If you’re a gardener — or even if you’re not — you know there are millions of varieties of plants. Whether you’re interested in houseplants or gardening outdoors, there is one common theme you need to understand: for healthy plants, you need to have healthy roots. No matter what you’re growing, your plants must have healthy roots to thrive. Since we can’t see the roots, we need to know as much as we can about how to take proper care of them. Here are 7 things you need to know.