To produce plugs, seed should be sown indoors at least 7 weeks before transplanting seedlings outdoors. Wild senna, as with many other legumes, has a hard seed coat. Scarify or chip the seed in order for water to be absorbed. Soak the seed in warm water for three hours before sowing.
If you take it for longer, your body can start to rely on it, rather than your bowels doing the work on their own. If you are still constipated after taking senna for 3 days, talk to your doctor.