You may not think you have a green thumb. Maybe you see yours as black, especially if you have had bad luck with various finicky houseplants such as ferns. Meanwhile, you know that herbs are important to Wiccan ritual and spellwork, but you would rather get your supplies online or from the nearest metaphysical bookstore. I understand and I am not one to judge.
But you may not know how easy herbs are to grow. Essentially, they are weeds. They thrive in the poorest, shallowest soil. They grow fast and remain hardy, even in harsh environments with wind and little water. Several can withstand cold temperatures. You can grow them in pots, in the ground, indoors (with enough sun or full-spectrum artificial light), or outdoors. They grow easily from seeds, and many can be propagated with cuttings. Even someone with the blackest of thumbs can probably grow herbs. They are very forgiving.
You may not ever make much time for gardening in your daily life. However, there is no harm in giving it a try before you decide to rule it out of your Wiccan spiritual practice altogether. If you grow your own herbs, you can save a lot of money in the long run. You will not have to pay the labor, overhead, packaging, and shipping costs associated with buying retail herbs. You will feel the satisfaction of having provided for yourself. You may awaken your own creativity as you learn to make custom-blended incenses, candles, and essential oils.
But the biggest advantage to growing your own herbs is the personal connection it forges between your daily reality and the passing of the seasons, which makes up the sacred Wheel of the Year. Nowadays, most of us work and live in climate-controlled buildings and buy all our food shrink-wrapped at the supermarket. We never have time to get outdoors or any reason to run our hands through the dirt. The ancient cycles of sowing and reaping are foreign to most of us.
In our increasingly technical and urban existence, we are losing touch with the earth itself, even as we attempt to practice our nature-based faith. For reasons of convenience and employment, we might have to live in a tiny apartment with no yard in the middle of a big, concrete city. We might live near the equator and not have the experience of the traditional four seasons, which can further disconnect us from an awareness of the agricultural cycles. But a tending to a couple of pots of herbs can be a step in the right direction toward reconnecting with nature, which is important for any Wiccan.