Thinking Outside the Box

Thinking Outside the Box display at RHS Wisley

There's always something new to see at Wisley and I'm particularly taken with their 'Thinking outside the box' trial plot. As you can see, it was an interesting display, even though it was raining at the time.

Enquiries to the RHS concerning box blight and the box tree caterpillar have increased substantially in recent years, and Wisley itself has succumbed to both woes. As it says on one of the information boards for this display... "Sadly we suffer from both problems at Wisley and have only a small amount of box left."

The RHS has plenty of suggestions on its website for suitable small-leaved alternatives to box such as Lonicera nitada, Ilex crenata, yew and various berberis. I've pondered many of these as I'm thinking about replacing my front lawn with a small knot garden. I've decided not to use box because of the potential problems, and had Euonymus fortunei from their list as my front runner. It's being used successfully for this purpose in the herb garden at Barnsley House (scroll down to see the photo on Chatty Gardener's blog post).

Hebe 'Pascal'

Wisley's design is loosely based on a knot garden, so it immediately caught my interest for my own project. It also has a wealth of new possibilities to consider, and has the potential to expand the list of suitable box alternatives considerably. The information display says:

"We haven't found it [Ilex crenata] a strong or reliable shrub at Wisley, so we're looking for alternatives."... 'We are quite confident some of the Berberis, Lonicera and Podocarpus should perform well, and other genera are more of an experiment, so please watch our progress!"

I'm particularly taken with the hebe pictured above as these thrive in my garden. I also like the idea of a tidy and clippable evergreen that flowers in the summer and is attractive to bees. This one has an Award of Garden Merit and won't mind the north facing location of my front garden.

The other striking possibility from this display is that my new garden doesn't have to be just one type of plant. The layout shown in my top photo is attractive in its own right, with a surprising variety (to me anyway) of colours and textures. It also demonstrates how a looser feel can be introduced into what's usually a quite formal layout.

It's just a matter of working through which plants have potential for my garden. I'm keeping an interested eye open for how this trial develops in future.

Here's a list of the plants in the trial

I'm interested if you have any experience of growing these as a hedging or knot garden style plant.

  • Berberis darwinii 'Compacta'
  • Berberis thunbergii 'Atropurpurea', 'Golden Rocket', 'Golden Torch', 'Helmond Pillar', 'Orange Rocket' and 'Rose Glow'
  • Corokia x virgata 'Yellow Wonder' 'Red Wonder' 'Frosted Chocolate' and 'Sunsplash'
  • Eleagnus 'Quicksilver'
  • Eleagnus x ebbingei 'Compacta'
  • Euonymus japonicus 'Microphyllus Pulchellus' (NB its common name is Box-leaf Euonymus)
  • Hebe 'Pascal'
  • Leptospermum grandiflorium
  • Ligostrum sinense 'Sunshine'
  • Ligostrum undulatum 'Lemon Lime and Clippers' 
  • Lonicera nitada 'Maigrun'
  • Lophomyrtus x ralphii 'Kathryn'
  • Luma apiculata 'Glanleam Gold'
  • Pittosporum 'Arundel Green', 'Collaig Silver' and 'Oliver Twist'
  • Pittosporum tenuifolium 'Golf Ball', 'Irene Paterson', Tandara Gold', 'Warnham Gold' and 'Wrinkled Blue'
  • Podocarpus 'Chocolate Box', 'Country Park Fire' 'Guardsman' and 'Young Rusty'
  • Podocarpus cunninghamii 'Kiwi'
  • Podocarpus lawrencei 'Blue Gem'
  • Podocarpus nivalis 'Kilworth Cream'
  • Podocarpus totara 'Aureus'
  • Taxus baccata 'Repandens'
27/10 The above list has been checked and updated thanks to the list posted by Leila Benamer in the All Horts Group on Facebook. I wrote my list in the rain, so a couple of the names were hard to read.

Finally, here's an interesting discovery I made via Chris Young's (The Garden's editor) Instagram feed recently, which shows Pittosporum tobira has the potential for a spot of topiary. This has a H3 hardiness rating, so it's unsuitable for many places in the UK. It'll be interesting to see if any of the hardier Pittospurum listed above have similar potential.

Pittosporum tobira public planting as seen in France

Update: Karen added some extra ideas she's been using via the Comments:

"We are using Ilex 'Green Gem' this year instead of box, the plants come already trained and trimmed as ball shapes, or small sections of hedging for connecting together. I'm also using purple beech trained into pebble or dome shapes. Clients still ask for box, but it's not worth risking it."

Update: Looking great at the end of October, courtesy of Wisley curator Matthew Pottage on Twitter:

October sunset at RHS Wisley and progress with the box alternatives study

Update August 2017: Love this overhead shot I found on Twitter

Overhead view from a cherry picker

Update October 2017: I've seen a couple of gardens using Euonymus 'Green Rocket' to add to the list of alternatives e.g. the revamped knot garden I saw at New Place earlier this year.

Update November 2018: Julie Penny tweeted this photo from the ALL Horts Facebook group visit which shows how the plot has developed. She confirmed that some of the original plants haven't fared well and have been substituted in the trial. Revised list to follow...

Updated view, November 2018

Update June 2020: The latest view from Wisley curator Matthew Pottage. Looking rather gorgeous, don't you think?


  1. We are using Ilex Green Gem this year instead of box, the plants come already trained and trimmed as ball shapes, or small sections of hedging for connecting together. I'm also using purple beech trained into pebble or dome shapes. Clients still ask for box, but it's not worth risking it.

    1. Fantastic to have news of your practical experience and further possibilities, especially for those looking for alternatives that can be shaped. Thanks Karen :)

  2. That hebe does look like a nice alternative to box. Good to see trials are being done as I think box sadly is not a viable option anymore. I look forward to seeing the plans and plants you decide on for your front garden.

    1. Thanks Gwenfar, and well done on all your mentions this week :)

  3. You might be interested in visiting the Bishop's Palace gardens in Wells - we were there today and I thought of this post as they were using a small-leaved variety of Euonymus as an alternative to box edging for one of the gardens, after losing their box to blight. I thought it worked well - not as pretty as the hebe, but quite striking and would be good for a knot garden.

    1. Ooh it's some years since I visited the Bishop's Palace and there certainly wasn't anything like that when I was there. I wonder if they've used the same Euonymus cultivar as the one at Barnsley House in Chatty Gardener's link?

    2. No, I don't think so, VP - it is a more upright-looking one clipped short, maybe green spire or green rocket? I'll try to sort out a photo to show you when I have time - might take me a week or two though as R is off work for a couple of weeks so we're really busy!


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