I built these alien plants a bunch of years ago, after collecting some pine cones in the woods of my home town. For years they'd languished in a tool drawer, until I rediscovered them and decided to tart them up...
To begin, I removed the spikes and their bases - they were originally on plastic 40k bases, but luckily I'd picked up some MDF bases at Vapnartak for this exact sort of thing! I glued the pine cones to the bases, then built up the rest of their bases with cork. I addd my usual sand and gravel, then took the cocktail sticks and whittled them somewhat to make them a little more natural. The spikes were then superglued in and the plants got a grey spray priming. I stuck pretty close to the original paint job I'd given them, which drew its inspiration from the classic 40k cacti (for which I bought some polystyrene ovoids back in March of this year...).
Let me know what you think of them in the comments below!