Since we like to grow large succulents, for those that are grown in containers weight becomes an issue. Many porous soil additives help to reduce container weight and working along these lines, we've been testing some new ideas. One of them is to use packing peanuts as space fillers.

Last fall we were given (by Vlad) a 3 ft Plumeria that clearly had suffered from excess of moisture in the winter before. While it still had some roots left, they were only very thick coils branching off the stem and no thin water-collecting strings were present. The roots were planted in an 8" container whose bottom half was filled with packing peanuts covered with a layer of cactus soil. Through this August - while the plant was growing healthy leaves - this container filled in completely with fine roots, including the lower half where the peanuts were fully enmeshed in roots.

Now the plant was upgraded to a 10 x 12 in (H x W) pot, in which added layers of cactus soil were alternating with layers of packing peanuts and shredded paper.

A related idea when transplanting to a pot that seems slightly too tall for the rootball is to fill the bottom space with inverted plastic containers, such as those for yogurt.

Those containers can be removed at the next repotting, if needed, and the gap filled with a mixture of packing peanuts and soil.

I totally dislike using packing peanuts...and the roots growing into them. Likely just a personal thing. Yes, they are light, make the big pot easier to move if needed, and will not kill the plant. I much rather use sifted perlite to make mix well draining. It also keeps mix lighter.

Sorry, I respectfully disagree... but making layers of different materials impedes drainage, since each layer drains differently. Mixing all different ingredients thoroughly makes for much better, evenly draining, evenly drying potting mix.

When repotting, roots that are circling the pot, are tangled mess or are damaged (rotted, dry, broken) should be pruned, and old mix removed from the root ball. Filling gasps with soil is just potting up, not repotting. Potting up is ok sometimes, but if roots have any problems at all, proper repot with taking care of problematic roots is much better for health of plant.

I have used empty containers (usually plastic bottles with caps on) to fill bottom of tall pots.