How to Grow Agastache
'Liquorice Blue' from Seed
Tall violet-blue bottle-brush spikes that smell of aniseed, flower from July to October in their first year from seed, and draw more bees to your garden than almost any other plant in cultivation
There are plants that are good for pollinators, and then there is Agastache — a plant that operates on a different level entirely. On a warm July or August afternoon, a well-established clump of 'Liquorice Blue' in full flower will be covered in bees from first light to dusk. Bumblebees, honeybees, solitary bees, hoverflies — they treat a flowering agastache not simply as a feeding stop but as a destination, returning again and again throughout the day in numbers that make the plant almost hum. It earns the RHS Plants for Pollinators designation more thoroughly and more visibly than almost any other plant on the list.
And beyond its remarkable ecological value, 'Liquorice Blue' is simply beautiful — tall, upright, architectural bottle-brush spikes of rich violet-blue that flower from July right through to October on aromatic plants reaching 70–90cm. The foliage is strongly scented with aniseed and liquorice, releasing its fragrance on warm days without even being touched, and the leaves brew into a refreshing herbal tea that has been valued in East Asian herbal tradition for centuries. This is a plant of considerable character and considerable usefulness — and unlike most perennials, it flowers in its very first year from seed.
Quick Facts at a Glance
Plant Type
Hardy Perennial (H4)
Sowing Time
Feb–Apr indoors
Flowering Months
July – October
Position
Full sun, free-draining
Height & Spread
70–90cm · 45cm
Difficulty Rating
2 out of 5 — Easy
Understanding the Plant
Agastache rugosa 'Liquorice Blue' — Korean Mint or Giant Hyssop — is a hardy perennial member of the Lamiaceae (mint) family, originating from East Asia where it grows in open, sunny, well-drained habitats. The species name rugosa refers to the wrinkled texture of the leaves. It is one of the hardiest agastache species, tolerating temperatures to around -10°C, which makes it reliably perennial in most UK gardens in well-drained soil — though in wet winters and heavy clay it can be short-lived.
The extraordinary bee-attractiveness is not accidental — agastache produces nectar in exceptionally high quantities, and the individual florets within each spike open progressively from the base upward over several weeks, meaning a single spike provides nectar continuously rather than in a single flush. This extended nectar production is precisely why bees treat an agastache plant as a reliable, returning food source rather than a brief stop. Your product listing captures it precisely: this is a plant that draws bees "from first light to dusk."
First-Year Flowering — The Rare Perennial Advantage
Most hardy perennials spend their first year establishing roots and only begin flowering in year two. 'Liquorice Blue' is one of the rare exceptions — sown indoors in February or March and planted out in May, it will be in full flower by July of the same year. This first-year flowering performance, combined with the long season from July to October, makes it one of the most immediately rewarding perennials available from seed. You sow in winter and are watching bees dance around the flowers by midsummer.
The Edible Plant — Aniseed Tea & Culinary Use
The strongly aniseed-scented leaves of 'Liquorice Blue' are entirely edible and make an excellent herbal tea — fresh or dried, steeped in hot water for five minutes, with a flavour profile that sits between aniseed, liquorice and mint. The tea has been used in East Asian herbal tradition as a digestive remedy for centuries. The flowers are also edible and make beautiful garnishes. Growing agastache gives you an outstanding pollinator plant, an architectural border perennial, and a genuinely useful culinary herb all in one.
When & How to Sow
Agastache is straightforward to germinate provided you surface sow and maintain adequate warmth. The seed is small, requires light to germinate, and does best at 20°C or above — a heated propagator or a consistently warm windowsill is ideal.
When to Sow
February to April indoors is the recommended window for first-year flowering. February and March sowings give the longest season and the best chance of flowers by July. April sowings may not flower until August or September in their first year but will establish strongly for an excellent second season. Do not sow outdoors until all risk of frost has passed — agastache seed needs warmth to germinate reliably.
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Fill pots or modules with fine seed compost and water from below. Moist, evenly damp compost before sowing. Agastache germinates reliably in standard peat-free seed compost.
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Scatter seed on the surface and press gently. Do not cover — light is required for germination. The seed is fine but visible. Scatter as thinly as possible and press firmly with a flat finger to ensure good compost contact.
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Cover with a clear lid and place at 20°C or above. A heated propagator is ideal. Germination typically occurs within 7–14 days. Remove the cover once seedlings are growing and move immediately to the brightest available position.
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Prick out at the two-leaf stage. Handle by the leaf. Pot into individual 7cm pots and grow on in cool, bright conditions — good light prevents legginess. Water sparingly once in individual pots; agastache dislikes sitting in wet compost.
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Harden off and plant out from May. Two weeks of gradual outdoor acclimatisation before planting. Space 45cm apart in full sun and free-draining soil. Water in well on planting but thereafter allow the soil to dry between waterings — agastache hates wet feet.
The Critical Rule — Free Drainage
Agastache will not tolerate waterlogged soil — in heavy clay or wet winter ground it is short-lived. Your product listing is explicit: "Agastache will rot in wet soil." If your soil is heavy, improve it significantly with grit and sharp sand before planting, or grow agastache in raised beds. In free-draining soil it is genuinely perennial and long-lived. In wet soil it behaves as an annual. Drainage is the single most important factor in long-term success.
