Does it really need soil or does it need mulch................right now is a good time, as this is the end of March, also treat with fungal spray first, then mulch, then in 2 week feed 12-12-12. Regular wood mulch breaks down into soil and keeps the weeds out. Pull out any weeds first. Don't shake the weeds, just dig them out. I just bag & trash them, I don't want to get the seeds all over the place.