Filipendula (meadowsweet) trial 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
Plants and location
What was planted?
The genus Filipendula comprises more than 10 species, the majority of which are clump-forming perennials originating from damp habitats – well suited to shady gardens or consistently moist sites. By contrast, the rosette-forming Filipendula vulgaris thrives in sunny borders. Across the genus, elegant plumes of tiny flowers, ranging from white and creamy-white to shades of pink, rise gracefully above the foliage, with some varieties offering a delicate fragrance.
As part of the assessment, photographs will be taken of each entry, capturing both the plant’s overall habit and detailed close-ups of the flowers. The RHS Trials team will also record key developmental stages, including the the timing of flowering.
Where is it planted?
For this small offsite trial, young Filipendula plants were set out in the open ground of the Demonstration Garden at the Royal Botanic Garden Edinburgh (RBGE), Scotland. They will grow on here, showcasing their qualities in both shaded and full-sun settings. 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
Judges and criteria
Judges of the trial
The 2023–2025 Filipendula judges include: 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) and Lewis Normand (Horticulturist and Garden Designer).
Judging criteria
The following factors are 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
Soft red Filipendula buds starting to form among the foliage
Lush green Filipendula trial beds at RBGE in May 2025
Cultivation
Planting process
Once ready, the Curatorial team at RBGE planted out the trial in specially prepared beds on the Sorbus Lawn. Each entry consisted of three plants, set out 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 the planting coincided with a period of unusually dry weather, the plants were carefully irrigated to support establishment. Although the original plan was to provide further irrigation during periods of prolonged drought, this was not carried out. This approach not only reflects the practical challenges of watering in this area, but also provides valuable insight into how Filipendula species respond to the changing Scottish climate.
How we’re managing plant health
In 2023, the judging panel recommended that two plants of Filipendula ulmaria ‘Aurea’ be lightly shaded to support leaf colour development. By mid-August, a combination of shading and naturally cooler, cloudier weather led to healthy new green growth in the shaded plants, while the uncovered plant also showed improvement.
For Filipendula vulgaris ‘Multiplex’, the panel explored whether deadheading might influence flowering. One plant was deadheaded while two were left untouched. By mid-September, all produced a comparable number of new stems, suggesting that deadheading does not increase flower production, but can improve the plant’s overall appearance.
The trial also provides an opportunity to observe how Filipendula responds to common health challenges. Some species may be susceptible to fungal leaf spots, while Powdery mildew can appear during dry spells. The Curatorial team continues to document these occurrences, building a clearer picture of how the genus adapts under varying conditions.
The frothy, showy flowerheads of Filipendula attract a wide range of pollinators, especially flies, while the leaves provide food for the larvae of many moth species, including the striking emperor moth.
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Discoveries
2025 | Seasonal resilience
In 2025, Scotland’s very dry spring temporarily stressed some plants, with cultivars like Filipendula ‘Kahome’ collapsing before recent rainfall encouraged recovery. These observations show that garden value depends not only on visual appeal but also on resilience through the season.
2024 | Powdery mildew observations
In 2024, mildew affected several plants in the trial. For example, every stem of Filipendula ulmaria ‘Flore Pleno’ was affected before flower buds had the chance to open. Interestingly, only the left plant of Filipendula ulmaria succumbed, 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 candidate would be Erysiphe ulmariae, as both species are commonly found on Filipendula ulmaria.
2023 | Longest flowering cultivars
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 displayed two distinct flowering periods: mid-June to the end of July, and again from early September to the first frosts in November.
Suppliers to the trial
List of plants in the trial
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For more information on our RHS Plant Trials or to access older trial reports, please get in touch with our team via email at [email protected].
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