Fleuroselect sunflowers (Helianthus) trial 2024

Objectives and purpose of the trial

The focus of this trial is on dwarf and semi-dwarf sunflower cultivars. Last trialled at RHS Wisely in 2015, since then, new selections have been introduced. The trial will compare these new editions against established cultivars to see how they perform. Those that performed best will be awarded the RHS Award of Garden Merit (AGM). The RHS has teamed up with Fleuroselect, an international organisation for ornamental plants, to bring the Fleuroselect sunflower (Helianthus) trial.
View of sunflower trial from the entrance to Floral Fantasia at RHS Hyde Hall
Sunflowers in full bloom during summer 2024

Plants and location

What was planted?

Fleuroselect has curated a selection of 85 Helianthus entries for the trial, featuring 83 different cultivars, with a few duplicates from different suppliers. The trial also includes sunflowers that already hold AGMs to compare them against new introductions. All seeds have been sourced from trusted Fleuroselect members.

Where is it planted?

The sunflower seeds were sown directly into the open ground in Floral Fantasia area at RHS Hyde Hall, Essex, and six entries, submitted as young plants, were planted directly into trials beds. Here are some considerations for planting out sunflowers:

  • Sow seeds indoors in early spring to give them a head start
  • Slugs and snails like to feast on young annual sunflowers, so it is worth waiting until your seedlings are strong, resilient and hardened off well to give them the best chance

  • Position in full sun and in a sheltered spot
  • Sunflowers like plenty of water, so consider applying a layer of mulch such as strulch to help retain moisture levels in the soil

Sunflower facts

During the summer, many annual sunflowers provide an excellent source of food for insects such as bees, hoverflies, butterflies and moths. In autumn, many sunflower cultivars then provide a valuable source of food for seed eating birds, like goldfinches. Therefore, growing sunflowers like Helianthus debilis ‘Vanilla Ice’ and Helianthus annuus ‘Velvet Queen’ in your garden is an excellent way for you to help support your local wildlife at home.

Judges and criteria

Judges of the trial

The trial assessment forum is made up of 10 invited experts with backgrounds in breeding, growing, retail, garden management, plant trials, horticulture and horticulture media. The forum will be gathering every two weeks during the summer to assess the performance of the entries.

Once the judges have concluded their overall assessment of the sunflowers, the results will be reviewed by the RHS Herbaceous Expert Group and announced in winter 2025.

The 2024 Fleuroselect sunflower forum includes: Mike Smith (Chair, Owner, WD Smith & Son Nurseries), David Creese (RHS Tender Ornamental Expert Group member), Phil Johnson (RHS Herbaceous Expert Group member and Director, Lion Seeds), Boyd Douglas-Davies (Managing Consultant, The Boyd Foundation), Alan Bourne (Owner, Perrywood’s Garden Centre), Adele Dyer (Principal Researcher and Writer, Which), Andy Bunker (Sales Director, Alton’s Garden Centre), Chris Finlay (Sales Director, Volmary), Michael Perry (Presenter and Influencer, Mr Plant Geek) and Molli Christman (RHS Horticulturist).

Judging criteria

The following factors are all taken into consideration as part of the judging of the trial:

  • Flower performance
  • Habit
  • Colour and appeal

  • Pest and disease resistance
  • Longevity

Plant portrait of Helianthus annuus ‘Ronnie Orange’
Bee feasting on Helianthus annuus ‘Ring of Fire’

Cultivation

Planting process

In early July 2024, six cultivars were supplied as young plants and were planted straight into the ground on arrival. The remaining entries were supplied as seeds, which were sown in two batches to extend the length of the display for visitors. The first sowing took place in early May 2024 and the second took place in early June 2024. Due to the unprecedented wet and cold weather, very few of these sowings were successful. Seeds were also sown under glass in the nursery at RHS Hyde Hall in June 2024, with the view that they would replace any seedlings in the trial beds that failed to produce a young plant.

