Plant lives and how we alter them.In a way a garden is not so much a thing as a process, even the soil changes over years. Meanwhile the plants come and go. In our vegetable and salad beds some last but weeks while top fruit seems permanent though in reality trees are also transient. Few garden fruit trees make a hundred years despite gnarled appearance and spurious measures. Surprisingly your hedge may contain your oldest plants as the continual cutting back confers real longevity far beyond the range of most. In similar manner some crops can be effectively pruned to live a tad longer. Particularly as many annual crops are not actually annuals even though grown as such, some are potentially longer lived anyway, and to our advantage.
Now one group of crops are effectively immortal. Potato varieties are propagated by sets not seed, so every, say King Edward, is effectively a distant disconnected part of the original sport. In a like manner Royal Sovereign strawberries are but rooted runners many times distant, but through one long single direct connection, with the original. A Cox’ Orange Pippin is exactly a twig of the original growing on a new set of roots.
Even so we can measure the duration of the individual plants themselves and how these life-spans change with some intervention.
Our vegetable plots have many rapid short lived crops. Almost all are sown, grow and finish within only part of a year. Some are true monocarpic annuals such as peas and beans; flowering and seeding once, then dying. But if we continually cut off the flower-heads of many annuals before they set seed we can keep a plant alive for a bit longer, and we may get a bonus in the process. This is of use with such brief crops as rocket, pak-choi and many annual herbs such as chervil, dill and so on where if we have failed to sow successional crops we can often get an additional small harvest from an older sowing. This works with a severe cutting back followed by copious watering and feeding, and warm light conditions. Unfortunately though the result is rarely as good as would be the production from a new sowing, but it’s still welcome anyway.
Now although we don’t deflower early we do remove the pods of seeds from peas and beans and hopefully before they have fully ripened so although weakened the plants may theoretically go on to give more. It is claimed to be worth cutting back beans and even some peas after picking to get a second growth, flowering and another, later, crop. I say claimed because despite numerous attempts I have never managed to make this work at all satisfactorily. Still in theory it should work and may be worth trying- especially with a vigorous early variety in a rich soil. The contrary mistake of leaving any pods on to ripen seed certainly stops all further current production of peas and beans which need to be picked clean to give you any chance of any more, let alone a bonus crop later.
Most root crops although grown as annuals have to be biennial by their very nature. Growing one year amassing a huge store of energy so they can flower and seed prolifically, and early, the following year. Their problem is us eating their swollen roots the intervening winter. If left undug the flowering stems from a parsnip or fat beetroot rival the herbaceous border’s best in sheer size and exuberance if not actual beauty. Now if the flowering stem of most roots is cut away as soon as seen and likewise all replacements then eventually non-flowering shoots usually arise. If these are detached with a bit of crown they can often be rooted. This is not awfully useful for such as carrots as not surprisingly it seldom gives a single straight fat root as will a seedling. Skirret and some other roots can do much the same of their own volition and merely need re-positioning. It’s worth doing with celery with the plantlets over-wintered to replace sowing more in heat the next spring.
Onions are naturally biennial bulbs but as with other alliums we have selected for forms that not only set seed but some also more easily form offsets from the side of their bulbs. They do especially so if their flowering stem is cut off and many varieties can so be made to throw more or bigger bulbs. Garlic, well some varieties, seems to multiply even if the original clove is allowed to go to seed. (And if their flower is left untouched then most alliums convert this into a mass of seedlings, or bulbils, giving more ways of propagating them.) We commonly de-flower and multiply by dividing and replanting the bulbs of chives, garlic, the potato onion and most shallots. However you can also do similar with many other onions and leeks which can be made to form offset bulbs if their flower stalk is removed.
Although perhaps more tricky than simply sowing another batch such vegetative propagation is a way of multiplying unusual specimens and keeping them true as is often practiced by champion leek growers.
Most of the Brassica family are grown as annuals but are also naturally biennial as with the roots. The cabbage is a big terminal bud that awaiting till the following spring to burst into flower. A cauliflower is exactly the same except the flowering buds are arrested, temporarily, before going on to flower. Now some brassicas such as romanesco and cauliflowers are most reluctant to live on longer and grow another crop for you after you remove their flower-buds. But sprouting broccolis are more obliging and may throw many flushes, there are even varieties that are near perennial with maybe three years cropping before they become too straggly and unwieldy.
