How to Grow Alyssum
'Royal Carpet' from Seed
Deep violet-purple ground cover that holds its rich colour all summer long, fills the air with honey on warm afternoons, and smothers the ground with bloom from early summer until the first hard frosts
If 'Carpet of Snow' is the classic white alyssum that every cottage garden has grown for generations, 'Royal Carpet' is its more dramatic, more visually striking counterpart — a deep violet-purple that provides the same spreading, carpet-forming, honey-scented habit but in a colour of real intensity and presence. Where 'Carpet of Snow' softens and lightens everything around it, 'Royal Carpet' enriches and deepens — it sits at the foot of roses in warm pinks and crimsons as a rich, harmonious echo, at the edge of a path as a ribbon of royal purple, or mixed with the white of 'Carpet of Snow' itself for a classic cottage garden contrast.
Your product listing specifies an important quality: 'Royal Carpet' has been selected for pigment stability — maintaining its deep violet hue even during the height of a British summer, rather than fading to a washed-out lavender in strong sunlight. This stability makes it a more reliable colour element in the garden than some older purple alyssum varieties, and allows it to hold its visual impact from June through to the first autumn frosts.
Quick Facts at a Glance
Plant Type
Hardy Annual
Sowing Time
Mar–May direct · Sep autumn sow
Flowering Months
June – first hard frosts
Position
Full sun — for deepest colour
Height & Spread
8–12cm · 25–30cm spread
Difficulty Rating
1 out of 5 — Very Easy
Understanding the Plant
Lobularia maritima 'Royal Carpet' shares the same botanical origins as 'Carpet of Snow' — both are sweet alyssum, members of the Brassicaceae family native to the Mediterranean — but the deep violet-purple pigmentation of 'Royal Carpet' is a distinct cultivar characteristic developed through selection. Like all alyssums, it is a low-growing, spreading, mat-forming hardy annual with tiny individual flowers massed into dense clusters, the characteristic honey scent, and a vigorous, easy-going nature that makes it perfectly suitable for beginners.
Where 'Royal Carpet' differs from its white cousin and from many older purple alyssum varieties is in colour stability. Your product listing highlights that this variety has been specifically bred for pigment stability — the deep violet hue holds through the season rather than fading to lavender in strong British summer sun. This is a meaningful distinction in practice: plants in full sun retain the richest, most saturated colour rather than becoming progressively more washed out as summer progresses.
Pigment Stability — The Key Difference
Many purple alyssum varieties produce vivid colour in early summer but become increasingly pale and washed-out by August in strong sun. 'Royal Carpet' has been selected to resist this fading — the deep violet hue holds with far greater consistency through the season. This makes it a more reliable and more visually impactful colour element in the garden, particularly in south-facing or exposed positions where other purple varieties would lose their intensity.
The Hoverfly Bodyguard
Like all alyssums, 'Royal Carpet' is a powerful attractor of hoverflies — whose larvae are voracious aphid predators. A border edged with alyssum is a border with its own natural pest-control system. The tiny, accessible flower structure provides nectar and pollen to hoverflies, bees, butterflies and other beneficial insects throughout the long flowering season. Your product listing describes it as "a legendary magnet for beneficial insects — particularly hoverflies — acting as a natural, chemical-free pest control bodyguard for the rest of your garden."
When & How to Sow
'Royal Carpet' is grown in exactly the same way as 'Carpet of Snow' — direct sowing is preferred as alyssum dislikes root disturbance, and surface sowing with light access is essential as the seed is photoblastic. The growing requirements and sowing method are identical for both varieties; only the colour differs.
Sowing Options
Direct outdoors, March to May — the preferred method. Scatter on prepared soil, press gently without covering, and keep moist. September autumn sow — your product listing specifically recommends autumn sowing for "a stronger, earlier display the following spring." Scatter on prepared soil in September, allow to overwinter as small seedlings, and enjoy earlier, more vigorous flowering the following year. Indoors in modules, late March to May — if earlier flowers are needed or the outdoor soil is still cold in spring.
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Prepare the soil to a fine tilth in a sunny position. Rake out stones and debris. Do not enrich the soil — lean, well-drained conditions produce the richest colour and most abundant flowering. Rich soil produces leafy growth and fewer flowers.
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Scatter seed as thinly as possible on the surface and press gently. Do not cover — light is essential for germination. Mix with dry silver sand if helpful for even distribution. Press flat with a hand or the back of a rake.
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Water gently with a fine rose and keep moist. Germination typically occurs in 7–14 days at 18–22°C. Do not allow the surface to dry out before germination occurs.
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Thin to 15cm apart once seedlings are large enough to handle. Overcrowding produces weak, floppy plants and increases fungal disease risk in the dense mat of growth. Thin promptly and decisively.
