Gaps between stepping stones can be among the most awkward spaces in the garden. The same goes for those narrow channels of dirt between loosely set flagstones or large pavers that compose rustic patios.
Too often, the gaps are neglected and a catchall for weeds. But it’s just as easy to fill the cracks with creeping plants. These little guys will travel the gaps, don’t mind being stepped on and may even smell good in the process. They can also choke out weeds for good.
Creeping thyme (Thymus serpyllum or Thymus praecox) is a perfect fit for hot, sunny paths in Central Coast gardens. The petite perennial herb comes in many variations, all of which bear tiny, rounded fragrant leaves in shades of dark green, lime green, and even gold with a white edging. Creeping thyme is tough. It will grow in difficult soils, from sandy to heavy clay, and it tolerates inconsistent watering.
A dwarf version is Elfin thyme (Thymus serpyllum ‘Elfin’), which bears leaves so small that one is hardly discernable from the next. Elfin’s foliage and occasional lavender flowers stay phenomenally flat.
That’s something to be aware of, with the various thymes. While most varieties form low-growing mats, some, such as Victor Reiter, bear summertime flower spikes that grow tall enough to stub toes. The taller spikes are pretty along the edges of paths or patios, but pose tripping hazards when planted in the midst of foot traffic.
Also, thyme’s rosy pink and lavender flowers attract honeybees. While that’s great for enhancing pollination in your garden, you might not want to plant it in within a primary patio or pathway next to your front door.
Dymondia (Dymondia margaretae) is a good alternative. It is extremely flat, and bears slender, oval leaves that are green on top and gray underneath. A slight upward curl on the edges of each leaf provides a frosted, two-tone look.
Dymondia occasionally bears tiny, flat yellow daisy flowers. But its best attributes are its tidy appearance, uniform height and low watering needs.
Sun or Some Shade
These creepers are content with full sun to partial shade along the coast. Inland, all prefer some protection from the hot, mid-day sun.
Many of the flattest stonecrops (Sedum) form prostrate mats of succulent stems, and will cooperatively traverse the gaps between stones.
Goldmoss sedum (Sedum acre) is a dainty succulent perennial that bears lime-green leaves and yellow, springtime flowers. Its trailing stems send out new roots as it ventures out. Pinch it back if it attempts to bust loose. Dragon’s Blood sedum (Sedum spurium ‘Dragon’s Blood’) trails as well, with small, succulent leaves that are a dark, purple-red.
Chamomile (Chamaemelum nobile) is a fluffy, moderate-water perennial that presents a meadowy appearance. Its dime-sized, white and yellow daisy flowers rise above apple-green, ferny leaves that are soft to walk on. It’s reasonably fragrant, although the more intensely aromatic chamomile tea is made from the flowers of Matricaria recutita, an annual species that reaches 2 feet tall.
Cranesbill (Erodium reichardii) grows in low, tidy clumps of dark-green, heart-shaped, overlapping leaves. Its cup-shaped flowers bloom in pink or white most of the year.
In clay soil, cranesbill starts to decline after a few years. In loam or sandy soil, it is much longer lived. Cranesbill requires regular water and is fine with overhead irrigation.
Jewel mint of Corsica (Mentha requienii) also requires regular water. It forms an inch-high mat of miniature green leaves that look like moss, yet are highly aromatic. Think toothpaste or ice cream when you step on it.
A number of other sun-to-shade creepers, including dichondra, green carpet, blue star creeper, Irish moss and baby’s tears, are far thirstier. While they tolerate full sun along the coast, they won’t dry out as fast in filtered shade.
Dichondra (Dichondra micrantha) bears lime-green leaves that look like a string of dainty lily pads. It was a popular lawn “grass” in the 1960s and 70s. But vast expanses require a huge investment in water, fertilizer and care.
Instead, it is better suited to slipping between stepping stones or edging a pond. Keep it barely wet enough to grow well and stay low. With too much water or fertilizer, it can become invasive.
Green carpet (Herniaria glabra) forms a fluffy, spring-green mass literally smothered in tiny leaves. It spreads via trailing stems as well, but it’s not difficult to control. Green carpet rarely blooms — and when it does, the flowers are so small that they’re easy to miss. Instead, it provides a punch of color in winter, when its leaves turn dark red with colder temperatures.
Blue star creeper (xPratia pedunculata, Isotoma or Laurentia) bears starry, pale-blue flowers atop a bed of very flat, light-green leaves. It blooms most heavily from spring through summer, with flowers appearing occasionally during the rest of the year.
Irish moss (Sagina subulata) is not a moss, technically speaking. But it sure looks like one, forming a dense carpet of miniature, velvety leaves.
It’s often sold in flats. Use kitchen scissors to cut it into strips or irregular shapes that you might need to fill between your stepping stones.
In full shade, Corsican sandwort (Arenaria balearica) forms a dense mat of slender, green leaves. Masses of simple, wildflower-like white flowers bloom from spring through summer. This sandwort grows best where the soil stays damp but not boggy. Good drainage is key.
Sweet woodruff (Galium odoratum) bears larger leaves than many creepers. Its fragrant leaves are also more distinct, appearing evenly spaced around square stems to form circular tiers of foliage. Small, white flowers bloom from late spring through the end of summer, then go to seed. An army of volunteers may follow. Pluck them early, to prevent them from spreading everywhere.
Tiny, new plants tucked between stepping stones face challenges that plants romping through the garden don’t.
First, the little ones need room — and soil — to grow.
Stepping stones or loose flagstone patios are often set on compacted soil, compacted base or several inches of sand.
You’ll need to make sure there’s enough loose, fertile soil between the stones, preferably at least half a foot deep, for roots to grow.
Also, the gaps between the stones should be at least a few inches wide.
Next, decide how you’ll irrigate the plants.
This might be by burying soaker hose a couple of inches below the surface; lining the path with pop-up micro-sprayers; adjusting nearby sprinklers so that their overspray covers the plants; or planning to water by hand.
If you’re planting from flats, pull or cut apart 2 to 3-inch wide chunks that contain several plants and their roots. Space the chunks 6 to 9 inches apart in the ground.
Cover the bare spots with topper or some other light, organic material that will help retain surface moisture until the plants fill in.
Seeds of Wisdom
Gaps between stepping stones should be at least 3 inches wide and up to 6 inches deep to provide sufficient room for creeping plants to take root.
Copyright, Joan S. Bolton. All rights reserved. Reproduction of text or photos in any form is prohibited without written permission.