Rock, Gravel, Sand and Soil Delivery in Scottsdale, AZ

Gilman loam on old desert deposits

The soil survey maps the center point of ZIP 85250 as Gilman loam, and the Gilman series fills 100 percent of that map unit. Its top mineral layer is a loam, a soft, even blend of sand, silt and clay that works easily when slightly damp.^[1]

The survey rates Gilman loam well drained, with hydrologic group B and moderate infiltration. A light rain soaks in without much trouble. A heavy one can outrun the soil and spread across the surface, especially where the ground has been packed by foot traffic or vehicles.^[1]

Shrink-swell in the top 100 cm is low, at 1.5 percent linear extensibility. The loam holds its shape through wet and dry periods, so a patio or rock border laid over it stays level.^[1]

The geologic map places the center point on Late and middle Pleistocene surficial deposits, made of gravel, sand, silt and clay laid down by old streams. The ground at that point sits 1,270 feet above sea level.^[2],[3]

Old stream deposits like these can hide layers of coarse gravel and pockets of hard, cemented soil a little below the surface. A digging bar is handy when planting trees, and a hole that will not drain after watering may need to be dug through a hard layer.^[1],[2]

Loam this even is easy to plant in, but it can crust after a hard rain and seal the surface. A layer of rock or mulch over bare soil breaks the force of raindrops and keeps the surface open so water can soak in.^[1]

Monsoon bursts and mild winters

Scottsdale Muni AP, about 7 miles away, is the nearest NOAA normals station. It averages 8.7 inches of precipitation a year. A large part of that can come in summer monsoon storms, which can bring heavy rain, wind and dust in a short burst.^[4]

The airport station logs 3 days a year with a low of 32 F or colder. Its median last spring freeze comes on January 6, and its median first fall freeze on December 26. Frost is rare, so tender plants only need cover on a handful of nights, and a stone base needs no extra depth for cold.^[4]

Long summer heat is the harder test. Bare soil bakes and crusts, and dark stone can get too hot to touch. Rock ground cover keeps soil cooler underneath and cuts down on dust, and lighter colors stay cooler on the surface.^[4]

Monsoon wind can strip loose mulch and fine soil off a yard in minutes. Rock and well-packed Decomposed Granite stay put where lighter materials blow away.^[4]

Dust storms that come ahead of monsoon rain can coat a yard in fine silt. Rock ground cover hides most of it, and the next rain washes it down between the stones where it does no harm.^[4]

Choosing between Decomposed Granite and River Rock

Many desert yards here use one of two ground covers, and each has strengths. Decomposed Granite is a crushed, sandy granite that packs into a firm, flat surface. It is easy to walk on, works well for paths and patios, and gives a soft, natural color that blends with the desert.^[1],[4]

River Rock is round, washed stone in a range of colors and sizes. It does not pack down, so it is less comfortable to walk on, but it drains instantly and stands up to running water. That makes it the better choice for washes, drainage paths and areas around downspouts.^[1],[4]

Plenty of yards use both: Decomposed Granite for the areas people walk and sit on, and River Rock for borders and the paths water takes. 3/4" Crushed Stone is a third option that locks in place and comes in more colors than either.^[1]

Whichever you pick, lay a heavy fabric over the loam first to stop weeds, and run edging between materials so they do not mix over time.^[1]

Rock size changes the feel of a yard. Small rock, such as 3/8" Crushed Stone, gives a fine, even look that suits courtyards. Larger rock, such as 1-1/2" Crushed Gravel or River Rock, reads better from the street and stands up to wind and water.^[4]

Washes, patios and desert planting

Monsoon storms can send a lot of water across a yard in a short time. A shallow wash lined with fabric and filled with River Rock and some larger cobbles carries that water around the house and out to the street or a low corner of the lot.^[1],[4]

For a patio, compact the loam, add a layer of Road Base and compact it, then either set pavers on a thin bed of Concrete Sand or spread Decomposed Granite and wet and compact it in a few passes.^[1]

Shaded sitting areas are worth planning in a hot climate. A Decomposed Granite floor under a tree or a shade sail stays cooler than pavers, and it drains well when a monsoon storm passes through.^[1],[4]

Desert trees and shrubs grow well in Gilman loam. Mix some Compost into the backfill for new plantings, and water deeply but not often to push roots down. Garden Soil in raised beds is the simplest route for vegetables.^[1]

Mulch helps around trees and in vegetable beds, where it shades the soil and saves water. Wood Chips or Brown Shredded Mulch work well. Keep the mulch a few inches from trunks.^[4]

Citrus and other fruit trees grow well in desert yards if they get deep, regular water and a wide ring of mulch. Keep rock and fabric back from the root zone of fruit trees, since the trees prefer a cooler, mulched soil.^[1],[4]

Housing in ZIP 85250 and Scottsdale

ZIP 85250 holds 9,931 housing units by Census count. Detached single-family houses make up 41 percent of them, against 52 percent across Scottsdale.^[5]

The median home in this ZIP was built in 1976, older than the city median of 1991. Owners live in 78 percent of the occupied homes in ZIP 85250. Scottsdale has 139,168 housing units in all.^[5]

Homes from that era often have yards that were planted as lawn and are now being converted to desert landscaping. Removing old turf, grading, laying fabric and spreading rock is a very common project here.^[5]

Townhomes and patio homes have smaller spaces where a Pea Gravel courtyard, a few planters of Garden Soil or a fresh layer of rock along the walls makes the biggest difference.^[5]

Many owners here plan yard work for the cooler months, when spreading rock and planting is far easier on both people and plants. Rock, soil and mulch can all go down then, ready for the next monsoon season.^[5]