Filipendula (meadowsweet) trial results 2023–2025
Objectives and purpose of the trial
A vibrant bed of pink and white Filipendula flowers in July 2025
Delicate pink Filipendula blooms stand out from the foliage
What is an RHS Recommended: Award of Garden Merit?
The RHS Recommended: Award of Garden Merit helps gardeners choose plants that are reliable and perform well in real gardens. Plants that receive the RHS Recommended: AGM have been thoroughly tested and shown to be:
- Easy to grow and reliable in normal garden conditions
- Readily available to buy in garden centres or online
- Healthy, robust plants with strong growth and appearance
- True to type, maintaining consistent shape, colour and form
- Reasonably resistant to common pests and diseases
Judging criteria
The following factors were all taken into consideration as part of the judging of the trial:
- General ornamental use within the garden
- Floral impact and duration of flowering
- Scent
- Use as a foliage plant
- Invasiveness
Filipendula – RHS Recommended: AGM winners
Filipendula purpurea
purple meadowsweet
- 0.5–1 metres
- 0.1–0.5 metres
Filipendula palmata 'Göteborg'
- 0.1–0.5 metres
- 0.1–0.5 metres
Filipendula purpurea
purple meadowsweet
- 0.5–1 metres
- 0.1–0.5 metres
Filipendula palmata 'Göteborg'
- 0.1–0.5 metres
- 0.1–0.5 metres
Filipendula offer so much – bright green early foliage, flowering that can last for months, bees and hoverflies love them, and many have decent autumn colour, too. Some of the best foliage and flowers come from smaller forms that most gardens could accommodate.
Why the RHS Recommended: AGM was awarded
Soft red Filipendula buds starting to form among the foliage
Lush green Filipendula trial beds at RBGE in May 2025
RHS Recommended: AGMs rescinded
Plants and location
What was planted?
The genus Filipendula includes more than 10 species, most of which are clump-forming herbaceous perennials suited to damp habitats, making them well suited to shady gardens or consistently moist soils. An exception is Filipendula vulgaris, a rosette-forming species that thrives in sunny, well-drained borders. Across the genus, airy plumes of small flowers in shades from white and cream to soft pink rise above the foliage, with some offering a light fragrance.
As part of the assessment, each entry was photographed to record its overall habit and floral detail. The RHS Trials team also recorded key stages of development, including flowering times.
Where was it planted?
For this small offsite trial, young Filipendula plants were planted in the open ground in the Demonstration Garden at the Royal Botanic Garden Edinburgh (RBGE), Scotland. The bed was partly shaded for part of the year and in full sun at other times, providing an opportunity to assess how the plants performed under changing light conditions. Here are some considerations for planting Filipendula:
- Plant in moist but well-drained, fertile soil; most species prefer partial shade, while Filipendula vulgaris thrives in full sun
- Keep the ground consistently damp, especially in warmer months; mulching helps retain moisture
- Clump-forming species need room to spread, whereas rosette-forming types stay more compact
- Airy sprays of flowers, ranging from soft whites to gentle pinks, stand above the leaves, with certain forms offering a subtle scent
- Filipendula is generally pest and disease free, requiring only light tidying and occasional division
- Ideal for shady borders or moist planting schemes, pairing well with other damp-loving perennials
Cultivation
Planting process
Once ready, the Curatorial team at RBGE planted the trial in specially prepared beds on the Sorbus Lawn of the Demonstration Garden. Each entry consisted of three plants, arranged in a triangular formation to allow for even growth and comparison. The first 11 entries were planted in early October 2022, with three additional cultivars – Filipendula multijuga BSWJ10950, Filipendula multijuga ‘Hjördis’ and Filipendula purpurea – added in May 2023.
As planting coincided with a period of unusually dry weather, the plants were carefully watered to help them establish. Although further watering had been planned during prolonged dry periods, this was not carried out, reflecting both the practical challenges of watering this area and a desire to observe how the plants coped with minimal intervention.
Maintenance was kept deliberately light. The beds were mulched over winter and plants were cut back in late winter, with edging and weeding carried out before assessments.
How plant health was managed
Throughout the trial, the Curatorial team and judging panel monitored the plants closely, assessing both growth and responses to environmental conditions.
Weather and growing conditions
The trial period saw a marked contrast in weather conditions. From August 2023 to June 2024, rainfall was consistently above average, with May 2024 recorded as the wettest on record at RBGE. In contrast, 2025 brought an exceptionally dry spring, from March to May, followed by continued low rainfall into the summer months.
