Many of us have tropical houseplants, and normally use a regular potting soil for growing them. Sometimes we add a little fertilizer, but for the most part there isn't much else in the potting mix. Houseplants languish inside, in an environment that has air too dry and soil rife with mold spores. Putting houseplants outside, and re-potting them this time of year are two steps along the path to success with houseplants.
The plant pictured here, Ilex guayusa, is one of my favorite houseplants. It is in the holly family, and is one of the tropical varieties from South America. It was grown in large plantings for years in parts of the Amazon due to the presence of stimulants such as caffeine and theobromine.It is one of the plants encountered by Richard Evan Schultes during his forays into the Amazon, and over the years it has seen a resurgence as a mild source of caffeine in the herbal supplement market. Like Yerba Mate (Ilex paraguensis) and the North American Yaupon (Ilex vomitoria), guayusa is one of the ethnobotanical treasures found in the holly family.
Unfortunately like many houseplants, it is a plant that doesn't always like to grow indoors in a small pot year round. A saucer placed beneath a ceramic pot is hardly large enough to catch all of the runoff from a proper watering, and the standing water in a saucer is a perfect place to grow microorganisms well suited to destroying your treasured plant.
As you can see from the picture of my guayusa's roots, I've encountered a problem with root rot. If left unchecked, this would surely kill my rare plant. It is important to cut out any of the affected areas, and to clean the cutting tool with rubbing alcohol between cuts. Don't place these clippings in the compost heap, as they would introduce potential pathogens to your compost pile.Many of the plants that we keep as houseplants are actually large trees in their native environments. Even if a plant such as this stayed healthy and free of root rot, it would still require periodic root prunings to maintain an appropriate size for indoor growth. Every year I take out all of my houseplants when it gets nice and warm, and I re-pot almost all of them. This gives me a chance to inspect the roots for pests or pathogens, and to give my houseplants a fresh growing medium sure to provide plenty of nutrients with no lingering mold spores.
A great starting point for the replanting medium is an organic, free draining potting soil that doesn't compact too heavily. Many of the major brand potting soils out there are way too dense, and create a heavy environment that breeds anaerobic microorganisms that are not good for the plants.Fafard potting soils tend to be really good, and their organic potting soil stays nice and fluffy. with the addition of an organic compost, you can create a really good mix for the yearly re-potting ritual. A good rule of thumb is to use 2/3 organic potting soil, and 1/3 compost of some sort that has a nice light texture. Farmer D organic compost, and Pete's Kickin' Chicken composted manure are two great commercially available types of compost (Found at B.B. Barns here in Asheville), but I tend to use my own homemade compost rich in aerobically growing beneficial microorganisms.
A final thought moving forward after re-potting is to use a bit of chemical warfare against potential future mold & fungus outbreaks. Hydrogen peroxide does a great job of inhibiting any ungerminated mold and fungus spores. As such, it is a great additive to the water you use for houseplants. I generally drop about 5-10ml of regular strength hydrogen peroxide in a gallon of water, and use this for all my houseplants. This is a particularly good idea once cold weather rolls back around, and our precious houseplants are languishing once more in saucers.
