Using a Heavier Mix for Older Trees?!

[ross]

What are your thoughts on the topic? Should I sacrifice container porosity for more organic matter to add more nutrients & water retention?

[cis4elk]

The general consensus is that older trees can handle the more dense..water holding capability of finer mixes, and they go through more water anyway. The thing to be careful with is dry pockets, it's easy for the grow mix to get too dry any end up with hydrophobic pockets. This is why, IMO using some calcined clay in your mix is good because it sucks up water like a sponge which then allows the dry grow mix to re-hydrate gradually. Last year I also started to experiment with putting a layer about an inch thick of calcined clay on the top of some pots, the results were very positive. I feel it keeps the upper layer of grow mix from drying out, which then allows the water to more evenly filter through the mix rather than running to the perimeter and going straight down the sides of the pot and out the drain holes in seconds, resulting in only a small portion of the water actually being absorbed by the mix. Sort of going along with what I mentioned earlier- the layer of CC absorbs a good deal of water to sort of slowly release. Now, this may be a totally different deal out East where you guys get more rain. We are pretty arid in my neck of the woods and the humidity is generally very low, so we maybe are working on opposite sides of the coin so to speak. I would try a tester or two and see how those trees respond to it.

[don_sanders]

I was thinking of using 100% compost in my sips. Or maybe substitute pea gravel for the perlite. The added weight would have benefits and disadvantages.

I make my own compost so the free base potting mix would be nice too especially when I fill the 30 gallon half barrels.

Mostly I have been using a 2:2:1 composteaterlite mix from cutting to 5 gallon. It has been working well but the base isn't heavy enough to keep the trees from tipping over in high winds.

[figgrower]

I've been wondering the same thing. I found several trees at one property that were planted behind a three foot high retaining wall in heavy clay. They were all up over twelve feet. In a pot, though, it might be different.

[AscPete]

Its been my observation that older potted fig trees with established mains and scaffold branches can actually benefit from the denser less aerated soils and potting mixes. This photo is of the roots of container grown fig trees with sandy soil used as the potting mix. But my preferred potting mix for older fig trees is currently a 2-4-1 (PBF - Peat Moss - Calcined Clay).


Since the mature trees are only growing out their yearly fruiting branches the denser less aerated soils will slow vegetative growth (due to decreased root growth) and create closer node spacing for possibly better fig production. If weight isn't an issue a large portion of coarse sand in the potting mix wouldn't hurt.

Calvin's cis4elk comment "calcined clay in your mix is good because it sucks up water like a sponge which then allows the dry grow mix to re-hydrate gradually" is one reason why I will continue to add it to my custom potting mixes. I've never had to add wetting agents and the mixes never get hydrophobic when dry.

[figgrower]

Nice trees!

[Kelby]

I think it depends what you mean by heavier. My main caution would be that a heavy mix can be hard to rehydrate.

Plus it's heavy.