This narrow bed is right at the front of our house at the foot of a south facing wall. It’s a hot, dry situation, and being less than 2ft (0.6m) deep but 12ft (3.6m) long, it has always been a challenge to plant successfully. As you can see the bed is surrounded by a low box hedge, which is in need of clipping. (See post on clipping this hedge here). A couple of years ago I redesigned it with several long-flowering perennials that might tolerate such an environment, and as you can see, it has been quite a success.
The effect is particularly good when viewed from the front door, where one looks along the bed. It has a naturalistic meadow effect reminiscent of dry steppes. The emphasis on yellows and purples helps the plants blend together nicely. I like the sword like leaves of the Sisyrinchium which provide the grass-like structure.
Plants for a hot dry bed
1. Allium atropurpureum
Height: 75-90cm Spread: 10-15cm Flowers: May-June
This ornamental onion is native to Hungary, the Balkans, and Turkey. It is widely grown as for its rich, deep purple flowers. It is easiest to grow from bulbs which can be planted in the autumn to flower the following spring in May/June. They are easy to grow and tolerant of dry soils. They open from large buds, exploding outwards like a slow motion firework into a spherical head nearly 3inches (8cm) across made up of many star-like purple flowers. The foliage dies back quickly leaving the seed heads to ripen.
2. Yellow-Eyed-Grass (Sisyrinchium striatum)
Height: 75-90cm Spread: 60-70cm Flowers: May-June
This unusual member of the iris family is an easy, if short lived, perennial that thrives in hot dry locations. It forms a clump of grey-green sword like foliage, reaching 2ft across in three years, from which rise numerous spikes of pale biscuit-yellow flowers to a height of 2ft 6 inches (75cm). The reed-like stems zig-zag slightly, with buds emerging at each node, creating a tiered effect with blossom on several levels at once. The flower colour is more vivid at the centre leading to its common name of yellow-eyed-grass. In the garden it needs full sun.
On the downside the foliage loses its freshness by late summer with some leaves turning black rather early. These can be removed to spruce it up. Also, the flower stems can become top heavy and flop over, so staking may be required. Plants may need replacing every four years or so.
3. Perennial Wallflower (Erysimum linifolium glaucum ‘Bowles’s Mauve’)
Height: 60-90cm Spread: 60-90cm Flowers: Mar-Aug
This perennial wall flower grows fast and flowers profusely. It needs full sun and prefers an alkaline soil. Flowers are produced from early in the year and continue until late summer, with new buds constantly forming at the tip of the stems. If left the plant can become leggy with masses of spindly stems, but these can be cut back regularly which encourages new shorter spikes to form. This plant believes in the adage ‘live fast die young’ and will burn itself out in a few years, but that’s a small price to pay for such reliable flower power. Unfortunately, this variety is not scented.
4. Perennial Wallflower (Erysimum ‘Walberton’s Fragrant Star’)
Height: 40-70cm Spread: 40-70cm Flowers: Apr-Aug
Less vigorous than Bowles’s Mauve, but this perennial wallflower is fragrant! Furthermore the foliage is variegated with a pale yellow edge to each leaf. The rich buttery yellow flowers emerge from purple-brown buds. Like Bowles Mauve flower spikes benefit from trimming if they start to get leggy.
5. Star of Persia (Allium christophii)
Height: 40cm Spread: 20cm Flowers: May-June
This ornamental onion can be grown from bulbs planted in the autumn. They produce large flower-heads nearly 8 inches (20cm) across composed of hundreds of fine starry metallic-purple flowers. By the time of flowering the leaves are already withering away. During August the seed heads dry to a tawny brown. They are quite ornamental, so can be left or removed.
An Englishman's Garden Adventures 
Your garden has turned out really lovely! I’ve come to really like Sisyrinchium. We inherited it in a garden in the far south of New Zealand. It not only tolerated our (few) dry periods really well but coped wonderfully with our ever-present gale-driven rainy westerlies and cold weather. Initially I didn’t like it because it had self-seeded all over the place but I found I could plant it as a (low) hedge against the horrid winds and it was enough to give other more sensitive plants a sheltered start. So easy to transplant so I’d just dig unwanted weedy ones out and then plant them together as a shelter, and they were so reliable!
Hello again Exploring Colour! That’s good to know. I actually like plants that self seed but are easy to remove. It’s like being given free plants isn’t it? Two of my favourite seeders are Assarum and Ruscus; oh and Hellebores as Its interesting to see what flowers they have. Aqualegia seed everywhere here too, even travelling 50ft from the front garden to the green roof at the back of the house! They too are always interesting for their colour or form, if a little too prolific. I try to remove their seed heads every year to stop too much self seeding. On the green roof the grasses and pasqueflower seed far too liberally – they would completely take over if not carefully cut back before setting seed.
I love pasqueflower but haven’t grown it myself so didn’t realise it spreads so liberally. Good to know thanks!
I think the conditions on the green-roof suit it perfectly. I have grown it in several other locations and it has been far more reluctant to self seed.
Very interesting! Thanks Keir!