Despite these extremes, the trial received no further watering after establishment. This provided a useful test of how Filipendula performed in both prolonged wet conditions and periods of drought, offering insight into its resilience in a changing Scottish climate. These observations helped build a clearer picture of how Filipendula performs in a range of garden conditions.
Performance and response
In 2023, the judges recommended lightly shading two plants of Filipendula ulmaria ‘Aurea’ to improve leaf colour. By mid-August, a combination of shading and naturally cooler, cloudier weather had encouraged healthy new growth in the shaded plants, while the unshaded plant also showed improvement.
For Filipendula vulgaris ‘Multiplex’, the panel explored whether deadheading affected performance. One plant was deadheaded, while two were left untouched. By mid-September, all three had produced a similar number of new stems, suggesting that deadheading did not increase flower production, although it improved the plant's overall appearance.
Challenges
The trial also offered an opportunity to observe how Filipendula responded to common health challenges. Although the genus is considered susceptible to fungal leaf spot, no instances were recorded during the trial. Powdery mildew was observed, particularly in 2024 when conditions favoured its development, in some cases affecting flowering performance.
Isolated damage was also recorded. A single accession of Filipendula purpurea was severely affected by sawfly in 2024 and again in 2025, while neighbouring plants remained unaffected, showing that susceptibility can vary across the genus.
Discoveries
Seasonal resilience | 2025
In 2025, Scotland's very dry spring temporarily stressed some plants, with cultivars such as Filipendula ‘Kahome’ collapsing before recovering after summer rainfall. Some entries also splayed under drought stress, with stems leaning outwards, while foliage browned earlier than in previous years and autumn colour was reduced. These observations show that garden value depends not only on visual appeal but also on how well plants cope with challenging conditions throughout the season.
Sawfly damage | 2024–2025
A single accession of Filipendula purpurea showed a clear and repeated susceptibility to sawfly, with plants heavily defoliated in both 2024 and 2025. The damage was severe enough to prevent proper assessment and, notably, remained confined to this accession despite other plants growing nearby. This contrast showed how the impact of pests can vary considerably between apparently similar plants, even when grown under the same conditions.
Powdery mildew observations | 2024
In 2024, powdery mildew affected several plants in the trial. For example, every stem of Filipendula ulmaria ‘Flore Pleno’ was affected before the flower buds had a chance to open. Interestingly, only the left-hand plant of Filipendula ulmaria was affected, despite leaning against and touching the middle plant, which remained unaffected. Leaf samples were analysed at Bangor University, where the powdery mildew was identified as Podosphaera filipendulae. Another possible cause was Erysiphe ulmariae, as both species are commonly found on Filipendula ulmaria. This uneven spread, even between neighbouring plants, suggested that susceptibility can vary between apparently similar plants.
Longest flowering cultivars | 2023
Filipendula ‘Kahome’ and Filipendula palmata ‘Göteborg’ were in flower from mid-July 2023 until the first frosts in early November 2023. In contrast, Filipendula palmata flowered in two separate periods: from mid-June to the end of July, and again from early September until the first frosts in November. In 2024 and 2025, Filipendula vulgaris ‘Multiplex’ flowered for the longest period, although its relatively low number of stems resulted in a less showy display. This illustrates the difference between flowering duration and overall visual impact.
Who Was Involved?
Judges of the trial
Judging took place fortnightly in July and August 2023. In 2024, assessment dates were more flexible to align with the Aruncus trial, with visits in June, July, twice in August and once in September, although one July session was cancelled due to a forecast storm. In 2025, the panel returned to fortnightly meetings from late May to early August, followed by a final assessment in September.
At the end of the trial, the panel recommended plants for the RHS Recommended: Award of Garden Merit, with final decisions confirmed by the RHS Expert Group.
The 2023–2025 Filipendula judges included: Kirsty Wilson (Head of Gardens, Balmoral), David Rae (Director, Stanley Smith (UK) Horticultural Trust, former Director of Horticulture and Learning, RBGE), Duncan Young (Garden Manager, Herbaceous Horticulture, RBGE), Simon Crawford (Plant breeder), Gavin McNaughton (Nurseryman), Lewis Normand (Horticulturist, Bernhard’s Nurseries), Catherine Erskine (Trustee, Cambo Gardens), Dougal Philip (Director of New Hopetoun Gardens), Craig Cameron (Estate Factor, Teasses), Pilar Medrano Dell (RHS Herbaceous Plant Expert Group) and Andrew Simmons (former Head Gardener)
Suppliers to the trial
List of plants in the trial
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