Mixing LECA and Bark?
 

Hi all,

I have my phals planted in a bark/perlite/charcoal mix right now and have noticed that I get a sort of "layering" effect where the bottoms of my pots remain wet but the middle and top dry out quickly. I'm wondering what you all think about adding LECA to the bottom of the pot and also mixing it with the bark throughout the rest such that the middle/top of the pot is about 75% bark and 25% LECA. My idea here is that the LECA would retain slightly more moisture throughout the pot but since my orchids are accustomed to bark I don't want to switch to full LECA. I just want something that will retain a little more moisture throughout (I water about twice a week currently). I thought about doing sphagnum moss but my experience of it in my environment (Pacific Northwest) is that it gets more soggy than I'd like, especially since I like to do more frequent waterings. I'm thinking the LECA might give me a better moisture balance and keep the environment around the roots airy.

We have lots of cool moisture in the air, but inside my house the winter temperature is about 70 F and the humidity level is between 40-50 since my furnace is running (I do use a humidifier if it gets below 50).

Thanks for any advice.. this website has been such a great source of info for me!

Maybe the pots are too big...The medium I use the most is bark+LECA. If I need something more water retentive I mix perlite and coco chips. To the extreme, I mix sphagnum. For rupiculous, only LECA and a layer of sphgnum at the bottom. This works well under my conditions.
Anyway, a layer of LECA at the bottom is always good for drainage.

Okay, so maybe add a layer of LECA to the bottom and more perlite to the mix throughout? Or, instead of the perlite could I not just mix LECA throughout with the Bark? I’m not sure which is more water retentive. I’m also not sure what the charcoal is for and if I really need it.

Oh, and this seems to happen even with smaller pots, although not as much.

Wht do you want a more retentive mix if the center of the pot is still wet? The solution for your humidity is to water once per week (assuming the pots are made of plastic). If you want to water twice (if you cant resist it ;)) drill some holes on the side of the pot to allow air circulation.

Sorry, I don’t think I explained the situation well. The centre of the pot dries out quickly. I’m currently watering twice a week to keep it wet. But, moisture sits at the bottom of the pot. Even though we have a good amount of cool moisture in the air, my house gets pretty dry in the winter with the furnace running. So the centre and top of the pot dries out while the bottom sits wet. I could probably even water it 3 times a week but I don’t because I’m scared of mold building on the bottom.

I was thinking if I add a layer of LECA to the bottom and disperse it throughout mixed with the bark it would disperse moisture more evenly. I am also considering using Orchiata bark. My questions are whether the bark (maybe Orchiata?) and LECA mix is a good idea, and if I should add perlite or charcoal to it.

A photo or two might help.

I know of several commercial growers, who mix small diameter LECA into a mix that is otherwise some combination of bark, charcoal, perlite and/or coconut husk. However, your problem seems to be the layering, than specific mix.

Traditionally (really old school), orchids were grown in clay pots, with a layer of broken pot shards in the bottom (about 1/4 of pot height). This allowed good air circulation, and fairly even drying out.

For those genera, that do not require drying out between waterings (Paphs, Phals, Vandaceous, etc.), it also meant that you do have to water more frequently.

Here is a photo of one of my phals that I watered 2 days ago. I always water by submerging the entire pot in the water for 5 mins.

I should also mention this was a grocery store purchase that I repotted from sphagnum moss about 3 weeks ago. The roots were okay, but not in the best condition.

In my humble oppinion, with a temp of 70F and 40<RH<50% you can solve your problem by watering once /week. Nothing more.
Use root color as a reference: green => no water needed / silver=> water it.

I was initially watering one of my other phals only once a week and had the same problem. I went to twice a week because the roots looked thirsty after about 4 days, but then I got worried cause the water sits at the bottom. :(

It all depends on environmental conditions and pot size (as well as medium degradation, which is not the case). What you describe is a typical issue with too large pots. Use root color instead and water according the above criteria.

I have a Pahl that was in a too large pot and had the same problem but, as I'm a lazy guy, I used to water it every 3 weeks, sometimes more. When I repoted it, in the same pot, the simple change of old to new medium, made me water it once/week.

Okay, thanks. Do the roots looks dehydrated to you? I wonder if moving them from sphagnum moss to bark was a bad idea. Maybe I should have tried semi-hydro instead, but I guess it wouldn't be a smart to move them again so soon?

Those roots in the photo looK great. Judging by their color, one more day and I would water it.

Thank you for your help!

Evaporation from a potting medium occurs from the top and along the pot/medium interface to a lesser degree. Any perforations in the pot wall will increase the latter. That means there will always be a moisture gradient in the mix, to one degree or another.

To overcome that, you can add a moisture-holding phase, such as sphagnum, but you have to be careful to avoid densifying the mix, suffocating the roots.

Another approach is to “top dress” with something that will hold moisture, so slow the evaporation rate from the medium.

That makes sense, thanks.

I wish I had known about semi-hydro a month ago when I re-potted these. I guess it wouldn’t be a good idea to repot them again now and disturb their roots. So maybe the best option is top-dressing for now? If I were to top-dress with sphagnum moss would I also have to change how I water? I’m currently soaking the whole pot in water for 5 mins.