Phormium cookianum 'Tricolor' (Tricolor Mountain Flax)
RHS Award-Winning Architectural Evergreen with Dramatic Striped Foliage
Transform your garden with the striking architectural presence of Phormium cookianum 'Tricolor', an exceptional evergreen perennial that delivers year-round drama through its spectacular variegated sword-shaped foliage. This RHS Award of Garden Merit winner produces bold clumps of upright leaves beautifully striped in green and cream with distinctive red margins, creating a stunning focal point that brings contemporary style and tropical flair to any garden setting whilst providing permanent structural interest throughout all seasons.
Key Features
- Plant Type: Hardy evergreen perennial
- Height: 1.5m
- Spread: 2.5m
- Flowering Period: July to August
- Flower Size: Large panicles of small flowers
- Flower Colour: Yellowish-green on tall spikes
- Foliage: Sword-shaped green leaves with cream stripes and red margins
- Hardiness: Hardy in the UK down to temperatures of -10 to -5 degrees Celcius (RHS hardiness rating H4)
- Growth Habit: Upright, clumping, architectural
Spectacular Tricolour Foliage Display
The outstanding feature of 'Tricolor' lies in its magnificent variegated foliage that gives the plant its distinctive name. The sword-shaped leaves display a beautiful combination of mid to dark green base colour with striking cream to yellow variegation running the length of each leaf, dramatically finished with bright red margins that intensify in cooler weather. This remarkable three-colour combination creates a luminous effect that brightens any garden area whilst providing bold architectural interest that commands attention throughout the year.
Bold Architectural Form
Each plant forms an impressive clump of rigid, upright, linear leaves that can reach up to 1.5 metres in length, creating a dramatic fountain-like effect that serves as a striking focal point in garden design. The sword-shaped leaves feature a central groove and gracefully arch outwards from the crown, producing a sculptural quality that brings contemporary style and exotic appeal to both traditional and modern garden settings.
Impressive Flowering Display
On mature plants, spectacular tall flower spikes emerge in summer, reaching up to 2 metres in height and bearing large panicles of small yellowish-green flowers. These dramatic flowering stems create an impressive vertical accent that extends well above the foliage clump, adding seasonal height and architectural drama to the garden display whilst providing valuable nectar for pollinators.
Year-Round Structural Interest
Unlike many perennials that die back in winter, 'Tricolor' maintains its full architectural presence throughout the year, making it invaluable for providing permanent garden structure. The evergreen nature ensures consistent visual impact and serves as an excellent backdrop for seasonal plantings whilst the bold form creates striking silhouettes against winter skies.
Versatile Design Applications
This architectural plant excels in contemporary garden design, providing excellent contrast with fine-textured plants and serving as a bold statement piece in mixed borders. The dramatic foliage creates stunning reflections when positioned near water features, whilst the upright form makes it perfect for creating vertical accents in flat landscapes or serving as a living sculpture in minimalist garden schemes.
Growing Requirements
- Soil and Position: Thrives in full sun to partial shade, with the best foliage colour developing in bright conditions. Prefers well-drained soil and adapts to various soil types including clay if drainage is adequate. Excellent tolerance to coastal conditions and salt spray makes it valuable for seaside gardens.
- Light Requirements: Performs best in full sun where the variegated foliage colours are most intense, but tolerates partial shade well. Some protection from harsh winter winds helps maintain foliage quality in exposed locations.
- Soil Preferences: Adapts to most well-drained soils including sandy, loamy, and clay conditions. Prefers consistent moisture during the growing season but tolerates drought once established. Avoid permanently waterlogged sites.
Care and Maintenance
- Pruning Requirements: Remove any damaged or dead leaves by cutting them back to the base using sharp secateurs. Trim flower spikes after flowering if seed production is not desired. Remove any all-green shoots that may appear to maintain the variegated character.
- Watering Requirements: Water regularly during establishment and dry periods, particularly during the first growing season. Once established, shows good drought tolerance but performs best with consistent moisture during summer months.
- Fertilising Programme: Apply a balanced fertiliser high in potash every spring to encourage healthy growth and potential flowering. Mulch annually with composted bark or garden compost to protect roots from frost and improve soil condition.
Design Applications
- Specimen Plantings: Outstanding as a standalone architectural specimen where the dramatic foliage and form can be fully appreciated. Perfect for creating bold focal points in contemporary garden designs or serving as living sculptures in minimalist settings.
- Mixed Borders: Provides excellent structural contrast in mixed borders, serving as a bold backdrop for softer perennials and creating striking textural combinations with fine-leaved plants.
- Coastal Gardens: Particularly valuable for coastal gardens where the excellent salt tolerance and wind resistance make it ideal for seaside plantings. The architectural form creates striking silhouettes against coastal skies.
- Water Features: Looks spectacular when positioned near water features where the dramatic foliage creates stunning reflections and the upright form provides vertical interest beside horizontal water surfaces.
Seasonal Interest
- Spring Emergence: New growth emerges with fresh, vibrant colouring as the plant produces new leaves from the crown, creating renewed architectural interest after winter.
- Summer Spectacle: Mature plants produce impressive tall flower spikes that extend well above the foliage, creating dramatic vertical accents whilst the variegated leaves maintain their striking colour combination.
- Autumn Intensification: Cooler weather often intensifies the red margins on the leaves, creating enhanced colour contrast that brightens the autumn garden.
- Winter Structure: The evergreen foliage maintains full architectural presence throughout winter, providing essential garden structure and creating striking silhouettes against winter skies.
