The process for cloning sativa and indica is identical in most ways, with results sometimes varying from breeder to breeder and from strain to strain. Growing media (soil, clay pellets, rock wool, etc.), rooting hormone, lighting and growing environment all have an impact on the success rate of the cloning, but genetics also play a role.
Most sativa and sativa-dominant hybrids are famously easy to clone. Many strains will take to the soil or rock wool and nutrient combination to form new roots before even using a rooting hormone. However, there are strains that can resist cloning at great lengths.
For some growers, indica strains and indica-dominant hybrids are more difficult to root. With that said, most indica strains are still reasonably easy to clone, even if you can’t just throw them in some wet dirt to grow roots like some sativa strains are apt to do.
Rooting times for each strain vary, especially among hybrid strains. There are a lot of factors that influence rooting time, not least of which is the skill of the grower. Many growers have seen root growth on sativa (and some indica) strains as early as 4 – 5 days after cutting, with roots developed enough for planning by 11 – 13 days after cutting.
In general, if properly handled, new roots can be seen forming on your clones within 12 – 16 days from initial cutting. With some strains, however, roots may start to pop out after 20 days, but when you get much more beyond 3 weeks (21 days from cutting), the viability of your cuttings is hugely deteriorated and it’s probably best to take new cuttings and start over.
For sativa and sativa-dominant strains, many growers will put clones into their flowering cycle as soon as they’ve grown enough roots to be planted. Rushing into the flowering cycle with sativa strains is advisable for anyone growing indoors or within a small greenhouse, as sativa strains can easily double their size, and triple or more during their flowering stage.