One year’s seed is seven years’ weed Who wants to spend hours bent double doing a job that will only need to be repeated in a matter of weeks? Well me, for one. Thanks to my strict Wisley Dormancy is a state of seeds and buds in which they are alive but not germinated. If all weed seeds were to germinate at one time, their seedlings could be destroyed. Dormancy allows storage of millions of weed seeds in soil and enables them to grow in flushes over years. In this context, the old gardeners saying “One year Seeding seven years weeding” is very appropriate. In fact, weed seeds have been found viable even after 20-80 years of burial in soil. Whenever fields are cultivated, weed seeds and propagules of perennial species germinate and grow. Most have been produced in situ in weedy crops of the past, a fact that has given rise to the prediction embodied in the title of this chapter. In the context of this…
One year’s seed is seven years’ weed
Who wants to spend hours bent double doing a job that will only need to be repeated in a matter of weeks? Well me, for one. Thanks to my strict Wisley training I find it difficult to concentrate on the greater picture when I know that there’s weeding to be done.
You could argue that a weed is only a plant in the wrong place. In New Zealand, lupin, gorse, cobaea and ginger, all of which are colonising native habitats, are treated as weeds by local gardeners, while in Britain we have a growing list of notifiable weeds that were originally introduced as garden ornamentals. Heracleum mentagazzianum, the giant hemlock, is using waterways to float its boat-shaped seed to pastures new. Japanese Knotweed is pushing up tarmac and buddleia, once introduced as an exotic ornamental, is now part of our industrial landscape. Indeed, it loves the urban jungle so much that it turned the bombsites purple after the Blitz.
My childhood friend Geraldine had a garden that was, by some standards, full of weeds. Her bearded iris battled it out with wild oats and scarlet pimpernel. She would part a tussock of grass to show me her thriving Fritillaria pyrenaica and the raspberries always came with a sting from the nettles. The truth is, she knew where her plants were and what they needed to survive the competition from these weeds: the pimpernel was a happy accident, the nettles food for the butterflies. It is all a question of interpretation.
My definition of a weed is a plant that does not fit in with the chosen scheme because – given a chance – it will overwhelm everything else. Brambles were not welcome in my London garden because there was simply not enough room for them and they took two years to clear, but in a country setting I would not want to be without a patch to pick in the autumn. Now that the garden is cultivated, the enthusiastic self-seeder Verbena bonariensis is potentially the greatest problem I have.
There is also the question of balance. The yarrow took over a newly established meadow that I sowed in a garden on the South Downs. It loved the thin alkaline soil and outgrew its companions in the first two years. The client was all for digging it out – hours of backbreaking work – but he was persuaded to leave well alone and, in year three, the slower-to-establish perennials and wild grasses caught up and crowded the yarrow out.
So a weed is a plant that competes for food, water and light, and will check the growth of anything more demure. Even a young tree will be at risk until it has established a large enough root system to supply it with sufficient water and nutrients. Keep a yard diameter clear at the base for the first three years and it will literally put on twice the growth of a plant left to fend for itself.
The great secret is to start with ground that is free of all perennial weeds. Couch, equisetum, ground elder, dock, bindweed and creeping thistle are just a few of the worst offenders and I would prefer to see ground left bare for a year to rid it of any of these than to plant a pending disaster.
To clear the ground you have several options. I am all for the organic approach if you have time. Forking over the soil to get the bulk of the roots out is worthwhile but every little piece left behind will be a potential cutting, so the process may need to be repeated several times and left for a month to six weeks in the growing season to make sure there is no regrowth.
Putting in potatoes is a good idea. Planting and cropping offer opportunities to turn the soil and most annual weeds will be smothered by the vigorous potato foliage. The reward for all your effort will be in the eating.
