When designing an outdoor space, landscape rocks can add beauty, texture and functionality. With so many sizes, shapes and styles available, how do you choose which rocks are right for your yard or garden?
The key is matching the rock sizes and types to your specific landscaping needs. Smaller gravel creates a smooth surface, while larger boulders make dramatic focal points. Angular crushed rock promotes drainage, and rounded river rocks feel pleasant underfoot.
This guide will overview the most popular landscaping rocks and provide tips on selecting the best sizes for your projects.
Common Landscaping Rock Types
Here are the main categories of rocks used in landscaping, along with their key characteristics:
Pea Gravel
- Size: 1/8” to 1/4”
- Shape: Small, smooth, round
- Colors: Tan, brown, white, gray, multi-colored mixes
- Best Uses: Walkways, patios, pet areas, accents
River Rock
- Size: 3/4″ to 2″
- Shape: Smooth, rounded
- Colors: White, brown, black, mixed
- Best Uses: Garden accents, mulch, borders, drainage
Crushed Granite
- Size: 1/2” to 2” angular chunks
- Shape: Irregular, jagged angles
- Color: Gray, brown, red, white
- Best Uses: Walkways, patios, drainage, driveways
Flagstone
- Size: Flat irregular slabs up to 2’ wide
- Shape: Natural, uneven cleft surfaces
- Colors: Blue, gray, brown, rust red
- Best Uses: Patios, walkways, stepping stones
Fieldstone
- Size: Medium to large rounded rocks
- Shape: Smooth, irregular shaped
- Colors: Various natural tones
- Best Uses: Walls, borders, accents
Lava Rock
- Size: 1“ to 3” chunks
- Shape: Very porous, uneven
- Colors: Black, dark red, dark gray
- Best Uses: Fire pits, gardens, drainage
Boulders
- Size: Over 2 feet in diameter
- Shape: Large, rounded, irregular
- Colors: Natural rock colors
- Best Uses: Focal points, statement accents
Guide to Choosing the Right Size
Now that you know the main styles, how do you pick the ideal rock sizes for your particular landscaping project? Here are key considerations:
Intended Use
Match rock size to your planned use. For example:
- Large flat flagstones work well for patios and stepping stones
- Small pea gravel makes a comfortable surface for pathways and play areas
- Angular crushed granite provides excellent drainage under hardscapes
- Rounded river rocks create natural-looking dry creek beds
Safety and Comfort
Larger rocks can shift underfoot andbecome a tripping hazard. Opt for smaller, smoother rocks in high traffic areas.
- Use small pea gravel or river rocks for walkways, paths and play areas
- Crushed granite, flagstone and large boulders work better in low traffic zones
Plant Compatibility
Take plant moisture needs into account. Gravel retains heat and sheds water, making it best around drought-tolerant plants that don’t need constant moisture.
- Use pea gravel and lava rock around cacti, succulents, herbs and other low water plants
- Avoid gravels around seedlings, shade plants and moisture-loving plants
Aesthetic Appeal
Larger rocks make impressive focal points, while smaller accents add detail.
- Use boulders as standout features in the landscape
- Mix pea gravel and crushed granite nearby to complement the boulders
Recommended Depths by Rock Size
In addition to choosing the right type of rock, you’ll need to determine the ideal depth for coverage. Some guidelines:
- Pea gravel and crushed rocks: 2″- 3″ depth is recommended
- River rocks: 2″- 3″ depth for mulch, a single layer of rounded rocks
- Flagstones: Depth is determined by stone thickness, space evenly
- Boulders: Used individually or in groupings, partially buried for stability
Landscaping Rock Size Guide by Project
To summarize rock size selection for common landscaping uses:
Pathways and Walkways
- Pea gravel – comfortable underfoot
- Crushed granite – tamp firmly to stabilize
- Flagstone slabs – steppable flat surfaces
- River rocks under 2” – won’t shift when stepped on
Patios
- Flagstone slabs – flat, steppable, variety of sizes
- Brick pavers – classic paved surface
- Crushed granite – tamp firmly, needs edging
Mulch / Groundcover
- Pea gravel – retains moisture well
- Crushed granite – excellent drainage
- River rocks – allow space between for weeds
Borders and Edging
- Lava rock – durable and decorative
- River rocks – softer linear outline
- Fieldstones – natural looking edge
- Brick – classic defined border
Fire Pits and Fireplaces
- Lava rock – high heat resistance
- River rocks – allow heat circulation
- Flagstone – flat surfaces for building
Retaining Walls
- Fieldstones – stack and mortar in place
- Flagstones – embed vertically
- Boulders – anchor in place on slope
Water Features
- River rocks – mimic natural streams
- Flagstone – use flat slabs for pond edges
- Boulders – create waterfalls and fountains
Accent Areas
- Crushed granite – bright whitepop of color
- Pea gravel – inject fine detail
- Marble chips – elegant garden accents
Tips for Choosing Landscape Rock Sizes
Keep these pointers in mind when selecting materials for your projects:
- Bigger is not always better – properly sized rocks suit the space
- Mix stone sizes and shapes for visual interest
- Use edging to contain smaller gravels and pebbles
- Allow proper drainage gaps between stones
- Purchasing rocks by the ton will provide cost savings
- Consider having stone delivered versus hauling it yourself
No matter your planned project, from a serene rock garden to a grand stone patio, choosing the ideal rock sizes and styles is key to creating beautiful, functional landscapes. Follow this guide to pick the perfect stones for all your outdoor spaces.
