Media for Mediterranean Terrestrial Species
 

So I recently ordered some Mediterranean Terrestrial orchids (Anacamptis coriophora/fragrans, Neotinea lactea, Orchis anthropophora) and with any luck they should be arriving later this week.

Having said all that, I haven't worked out what to pot them in. Most resources I have been able to find suggest 80% inorganic (I'll probably be using perlite for this since it is what I have on hand) and 20% organic material. As far as organic material, what do you all suggest? I have heard about Wood Fiber (seems to be some specially treated type?) and Buffered Coco-Peat. I am having difficulty finding a way to get either of those in the short time before the orchids arrive, does anyone have any other ideas?

I might be able to order them online, but the tubers would have to sit around for a while while it shipped in. Otherwise I have access to the few random potting mixes that are in stock at hardware stores.

I would use a high-grade bagged potting soil. Some contain fertilizer so pay attention to that.

Edit: I grow Mediterranean-climate non-orchid bulbs from seed. My initial response was to your question of what organic matter to mix with your perlite. I haven't studied Mediterranean orchids.

Many bulb growers mix something inorganic with a small amount of potting soil, usually 10%-25%. I find mine do better in pure inorganic substances with no organic matter added.

I use builder's sand from the hardware store for most of my bulbs. If you have only coral-derived ocean beach sand this not a good idea, and you must rinse ocean beach sand.

I have also used native stream bed soil screened to remove the fines. I dig the soil, then screen it with 1/4" / 65mm hardware cloth. I toss the big stuff back. I screen the remainder through this strainer, which I bought at a large Chinese supermarket here. Sorry about the dark image; that's the best my phone flash can do tonight.

Attachment 154540

Attachment 154541

I plant the bulb seed in the stuff remaining in the strainer, and use the fines for bulbs that come from very wet environments.

perlite is very water retentive so you have to mix 20% of something that is less water retentive.

This comes from experience working with perlite. It acts differently in a large amount to a small amount.

As a top layer perlite dries very fast but if you fill a pot with 80% perlite it acts more like moss.

So I would use medium sized bark 20% and 80% perlite.

You would not add soil to moss so just be careful doing the same with perlite.

Every inorganic substrate has it's advantages and diadvantages.

That reminds me, my answer is based on small grade perlite but one can also buy 8-10mm grade.

So what grade perlite do you have? If it is fine grade you need to add less water retentive media,

if it is large grade it will dry faster and you could use something more water retentive to supplement

Thanks for the input! I have small perlite (about 5mm pieces) large perlite (1-2cm chunks). I would prefer to use the smaller stuff as I have a lot and it's not as useful for my epiphytes, but obviously whichever is best for the plants is my priority.

I grow quite a few European terrestrials (Ophrys, Orchis mostly). My mix is about 80% inorganic - i use pumice and some sand. For the organic portion, a well-drained potting soil such as a cactus mix. I add some marble chips, very slow-release calcium carbonate, since most of these grow on calcareous soils. Success rate is pretty good... my tubers have, for the most part, been coming back and multiplying each year so I must be doing something right....

---------- Post added at 02:24 PM ---------- Previous post was at 02:07 PM ----------

If you can get your hands on a copy of the Orchid Digest Vol 83-2 (April-June 2019) there is an article by Phyllis Prestia "Growing Mediterranean Native Orchids: Serapias, Ophrys, and Orchis—An Interview with Scott McGregor". Scott has been my mentor in growing these terrestrials - he has been very successful at it!

---------- Post added at 02:29 PM ---------- Previous post was at 02:24 PM ----------

The reason for using pumice rather than perlite is weight - when the pots are dry, they are very light and with perlite, the slightest breeze can dump them. Less of an issue if you're growing indoors, mine (and Scott's) have to deal with occasional strong winds.

Oh as far as marble chips, would these work? (just regular landscaping stuff that I think I can get at the hardware store).
https://cdn.discordapp.com/attachmen...68/unknown.png

If those work, I can pick up some pumice etc. at the same time. If not, would it work to put some gravel or peastone at the bottom of the pot for weight?

For marble chips, I got a bag like that at Home Depot, and broke into smaller pieces with a hammer. Not high tech. (Scott suggests that limestone or shells are much too alkaline. The marble leaches very slowly, so is gentle) You could put some gravel at the bottom of the pot for weight if you can't get pumice and have to use perlite. They have similar characteristics. Lava rock works too - all have lots of air space. For the organic part, Scott suggests adding a some orchid seedling bark to the cactus mix. I typically just use the cactus mix. The point is, it needs to be fast-draining whatever you use. The enemy is rot, so you absolutely don't want it staying wet. Especially before the plants sprout.

Thanks so much for all the help! My order just shipped out, so I should be able to scramble to the hardware store and get everything I need!

Orchids and potting supplies have arrived! I was not able to get marble chips, but I think it should be alright for now.

Do they prefer narrower pots or wider pots?

I wouldn't worry about the marble chips. If you get some later you can use them as a top dressing, but I sometimes skip them and the terrestrials do fine. (Probably helps that my RO water isn't complete pure, about 15-20 ppm, and slightly alkaline) I don't think they care much about the pot - being terrestrials, it is just dirt to them. For the larger tubers you just want enough depth to have enough room for them. Smaller ones, doesn't matter, I plant them about an inch deep. One thing to note... the new tubers tend to work their way toward the bottom of the pot, so next year you'll probably want to "re-center" them. (They're likely looking for water...) But then, you'll want to see what's gong on in the pot anyway. July/August is a good time for repotting, they're completely dormant at that time.