How to Grow Bupleurum
griffithii (Hare's Ear) from Seed
The florist's secret weapon — acid-lime-green stems with rounded blue-green foliage and chartreuse bract clusters that make every colour they are paired with more vivid, outlasting the main flowers in the vase, and drying beautifully for winter
Every experienced florist and cutting gardener has a shortlist of plants they rely on to elevate everything else — the supporting cast without which the star performers lose their edge. Bupleurum griffithii is on nearly every such list. The lime-chartreuse colour of the flower bracts is what designers call an acid green: a colour so vivid and so electrically alive in the right context that it makes warm orange and red tones vibrate with intensity, makes cool blues read as deeper and more saturated, and makes white arrangements feel crisp and fresh rather than simply pale. This is a plant that does not compete with the flowers it is paired with — it makes them look better.
Bupleurum has a reputation for being tricky to germinate, but this reputation comes from a single easily-avoided mistake: treating it like most other annuals and surface-sowing without covering. The seed requires darkness to germinate. Cover it properly, and it germinates reliably within ten to twenty-one days. Know this single fact, and bupleurum becomes one of the easier and more rewarding cutting garden annuals — direct-sowable, self-seeding in the right conditions, and producing stems that outlast most other cut flowers in the vase when properly conditioned.
Quick Facts at a Glance
Plant Type
Hardy Annual
Sowing Time
Sep–Oct direct (best) · Mar–May direct or indoors
Flowering Months
June – August
Position
Full sun; well-drained
Height & Spread
50–60cm · 30cm
Difficulty Rating
2 out of 5 — Easy (once you know the seed secret)
Understanding the Plant
Bupleurum rotundifolium 'Griffithii' belongs to the Apiaceae family — the same carrot and cow-parsley family as Ammi majus, Daucus carota and fennel — and it shares the characteristic flat-topped umbel flowerhead structure of all members of the family. What makes bupleurum distinctive is the quality of its bracts — the modified leaves that surround each flowerhead cluster. Rather than the green, leaf-like bracts of most plants, bupleurum's bracts are large, oval, pointed, and the same intense acid-lime colour as the stems themselves. It is these bracts, not the tiny yellow flowers within them, that provide the ornamental value: they are not petals and they are not delicate, which is why they do not wilt in the rain, bleach in the sun, or deteriorate in the vase the way flower petals do.
The 'Griffithii' selection was bred specifically for the cut flower industry — it has longer, more uniform stems than the wild species and a more consistent acid-green colouration. The RHS Award of Garden Merit confirms its outstanding performance in British garden conditions. Once established, bupleurum self-seeds readily in sunny, well-drained positions, making it essentially self-perpetuating in the right garden.
⚠️ The Critical Germination Secret — Cover the Seed
This is the single piece of information that separates gardeners who grow bupleurum successfully from those who give up on it in frustration. Unlike most annuals in this guide, which require light to germinate and must be surface-sown, bupleurum seed requires darkness to germinate. If you leave the seeds on the surface — as you would for antirrhinum, aquilegia or ammi — they will not sprout. Cover the seed with 1–2cm of soil or fine compost. This is not a suggestion; it is the defining condition for successful germination. With covering, bupleurum germinates freely. Without it, it refuses entirely.
The Searing Trick for Vase Life
Bupleurum, like all members of the Apiaceae family, has a milky sap in its stems that quickly blocks the water-uptake channels when cut, significantly reducing vase life. To overcome this, sear the cut ends of stems in boiling water for ten seconds immediately after cutting, then plunge into cold water for several hours. This briefly seals the stem end in a way that paradoxically improves water uptake, and can extend vase life from four or five days to eight to ten days or more. This technique — also useful for Ammi and fennel stems — is standard practice in professional floristry and transforms bupleurum from a serviceable filler into an exceptionally long-lasting one.
When & How to Sow
Bupleurum is a hardy annual that thrives in cool conditions — an autumn direct sowing produces the strongest plants and the earliest and most prolific stems. Spring direct sowing also works well. Indoor sowing in modules is possible but bupleurum does not like root disturbance and transplants with some reluctance, so direct sowing is strongly preferred.
Autumn Sowing Produces the Finest Stems
Direct sowing bupleurum into its final position in September or October produces plants that overwinter as small rosettes, establish strong root systems through the cool months, and produce significantly longer, stronger stems from June onwards than spring-sown plants. A well-established autumn-sown bupleurum is one of the finest lime-green fillers available in the cutting garden — stems reaching 50–60cm, branching freely, and lasting ten days in the vase when properly conditioned.
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Choose a sunny, well-drained position and prepare a fine seedbed. Bupleurum thrives in average to moderately fertile, free-draining soil in full sun. It tolerates poor, dry soil well. Avoid heavy, waterlogged ground.
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Sow seeds at 1–2cm depth — this is non-negotiable. Cover completely. The seed requires darkness to break dormancy and germinate. Sow in short drills or scatter thinly, covering with at least 1cm of fine soil or sieved compost. Water gently.
