3. When is the best time to re-pot them and/or divide?

3. When is the best time to re-pot them and/or divide?

Well as a general rule plants require repotting when the mix which they are potted in becomes 'sour' or breaks down in some way. The term sour is a good one as if you examine the mix by putting your nose close to the surface of the mix and inhale you will certainly detect the strong sour smell given off by rotting organic potting mix. In the case of inorganic mixes like scoria or gravel this can be a little more difficult but due to the mix being invaded by weeds and subsequent rotting of old roots the same smell will be evident.

The timing of any repotting can be decided by the urgency at the time you detect a problem with the mix OR if you program your repotting as a regular maintenance job can more depend on the type of plant you are growing.

For instance if you find a plant is very sick and the cause seems obviously related to a very mushy, stinking mix then most people would advise you should repot immediately. "What if it is mid winter and a long cold or wet period is ahead", I hear many out there saying? Well I would still rip the plant out of the rotten mix and wash all traces of that mix from the plant using a sterilising agent such as Hydrogen Peroxide (see here) to ensure the roots were disease free. Then I would probably place the plant in an empty, slightly oversize pot, and put it back on the bench where it had been to await better conditions for the repot. I would give that pot some extra attention with extra watering and may even place the pot on a saucer of gravel to keep a moist atmosphere near the roots.

In the case of programmed repotting (the best way to go in my opinion by the way) you need to research your plants well as there are simply so many species out there with differing likes and dislikes it is impossible to generalise. This also applies to the type of potting mix you choose to use.

BUT (yes - there is always a but) you can generalise for some groups of orchids so I will list a few here which I am familiar with. Others may like to add more in comments.

Paphiopedilums seem to like an annual repot into a fresh mix. The roots will simply take off once in the new mix with little or no setback if the timing is right. I like to start in early spring when it is a safe bet that no bitterly cold periods are ahead. In most years I choose to repot my entire slipper collection as a matter of course although when times are busy I have been known to skip a season here and there with no major problems detected. The best grower I know does not at all waver from annual repotting and has better conditions than me so commences his repotting even before spring hits here in SE Qld.

Dendrobiums on the other hand are happy enough in the same mix until they either need a repot because the pot is too small or the mix breaks down. So long as a good quality mix is chosen and watering is carefully monitored I find that most repots are due to the plant becoming to big for the old pot. Don't make the mistake of rushing to repot when the plant looks large for the pot it is in though. Dendrobes often like to overhang the pot a little for a while and from my experience a lead or two hanging over the edge can send the growth to new areas (previously dormant buds) and make for the formation of a larger, bushier specimen forming.

TO BE CONTINUED>>>>>