Nothing rubber! Nothing dyed! Visit your local Agway, Lowe's or Home Depot and check out their offerings. I prefer the "crushed pine needles" but only one Agway carries it and none of the big stores, here, have it.
Pine Bark mulch is also fine but those bags are heavy! The long needled pine are in lightweight bags. Both types are 3 cu. ft. per bag.
Don't put either one too close to the stems - keep it about 2 or 3" away. Apply about 2" thick.
Crushed:
Pine Bark Mulch:
