There is much detail to be found on the web about growing and looking after Salvia divinorum. As you might expect, some of the information is contradictory [...] Here are some summary notes based on personal experience.
Frequently Asked Questions When Starting: I'm often asked, "What do I need to start with?" Well, initially, you don't need anything! You won't want to re-pot straight away. It's best to let a newly received plant 'settle in' for a few weeks. After that, at some point, you'll need a bigger pot, a stick (for support), some compost and some vermiculite. Over all Salvia plants are quite hardy, adaptive and easy to grow indoors [ - check the above link for more Initial FAQ]
Cuttings: Salvia divinorum propagates naturally and easily by rooting from cuttings. They will root in plain tap water normally within two or three weeks. Use a clean sharp knife to take a cutting about 20-40cm in length. The cuttings will not be able to sustain too many leaves so remove those nearer the bottom of the stem, leaving no more than half a dozen or so of the smaller top leaves [...]
Potting and Pinching: I recommend fairly big pots (25 - 30 cm). The plants grow quickly in the summer and can get fairly large. Cutting the plant back (pinching) will allow you propagate new plants as well as turning the existing one into a bushier, leafier entity. Even so, after a while you will need to support your growing plant with a bamboo cane or some such. When potting, place the rooting stem deep in the soil, almost to the bottom of the pot if you can [...]Soil: I use a peat-based multipurpose compost. I cook my soil in the microwave before using it. After which I mix with about one third vermiculite. I put the vermiculite in the pot first then about another third compost, mixing up, potting and topping up with just compost. This way the vermiculite / soil mix is graduated, being more concentrated in terms of vermiculite at the bottom of the pot where water will settle [...]
Feeding: I feed my plants during the spring and summer with a standard inexpensive fertilizer (e.g. Phostrogen), adding a pinch to the water before watering. Feeding is not recommended during the winter when the plants are not growing (unless you're growing under artificial lights).
However, note that a newly potted plant should be in fresh compost. It will have plenty of nutrients, so there should be no immediate need to feed. I don't feed plants during their first year.Generally, with the cultivation of any plant, it's quite easy to get carried away and over feed, and (generally again) this can be quite harmful to plants.
Watering: Some advice will emphasise the plants thirst without warning of the dangers of over-watering. Over-watering may encourage root-rot. How often you need to water depends on the capacity of the pot. For plants in large pots I usually water about once a week during the summer, possibly more often during a particularly hot spell. During the winter I water every fortnight (approximately). If you are forgetful then the plant will tell you it's thirsty by wilting. After watering it will soon perk up [...]
Humidity: You may hear that Salvia divinorum likes humid conditions. This is true to some extent but there is no need to mollycoddle the plants. A humidity tent might be an idea for young plants or rooting cuttings, but I prefer not to use them at all. Apart from maybe during particularly dry conditions, when an occasional misting from a hand held spray gun might be appreciated, the plants should do fine. They will adjust to the ambient humidity. Having said that, if you do have your plants under some kind of humidity cover and you want to take them out, then you will need to acclimatise them gradually [...]
Light: The plant likes as much light as it can possibly get without getting too much direct sunlight. Venetian blinds on a south facing window will protect them from excess, otherwise ideal is if you have a window that gets just a little morning or evening sun. Ensuring enough light will encourage growth and the production of rich dark green leaves. Also, I’m having success growing under artificial light. [...]
Temperature: The plants can tolerate moderately cold conditions but are killed by frost. For growing them indoors frost is is not a particular problem, however, I have received a number of enquires such as, "Can I keep my plants in a greenhouse or a conservatory?" The basic answer to this is that you need to consider all the environmental factors (e.g. not forgetting humidity, type of soil) but with special consideration to the amount of light and the temperature. See the next section.
Suitable Environments: Salvia should be treated as an indoor houseplant, it should be okay in a conservatory and possibly even a greenhouse given special considerations [...]
Hydroponics: Salvia can be cultivated using hydroponics [...]
‘Unhealthy’ Signs: Root-rot, branches dying off, leaf yellowing, browning or mottling or drying at the edges, pests [...]