I've discovered that wild rocket is a really useful perennial vegetable! Although the 'wild rocket' that is grown for selling in supermarkets is sometimes an especially peppery form of the annual or salad rocket Eruca sativa, the plant I'm interested in here is Diplotaxis tenuifolia, also commonly known as perennial wall rocket.
Wild rocket (left) Salad rocket (right)
A comparison of just the leaves of the two plants reveals that perennial wall-rocket has rather finer, more deeply serrated leaves than you usually see on salad rocket and that the leaves are similar but more fiery in taste. If you see the whole plant, especially in its second or later years, you'll be looking at a low-growing spreading clump with slender but quite woody-looking stems. Provided you're happy with its hotness you can use it in all the same ways as salad rocket.
Wild rocket has been a revelation to me. The first time I grew it it didn't come to much - becoming straggly and unproductive rather quickly and rotting off over the winter. But then I saw that a plant I had given a friend had grown into a beautiful dense mound of fresh green leaves and had, she told me, been supplying herself and her daughter with plenty of salad leaves for weeks.
Its name came up again in the course of my efforts to find a better range of plants for a narrow dry shady border at the base of a wall in our backyard. Planted there it suddenly flourished and overwintered with no problem. I trimmed the branches by about two-thirds in the late autumn to stop them flopping over the bricks onto the path and to keep it bushy when they began to sprout again early the following spring.
Wild rocket in April
I've been amazed by just how obliging it is. It would be interesting to see how it would get on in a gravel path, in pockets of soil on the top or sides of a wall or in a hanging basket. We pick it a lot for salad leaves and it doesn't get much of a chance to flower - but when flowering has taken place it doesn't seem to have been to the detriment of leaf production.
I made wild rocket pesto tonight to eat with spaghetti. I harvested quite a lot of leaves and left the plant with a messy crew cut but snipped each bunch of leaves above the growing point so that they will replenish themselves quickly.
I wanted 100g of rocket leaves for the recipe I was following - loosely following: I used hazelnuts instead of pine nuts to reduce the cost (and also because I like to use ingredients that I could easily grow myself) and I used hard goat's cheese instead of pecorino because there was none of the latter in the shop! But I could only gather 50g of leaves from my plants and so Caucasian spinach leaves and parsley made up the weight.
Wild Rocket Pesto
Wild rocket is fairly expensive to buy in bags from the supermarket but it's very easy to grow your own from seed (I may have plants available to buy). It doesn't need a fully sunny spot, is happiest in poorer, dryer soil and produces lots of leaves in a small space and for a long time. Other than the shade-tolerant, climbing Caucasian spinach I can't think of a more useful plant for a backyard larder.
N.B. I sell a range of perennial vegetable plants on my website.