gardening shoes

Does anyone know how to keep laces tied up ? i have a really nice pair of walking boots which i use for gardening but if i have to stop and tie the laces up twice i have to do it 6 times. They seem to come unravelled and could be dangerous if i were perched on a ladder to cut the hedges or following behind a mower and accidentally step on the blinking things.

i double knot them and everything ...................
Janet Tweedy