Show posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.

Show posts Menu

Messages - Steve Marak

General Discussion / Re: Vapour-pressure deficit
June 09, 2024, 12:25:05 PM
As far as I can tell, if you have the basic information - temperature, air pressure, and partial pressure of water vapor - then RH, dewpoint, and VPD are different ways of looking at the same thing. There are formulas and tables that let you get to any of them or convert between them. I grew up with RH. The weather people now, at least in the US, like dewpoint, for technical reasons, and the crop science people like VPD, also for technical reasons.

I also use Bluetooth enabled sensors (SensorPush), and it lets me display any or all of those three values. I tend to look at RH first since I'm most familiar with it, but I've got the VPD display turned on and am trying to get used to looking at it for the greenhouse sensor.

I agree strongly with Peter that leaf temperature is in many, maybe even most, cases, more important in knowing whether the plant is too hot than is air temperature, especially with C3 plants. High levels of photorespiration can become detrimental very quickly. (What I can practically do about that in my growing situation, other than more shade, is unfortunately a whole other question.)

The only real use I make of any of those numbers is deciding whether to spray water on the GH floor to increase RH/reduce VPD for the cuttings and seedlings, since they're so sensitive to water stress.

Thanks for the link to "Plant Empowerment", Peter. Looks like some good information there.
General Discussion / Re: Xerophyta retinervis
November 10, 2023, 02:40:22 PM
I can't help with the question, as I've never gotten seeds from either of the two Velloziaceae I have - this one, Xerophyta retinervis, and X. (formerly Talbotia) elegans. 

I don't want to hijack the thread, but if you have advice on pollination, I'd love to hear it. X. elegans in particular flowers freely every spring, but has resisted all my attempts to self it. I don't know if this is due to self-incompatibility or if there's a trick, and haven't found much information.

A friend who spent time in Brasil with Burle-Marx and saw a lot of Vellozia in habitat, and grew some, thinks it should be straightforward, but Xerophyta are from the African branch of the family so ??

I'd also appreciate a pointer if anyone knows of sources for other Velloziaceae.

General Discussion / Re: Hand Pollination
September 25, 2023, 11:03:02 AM
Depends very much on the size/shape of the flowers and the particular species, since some things have special requirements. But for general pollination I use cotton swabs a lot, sometimes clipping or shaping the cotton a little, sometimes dry, sometimes damp. Very cheap, available in quantity, disposable (the ones with paper spindles are compostable), and seem to work pretty well. If I'm doing controlled pollinations among specific plants I can mark the spindles with a felt-tip pen to help track whose pollen is where.

I haven't tried Lachenalia, but have had good results with them on various Ledebourias.

General Discussion / Re: Spider whisperers
September 24, 2023, 10:08:01 AM
Quote from: David Pilling on September 24, 2023, 10:01:36 AMspider repellent... things like ticks and chiggers are spiders, and things like deet are repellents for them.
Or if not repel them, at least leave them confused:

Lee, this is very interesting. I've been fascinated by color since I heard a talk by an ornithologist who was studying the visual system of birds (this was back before I paid much attention to birds, so I don't recall now why I was even there). He showed examples of colors that looked identical to most humans, but were composed of different frequencies of light and look very different to birds. Many birds are tetrachromats, with different color sensitivities than ours, including into the ultraviolet.

I started casually following the efforts of plant breeders, and in some cases gene shufflers, to achieve colors not found in nature, such as the blue rose or blue Phalaenopsis orchid (which was modified to produce the blue pigment in Delphiniums). But I hadn't considered the question you asked, which is a great one. And I like your answer! I've seen pictures of 'Masquerade'. If only I could keep Anigozanthos alive.

David, re your question of other ways to produce color than pigments, some plants also produce "structural color", derived from the way light interacts with nanoscale structures. (As do some birds and insects; I've read that all blue color in bird feathers is from structure rather than pigment.) I've been slowly accumulating research papers on this topic for years, and still don't have very many.