An organic nitrogen feed was added to the soil in spring before sowing and planting at a rate of 50g per metre squared. Once ready, the Floral Fantasia trial beds were marked out in April 2024 into 86 rows of sunflowers, one for each entry with five plants per entry. Each of the entries were arranged in height order according to the heights detailed by their suppliers. The rows were spaced 64cm apart and the five plants within each row were spaced 40cm apart.

A thin layer of strulch (a straw based mulch) was applied to the ground after the seedlings had established. The horticulturists working on the trial were careful to leave a space between the seedlings and the strulch to avoid burning the young plants. The strulch was applied to help retain moisture levels in the soil over the summer.

Additionally, soil analysis concluded that the soil in each trial bed was high in nutrients. Therefore, strulch was also selected for its ability to improve soil structure without overloading the soil with excess nutrients.

The sunflowers are watered regularly during the to prevent them from drying out.

How we’re managing plant health

After sowing, the trial beds were covered with netting to prevent birds from eating the seeds. Once the seedlings and young plants had established, a thin layer of strulch was applied to the ground to supress slug and snail damage. The horticulturists on the trial found the strulch successful at supressing weeds and slugs. During the trial, no significant disease or pest damage has been observed.

We had a challenging start to the trial with unprecedented wet and cold weather in spring, which had a detrimental effect on the seeds sown outside. However, the weather did not prevent us from showcasing a broad range of different sunflowers thanks to the nursery staff at RHS Hyde Hall.

Mandy Jayne Ellison-Tout, Trials Coordinator
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Plant portrait of Helianthus annuus ‘Mezzulah’
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Sunflower seedlings in RHS Hyde Hall Nursery in June 2024
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Young sunflowers in the trial bed at RHS Hyde Hall in July 2024
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Plant portrait of Helianthus annuus ‘Mezzulah’
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Sunflower seedlings in RHS Hyde Hall Nursery in June 2024
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Young sunflowers in the trial bed at RHS Hyde Hall in July 2024
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Field of sunflowers
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Discoveries

While carrying out the trial, a lot of time is spent observing the plants, and details are noticed that do not relate to the formal trial assessment. Here are some of the interesting findings from the trial:
Helianthus annus ‘Desire Red’

August–September 2024

Visitors to RHS Hyde Hall were given the opportunity to vote for their favourite sunflower on display in the RHS People’s Choice Award poll, which ran between August and September 2024.

See the winners

Suppliers to the trial

Fleuroselect Members:

Extended trials area:

