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Family: Cupressaceae · Pot diameter: 13cm · Height: approximately 20cm
Juniperus ‘Wiltonii’ spreads like fine silver-blue fabric across the ground, following its contours with remarkable natural ease. Long, flexible branches unfold almost flat and carry tiny side shoots, creating a surface that looks calm from a distance and beautifully intricate close up. Among stones and clean edges, its cool colour suggests that a small piece of open sky has settled gently onto the earth.
Its charm lies in how little height it adds: stones, edges and taller plants remain visible while their bases are connected by a continuous silver-blue flow. At the edge of a low wall, the branches can continue downwards. An otherwise formal structure gains a more natural finish, and the garden seems to extend beyond its boundaries.
‘Wiltonii’, also known as ‘Blue Rug’, combines an exceptionally low spread with long flexible stems and fine, predominantly scale-like foliage.
Main stems follow the ground rather than forming a strongly raised central canopy. This broad, flat line is an essential cultivar characteristic.
Very small, mainly scale-like leaves clothe slender branches. The texture is finer than that of densely needle-bearing creeping forms.
Foliage remains through every season. In cold winters it may acquire a subtle purple tint without changing its basic flat architecture.
Why you will love it: it connects broad surfaces with fine silver-blue texture without hiding the stones and clean edges that give the space its character.
Give it an open sunny area in a rock garden, on a broad slope or in a raised border. It can pass over a low edge without becoming an upright shrub. Allow approximately 2–2.5m of spread at ten years and potentially more at maturity, avoiding narrow paths or positions that are walked over.
Small flowering cushions and low succulent-leaved perennials create clear, gentle contrasts around its silver-blue surface. Place them on the outer part of the composition, beyond future juniper cover, in sunshine and freely draining soil.
Full sun encourages dense low cover. Avoid heavy shade, which thins its fine-textured surface.
Water thoroughly during establishment and check when the soil dries. Drought tolerance improves once established; pots need closer monitoring.
RHS H7: very cold hardy, including temperatures below −20°C in a suitable position. Free drainage remains important, particularly in winter.
Harmful if eaten and a potential skin allergen. The small cones are not for consumption; wear gloves and prevent access by pets that chew plants.
Choose open ground that you do not need to cross when maintaining other plants. Fine woody branches need room to spread and cannot serve as a walked-on path.
Water deeply when moisture declines within the soil, without keeping it permanently saturated. A new planting in summer heat needs more frequent checks than an established carpet.
Well-drained sandy or stony soils suit its use particularly well. If water stands after rain, improve the position first or use raised planting with an adequate depth of soil.
Conservative feeding is enough. In poor soil or after long-term pot cultivation, apply a gentle spring feed according to the product instructions, avoiding excessive amounts.
Remove damaged or dead shoots and adjust the perimeter selectively. Do not shear the entire surface or cut into bare wood expecting a quick recovery.
Keep the existing planting depth and arrange the branches carefully without forcing them to bend. A pot needs a broad surface, a freely draining mix and an unobstructed outlet for water.
Remove weeds before the cover closes and collect leaves trapped in the shoots. Keep the border edge accessible so you can check growth without stepping on it.
Individual branches remain visible and cover is still incomplete. Its appearance in a pot does not show the width it can eventually achieve in the ground.
In suitable conditions, it can reach approximately 0.1m in height and 2–2.5m in spread. Fine stems form a very flat, dense surface.
At maturity, it can reach 0.1–0.5m high and 2.5–4m wide, over 10–20 years. This allows for differences in site and growth, not a change into an upright shrub.
Indicative ten-year growth with stems close to the ground. At maturity, it can reach 0.1–0.5m high and 2.5–4m wide.
Where a winter tint develops, it is subtle and depends on cold conditions. Stems remain clothed in foliage and retain their flat habit.
What to expect after planting: Branches will cover more ground while retaining an exceptionally low profile. Do not treat the ten-year measurement as a permanently fixed limit to its spread.
In 1914, on Vinalhaven Island off the coast of Maine, Jacob van Heiningen found a natural variation of Juniperus horizontalis. That plant marks the beginning of ‘Wiltonii’, the cultivar known for its long flexible stems and exceptionally flat silver-blue cover.
Van Heiningen was associated with South Wilton, Connecticut, and the cultivar entered nursery production through South Wilton Nurseries. Its journey therefore begins with a wild plant on an island in north-eastern America and continues into organised cultivation, rather than starting with a documented controlled cross.
The name ‘Blue Rug’ also became established in commerce, neatly describing the appearance of a blue carpet. It does not identify a different cultivar from ‘Wiltonii’. The 1914 discovery remains its clear historical milestone, while its later nursery distribution explains why the same flat form is now found in so many gardens.
‘Wiltonii’ is a female selection and may produce small fleshy seed cones with a blue-black appearance and waxy coating. Although they resemble berries, botanically they remain conifer cones rather than fruits formed from flowers; their appearance does not make them edible.
Essential answers about its genuinely low habit, space requirements and use as groundcover.
No. ‘Blue Rug’ is a widely used synonym for ‘Wiltonii’, describing its exceptionally low silver-blue cover.
No. It is a woody conifer, not a walking surface. Its branches can be damaged by foot traffic even though it looks like a carpet.
A spread of approximately 2–2.5m is a useful ten-year guide, but mature spread may reach 2.5–4m. Plan around the space available over the longer term.
Yes. Fine flexible branches can follow the rim and continue downwards, provided roots have enough room and watering is monitored carefully.
No, it is evergreen. Cold conditions may bring a gentle purple tint; extensive dry brown sections are not its normal winter appearance.
No. It is not grown as an edible plant. The cones’ resemblance to berries does not make them suitable for consumption or safe for pets to access.