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Thin to 15–20cm spacing when seedlings have two true leaves. Bupleurum branches freely — adequate spacing produces much better-branched plants with more cutting stems than overcrowded ones. Thinned seedlings can be carefully transplanted while small, but handle the roots gently.
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For indoor sowing, use deep individual modules. Sow at 1cm depth (covered — the darkness rule applies indoors too). Germinate at 15–20°C. Transplant while still small and the root ball is intact — bupleurum resents rootbound conditions. Handle gently at transplanting; the stems are somewhat brittle.
Growing On Tips
Full Sun
Full sun produces the most intensely acid-lime bract colour and the strongest, most upright stems. In partial shade the colour softens toward a muted olive-green and stems become drawn. The acid quality of the colour that makes bupleurum so valuable as a florist's filler is at its most vivid in maximum sun.
Cut Regularly
Bupleurum is a genuine cut-and-come-again plant — cutting stems back to a visible side shoot junction triggers new lateral shoots from the cut point. Regular cutting extends the season significantly. In established autumn-sown plants, cutting can begin from late May and continue through August with regular harvesting.
Sear Stems for Longevity
Plunge cut stem ends into boiling water for ten seconds immediately after cutting, then into cold water for several hours to condition. This overcomes the Apiaceae family's tendency to block its own water channels when cut, and extends vase life from four or five days to eight to ten days. Searing should be done immediately after cutting, before moving to a vase.
Self-Seeding
In the right conditions — sunny, well-drained, with some bare soil — bupleurum self-seeds prolifically and reliably. Leave some plants to set seed each season and the planting sustains itself with minimal effort. Self-seeded plants generally perform better than transplants as their taproots develop undisturbed from germination. Mark self-seeded patches to avoid accidentally weeding them out in spring.
Support in Windy Sites
At 50–60cm, bupleurum benefits from support in exposed or windy positions — place pea-sticks or horizontal netting before stems reach 25cm. In sheltered gardens, the branching stems are generally self-supporting. A well-established autumn-sown plant with a strong root system is significantly more wind-resistant than a spring-sown transplant.
Dried Arrangements
Bupleurum dries well for winter wreaths and arrangements. Cut when bracts are fully developed but before they begin to pale or dry on the plant. Hang upside down in small bunches in a dry, well-ventilated space. The dried stems maintain a soft, olive-green colour that provides a natural, botanical quality to winter arrangements.
Common Problems & How to Fix Them
| Problem | Likely Cause | What to Do |
|---|---|---|
| No germination | Seed not covered with soil | This is by far the most common bupleurum problem. The seed requires darkness to germinate — surface-sown uncovered seed will not sprout. Re-sow, covering with at least 1cm of fine soil or compost. The germination rule is the opposite of most annuals in this guide and must be applied consistently. |
| Short vase life | Stem channels blocked by Apiaceae sap | Sear cut stem ends in boiling water for ten seconds immediately after cutting, then condition in deep cold water for several hours. This technique transforms vase life from four or five days to eight to ten days. It should be done every time stems are cut, not just occasionally. |
| Stems collapsing in wind | Insufficient support in exposed position | Install pea-sticks or low horizontal netting before stems reach 25cm. Autumn-sown plants with established root systems are more wind-resistant. In very exposed positions, transplanting from indoors often produces weaker, less anchored plants than direct sowing. |
| Colour looks olive rather than lime-green | Insufficient sun or plants past peak | The acid-lime quality of the bract colour is most vivid when plants are in full sun and the bracts are freshly developed. In partial shade the colour softens to olive-green. Cut stems before the bracts begin to age for the brightest colour in arrangements. |
| Poor transplanting success | Root disturbance at planting out | Bupleurum dislikes root disturbance. Transplant from modules while still very small, retaining the complete root ball. Direct sowing is always preferable to transplanting and produces more reliable, more vigorous plants. In future seasons, use direct autumn sowing rather than indoor sowing. |
When to Expect Flowers
From an autumn direct sowing, bupleurum produces cutting-quality stems from June. From a spring direct sowing, from July. The main season runs from June through August in most UK locations, with regular cutting extending the season significantly. The lime-green bract clusters are ornamentally useful from the moment they develop in late spring, before the tiny yellow flowers open, and remain attractive until well after the flowers have faded.
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| 💚 Stems Ready |
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Plant Specifications
The filler that makes every flower it touches look better
Bupleurum griffithii is the florist's secret — the plant that experienced arrangers reach for because they know what that acid-lime-green does to every other colour in the vase. The one thing standing between most gardeners and successful bupleurum is the germination rule: cover the seed. Know this, sear your cut stems, sow in autumn for the finest results, and discover one of the most transformative and most long-lasting cut flower fillers available from seed. Once you have grown it, every summer arrangement without it will feel like it is missing something essential.
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