Updated/Fact-Chacked on April 18, 2023 by Gareth James
Spiky outdoor plants in a border or pots will give your garden a modern twist by adding architectural qualities. Though most plants with spiky foliage prefer hot, humid climates, a few will thrive in the UK.
How to use spiky plants in your garden
Spiky plants can be used in areas of your garden to give an exotic feel and work very in patio and seating designs.
Spiky plants can also be used in borders to break up the traditional English garden look and add vertical interest; some grasses and cordylines can grow to 2M tall.
Though many exotic spiky plants are difficult to grow in the UK, you have three main options: spiky thistles for small flowering perennials, grasses or larger shrubs.
Max height: 2.5 M
Cordylines have fantastic architectural foliage that can contrast well with other plants. They are exotic-looking plants that can grow well in UK climates – as long as temperatures don’t fall below -5 C. If you live in a very cold area, you may have to cover the plant up over winter. Cordylines also do well in coastal regions as they thrive in salty winds.
Note that cordylines can grow very large over a few years, if you are worried about the size, grow them in containers instead.
My favourite cordyline varieties are the Cordyline australis ‘Albertii’ with variegated leaves and the Cordyline australis ‘Purple Tower’ with dark purple foliage.
Agaves are succulents native to Mexico and come in hundreds of varieties. Many are not frost-hardy, but you can find varieties that will withstand a UK winter. The two best agaves to grow in the UK are Agave americana and Agave parryi. Agave Americana can grow for 30 years and reach a height of 5m, but they die once they bloom.
Eryngium (sea holly)
If you are looking for a plant to add a spiky contrast to borders, Eryngium is perfect.
Eryngium is a thistle-like plant native to coastal regions. They are easy to grow and loved by bees and other pollinators.
Eryngium is also great for adding winter interest with its architectural spiky heads that remain after flowering. The dead heads look fantastic with snow on them, especially if surrounded by winter flowers.
There are many varieties of sea holly; I recently bought ‘Eryngium varifolium’ and ‘Eryngium x tripartitum’ and planted them in my new border – I’m just waiting for them to flower. The plant stem of the varifolium is very spiky (and sharp!) and should look good in front of my astilbes once they both flower together. I do think the Eryngium leaves are ugly, though, but they tend to sit on the soil and can’t really be noticed.
Globe Artichoke (Cynara scolymus)
Globe artichokes have great spiky heads that sit on 1.5M thick stems, towering above most other border perennials. They contrast well with other plants and can also be eaten; harvest during the summer when the size of your fist. If they have started to open, you have missed the eating slot and will have just to let them flower.
We had artichokes growing in the border of our last property and I miss them; they added amazing drama to the border. I always used to let the flower as I liked the heads with their blue hair, much to my Italian neighbour’s disgust as he loved eating them.
Ferns can be grown in shaded areas of a garden and are perfect for adding textures and different foliage patterns to an area. Ferns come in many varieties, some with flat glossy leaves; for architectural ferns, choose Athyrium niponicum or Dryopteris wallichiana.
Yucca plants are generally grown indoors in the UK as many varieties are not frost-hardy. Yuccas can be grown in pots and left out over summer, but you will need to bring them indoors over winter.
A couple of hardy yucca varieties may survive a UK winter, especially if you live in southern parts of the UK. Both yucca gloriosa and yucca filamentosa have an RHS hardiness rating of H5 – they can withstand temperatures down to -10 C.
Blue Grass (Festuca glauca)
Grasses are fantastic for adding architectural qualities to outdoor space; I particularly love this blue grass variety and have it in multiple areas of my garden. Festuca glauca is very hardy and regarded as ‘drought-proof’, so it can be left unattended if you go on holiday. This grass works well in a rockery setting with alpines or in containers with a few annuals.
Phormium Tenax ‘Joker’
This plant gives you evergreen foliage, providing winter interest when most perennials have died back. Like cordylines, they love salty sea air so do well in coastal regions. Phormium Tenax can reach a height of 100 cm and looks stunning in a contemporary pot. Phormium Tenax also produces unusual flowers July-August.
Gareth is the owner of Plantsman Media. Gareth lives in the North East of England and is obsessed with flowers. He has just started RHS level 2 certification.