Growing On Tips
Full Sun — Essential
Full sun is essential for maximum flower production and the richest violet-blue colour. In shade, agastache produces fewer and shorter spikes with paler colour. A south or west-facing position is ideal. The plant also appreciates reflected warmth from walls or hard landscaping.
Water — Less is More
Once established, agastache is drought-tolerant and actually performs better in drier conditions. Water young plants to establish them, then allow the soil to dry between waterings. The deep taproot that makes it drought-tolerant also makes it susceptible to root rot if the crown sits in wet soil, particularly in winter.
Deadheading & Cutting Back
Cut back spent flower spikes promptly to encourage the plant to produce new spikes — this extends the flowering season significantly. Do not cut back hard in autumn; leave the crown intact to protect it through winter. Cut back to fresh basal growth in early spring. The dried spikes also provide winter structure and bird food.
Self-Seeding
In sheltered spots with free-draining soil, 'Liquorice Blue' self-seeds readily — volunteer seedlings appearing around the parent plant in spring. These transplant well when small. If different agastache varieties are grown nearby they will cross-pollinate, so collect seed from the best performers and weed out inferior seedlings.
Short-Lived Perennial
Your search results note it honestly: agastache is typically short-lived, with most plants giving their best over three to four years before declining. This is not a failure — it is the nature of the plant. Treat it as a short-lived perennial: save seed each year, sow fresh plants, and you will never be without it. Self-seeding often provides replacement plants naturally.
Winter Hardiness
Hardy to H4 — survives to around -10°C in well-drained soil. In heavy or wet soil it is much less hardy and may not survive cold winters. A light mulch of grit around the crown in autumn improves winter survival. In the coldest gardens, treat as an annual and resow each spring for certainty.
Common Problems & How to Fix Them
| Problem | Likely Cause | What to Do |
|---|---|---|
| No germination | Too cool or seed covered | Agastache needs consistent warmth — 20°C minimum. A heated propagator is strongly recommended for February and March sowings on a cold windowsill. Resow on the surface without covering at 20°C+. |
| Plant dies in winter | Wet or heavy soil | The primary cause of agastache loss in UK gardens. Improve drainage radically before replanting — add grit, raise the bed, or grow in containers. In well-drained soil, H4 hardiness is reliable. In wet soil it will not survive cold winters. |
| Leggy, floppy stems | Insufficient sun or rich soil | Full sun and lean, well-drained soil produce the most upright habit. In rich soil, stems are lush and floppy. Avoid feeding with nitrogen-rich fertilisers. Support if needed with discreet bamboo canes. |
| Short-lived plant — dies after 2–3 years | Natural lifespan | Entirely normal. Save seed annually, sow new plants each spring, and allow self-seeding where conditions suit. The plant is best thought of as a short-lived perennial rather than a permanent fixture. |
| Few bees visiting | Too shaded or too young | Bees discover agastache reliably once the plant is in full flower in a sunny position. First-year plants may be visited less than established second-year plants. Ensure full sun and patience — the bee activity that develops once the plant is well established is remarkable. |
When to Expect Flowers
Sown indoors in February or March, 'Liquorice Blue' typically begins flowering in July of the same year — making it one of the very few hardy perennials that rewards you with flowers in its first season from seed. The flowering season runs from July right through to October, giving an exceptionally long late-summer and autumn display that fills the gap when many summer perennials are fading. The violet-blue spikes are particularly valuable in September and October when bee-friendly flowers become scarce.
Sow indoors from February — 'Liquorice Blue' is the rare perennial that rewards early sowing with flowers in its first season, providing a bee-rich violet-blue display from July through October.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
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| 🌱 Sow Indoors |
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| 🪴 Plant Out |
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| 💜 Flowering |
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Drying & Culinary Use
The spent flower spikes of 'Liquorice Blue' dry beautifully on the plant and can be cut for dried arrangements — the violet-blue colour fades to a soft grey-violet that holds well and adds interesting texture to winter bouquets and wreaths. Cut stems when spikes are fully open, strip leaves, bunch loosely and hang to dry in a warm, ventilated space.
Making Agastache Tea
Harvest young leaves throughout the growing season — the smaller, younger leaves have the most concentrated aniseed flavour. Fresh or dried, steep a small handful in just-boiled water for five minutes. The resulting tea has a refreshing aniseed-liquorice flavour with a gentle, digestive quality. Dried leaves can be stored in an airtight jar for use through winter. The flowers are also edible and make beautiful tea garnishes or salad additions.
Plant Specifications
The plant that turns your garden into a bee sanctuary from July to October
There is no simpler way to fill a late summer garden with life, colour and the deeply satisfying sound of bees at work than to grow a drift of Agastache 'Liquorice Blue'. It flowers in its first year from seed, asks for nothing but sun and free drainage, perfumes the air with aniseed on warm afternoons, and keeps producing violet-blue spikes long after most other summer perennials have given up. Our Agastache 'Liquorice Blue' seeds are selected for strong germination and vigorous first-year flowering — sow in February and let the bees find it by July.
Shop Agastache Liquorice Blue Seeds →