You also reminded me that I saved a couple of papers on how to use a cheap plastic diffraction grating and the standard camera in a smartphone, with some software from the Android app store, to make a spectrometer. I need to dig those out and actually try it. One more project for my overflowing list.


Mystery Bulbs / Re: Del Puerto Canyon
May 15, 2023, 08:23:03 AM

I'm no expert on California native plants, but as a milkweed enthusiast I'll suggest a nearly spent Asclepias californica.

Plants of the World (Kew) says they are native to Burundi, Chad, Ethiopia, Malawi, Mozambique, and Tanzania, and that "It is a tuberous geophyte and grows primarily in the seasonally dry tropical biome".

I grew them (NW Arkansas, US) long ago. They came back and flowered for several years, more reliably than the hybrid gladiolus sold everywhere do here, until an unusually cold winter - a fairly common story for me. Of course that was back when winters were significantly colder, so maybe I should try again.

I believe this just means that while the names are considered synonyms, the heterotypic synonym is based on a different specimen ("type") than the one on which the currently accepted name is based. A homotypic synonym is a name that is not the currently accepted name, but was based on the same specimen. You can see the definitions here:

A botanist publishes a new species, Species A based on specimen A. Another botanist decides later that it has to be renamed for some reason so it's now Species B, but since that name is still based on specimen A, the original name (Species A) becomes a homotypic synonym. Meanwhile, someone decides Species C, whose name was based on specimen C, is really the same species, but is a junior (later) name, so Species C becomes a heterotypic synonym.

I welcome correction from those more knowledgeable about botanical nomenclature.

As to what name you should use, I can only tell you what I do. In general, I use the currently accepted name (i.e., the newest one, even if that happens to be an old name that's been revived). If I happen to know that species or genus is the subject of ongoing work and is still in question, or if I know that very few people have switched over to the currently accepted name yet, I'll put a couple of names on the tag. If I think for some reason the name given by the collector is wrong, I'll use what I think it is and note "received as" on the tag. (Yeah, my tags get pretty cluttered. Sometimes there's more than one.)

General Discussion / Re: Trying a few root crops
December 04, 2022, 02:29:42 PM
Thanks for that information, Martin. I'm interested in this topic too, so I hope others will contribute their experiences. Of your list, I've only intentionally grown oca, Oxalis tuberosa. I ordered several cultivars in the spring. I had tremendous foliage growth from all of them all summer long, but in the fall, zero tubers. I knew they were a long shot with the summer heat here (NW Arkansas, US) and this year the heat lasted even longer than usual, so I was prepared for the failure. I've looked for heat tolerant cultivars but never found one.

Unintentionally, Cyperus esculentus is considered both native and introduced across most of the US, including here, and I think I killed off a stand of it in the yard when we moved here. Maybe I should try growing it intentionally. (But potted.)


General Discussion / Re: How to coccinia?
October 31, 2022, 01:54:37 PM
Quote from: Martin Bohnet on October 31, 2022, 05:18:55 AMAs he mentiones it: I'm really not too afraid of Cucurbitaceae going invasive here - I'm only mildly aware of Bryonia alba in Middle Europe, and I've never seen it out of control outside of strongly disturbed areas.
I was asked about the hardiness of C. abyssinica, but perfunctory Googling didn't show much. Several sites gave USDA zone 8 for C. grandis. But the USDA site shows C. grandis as known in the U.S. only from Hawaii, Texas, and Florida, and even Florida, which is understandably rather sensitive about aggressive exotic plants, doesn't seem to consider it a problem, so I wonder if zone 8 is an overstatement.

Bob, same problem here in NW Arkansas, where they're only hardy in medium or mild winters. I only grow a few species, but I've been able to dry them out going into fall, then store the mostly dry pots under benches in the greenhouse until spring. They get a little drip from above which keeps them from desiccating, and don't seem to mind as long as I don't forget them in the spring. (And a couple have forgiven me even that.)

