I'm reading a book "Core Performance Endurance" that talks a lot about obtaining balance, posture, and a strong core. It provides some specific short warm-up exercises, as opposed to stretching. Every study I've read on stretching comes to the conclusion that it does not help prevent injury. Nor does it aid cycling performance. Post-wokout stretching definitely aids recovery from the workout and general muscle health.

But what you are talking about isn't stretching to prevent injury, it's trying to prevent discomfort during the exercise. I would interpret your experience thusly: The gardening doen't allow for a warmup. You did some stretching exercises that warmed up and loosened your muscles, preventing the discomfort.

Fortunately cycling is a sport where it is easy to include a good warmup; just spin quick and easy for 10-20 minutes and your muscles are ready for more intense exercise.