How to Grow
Sweet Pea 'Purple Pimpernell' from Seed
The sophisticated deep purple sweet pea — Hardy Annual H3; Spencer type; rich velvety deep purple bicolour (brownish-purple + violet-pink undertones); specifically selected for colour depth that holds without fading; long sturdy stems; strong fragrance; pair with Ammi Majus (white lace) to reveal the full depth of the purple; sow Oct–Nov (best) cold frame or Jan–Mar at 15°C; TOXICITY: all parts mildly toxic
Sweet Pea 'Purple Pimpernell' is the deep purple sweet pea — and within the broad category of "purple sweet peas," it occupies a specific, distinguished position: a richly velvety, deeply saturated bicolour in two harmonious shades of purple (a deep brownish-purple with violet-pink undertones in the wing petals) that provides the specifically sophisticated, dark-end elegance that the sweet pea colour range needs alongside its creams, corals, lavenders and pinks. Specifically selected for the depth of its purple hue" — a quality that holds in summer sun without fading to a washed-out blue-grey.
The provenance of Purple Pimpernell is pleasantly cottage-garden in character: Thompson & Morgan introduced it to commercial cultivation after receiving seed from an amateur breeder who had developed the colour combination, noting they liked it "so much" they produced a seed crop. This direct line from amateur enthusiast to commercial cultivation is characteristic of the UK sweet pea world, where serious amateur breeders have historically contributed some of the finest named varieties in existence. Purple Pimpernell's enduring commercial success across multiple UK suppliers confirms that the amateur breeding instinct that produced it was correct: the variety delivers everything its appearance promises.
Quick Facts at a Glance
Plant Type
Hardy Annual H3 — Spencer type; deep velvety purple; long stems; sophisticated and bold
Colour
Rich velvety deep purple; bicolour with two shades: deep brownish-purple + violet-pink undertones
Velvet intensity
Specifically selected for depth of purple that holds without fading in sun
Stems
Long, sturdy; large fragrant blooms; outstanding for cutting and exhibition
TOXICITY
All parts mildly toxic — do not eat; keep away from children and pets
Difficulty
2 out of 5 — same care as all Spencer sweet peas; the deep purple rewards excellent growing conditions
Understanding Purple Pimpernell
Toxicity Warning — All Parts Mildly Toxic
Sweet pea seeds and all parts of the plant are mildly toxic if ingested. They must not be eaten and should not be mistaken for edible garden peas, which they closely resemble in seed form. Keep seeds and plants away from children and pets at all stages.
The Velvety Deep Purple — Two Shades Together
Sweet Pea Purple Pimpernell produces large, fragrant blooms in a rich, velvety shade of deep purple — but the colour is more nuanced than a single purple tone. Descriptions of the variety reveal a bicolour character with two distinct but related shades: a deep, brownish-purple with a violet-pink or lavender-blue undertone in the wing petals, creating the specific quality described as "a romantic, bohemian air." The combination is not a contrasting bicolour (like the raspberry ripple of Parfume Promise) but a harmonious one — two shades of purple that work together to give the flower more visual depth and complexity than a single, flat purple would provide.
Thompson & Morgan and the Amateur Breeder
The Thompson & Morgan catalogue description for Purple Pimpernel notes an interesting provenance: "the original seed was sent to T&M by an amateur breeder and we liked it so much, we've produced a seed crop to offer to our customers." This origin story — a named variety introduced to commercial cultivation from amateur breeding stock — reflects the ongoing tradition in UK sweet pea culture of serious amateur breeders developing and sharing new varieties. The variety's commercial success across multiple suppliers since its introduction confirms that the amateur breeder's selection had genuine horticultural merit beyond novelty.
Sowing, Establishing, and the Golden Rule
Sow in root trainers or deep pots at 1cm depth after soaking seeds for a few hours. Autumn sowing (October–November in a cold frame) for May flowers and the strongest plants. Spring sowing (January–March) at approximately 15°C. Pinch at 4 pairs of leaves for bushy multi-stemmed growth. Pick every 2–3 days — never allow seed pods. Feed fortnightly with high-potash fertiliser from first buds. Water at the base; mulch generously to protect roots from summer heat.
Sowing & Growing On
Sow Oct–Nov (best) or Jan–Mar at 15°C — Root Trainers — 1cm Deep — Soak First — Plant Mar–May — Support to 1.8m — Pick Every 2–3 Days
Sow in root trainers at 1cm after soaking. Best: October–November in a cold frame for May flowers. Spring: January–March at 15°C. Plant March–May in rich deep soil. Pinch at 4 pairs. Pick every 2–3 days. White-flowered companions (Ammi Majus) are essential to reveal the depth of the purple.
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Soak seeds in tepid water for a few hours before sowing; nick any that do not swell. Sow at 1cm depth in root trainers or deep pots. Autumn sowing (October–November, cold frame): overwinter for May flowers and the strongest plants. Spring sowing (January–March): maintain approximately 15°C — heat above 18°C significantly inhibits germination. Germination 10–21 days.
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Grow on in cool, bright conditions and plant out once established. Do not allow plants to become rootbound in their pots before planting. Plant March–April (autumn sown) or April–May (spring sown) into deeply-dug, generously-manured soil. Erect support structures before or at planting — never after climbing has started.
