Dilemma... Potting soil for faster ficus growth?

Hello,

I have several ficus (benjamina, retusa) that I've had for 2-3 years. They are healthy from what I can tell, but not growing as fast as I would like. Whenever I see other ficus, for example in a shopping malls (as in a part of the decoration), they look equally happy and are all in potting soil.

Would me using organic  potting soil increase the growth rate compared to what I am using now (turface and pine bark mulch)? Is fertilizing well, with inorganic soil as good?

My trees are inside 5-6 months per year because of location.

My question is assuming that root quality is not a concern at the moment

It will grow no faster in potting soil than in turface or marbles for that matter. The soil only holds the tree up. You control water and fertilizer. In fact it should actually grow better in a free draining substrate. More little oxygen pockets,less chance of root rot.

My thoughts as well. And remember that turface is hydrophobic when dry.

I noticed you are in Quebec, your climate will strongly influence the growth of the ficus. Ficus are warm weather tropicals (warm compared to Quebec). If your indoor growing area is kept above 70 F or warmer, you can get fairly rapid growth indoors, but in January, in Quebec this is not easy to do. When is is cool, ficus slow their growth dramatically. When night temperatures drop below 60F, Ficus tend to be completely dormant, and will rest. They won't "wake up" until they have had several weeks of warmer weather. If you are growing under lights, and can keep the growing area warm, you can get vigorous growth all year round. But heat, sun and water are the strongest influences on speed of growth. Fertilizer is next, potting mix has little effect.

Most of us cold climate growers, just work with the fact that we only get 2 or 3 months of vigorous growth out of our ficus each summer. We do all our styling work, and repotting, during these warm months. The rest of the year the ficus grow slowly or not at all. But they do survive, and become nice bonsai, so even though this is the case, they are well worth working with.

Key is only do repotting, and pruning while the tree is in active growth. If the tree is not showing much activity, leave it be until growth returns.

I think there is one condition where use of "potting soil" (or nursery/container mix) can lead to faster/better growth, and that's if you tend to under-fertilize. I believe those types of mixes hold nutrients better than the coarse aggregate based mixes. In fact, I started a series of tests this past spring, where I'm growing trident maple seedlings in a variety of mixes. One mix is turface-based (turface/grit/bark), two are "Boon mix" (one with turface-sized particles, one larger), and last is a nursery container type soil amended with perlite. The plants in the nursery mix did slightly better but the difference among the plants was small. I think I am a chronic under-fertilizer and will be increasing my rates next year. It will be interesting to see if the results change.

I think soil influencing growth rate is undervalued in some of the comments.

The wetting/drying cycle is an important consideration. Here is my simplistic understanding which can no doubt be refined/corrected by others:

When the roots are wet they drink(or rot if wet too long for that species).
When the roots are dry they grow(or shrivel if dry too long for species).

Roots develop faster if they have dry spells in which they grow to seek out water/punctuated by watering to give them a drink.
If the wetting/drying cycle is fast, then there is more root growth, allowing faster branch and leaf growth.

Slow draining soils slow the wetting/drying cycle (wetter longer) and slow growth. Thus potting soil will slow growth but reduce the need for your attention to watering. Fast draining soils will speed growth, but demand strict attention as in summer they may need to be watered 1-3x/day.

5 replys in a row on soil and we're all agreeing! Oh my.
Good tidings and cheer you guys!