I'm more green-fingered than black-thumbed but my garden sin remains watering. Over-watering to be exact.
I (often) can't quite remember when I last watered and so watering is on a sporadic schedule at best. Luckily this works out pretty good but for all other instances a water bulb is the way to good.
The water bulb by Anderssen & Voll for Mjolk is by far the most aesthetically pleasing one out there. Mouth-blown, hand-shaped and experimental all-round this baby doesn't even need the plant!