They haven't broken down yet, but I presume it will all turn to mush eventually like you said. So we need media that will have these qualities and last at least 4 years without re-potting. What will happen to bark chips in 4 year old 5-1-1?

I tried sand, gravel and such but it really dries out too fast, especially on the surface. However sand proved to be best media for me to root cuttings.

Bark will break down pretty quickly. For outdoor plants it will be faster and 511 mix will have to be replaced almost every yr. For indoor plants every other yr may be OK. The bark near the surface may still look good but it may be mush deeper in the pot.

In a good mix the plants will make lots of roots pretty fast and so that is another factor to consider when deciding to repot. In a gritty mix the bark component is much smaller than the other very stable components (grit and turface). So a 3 yr cycle of repot is achievable depending how vigorous the plant is and how much you want to let it grow. Even in a bark-less mix you can end up repotting every -2/3 yrs.

So what I am getting at is - the issue is not just how long the media will last but also how long the plant will thrive in that media in a container.

The bark fines in my mix don't break down all that rapidly. I have mostly permanent (aka, long term) container plantings and repot only every three years or so and the bark is still very much intact at that time. Might depend on the type of bark used but one of the major pluses of a bark based mix, aside from its textural characteristics, is its durability.

I just did some 'digging' - in need of total repot, but here is the 5.1.1 since 2012 (could be 2013, have to find a date, but am sure no later): bark did not decompose totally. Just as gardengal said above. Not sue what it looks like deeper...

You are right, there is variation in how fast bark breaks down depending on type/quality. Flaky/thin pieces do tend to breakdown quickly.

rina: Near the surface it often looks much better than it is deeper inside the pot. For tropicals, that are not subject to harsh winter conditions, bark breakdown is slower. So it is possible to get a longer working life out of the mix. I try to repot tropicals in 511 every 2 growing seasons.

Sometimes, when time permits, I would dry out the 511 mix that I use for annuals and store in bags for the winter. They fare much better than the mix left outside in the open.

I would like to also add that bark will take a long time to become real mush like peat based soil

vermiculite? nope breaks down too fast.

If you can't water frequently set up an irrigation system.

Here is some pictures of a rose I planted in the gritty mix last spring. I pulled it from its pot on Friday amazed at all the roots.

tropic

I agree, that's why I said do not know how it looks deep in pot :) Will see this summer when I do the overdue repot. I do believe that typically, the 5.1.1 lasts well until the major repot that is suggested after about 3years. You are doing much better than me, repotting after couple of growing seasons.

Haha rina. Two plants give me the most trouble - hibiscus and a strawberry guava. They seem to do a number on the mix in a single growing season. Sometime I think the roots are actively destroying/consuming the bark.

Nancy: What are the ingredients and proportions in your mix? It looks more like it has lots of bark and may be a bit of grit.

1-1-1 but my bark was not the right size, that was my first try at gritty.

Here is the consistency of the mix I use for the Citrus Limetta and other seedlings and cuttings.

Citrus Aurantifolia (Key Lime) seedlings.

Thuja Occidentalis Columna cuttings.

At this point the media is 6 months old.