First, select the best specimens and make sure they are meticulously clean. You want the supermodels of the plant world, and like any model, hair and makeup matters. Any defects that are present should be tiny or facing the back.
In general, you'd probably want natural-looking lighting, which will mean something middling soft (you want some specularity and shape, so flat lighting is out) at a relatively high angle, as far from the plant as you can get it to minimise fall-off, and to camera left (or right, depending on the setting; I'll get to that in a bit). Along with the key, you'll want a very soft fill (a large parabolic umbrella, a v-flat or a whitish wall would do nicely). I wouldn't use natural light unless there is enough window area to provide for reflector fill and the windows are tall enough to provide a substantial downward angle of light. You will almost certainly want to use a polarizer to get good saturation in the leaves/fronds, and sometimes in the bark. Indoor plants tend to be waxy varieties, so you can expect a lot of diffuse polarized reflection from a layer above the colour.
As Nir pointed out while I was typing, you probably want images of the plants in context. There should be something that can be used as a size reference at least partially in frame, whether that be a piece of furniture or a bit of wainscotting. If you don't have suitable locations, it's easy enough to create one from a few 2x2s and a couple of sheets of cheap luan plywood. A bit of paint or wallpaper and you have the corner of a room without the real constraints of typical home-sized overall dimensions and ceiling height. (Since these "walls" will be neither structural nor permanent, you can get away with used or imperfect materials; a bit of plaster will cover a multitude of sins. And you may find that having a couple or three portable walls in your studio that can be cheaply and easily redecorated can come in very handy.)
And yes, you will want detail shots to go with the context shots. The colours and textures are why people buy these things, so you want to emphasize the interesting bits. That will usually include the leaves, but may also include flowers, bark, thorns/needles, and so forth.
The photography, though, is only one part of the equation. Page design matters a lot too, so if the site is really bad (ransom note typography that includes Comic Sans in the mix, jarring and incongruous colours, or anything of that sort) you may want to address that as well as soon as possible. (Navigation, etc., might be able to wait if you're getting product-specific click-throughs and there's an obvious way for the user to get what they want.) If your photography says "Harrod's" but your design says "boot sale", people will assume the photos were taken from somewhere else. (If there is any fairness in the world, that should be a simple matter of changing the CSS to fix the worst of it. If the gods of the intarwebz are angry, you'll have inline styles created by a rich text editor to deal with.)