List of plants in the trial

View all of the Fleuroselect sunflowers on trial at RHS Hyde Hall
  • Helianthus annuus ‘Petisol’
  • Helianthus annuus [Sunsation Lemon] (Sunsation Series)
  • Helianthus annuus [Suntastic Golden Yellow with Brown Centre] (Suntastic Series)
  • Helianthus annuus [Pacino Cola] (Pacino Series)
  • Helianthus annuus [Sunray Yellow] ‘Bnlhe01yel’
  • Helianthus annuus [Bert]
  • Helianthus annuus ‘Firefox’
  • Helianthus annuus ‘Sunspot’
  • Helianthus annuus ‘Desire Red’
  • Helianthus annuus ‘Ms Mars’
  • Helianthus annuus ‘Tiger Eye’
  • Helianthus annuus ‘Irish Eyes’
  • Helianthus annuus ‘Sunsation Yellow’ (Sunsation Series)
  • Helianthus annuus [Royal Yellow Brown Centre]
  • Helianthus annuus [Royal Yellow Light Centre]
  • Helianthus annuus [Royal Early Yellow Yellow Centre]
  • Helianthus annuus [Suntastic Golden Yellow with Brown Centre] (Suntastic Series)
  • Helianthus annuus ‘Lemon Cutie’ (d)
  • Helianthus annuus ‘Solar Flash'
  • Helianthus annuus ‘Big Smile’
  • Helianthus annuus ‘Paquito Colorado’ (Paquito Series)
  • Helianthus annuus ‘Paquito Sol’ (Paquito Series)
  • Helianthus annuus ‘Teddy Bear’
  • Helianthus annuus ‘Baby Face’
  • Helianthus annuus ‘Little Dorrit’
  • Helianthus annuus [Music Box Mixed]
  • Helianthus annuus ‘Zebulon’
  • Helianthus annuus ‘Mezzulah’
  • Helianthus annuus ‘Orange Mahogany Bicolour’
  • Helianthus annuus ‘Waooh!’
  • Helianthus annuus ‘Garden Statement’
  • Helianthus [Sunbelievable Brown Eyed Girl] (‘Sunbeliv01’) (Sunbelievable Series)
  • Helianthus [Sunblast] (‘Heiz0002’)
  • Helianthus [Sol Seeker Bee Yellow] (Sol Seeker Series)
  • Heianthus [Sol Seeker Golden Nectar] (Sol Seeker Series)
  • Helianthus [Sunfinity Yellow Dark Centre] (‘Heiz0001’) (Sunfinity Series)
  • Helianthus [Sol Seeker Honey] (Sol Seeker Series)
  • Helianthus [Sol Seeker Bronze Burst] (Sol Seeker Series)
  • Helianthus maximilliani ‘Early Bird’
  • Helianthus annuus ‘Buttercream’
  • Helianthus annuus ‘Soleo’
  • Helianthus annuus ‘Gummy Bear’ (d)
  • Helianthus annuus ‘Florenza’
  • Helianthus annuus [Sonja]
  • Helianthus annuus [Solbrite]
  • Helianthus annuus [Solcito]
  • Helianthus debilis ‘Soluna Bronze’ (Soluna Series)
  • Helianthus debilis ‘Soluna Cream’ (Soluna Series)
  • Helianthus debilis ‘Soluna Gold’ (Soluna Series)
  • Helianthus debilis ‘Soluna Lemon’ (Soluna Series)
  • Helianthus annuus ‘Solar Power’
  • Helianthus annuus ‘Jua Maya’
  • Helianthus annuus [Pradera Gold]
  • Helianthus debilis subsp. cucumerifolius ‘Italian Green Heart’
  • Helianthus debilis subsp. cucumerifolius ‘Italian White’
  • Helianthus annuus ‘Sunrich Orange’ (Sunrich Series)
  • Helianthus annuus ‘Ring of Fire’
  • Helianthus annuus ‘Valentine’
  • Helianthus annuus [Autumn Beauty] (mixed)
  • Helianthus annuus ‘Hallo’
  • Helianthus debilis ‘Vanilla Ice’
  • Helianthus annuus ‘Moonshine’
  • Helianthus annuus ‘Velvet Queen’
  • Helianthus argophyllus ‘Gold and Silver’
  • Helianthus annuus ‘Taiyo’
  • Helianthus annuus ‘Red Sun’
  • Helianthus annuus ‘Golden Hedge’
  • Helianthus annuus ‘Soraya’
  • Helianthus annuus ‘Ronnie Orange’
  • Helianthus annuus [Solano Orange Summer] (Solano Series)
  • Helianthus annuus [Solano Double] (‘He2302’) (Solano Series) (d)
  • Helianthus annuus [Solano Gold] (Solano Series)
  • Helianthus annuus [Solano Orange Nr. 12] (Solano Series)
  • Helianthus annuus [Solano Orange Nr. 14] (Solano Series)
  • Helianthus annuus [Solano Flame] (‘He2301’) (Solano Series)
  • Helianthus annuus ‘Black Magic’
  • Helianthus annuus [ProCut White Lite] (ProCut Series)
  • Helianthus annuus ‘Sunbright’
  • Helianthus annuus [Solano Deep Orange] (Solano Series)
  • Helianthus annuus ‘Claret’
  • Helianthus annuus ‘Moulin Rouge’
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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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