
>seeds. Andrew's plants have bloomed twice (blooming now) and are really
>pretty. I'll try to get a picture on the wiki. I had a hard time getting my
>seedlings from Silverhill to start growing again after they went dormant,
>but they still look alive.

P. echinatum is an interesting plant.  Its a stem succulent with tubers on 
its roots.  Its "special" characteristic is the spines on its stems, which 
give it its name.

>The same was true for P. magentum seedlings (is this a tuberous one?) We
>saw that one in South Africa and it was a beauty.

Yes this plant has tuberous roots (from Section Cortusina).  It is in Van 
der Walt's Pelargonium of South Africa as P. rhodanthum, since corrected to 
P. magenteum

>  I also have some
>seedlings of P. barkeri from Silverhill Seeds last year that have made a
>tuber and one even started to bloom less than a year from seed, but kind of
>gave up quickly.

I think that this is probably P. barklyii, which is one of the most 
commonly grown tuberous species.  A great small plant with typical 
Pelargonium leaves and great long flower stems, with pale yellow flowers.

>I agree with David that one of the interesting things about these plants
>are the leaves. The flowers are a bonus and the tuber often very
>fascinating as well. When I looked through the information on the wiki I
>was surprised to see the different times of year they bloom. I assumed they
>would all be spring flowering.

Flowering times are widely spread.  With me, as the last finish flowering 
and go to sleep, around now, others are just waking up to start to put on 
leaves.  There is normally one of them in flower.  However, the peak 
flowering with me is in the main part of the summer, say June time.

>This group of geophytes is absolutely new to me and I've read your 
>introduction with great interest. Great job! I don't suppose any of these 
>have been trialed for winter hardiness in the USA?
>Many thanks,
>Boyce Tankersley


As far as I know no trials of the type you suggest have been 
undertaken.  However, my feeling is that they will survive quite happily 
with a minimum temperature just above freezing.  I have some of the 
succulent ones growing in a cold greenhouse (in the plunge) and the 
temperatures in there fall below freezing on winter nights.

>This is very interesting.  I'm curious about sources of tuberous
>Pelargonium varieties -- seeds or tubers?  If it is so tricky to get them
>past the one-year mark, I'd rather buy a few established plants, either as
>dormant tubers or as plants.

I obtain my material from a wide variety of sources.  However, many are 
grown from seed: Silverhill have some, Penrock probably have more, both 
from South Africa.  I also grow seed from the Geraniaceae Group seed list, 
which carries many species from the small group of enthusiasts in the UK 
and one or two from the US.  I do get tubers themselves from Monocot and 
Whitestone nurseries in the UK and Capeflora in South Africa.  Whitestone 
is a Cactus nursery and other such nurseries sometimes carry these plants 
at times.

>Dear Boyce:
>In the 2nd edition of BULBS I write about some 50 species with 8 or so
>being illustrated. Many can be grown in USDA Zone 9, with just a little
>protection, but most, if not all, will not stand frost and temperatures
>at night in the 40 F range are needed. Thus it should be possible for
>those who can provide some protection, to grow them. They are, in my
>opinion, quite beautiful and it is interesting to think about crossing
>some, especially the yellow species, with Pelargonium zonale or with Ivy
>Leaf species. The question of hardiness has not, to my knowledge, been
>factually established. I would not be surprised at all to find them
>hardier than supposed, but I would not think they would ever be hardier
>than, (or less hardy) than our common window box cultivars, which have
>survived many winters for me in San Francisco. Cheers, John E. Bryan
>Message-ID: <>
>Content-Type: text/plain; charset=US-ASCII


I must say that I have you to thank, at least in part, for my early 
interest in these plants: I read you first edition comments on them and 
then found out more!  I really do think that many South African plants are 
much hardier than is generally thought: Many of them exist through very 
cold night time temperatures.  However, a key issue is how dry they are 
kept.  The places in which they grow are very dry for long periods and the 
combination of cold and wet would often be a killer.


>Like Jim, I'm also interested in summer growing geophytic pelargoniums.
>The one I'd really like to try is P. luridum, native to the grasslands of
>Natal and other summer rainfall portions of southern Africa.  It's
>illustrated in Phillips and Rix's Random House Book of Bulbs and doesn't
>look lurid at all. Flower color can range from white to dark purple,

This is one of the non-Section Hoarea plants that shows wide variability of 
leaf shape during a single season.  Early leaves are shallowly lobed and as 
the season progresses, they become larger and increasingly dissected, so 
that late leaves can be filiform.  It is a widespread plant whose territory 
extends across much of the Eastern side of South Africa, into Angola, 
Malawi, Mozambique, Tanzania, Zambia, Zaire and Zimbabwe.

As for colour, it can vary from white to pink to red to yellow or green or 
can show variations on a single petal.  Perhaps not a bad name for the species!

>P. schlecteri is pictured in Elsa Pooley's Wild Flowers of
>KwaZulu Natal.  It looks interesting, with vaguely pea shaped flowers in
>two tiers, like a candelabra primrose.  I don't know of any source of seeds
>for these two.  I imagine seed would be somewhat difficult to collect, as
>is the case with most pelargoniums.

I don't know this plant at all and would welcome any further information 
you have about it, as I don't have access to this book.  However, I am a 
little confused about your comment that seed is difficult to collect from 
most pelargoniums.  Unlike other members of the Geraniaceae, the seed 
containing mericarps remain attached to the plant until disturbed and 
generally are easier to collect than their cousins.

>One winter growing pelargonium I'd like to see is P. sibthorpianum, (I
>think I've spelled that right...) a very low growing species.  There's a
>nice illustration in Rowley's caudiciforms book.

I think that you mean P. sibthorpiifolium, which is a tuberous plant that 
grows in the extreme North West of the Cape Province and the Southern edge 
of Namibia.  A very low growing plant with white flowers, marked in 
red/purple.  A beautiful small plant, though rare in cultivation.

Many thanks everyone for your interest.  If there are any further questions 
or comments, please do not hesitate to reply.

Best regards,
David Victor 

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