Hello – looking for options to plant between flagstones in a west facing backyard with a large black walnut tree so quite shady. Planting area under drip line. Scarborough bluffs, so very sandy soil. Many thanks for your advice.
Hello: you have an interesting question, with several perplexing components: sandy soil, shade and your walnut tree. In addition to these three items we must consider traffic patterns.
If the foot traffic along this path is anything but occasional, it might be best to add some interesting hardscape between the flagstones, for example pea gravel, oyster shells, pine needles or large sized pine bark pellets, or plant annual white clover. Consider lining the sides/edges of the flagstones with shade and Juglan tolerant plants, some of which may hopefully creep around the stones. These edging plants could be combinations of early flowering bulbs like grape Hyacinths, native viola’s or Dog tooth violets (Erythronium americanum), Primula, such ferns as Christmas fern (Polystichum) or Wood ferns (Dryopteris), Ajuga reptans (bugle weed), Heuchera (Coral Bells), Creeping Phlox and Alchemilla mollis (Ladies Mantle), and European and Canadian Gingers. If you wish to try some plants among your stones, try Saxifrages, Gaultheria procumbens, Aquilegia jonesii, Cornus canadensis (Creeping Dogwood). All these plants will require watering and feeding with compost and manure as you large tree will absorb the majority of nutrition and the sand will carry away most of the water. Over time the plants that survive and thrive will be the ones you want to plant again.
Most all the plants recommended here come from the extensive list published by Kansas State University of plants deemed tolerant to Juglans. Enjoy creating your new side garden.