Hello John,

It might be part of an underlayer (to stabilize the surface) or scrap material buried by the construction company adjacent to the driveway...it's unfortunately fairly common for rock piles and other debris to be buried in yards, especially near paving. We are happy to share some ideas, but more information would be helpful to narrow-down your options:

• How far out from the edge of the driveway was the buried material? A foot or less, or several feet? We're trying to determine if the spacing of the planting hole will give the roots more room on the side of the root ball facing away from the driveway.
• How much summer sun does the location receive? (Full sun would be about 6-8 or more hours of direct light once any nearby trees have leafed-out.)
• Does the area drain well, buried obstacles aside? Does it receive extra water from a nearby roof downspout outlet, or does it dry out more normally after rain and not stay soggy for long?
• Do deer habitually browse in that part of the yard? (Rabbits are another threat to some plants, but we have less reliable information about what they tend to leave alone compared to deer.)

Miri

Thank you for the additional information. Yikes...four feet (or more) of buried pavement or pavement rubble is quite a distance. It's hard to predict whether the soil above it will skew dry or wet (due to impeded drainage)...possibly both, depending on the weather at the time, which makes plant selection trickier. It will also be harder to physically plant there, only since most nursery pots are 6 inches or more deep already. Those that aren't too root-bound can be loosened so that some of that lower soil can fall away, though, making the resulting root ball shallower and easier to plant. Careful attention during the establishment period (at least the first full year in the ground) to watering needs will be needed as the root systems expand where they can, even for species that will be drought-tolerant once they're settled.

Since you mention that no extra water seems to keep that area soggy, we'll assume for now that it will be on the dry side given how much faster water will evaporate from that shallow of a soil layer, plus the limited space for roots to grow deeper to access moisture. The deer browsing pressure will also narrow the candidate list down considerably, but we'll include a few species whose palatability to deer is either in question (that is, references don't always agree on whether it's eaten or not) or unknown.

This list is in no order of importance, and it's not exhaustive. Botanical names are in parentheses, as sometimes plants have more than one common name in use. Some species bloom at different times of year, and using a mix of species in the planting area is advisable (not only for aesthetic appeal throughout the year, for flower variety and leaf textural contrast) because it reduces the risk of a potential problem (pest or disease outbreak, unusual weather, exploring deer, etc.) affecting the entire planting equally harshly.

• Moss Phlox (Phlox subulata) -- evergreen; creeping/sprawling and low-growing; native and often found in rocky habitats where they root into the pockets of organic matter between boulders
• Spurge (Euphorbia, several species and cultivars) -- some are evergreen, and the sprawling/low-growing forms are those we had in mind, though some of the shorter upright types might also work; while we do have a few native Euphorbia, those well-suited to this kind of site will be non-native; although probably not available at a local garden center, avoid using Cypress Spurge (Euphorbia cyparissias) in particular, as it can be weedy
• Yarrow (Achillea millefolium) -- might keep some leaves in winter; may or may not be native (this is under debate)
• Sedum / Stonecrop (Sedum, many species and hybrids) -- evergreen; some upright, some creeping, some in-between; deer palatability is debatable
• Hens and Chicks (Sempervivum, several species) -- evergreen; clump-forming, but spreading in that the clump expands over time; deer palatability is debatable
• Thyme (Thymus, several species) -- might be evergreen; sprawling growth habit, though some are more upright (but still low) than others
• Adam's-Needle Yucca (Yucca filamentosa) -- evergreen; matures into a shrub-like size, though slowly; included here because the roots of yucca are so tough that they might be able to punch through any existing cracks or splits in the buried pavement (after all, they can break through plant pot walls); the trick will be getting one to fit in the ground with its current root ball depth, since they are often sold in pots larger than perennials come in
• Lyre-leaf Sage (Salvia lyrata) -- somewhat evergreen; not spreading, but can self-seed if the area is not too heavily mulched or covered in other vegetation; native
• Nodding Onion (Allium cernuum) -- clumping small bulb, but may slowly spread into a colony; native
• Hardy Plumbago (Ceratostigma plumbaginoides) -- aggressive spreader as a groundcover, but not invasive (does not seem to ever spread from seed); low-growing; can get showy fall foliage color
• Wormwood (Artemisia schmidtiana variety 'Nana' or 'Silver Mound') -- low-growing, wide-sprawling; essentially just grown for foliage color (silvery) and texture (feathery)
• St. Johnswort (Hypericum, several species and hybrids) -- some are low groundcovers while others (which might be too big for this area) are shrubs; a few are native, but usually not those widely available for sale as groundcovers or flowering shrubs
• Catmint (Nepeta) -- fragrant foliage; might self-seed a bit, but not excessively

Miri

You're welcome.

Ice Plant (Delosperma species) is another potential candidate, yes, as they thrive in full sun and, being a succulent, handle drier soils well. We don't know if deer would bother them, but various online references suggest they are not usually eaten.

Miri