You will need to try a range of plants underneath your pine tree. Why is this? Because some pine trees are allelopathic, meaning that they produce poisons in the soil around them to stop other plants from growing there as well. What happens is the pine needles drop to the ground and decompose. Then the soil absorbs the acid from the needles, this acid in the soil keeps unwanted plants from growing near to the pine. Some plant that you may try: Heuchera, hosta, hardy geranium, ferns. Your local garden centre may help you discover more. You may want to put wooden containers beneath the plant and plant in them hostas. Their arching growth with make the containers hard to detect. These plants seem to be fairly drought tolerant. Good luck. If nothing will grow under your plant you will at least know about allelopathy.
I have a Pinus nigra at one site and Gaultheria shallon loves it underneath. hostas seem to struggle and I haven had much luck with ferns that I have tried. also consider Arctostaphylos species.
Here are some ground covers that I grow under hemlock trees in their dry shade. Periwinkle, Lily of the Valley, the native False Lily of the Valley, creeping Oregon Grape, Robb's Euphorbia, and Epimediums. I have some hostas there and they live but don't grow much because it is too dry. Snow on the Mountain, also called Bishop's Weed, would also grow but it spreads very fast and can be invasive. That is the other thing I want to caution you about, these are very fast, easy to grow, spreading plants that could easily become a problem in a better place because they would take over anything.
