Potato, late maincrop trial results 2024–2025
Objectives and purpose of the trial
Potato plants showing progress in early summer at RHS Wisley
Solanum tuberosum ‘Caledonian Rose’ after harvesting
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:
- Habit and uniformity
- Yield
- Taste
- Resistance to pests and diseases
- Storage (October to March)
Potato (maincrop) – RHS Recommended: AGM winners
Solanum tuberosum 'Desiree'
potato 'Desiree'
- 0.5–1 metres
- 0.1–0.5 metres
Solanum tuberosum 'Harmony'PBR
potato 'Harmony'
- 0.5–1 metres
- 0.1–0.5 metres
Solanum tuberosum 'Alouette'PBR
potato 'Alouette'
- 0.1–0.5 metres
- 0.1–0.5 metres
Solanum tuberosum 'Desiree'
potato 'Desiree'
- 0.5–1 metres
- 0.1–0.5 metres
Solanum tuberosum 'Harmony'PBR
potato 'Harmony'
- 0.5–1 metres
- 0.1–0.5 metres
Solanum tuberosum 'Alouette'PBR
potato 'Alouette'
- 0.1–0.5 metres
- 0.1–0.5 metres
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Trialling on a new site conveniently offered all the challenges people would face growing potatoes for the first time, so the results and recommendations will hopefully both encourage and benefit you to experience similar results.
Why the RHS Recommended: AGM was awarded
New award winners with forum comments
Reconfirmed awards with forum comments
Retained awards with forum comments
Potato taste testing results
Solanum tuberosum ‘Twister’ ready to be stored over winter
Lush potato plants thriving in rich soil in summer 2024
RHS Recommended: AGMs rescinded
Rescinded awards with forum comments
Plants and location
What was planted?
Throughout the trial, each entry was photographed to capture plant habit and detailed tuber characteristics. The RHS Trials team monitored key growth stages, from the emergence of the first shoots to flowering dates, while the RHS Herbarium collected plant material, including flowers, to document the differences in flower colour between cultivars.
Where was it planted?
The maincrop potato tubers were planted in carefully in the beds of the new Edible Trial Garden at RHS Wisley, providing the basis for a season of robust growth, impressive yields and flavourful harvests. Here are some considerations for planting out maincrop potatoes:
- Potatoes are grown from ‘seed potatoes’ (small tubers that are certified virus-free)
- Plant them in April, in a sunny, sheltered spot
- Improve the soil before planting with well-rotted manure or homemade compost, and feed while in growth with liquid seaweed
- Water well in dry weather
- As they grow, soil can be gradually piled up around the stems, known as ‘earthing up’, to bury the developing tubers
- They will be ready to harvest in the autumn
Cultivation
Planting process
In March 2024, the tubers were set out to chit, encouraging the development of sturdy sprouts that would give the plants a strong start once in the ground. When both the chitted tubers and the prepared beds were ready, planting began in May. Eight tubers per entry were set out in three of the four beds, arranged alphabetically, spaced 38cm (15in) apart in rows 76cm (30in) apart. By the end of the month, the first shoots were already breaking through the soil.
June saw the plants being earthed up to shield developing tubers from light, preventing them from turning green and becoming unusable. By late June 2024, flowering was underway, signalling strong growth across the trial. From the end of June onwards, the plots received a weekly watering schedule to support consistent development through the rest of the season.
How plant health was managed
Challenges
Although potatoes are generally reliable croppers, they are still vulnerable to problems that become more pronounced in warm, wet seasons. Blight can render tubers unsuitable for storage if not addressed quickly, and rotating the crop each year helps limit soil-borne diseases. In areas with high slug activity, lifting maincrop potatoes as soon as they mature is often the best approach.Early in the season, when one plant from each entry was lifted in July 2024, scab was found on some tubers, with most cases concentrated in a single bed. Around the same time, bacterial potato blackleg appeared, causing sections of foliage to rot. These plants were removed to prevent further spread. Blight remained limited across the site, although the foliage of Solanum tuberosum ‘Rooster’ was cut back in August 2024 after early symptoms were detected. By November 2024, as the crop was lifted, rot was recorded, highlighting how both in-ground health and post-harvest condition contribute to the overall performance of each cultivar.
How to grow potatoes
Explore all the information you need to know to grow and care for potatoes in your garden
Discoveries
Taste testing results | 2024–2025
The results of the potato taste testing highlighted Solanum tuberosum ‘Pink Fir Apple’ (pictured) as the favourite, followed by Solanum tuberosum ‘Blue Belle’, Solanum tuberosum ‘Caledonian Rose’ and Solanum tuberosum ‘Twinner’. Although ‘Pink Fir Apple’ topped the taste results, it was not assessed for the RHS Recommended: AGM, as it is classified as a salad rather than a maincrop potato.
Blackleg spotted | July 2024
In July 2024, the trial faced a challenge when bacterial potato blackleg (pictured) began affecting some of the potato plants, causing parts of the foliage to rot. Quick action by the team ensured the affected plants were removed, protecting the rest of the crop and keeping the trial on track.
Who was involved?
Judges of the trial
The potato trial judges comprised: Barry Newman (RHS Wisley Forum Chair and RHS Fruit, Vegetable and Herb Expert Group member), Ian Clemens (RHS Fruit, Vegetable and Herb Expert Group member), John Constable (formerly with Elsom Seeds and Allium Seeds), Keith Hine (National Vegetable Society judge), Richard White (former Trial Garden Manager, Tozer Seeds), Sarah Wain (formerly West Dean Garden), Elizabeth Mooney (Horticulturist Edibles, RHS Wisley), Lucy Chamberlain (RHS Fruit, Vegetable and Herb Expert Group sustainability and biodiversity lead) and Jim Buckland (formerly West Dean Garden).
Suppliers to the trial
List of plants in the trial
View all the potatoes trialled at RHS Wisley
Handy tools and information
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Gardening advice
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Hardiness ratings
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Get in touch
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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