General Discussion / Re: How to coccinia?
October 29, 2022, 02:23:02 PM
I haven't grown this, Martin, but asked some people I know with Ethiopian connections. They didn't know it either (now they want to try it, if we can find a source) but in the process we found another video I thought more helpful:

About 21 minutes, the experience of an anchote novice over two seasons with growing and eating it (in Pennsylvania, U.S.).

During the discussion about genus Coccinia, a member of our little group in Hawaii mentioned that C. grandis is a major problem there. He said the tubers can get enormous and that he weeds out volunteer seedlings regularly.

I agree this is an important point and I suspect the answer depends on the the grower, i.e., those who are aware of and concerned about the issue take care to avoid it, or clearly mark the seed as open-pollinated. And I think it's great that people donate OP seed.

When I want to be sure, I protect the inflorescence from insects (and, sometimes, hummingbirds) for the entire time of flowering. I also have some rules of thumb. If I've grown it for at least a few years and never had any spontaneous seed set, I assume no hybridization. Likewise if there's nothing closely related flowering at the same time, especially during cold weather when the greenhouse is closed and fewer flying insects are around. And there are a few things, e.g. Hippeastrum striatum, which set copious seed every flowering without help. Otherwise I assume there's a reasonable chance of hybridization and mark as OP.

I can't recall anything from SX seed that seemed a likely hybrid except things that were marked as OP. But I'm not confident I'd know, unless it was a species with which I was very familiar, and of course I rarely request those.

General Discussion / Re: Cyrtanthus montanus pollen
September 06, 2022, 03:12:03 PM
Quote from: unhappykat on August 16, 2022, 08:33:17 PMAlso, if anyone might have a source for this species in the US I would be interested in obtaining any new material for future propagation efforts.
Quote from: jshields on August 20, 2022, 04:54:22 PMI have Cyrtanthus montanus that came from Greg Pettit in South Africa.  There were 4 bulbs which have increased nicely over the years.  I think all 4 were the same clone, as they have all increased nicely from bulblets and are mutually infertile -- no seeds in many years.  This accession has my number JES #1328.
Better late to this thread than never, I guess. Jim, I have Cyrtanthus montanus labeled "BX 156 2007 ex Shields ex Pettit" so thank you! I only grow a few Cyrtanthus but this one is my favorite. I self-pollinated one year and did get seeds, which germinated, but they've never set seed spontaneously. That was just an experiment, which I've never repeated because it makes plenty of offsets.

And speaking of offsets, Edwin if you'd like a couple shoot me a private message - I gave away a bunch of these earlier this year but I'm sure I missed a few.

General Discussion / Scadoxus multiflorus question
June 14, 2022, 11:56:21 PM
I have two clones of this species. The tag on one says "1987", with no source. The other has "Croft 2003" on the tag. They are grown side by side in the greenhouse, moderate light, and LOTS of water, almost every day year round, whether dormant or not, because the things around them get watered often. They don't seem to care, and obviously are very tolerant in general. Both clones exhibit dormancy of a few months every year, and generally flower every year. But they're different in behavior.

The 1987 clone flowers with no leaves (picture attached of inflorescences from about 3 weeks ago). Leaves start about the time the inflorescence fades. It has produced only 2 offsets in the ~35 years I've had it. The 2003 clone puts leaves up before flowers (it currently has leaves almost fully developed and has yet to flower this year), and has produced 5 offsets in 19 years. After reading the PBS wiki entry for this species, my question is what subspecies are these?

The wiki entry says ssp. katharinae has "very short to no dormancy in cultivation" and "multiplies rather rapidly by rhizomes", which doesn't seem to match either of these. Ssp. multiflorus might match the 1987 clone - flowering in late May (before midsummer here in NW Arkansas), slow to offset, goes completely dormant, like Bob Lauf's picture flowers without leaves. But which subspecies is the 2003 clone? Or am I misinterpreting the "multiplies rapidly" part of ssp. katharinae?

Kew lists a ssp. longitubus, but the only hits I get in online searches are just for the nomenclature, and the wiki suggests it's rare in cultivation.