Most gardeners probably know the trick with cabbages- after cutting off the head you cut a cross in the stalk left in the ground. Almost invariably four or more bonus heads will form and, although perhaps not as good as the first, these are still useful. What few may also know though is that if you cut a stalk down low and earth it up you can induce a whole load of rooted shoots. These can be detached and grown on vegetatively so reproducing the original. I thought I’d discovered this for myself but it’s an old trick often practiced in the Tropics and once thought to be a way of avoiding club root. This trick works well with most cabbages, kales and some Brussel’s sprouts but not so well with the other brassicas. Pak-choi and some of the other Chinese cabbage family can be similarly treated- if you cut off their flowering stems repeatedly they throw batches of new leaves and some can be induced to form shoots.
Tomatoes, cucumbers and even melons are short lived perennials and much longer lived and potentially more productive if all fruits are removed as soon as practical. Ripening fruits suppresses new ones forming and especially if conditions are deteriorating ripening seed often brings about the plants demise particularly with the cucurbits. (If your plant is yellowing and dying- you probably missed a fruit!) If enough warmth is available tomatoes and cucumber plants grown from cuttings and slips rooted in late summer can be over-wintered. I must admit the low light makes these difficult and prone to mould, however the aim is not for these to become cropping plants themselves but to be sources of cuttings from which to grow your cropping plants. Because these will come from cropping plants they usefully flower and fruit much sooner than new batches of plants from seed.
On the other hand peppers and aubergines are more dominantly annual and more difficult to root though conveniently most of the hot peppers are actually short lived perennials so given warmth and light those can simply be kept growing and cropping for two or three years with little difficulty.
Sweet potato ‘tubers’ are hard to keep in good condition long enough to start a new batch in spring however if growing tips are rooted to form new plants in late summer then again these can be over-wintered to supply new slips in the spring.
Now the converse- turning to the longer lived crops -although some might live on further it’s the case more often that they are better replaced with newer stock long before then. Asparagus beds could be kept for many decades if initially well prepared and scrupulously maintained. The problem is the crowns expand, eventually becoming dead in the middle as each crowds into the next. Thus in practice fifteen maybe twenty years life for a bed is a likely prognosis. And it’s simply not worth dividing up an old crown- you can divide asparagus but not very successfully unlike with most herbaceous ornamentals, it’s better to start with new. It’s not that you can’t do it but that there is nothing to be gained unless it’s a scarce variety. Likewise rhubarb really does better if divided and moved every five or ten years and globe artichokes the same (And do not let either flower and set seed as it weakens them appallingly). I’m not disputing leaving the plants longer in position is possible, but a prompt replacement will soon be more productive.
Strawberries are another prime example. The books say three or possibly four harvests is all you can hope before you must replace the plants. I have tried several ways to extend their life without success. Even with two dozen varieties in a trial all showed extensive deterioration with only Maxim plants giving any decent fruit by their fifth year.
Raspberries may last longer but even so there are few beds worth keeping beyond ten years, and exactly the same goes for blackcurrants, especially as both pick up virus problems easily. As with a hedge you find methodically hard pruned blackcurrants live longer than those left to run. Both these and raspberries also become obsolete as better varieties soon replace older. Gooseberries and blueberries often simply peter out after fifteen to twenty years though those grown as stools may last longer. Red and white currants go on many decades as they often re-sprout new tops from their roots. The blackberry tribe are also generally long lived making several decades, though their hybrids last somewhat less.
Of the tree fruits any grown in pots are likely to be short lived compared to those in the ground especially cherries. Most stone fruits are not long lived anyway, peaches often live only a couple of decades, plums and cherries not many more. Apple trees are frequently much younger than thought and most live about a human span. Pears can be much long lived if on their own roots, figs and mulberries the more so. The last and hazels if coppiced regularly become very long lived from the treatment much like hedge plants.
But the prize has to go to grapevines which will outlive not just the gardener but even the grandchildren as they grow on and crop on, not just for many decades but for many centuries.