Hi Karen and thanks for this.
My experience with “biodegradable” black polythene from maize starch was not good.
1 It lets light through so is no use for killing existing weeds, unless you lay cardboard first, effectively using the polythene as a way to hold cardboard in place.
2 It biodegrades in perhaps 5 years, or less in sunlight so you need to leave it out and watch the unbeautiful process! Mine looked the same after 4 months as when I laid it.
3 It’s pricey, certainly compared to cardboard!
