A) use an appropriate, well-aerated soil
B) use proper watering technique
C) if you find your soil retaining too much water, insert a wick through the drain hole and tilt the container at a steep angle after every watering
D) use distilled or RO water to prevent soluble salt accumulation if you cannot use a proper watering technique
E) try to maximize light levels if you suspect a slow soil - it increases water usage

I do LOTS of repots and dig around in the root balls of plenty of woody plants every year (easily more than 100 annually), and I usually only see evidence of mycorrhizal colonization in early spring and late fall when soil temperatures are appropriate. I've never seen evidence of colonization in plants kept indoors. While mycorrhizal symbiosis does make water more available to plants by extending the range and efficiency of roots, an appreciable presence does not necessarily insure that water will be used from the soil any faster than if the extent of colonization was nearly negligible. Additionally, use of disinfectants, and particularly fungicides, will destroy mycorrhizae.

Al

Thanks Al,

That's my discovery too about the mycorrhizae, the benefits is marginal, so I discontinued to use it indoors. I am keeping the peroxide though. So a sterilize soil it is in the container. No sure about the benefits of disinfectants like RD-20 in container culture.

I grow an extensive collection of bulbs indoors, and I'm in zone 5, where the winters are frigid and long. I have found that healthy roots can be maintained by planting in clay pots, using a very porous medium that doesn't retain too much moisture for too long a time. Good air circulation helps a lot, as does the proper amount of light. Careful and proper watering techniques are essential, as well.

I use un-softened water, and I leach my potted plants on a regular basis to help eliminate accumulated salts and minerals. I also make certain to keep each bulb or plant in the proper sized pot, re-potting when necessary.

All of these things combined, keep my plants' root systems healthy and growing well.

I recently un-potted a group of Sprekelia bulbs to separate them, and they had the most beautiful root systems I've ever seen! They were potted in a clay pot using a porous medium that drains quite freely, and they have been outdoors since spring. I really feel that allowing them to grow outdoors helped immensely, and I wish I had the proper place to bring all of my potted plants outdoors for the summer months. The combination of sunlight, natural breezes and air flow, and all the rain we've gotten have really made a difference in the health of those bulbs!

And I have Al to thank for pointing me in the right direction for the excellent medium I'm now using!

In addition to all the other great ideas on this thread, I use terracotta planters with pot feet, to encourage air circulation.