Perennial vegetables are a beautiful, low-carbon alternative to sowing from scratch every year, says expert edibles grower Mark Diacono
By Mark Diacono
The neighbours think I’ve lost it. For the past few weeks they’ve seen me kneeling in the garden, head close to the ground, looking like Jack Nicklaus lining up a winning putt. What they don’t know is I’m at the head of a line of asparagus, looking for the first green noses to break the surface. The first harvest of the growing season – and to my mind the best.
The secret to the finest asparagus in the world is time – getting it from plot to plate as quickly as you can. If you’re a bit of an anorak you’ll have the water boiling before you cut the spears so that you can enjoy them sweet and succulent before the rapid conversion of sugars to starches takes over. Taste home-grown asparagus once and you’ll never reach for the year-round Peruvian supermarket stuff again.
This month, buy year-old plants (known as crowns), and when they arrive choose a well-drained space. Dig a trench to a spade’s depth and width, incorporating a little compost or well-rotted manure, and create a 4in tall mound along the floor of the trench.
Space the crowns 20in apart along the ridge, backfill and water well. Allow 30in between rows. You can even sow sorrel and chicory (both delicious, perennial salad leaves) in the space between rows. The rows will need weeding once in a while but other than that you’ll just need to sit on your hands until next spring when the spears poke through the soil.
However tempted you are, don’t cut any – let the crowns establish. The torture of the wait is more than repaid by decades of springtime eating, starting the following year when you can slice off the wonderful spears that keep popping up for a month or so. When growing such fine food is this easy it almost feels like cheating.
So good, so early and so effortless… so why aren’t we growing more food that works like this? Planted once, then harvested for ever and a day? Most fruit and herbs are perennial but when it comes to veg, a combination of history and habit seems to dictate a frenzy of planting and sowing from scratch every year.
We copy commercial growers who’ve relied on cheap energy, once provided by horses and now by fossil fuels, to do all the turning of the soil, sowing, weeding, watering, fertilising, harvesting and collecting of seed that goes with growing annual vegetables.
This has reached such an extraordinary state of affairs that the food we buy takes around 10 times the energy to produce as the energy it gives us. According to research carried out by London’s City University (An Inconvenient Truth About Food, Soil Association, 2008), its carbon footprint is huge, due in large part to the use of man-made nitrogen fertilisers – a tonne of which requires one tonne of oil and 108 tonnes of water to make, releasing seven tonnes of greenhouse gases in the process.
Rising prices and dwindling resources are further incentive to grow some of your own food, but if you take out the oil you have to replace it with elbow grease. The alternative is to grow more delicious, low-maintenance, low-energy perennials like asparagus.
Perennials are an increasingly important part of how we feed ourselves and how we garden. They offer the ornamental garden productivity and the productive garden beauty.
Many allotmenters tend to graduate to perennials having served their apprenticeship on annuals; newcomers to edible gardening are often interested in permaculture and low-carbon growing; others who just fancy delicious food without the slog are increasingly starting off with them.
Low carbon food has some compelling arguments going for it – but perhaps the best reason to grow perennial edibles is this: when you can be eating the very best home-grown asparagus, rhubarb, sea kale and garlic cress right now, it’s hard to think of a reason not to.
Plenty of choice
There are dozens of perennial vegetables from every corner of the vegetable world to choose from, and to suit all sizes of garden, including salad leaves, brassicas, roots, onions and edible flowers.
If you’re looking for something architectural, you could do worse than globe artichokes, with their ragged grey/green leaves and towering flowers. It not only looks a treat, but the flesh of the immature flower heads is delicious.
The almost identical cardoon will serve the same ornamental purpose, but it’s the main rib of those huge leaves that makes it to the kitchen. Both can be raised easily from seed or bought as fast-growing, hardy plants.
There are wonderful perennial alternatives to the staples – of the many perennial onions, my favourite is the Egyptian walking onion. You can snip off a few early chive-like leaves, leaving the rest to grow on into spring onions. Pinch some off to enjoy in April and May – the rest will grow taller and begin to develop bulbils on the end of the leaves.
As these grow, the leaves struggle to hold them up and bend slowly to the ground, where the bulbils take root. Harvest a few and allow some to grow into new plants that repeat the cycle as they “walk” around your garden. At the base of the original plant you’ll find shallot-like bulbs, making four harvests every year from the one perennial plant.
And if you’re looking for an alternative to the potato, try oca, another South American tuber that resembles a new potato but tastes a little lemony when just picked, sweetening if matured in the sun, and immune to blight.
There are perennials to harvest at any time of year, but where they really come into their own is early in the season, during the “hungry gap” when few annuals have germinated, never mind grown. This week you could be enjoying garlic cress, sea kale, asparagus and forced rhubarb.
Things of beauty
Generally speaking, perennial vegetables tend to be more beautiful than annuals – or rather, we allow them to be.
Think of day lilies, globe artichokes, cardoons, Jerusalem artichokes – all make a striking presence in the garden, largely because we don’t chop or dig up the whole plant in its prime.
Our relationship with them is quite different from annual veg – it’s in our interest to keep the plant alive and healthy, harvesting a little each year while nurturing the plant for the next.
They’re around for longer, which allows you to include them as a more enduring part of a garden. Being there year-round, in varying states, also broadens their ecological value for a wider range of other organisms.
The soil is also nurtured when growing perennials, as it is rarely, if ever, left exposed to the forces of erosion, rain compaction and nutrient leaching. Digging – which can upset a perfectly balanced soil ecology, expose weed seeds for germination, as well as releasing carbon into the atmosphere – is also minimised. You’ll generally find disease and pest problems much reduced as most perennials out-compete weeds and resist slugs.
I’m not advocating a wholesale move of your garden or allotment over to edible perennials – well, I would but most of you would ignore me – but I am encouraging you to integrate some with the annuals and ornamentals.
Add a few true perennials, some edible prolific self-seeders such as nasturtiums and sweet cicely, along with some cut-and-come-again leaves and you’ll have a productive, beautiful and low carbon garden.