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For indoor sowing, use modules. Sow one to two seeds per module, thin to the strongest, and plant out after hardening off from late April onwards. Handle root balls carefully — alyssum recovers well when transplanted as a whole root ball but resents being split or disturbed.
Growing On Tips
Full Sun for Best Colour
Full sun is essential for the deepest, most stable violet-purple colour. In shade, even 'Royal Carpet' will become paler and less saturated. A fully sunny position brings out the full intensity of the pigment and produces the most abundant flowering. The scent is also strongest in warm sunshine.
Poor Soil — Richer Flowers
Lean, well-drained soil produces the richest colour and the most flowers. Fertile soil produces lush leafy growth at the expense of bloom. Do not fertilise unless the soil is extremely impoverished. Gravel, path edges, dry walls, rockeries and coastal sandy soils suit 'Royal Carpet' particularly well.
Shearing Back in August
When flowering slows in midsummer, shear back by one-third to encourage fresh growth and a new flush of flowers. This is the most effective technique for extending the season — after shearing, new growth appears within a week and fresh flowers within two to three weeks, giving a second full flush of deep purple through autumn.
Self-Seeding
Like 'Carpet of Snow', 'Royal Carpet' self-seeds in sheltered, well-drained spots. Note that seedlings may vary slightly in colour from the parent plant — most will be purple, but variations toward lavender or white can occur. Weed out any that produce unwanted shades and keep the best-coloured plants for further self-seeding.
Companion to Carpet of Snow
The most classic and most effective use of 'Royal Carpet' is combined with 'Carpet of Snow' — white and violet-purple, two carpet-forming plants of identical habit and growing requirement, creating the traditional cottage garden purple-and-white edging combination. Scatter mixed seed or plant the two varieties in alternating drifts.
Between Paving Stones
One of the finest uses for any low-growing alyssum is seeding into the gaps between paving stones and path edges. 'Royal Carpet' in the cracks of a stone path, releasing honey scent when brushed by feet, is one of the most charming effects in the cottage garden and requires almost zero care once established.
Common Problems & How to Fix Them
| Problem | Likely Cause | What to Do |
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| Colour fading to pale lavender | Insufficient sun, old variety, or heat stress | 'Royal Carpet' is selected for pigment stability, but full sun is still required for the deepest colour. In shade or partial shade, the purple will always appear less saturated. Ensure maximum sun exposure. In very hot summers, light afternoon shade can help maintain colour quality. |
| No germination | Seed covered or soil too cold/dry | Surface sow without covering. Ensure soil temperature is at least 15–18°C. Keep moist until germination. Cold April soil often causes poor germination — wait for the soil to warm or sow indoors first. |
| Flowering slows in August | Natural midsummer pause | Shear back by one-third. Water at the base. Fresh growth and new flowers appear within two to three weeks. This is entirely normal and expected — the shearing technique is the standard response. |
| Leggy, floppy growth | Rich soil or shade | Do not feed. Ensure full sun. Shear back floppy growth to encourage compact regrowth. This is the clearest indicator that the soil is too rich for the plant. |
| Colour varies in self-sown seedlings | Natural seed variation | Self-sown seedlings from 'Royal Carpet' may show some colour variation — mostly purple but occasionally tending toward lavender or even white. Weed out any with unwanted shades and allow only the most vivid purple plants to set seed. Over several generations of selection, the best-coloured plants will dominate. |
When to Expect Flowers
Spring-sown 'Royal Carpet' typically begins flowering in June, around eight to ten weeks after germination. Autumn-sown plants, which overwinter as small rosettes and establish more extensive root systems before the growing season begins, typically flower earlier — from late May or early June — and flower more vigorously than spring-sown plants. The flowering season runs until the first hard autumn frosts, which in many UK gardens means October or November.
Direct sow in spring or autumn — autumn sowings produce earlier, more vigorous plants, while succession sowings in spring extend the season. Self-seeded plants return year after year in sheltered spots.
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| 🍂 Autumn Sow |
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| 💜 Flowering |
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Plant Specifications
A royal purple carpet that holds its colour all summer
There is something quietly magnificent about a border edged in deep violet-purple alyssum on a warm afternoon — the colour rich and stable in the sun, the honey scent drifting across the path, the hoverflies working steadily through the dense flower clusters. 'Royal Carpet' provides all of this from a direct sowing in spring, requires nothing but sun and lean soil to perform at its best, and in sheltered spots will return year after year through self-seeding. Pair it with 'Carpet of Snow' for the classic cottage garden contrast, or use it alone as a bold purple ribbon along border fronts and path edges. Our Alyssum 'Royal Carpet' seeds are selected for strong germination and pigment-stable violet colour — scatter and enjoy.
Shop Alyssum Royal Carpet Seeds →