Hi, I have some ground covers, mostly various tymes like Wooley thyme, growing on a slope i have in my back yard. There seems to be weeds growing through them! If I put bark/mulch around the plant (they aren't too big yet about 2ft x 2ft) by lifting the trailing parts and finding where its rooted - will I prevent it from spreading or will it grow right over the bark/mulch? Wasn't sure if it just spreads or needs to grow up and spread too? If that make sense. So basically if I planted a 5in planter and it's grown to 2ft by 2ft - it seems by lifting the trailing parts that it's still only 5 inch but has spread by 2ft x 2ft or is it actually getting a bigger base as well? And either way does mulching by the base prevent it from spreading? Any responses would be great!!!