Welcome to the Organic Growers Alliance, and to the first issue of The Organic Grower – its magazine.
A weed, they say, is a plant growing in the wrong place. However, there is more to it than that.
We have an “arable weed” - weasel’s snout (or lesser snapdragon), Antirrhinum orontium, which crops up now and again. When I see it in the row I build a little palisade of stones around it so that it doesn’t inadvertently get grubbed out. It’s a rarity you see. What makes a real weed is numbers.
By this reckoning Fat Hen, Chenopodium album, is a weed indeed, common on disturbed ground throughout the temperate and not so temperate world and associated with the cultivation of soil since cultivation began. As such it has many local names. In the Westcountry we call it lamb’s tongue. Another name, “muckweed”, speaks of its liking for dung heaps. In Old English it was called melde - commemorated now in places with names like Melbourne (Cambs) and Milden (Suffolk). At least - the villagers of Milden believe so and in this belief have erected a six foot high wrought iron statue of Fat Hen as their village sign. Not so daft as we might think - the plant long had an honourable place in the diet both for its quite tasty (and high vitamin C) leaves and for its nutritious seeds.
When provided with the conditions that it likes Fat Hen can become not just numerous but beyond enumeration. One plant here or there would bother no one, but it won’t stop there. A neighbouring vegetable holding to ours became submerged in it - to the extent that first the crops and then the business went under. Obviously it doesn’t have to be like that, but before considering control it is helpful to know something of the nature of the beast.
There are several characteristics that give Fat Hen its ability to become dominant in vegetable crops. One we have to accept is its liking for high fertility. Another - its preference for open spaces, and hence its partiality for row crops rather than cereals - we may be able to influence through undersowing. Its special strengths lie in its adaptability, its seed producing abilities and in the nature of the seeds produced.
C.album is morphologically plastic, that is to say its form is markedly influenced by surrounding plant density and by soil fertility. A late germinating plant or one growing in unfavourable conditions, will flower on a stem no more than two or three inches high, if that is the best it can do; while an early established plant with everything to its liking is capable of forming a substantial spreading bush, and even of standing taller than a man. Emergence is concentrated in the late spring (the plant is not frost hardy) but seeds will germinate throughout the summer. It steals a march on other weeds (and often the grower) by its ability to germinate even in dry conditions. Once beyond about the six leaf stage it is very tenacious of life. When pulled up the least contact of root and even faintly damp soil will enable it to re-establish itself.
A disadvantaged plant may produce only a few dozen seeds, but a well-grown specimen can shed 150,000 or more. The average yield is around 3,000. About 5% of these seeds are soft-coated and brown in colour. These and immature, greenish seeds germinate readily. The majority are hard-coated and black, and remain dormant for varying periods of time. Research has shown that 65% can remain viable for 20 years in undisturbed ground, while a small proportion may stay dormant for 100 years and more. In our first year of cultivating ground that had not been ploughed within the memory of the oldest farmer in the parish (he was then about ninety), lamb’s tongue and black bindweed were the only annual weeds we saw.
Seeds will survive either ensilage or digestion by ruminants, but usually not both. They germinate readily from stacked manure, and although at least 90% are destroyed by composting - that may still leave many that remain viable.
While cultivation does little to deplete the seedbank (due to the seed’s potentially long dormancy), the greater the soil disturbance - the greater the germination of Fat Hen seeds whose time has come. Additionally, more seedlings will emerge from a fine seed bed than a rough one. These two factors indicate that cultivation should be kept to the minimum.
Despite the above advice - one extra cultivation is always desirable when the grower is faced by any annual weed problem, and that is the making of a false seedbed. It may indeed be crucial, if a massive weed control operation is not to become necessary in order to save the crop. Often the weather fails to co-operate (and irrigation is a poor substitute for rainfall in stimulating weed germination), but a delay in sowing a crop to allow for the working out of a weed flush will usually pay dividends, particularly as weeds that get away have implications not just for the host crop but for many cropping years to follow. With Fat Hen one might even say - ‘one year’s seeds, a hundred years of weeds’.
If the false seedbed can be followed by a stale seedbed so much the better. Weeds can then be flamed off before a drilled crop emerges, or rubbed out by the planter bodies in the case of transplanted crops. Other than its lack of frost hardiness, susceptibility to flaming is Fat Hen’s only weakness.
Once the crop is growing normal methods of control apply to Fat Hen as to other weeds. Keeping its tenacity in mind it should be dealt with when small. This rule applies to all weeds, of course, but because of the number and the nature of the seeds produced by Fat Hen there is a case for giving the work priority if it is present. The final line of defence is to hand pull mature plants before they shed their seed. This is only feasible if prior control has had an effect and they are not present in vast numbers. When the frost comes and all your Chenopodium album plants are reduced to tatters and stalks their presence may be less obvious on the eye but their posterity lies assured, in the ground.
Tim Deane
An excellent range of comprehensive and concise leaflets on individual weeds, and a guide to annual weed control in general, have been produced as part of the DEFRA funded, HDRA led project “Participatory Investigation of the Management of Weeds in Organic Production Systems”. These are of great practical use and highly recommended.
The website also contains pages on:
• Individual weed species or problems
• Management techniques and weeding kit
• Crop management strategies for individual crops
• Individual farm case studies.
Leaflets are downloadable from www.organicweeds.org.uk or on request from HDRA.
Contact Gareth Davies: gdavies@hdra.org.uk (024) 7630 3517