Award Recognition
This variety has received the RHS Award of Garden Merit, recognising its exceptional garden performance, reliability, and outstanding ornamental value. This prestigious award confirms its suitability for British gardens and its exceptional characteristics as a garden plant.
Hardiness and Protection
Hardy in most UK locations down to -10°C, though may suffer some foliage damage in harsh winters in cold gardens. In borderline hardy locations, choose a sheltered position and consider mulching around the crown for additional winter protection. Young plants may benefit from fleece protection during their first winter.
Mature Size Expectations
The plant typically reaches 1.2-1.5m in height and spread, forming an impressive clump of architectural foliage. Flower spikes can extend up to 2m in height on mature plants, creating dramatic seasonal height that adds vertical interest to garden designs.
Why Choose 'Tricolor'?
Phormium cookianum 'Tricolor' represents the perfect combination of architectural presence, year-round interest, and dramatic foliage colour in a single outstanding plant. The RHS Award of Garden Merit recognition, combined with excellent hardiness and coastal tolerance, creates a perennial that provides maximum garden impact with bold contemporary appeal.
This award-winning variety offers exceptional value for gardeners seeking permanent structure and dramatic foliage interest with the added benefits of impressive flowering and excellent reliability. Whether used as specimen plantings, architectural accents, or bold border features, 'Tricolor' provides the perfect balance of structural presence, foliage drama, and garden dependability that makes it an essential addition to any garden seeking striking architectural appeal with year-round colour and contemporary distinction.
Buying Shrubs from Jacksons Nurseries
At Jacksons Nurseries we sell a variety of shrubs both evergreen and deciduous with a variety of flowering times throughout the year. At certain times of the year our shrubs you buy from us may not look like the images shown on our website when deciduous leaves have fallen, the shrub has finished flowering or has been trimmed back.
Some leaves on evergreen shrubs can be damaged in winter by frost or harsh winds but in spring new leaves will readily replace those damaged. This is quite normal on many evergreen varieties and is preferable to plants grown with excessive protection that show cold shock once planted out and establish less satisfactory initially.
Availability: Stock availability figures are provided as a guide only. There is a delay between orders being placed and the plants being gathered by our pulling team. During this time it may be possible for a member of the public to purchase these plants from our Garden Centre, while this is rare it is a possibility and we will notify you of any problems as soon as possible. This figure may also include plants that have not yet be flagged as unsaleable.
Pre-order: Pre-order times are given as a guide only and may vary dependent on the growing season. Orders containing Pre-ordered products will be shipped as a single order when all items become available. Large orders may be part shipped, please contact us on 01782 502741 or email sales@jacksonsnurseries.co.uk.
* Please Note: Shrubs in 20 litre pots and above might require a pallet delivery starting at £79.99 per pallet. Depending on the exact pot size and height it may be possible to get approximately 5 plants per pallet at no extra cost. The maximum height we can dispatch on a pallet is 2.0m, this includes the height of the pallet and pot.
Shrubs are deciduous or evergreen woody plants, and often provide fragrant flowers, berries and foliage. They are good for structural framework, and they can provide a wonderful shelter and food source for wildlife.
Planting and Conditions
Container grown shrubs can be grown at any time of year. It is a little known fact that shrubs planted in the autumn and winter will be easier to look after than those planted in the spring and summer, because they will have time to establish and become hardy in the cooler months.
Plant the shrub at the same depth as it was in its original pot. Planting too deeply can result in root and stem rot.
One of the biggest causes of death in new shrubs is drought stress, so keep it well watered until it’s established.
Make sure you loosen the soil prior to planting. Most shrubs are tolerant of most soil types as long as it is fairly well draining.
Most shrubs will grow happily in containers, but they will be much more demanding on feeding and watering than shrubs in the ground would be. They will also need potting on every couple of years so that they don’t suffocate or become stunted in their pot.
Aftercare and Pruning
Once established, shrubs generally do not require much water. However, at first they need careful, frequent watering and should not be left to dry out.
Shrubs in the ground are generally not demanding and in most cases, annual feeding with general purpose fertilizer will suffice. Shrubs in containers may need more feeding; usually from early spring until late summer.
Shrubs also benefit from mulching in order to supress weeds, conserve moisture and provide vital nutrients. Mulch also greatly improves soil conditions. Shrubs can be mulched in late winter, after fertiliser has been applied, but it can be mulched through autumn to late spring as long as the ground is damp.
All shrubs benefit from dead-heading once spent flowers become apparent. Rhododendrons and Lilac especially benefit from the removal of dead flowers.
Some shrubs may show signs of reverted growth or ‘sporting’. This is where random shoots of different leaves associated with the plant’s parentage begin to appear. Most commonly this is where plants with variegated leaves sprout pure green growths instead of variegated ones.
To control reversion, remove reverted shoots promptly to discourage them. Reverted shoots are usually much more vigorous than the variegated ones, and thus should be completely pruned out and cut back into wood containing variegated foliage.
Potential Issues
Although shrubs are usually very robust garden plants, they can sometimes start to decline with no apparent or obvious reason.
This will start with browning leaves, which could indicate plant stress due to lack of water or waterlogging, an establishment failure or, in the worst case scenario, honey fungus. Another cause of leaf browning is a high salt content in the soil. This could be a natural occurrence, especially if you live near the ocean, or it could be from over fertilisation.
To remedy a high salt content, cut back on fertiliser and step up your watering regime for the next few weeks. If you live by the ocean, this will be harder to remedy—but stepping up your watering will help to wash some of the salt away all the same.
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