To make sure you have enough, it is best to shop in a couple of stores. It can take several weeks, or even months to treat the problem depending on how severe it is. Fertilizers should be applied at half or quarter strength approximately every two to three weeks. A few other gardeners add a layer of gravel or sand to the top of the soil, which serves two purposes. You can make your own by mixing three cups of regular potting dirt with two cups of sand, and one cup perlite. If you only use succulents, you can make your bouquets or boutonnieres 2-3 days in advance.