Opaque mulches are another alternative which can be very successful. A layer of black plastic or several layers of cardboard laid over the ground will kill most perennial weeds in a growing season. Some weeds, however, are more persistent than others – in one garden I was astonished to find bindweed writhing around after a full year of mulch. This was the same plant that went 7ft deep in the clay bank we excavated. That would require some digging out, so we resorted to Glyphosate. The safest of all the systemic weed killers, this is rendered inert when it comes into contact with the soil and works best when applied to foliage that is in full growth.
Only this spring, I was forced to delay a client’s planting because a new garden that had been prepared over the winter came back with flushes of couch and thistle in April. I was intending to plant most of the garden with ornamental grasses, but weeds among the ornamentals spells complete disaster. Once entangled, they are impossible to separate. We had thought the autumn spraying of Glyphosate would be sufficient, but hadn’t bargained for the slowdown in autumnal growth.
Weed seed in the ground presents a less serious problem. Once you’ve dealt with the perennial bullies, seedlings and annual weeds will be the main issue. These need to be pulled before they seed or get a hold, as one year’s seed is very definitely seven years’ weed. It is best to do this little and often, parting all foliage to find those lurking in the shadows. Hoeing is a great way to work through your beds on a sunny day if the ground has not been mulched – if it has, you would not want to disturb the mulch and reduce its weed smothering properties. A final reworking over the same space immediately after you have finished will always reveal a straggler or two just waiting for your back to be turned.
One Year’s Seeds Seven Years Weeds
Dormancy is a state of seeds and buds in which they are alive but not germinated. If all weed seeds were to germinate at one time, their seedlings could be destroyed. Dormancy allows storage of millions of weed seeds in soil and enables them to grow in flushes over years. In this context, the old gardeners saying “One year Seeding seven years weeding” is very appropriate. In fact, weed seeds have been found viable even after 20-80 years of burial in soil.
1. Enforced dormancy – It is due to deep placement of weed seeds in soil during ploughing of the field. Weed seeds germinate readily when they are restored to top 3-5 cm. Enforced Dormancy is a non-specific character of seed. Cultivation encounters enforced dormancy by bringing the weeds to surface where they are exposed to light besides better aeration. High soil temperature and NO3 content of surface soil may further help in breaking seed dormancy.
2. Innate dormancy – It is a genetically controlled character and it is a feature of specific weed seeds, which fail to germinate even if they are present in the top 3–5 cm soil, and adequate soil moisture and temperature provided to them. The possible reasons are the presence of (i) hard seed coats e.g., Setaria, Ipomoea, Xanthiums pp. and (ii) immature embryos e.g., Polygonum. In certain weed seeds particularly of Xerophytic origin, presence of inhibitors is responsible for innate dormancy. It can be overcome with passage of time, or under the influence of some climatic pressure.
3. Induced dormancy – Induced dormancy results from some sudden physiological change in normally non-dormant weed seeds under the impact of marked rise in temperature and or CO2 content of soil, low O2 pressure, water logging etc. Wild oat (Avena fatua) seeds exhibit all three kinds of dormancy.
One Year’s Seeds, Seven Years’ Weeds
Whenever fields are cultivated, weed seeds and propagules of perennial species germinate and grow. Most have been produced in situ in weedy crops of the past, a fact that has given rise to the prediction embodied in the title of this chapter. In the context of this book the term seed includes true seeds and the functional seeds (actually fruits) produced in the grasses and in several other plant families. Most perennial weeds produce seeds but may in addition reproduce asexually by means of bulbs, rhizomes, runners and other structures. Seed production by several species, including Dandelion (Taraxacum officinale) and Bramble (Rubus fruticosus) is essentially asexual because the seed is not always produced following sexual fusion, but instead generally contains diploid cells which are identical genetically with each other and with the parent. From the weed control point of view, such apomictic seeds are essentially similar to the homozygous ones produced by habitually self-pollinating species. In addition to increase by seed and vegetative means in situ, seeds are brought to the field as contaminants in crop seed, in soil, manure, straw or on farm machinery, in irrigation water and attached to animals; many seeds, especially those of the Compositae and of some trees, are windborne. Propagules arriving with the crop seed are in a specially advantageous position, often providing new introductions.
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