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Pinch out at 4 pairs of leaves (approximately 10cm) for bushy multi-stemmed growth. Guide the stems to the support structure regularly. Feed fortnightly with high-potash fertiliser from first buds. Water deeply at the base; mulch to insulate the root zone against summer heat.
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Pick every 2–3 days without exception; remove all seed pods immediately. This is the single most important action for a long sweet pea season. A plant that is allowed to set seed stops producing flowers within a week. Regular picking is both the reward and the management requirement simultaneously.
Growing On & Care
The Deep Purple in the Garden
Deep purple sweet peas provide a specific visual quality in the garden that no other colour in the sweet pea palette offers: the saturated, velvety depth that reads as simultaneously bold (visible from distance) and sophisticated (at close range the colour complexity of the brownish-purple and violet-pink two-shade character reveals itself). Purple Pimpernell is "specifically selected for the depth of its purple hue. The petals have a saturated, almost velvety sheen that holds up remarkably well without fading, even in the bright sunlight of a British summer." This depth and fade resistance is the specific practical achievement of the variety.
White Companions — Essential
Ammi Majus is the primary companion, calling it "The Monochrome Mist" — the frothy white lace that "provides a magnificent airy background that makes the solid, velvety purple of the Sweet Peas really stand out and glow." This companion pairing is horticultural good design: very dark colours (deep purple, near-black) require light contrast to reveal their full depth at visual distance, and the delicate white lacework of Ammi provides the lightest possible contrast that neither competes with nor overwhelms the purple. In a vase, the same combination produces one of the most elegant classic summer arrangements: deep purple sweet peas threaded through white Ammi.
As a Cut Flower
Purple Pimpernell produces long, sturdy stems bearing large, fragrant, deep purple blooms that are striking in any cut flower arrangement. Cut in the early morning when 2–3 flowers are open. Re-cut at an angle under water; condition in deep water for 4 hours. In a simple glass vase, deep purple sweet peas with white Ammi Majus is one of the most visually striking and elegantly simple mixed summer arrangements available from garden-grown material. The two shades of purple within the bicolour character of the individual blooms provide sufficient visual complexity without requiring additional colours.
The Sophisticated Dark Palette
"Sophistication" — a quality that reflects the specific visual register that deep, saturated purple occupies in floral design. Unlike the cheerful warmth of rose-pink, the romantic blush of cream picotee, or the vivid energy of crimson, deep purple has an elegance that reads as grown-up, serious, and deliberately chosen. In garden border design, a wigwam of Purple Pimpernell provides a bold, sophisticated vertical statement that stands apart from the cottage garden informality of mixed pastels, commanding attention without the aggressive energy of vivid red or orange.
The Larkspur Companion
Larkspur Giant Imperial Mix, described as "The Vertical Duo" — the towering spikes of Larkspur in blues and pinks complementing the scrambling habit of the Sweet Peas "providing structural depth to a traditional cottage garden display." This pairing works because the spire form of Larkspur and the climbing scrambling form of Sweet Peas occupy different visual space while sharing the cooler end of the colour palette (blue-pink Larkspur against purple Sweet Pea) in a harmonious colour combination that sits entirely within the cooler half of the spectrum.
Pollinators
Purple sweet peas are particularly attractive to bumblebees, which are known to favour purple-coloured flowers. The combination of the intense fragrance (a long-range pollinator signal) and the purple colour (highly visible to bees, which perceive colour differently from humans but show strong attraction to purple and violet tones) makes Purple Pimpernell one of the most pollinator-attractive sweet pea varieties. A well-established wigwam buzzes consistently with bumblebee activity throughout the May to September flowering season.
Sowing & Season Calendar
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
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| Autumn sow (Oct–Nov; root trainers; cold frame) |
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| Spring sow (Jan–Mar; cool 15°C; deep pots) |
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| Plant out (Mar–May depending on sow) |
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| Pick every 2–3 days (never allow pods) |
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Common Problems & Solutions
| Problem | Likely Cause | What to Do |
|---|---|---|
| Purple appearing less vivid or more blue-grey than expected | Soil pH too alkaline; plant stressed; insufficient light | Sweet peas prefer a near-neutral soil pH (6.5–7.0). Highly alkaline conditions can shift purple pigments toward blue-grey. Ensure good nutrition and full sun for maximum colour saturation. |
| Dark flowers disappearing in border or vase | No light contrast companions | Plant or arrange with white-flowered companions — Ammi Majus is specifically recommended in the Bishy listing as essential for revealing the depth of the purple against a light background. |
| Flowering stopping mid-summer | Seed pods forming; root overheating | Strip all seed pods. Mulch 8–10cm. Water at the base every 2–3 days. Resume fortnightly high-potash feeding. Production resumes as conditions improve. |
| Mildew on foliage | Normal late-season occurrence; poor air circulation | Water at the base only. Ensure good spacing. Accept some late-season mildew as normal for well-established plants. |
Plant Specifications
The deep velvety purple that holds its colour through summer sun — sophisticated, fragrant, and transformative against white Ammi Majus
Sow in root trainers at 1cm after soaking seeds. Best: October–November in a cold frame for May flowers. Spring: January–March at 15°C. Plant March–May in rich deep soil with support. Pinch at 4 pairs. Pick every 2–3 days and feed fortnightly from first buds. Pair with Ammi Majus (white lace) to reveal the depth of the velvety purple. The rich fragrant blooms continue from May through September.
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