Moisture availability in peat-based mixes

[cobra2326]

OK, so as I've been monitoring some of my new palm aquisitions, I'm noticing a trend: when the top of the soil even begins to dry out, the plants basically stop growing. A few inches down in the mix all the way to the bottom is still quite wet. As soon as a water them again (thoroughly), they start right back up. Everything is potted, this doesn't apply to stuff in-ground.

Does moisture availability to the plants become low once it's no longer saturated (basically being locked up in the peat)? The soil mix is basically 30% peat, 30% perlite, 30% woodchips/compost and a bit of lava rock.

Do I continue with watering them at the first sign of drying to keep them growing? I'm actually not watering very often, but thoroughly when I do, probably once a week for most stuff. All the roots look very healthy and are starting to penetrate into the new substrate.

Edited March 29, 2013 by cobra2326

[Pedro 65]

Come on Jon, its Spring, get em in ground so you don't have to fuss with pots. OK I don't know the size of your potted palms but "most" palms love going in ground when small where they are connected with mother earth to put down their roots , and when it rains the roots keep going deeper and wider... which is healthier than being locked up in plastic. Your choice Jon, sorry if they are only small seedlings which gives good reason for being in pots.. Pete

[cobra2326]

Wish I could, but the stuff in pots is way too cold-sensitive to go in the ground here E.g. Areca macrocalyx 'red', some less tolerant Pinanagas, etc.

Yes, I totally agree though, stuff is pretty much maintenance-free in the ground. Growing stuff in pots is hard, but I don't have the benefit of your climate!

[sonoranfans]

making a soil with a long dry cycle(heavy peat, low in sand) will cause you to either over or under water. Perlite is not a sand substitute as sand has far more surface area/volume. Perlite lightens soil, and that is needed, but it does not provide the surface area to permit even drainage. A faster dry cycle is more consistent, easier to make sure you are getting the proper watering frequency. There is also a larger moisture differential with depth in heavier soils that have a longer dry cycle. I would suggest a palm and cactus mix that has some sand, better drainage and water 2x weekly. And I only use mulch/chips on top the soil to trap moisture from escaping via evaporation, I dont mix it in. Long term you will have salt buildup(bad for palms) if you do not use RO or distilled water. If this is the case, you can use humic acid to rinse the soil of salts, works fine... I would also remember that the best soil mix depends onthe palm species in many cases.

[cobra2326]

Tom,

Thanks for the info. I should probably incorporate a bit more sand into my mixes, but the rest of what you've said I'm basically doing. I haven't really considered length of drying cycles enough, appreciate your thoughts there!

I actually oversimplified a bit when I listed the mix. It's 1.5 parts Cactus Mix, 1 Part "Jungle Growth" and 1 part Perlite. The cactus mix is basically peat, wood shavings, perlite and sand. "Jungle Growth" is a bit denser with peat again, some organic compost (looks like humus), perlite and a bit of woody matter.

I also use RO water for the exact reasons you outline, and basically water the mix to saturation (water runs through the bottom), then let it dry as much as possible between waterings.

On another note, I just watered the palm and the spear has moved about a tenth of an inch in about 2 hours. It previously had stopped moving for almost a day! I'm still a bit nervous about rot considering the mix seemed reasonably wet still, but it's hard to argue with growth!

Edited March 30, 2013 by cobra2326

[sonoranfans]

Tom,

Thanks for the info. I should probably incorporate a bit more sand into my mixes, but the rest of what you've said I'm basically doing. I haven't really considered length of drying cycles enough, appreciate your thoughts there!

I actually oversimplified a bit when I listed the mix. It's 1.5 parts Cactus Mix, 1 Part "Jungle Growth" and 1 part Perlite. The cactus mix is basically peat, wood shavings, perlite and sand. "Jungle Growth" is a bit denser with peat again, some organic compost (looks like humus), perlite and a bit of woody matter.

I also use RO water for the exact reasons you outline, and basically water the mix to saturation (water runs through the bottom), then let it dry as much as possible between waterings.

On another note, I just watered the palm and the spear has moved about a tenth of an inch in about 2 hours. It previously had stopped moving for almost a day! I'm still a bit nervous about rot considering the mix seemed reasonably wet still, but it's hard to argue with growth!

Jon,

I know that jungle growth mix, that stuff is heavy! I do not use it in pots, only to ammend sandy soil when my palms go into the ground. I remember reading a fairly detailed article on how water tends to hold up in the bottom of pots, making the bottom 1-2" useless. The way to counter this is to use a lighter mix(more perlite/sand) in the bottom 2-3" and a little heavier up top. This will also tend to reduce the depth gradients of water in the soil. I have been doing this for 2 years, seems to keep the moisture pretty consistent. When the bottom drain holes are somewhat dry, I water again.

Edited March 30, 2013 by sonoranfans