So once again, there is a hosepipe ban imposed across eastern and south-eastern England and Grantham is included.
The reasons for the ban are clear – if everybody takes care over their water usage now, the supplies we have will last longer, the rate at which we deplete them will decrease and the chances of more serious problems down the line will be reduced. It will also reduce pressure upon our reservoirs and waterways which will have clear ecological benefits. In summary, I am in favour of the ban.
However, it does appear short-sighted of the water companies to not exclude watering vegetables from this ban. It shows just how far we have become separated from our food and any form of self-sustainability that watering vegetables is considered a non-essential use of water, along with washing the car and hosing down the patio. Growing your own food should not be considered a luxury we can do without.
Technically, we can water with a watering can and therefore keep our own crops alive, but I know of many people who are not growing their own this year because the time and effort required to keep them alive without the use of a hosepipe are too great. This means, that more people will be buying their vegetables from the supermarket.
There was a study produced by the WWF in 2008 which looked at the water footprint of different countries and different crops. In the same year, a paper was published at waterfootprint.org which provides a table of average water footprints for a range of different produce. This takes into account, not only the quantities of water required for the industrial scale watering and growing of these crops but the water uses involved in processing, transportation and retail as well as accounting for pollution caused by nitrogen fertilisers and other harm to water supplies.
Taking a simple example, the average water footprint of 1kg of tomatoes is quoted as 180 litres of water.
Now logic dictates that removing all of the supply chain, haulage, processing, retail (including spraying vegetables with water to keep them fresh and other such activities) should reduce the water footprint of a home-grown tomato drastically. Even in terms of simple watering, your garden soils will hold a lot more water than arable fields where the soil structure is damaged from years of intensive agriculture.
So how much water would it use to grow tomatoes at home? A quick back of the envelope calculation from a few sources on the internet:
The average tomato plant produces around 2.5kg of tomatoes.
The water requirement of a tomato plant varies between 0.14 – 1.8 litres per day, depending upon the weather conditions. I am taking the figure of 1 litre per day as the average for ‘fairly sunny’ – ‘sunny’ weather as this will probably work out approximately correct across the average English summer. This is for the grown plant as well so it would be a conservative average as I am including the pre-flowering and pre-fruiting stages in the next step.
The average growing season, from the point at which the seedlings have developed to the point at which they are ready for harvest, is around 3 months, 90 days.
In theory therefore, a home grown tomato should be able to produce 2.5kg of fruit for 90l of water. If we scale the water footprint of commercially grown tomatoes up to the 2.5kg level, this is a huge 450l of water. A home grown crop of tomatoes should produce the same yield using one fifth, 20%, of the water required for a commercial crop of the same weight.
Whilst I accept that a few things may be missing from this calculation; you will probably wash your tomatoes when you bring them in, you may use a small amount of fertiliser etc., this is unlikely to make a big impact on the huge scale of the difference between these two figures.
Overall therefore, people should be encouraged to continue growing their own produce if we want to save on water use and deterring people from doing this seems short-sighted on the part of the water companies. I have framed this argument entirely in terms of water but there are of course multitude other advantages to growing your own – it cuts down on fertiliser, pesticides and carbon emissions as well as other greenhouse gasses and, of course, it tastes better.
Therefore, whilst I do support the hosepipe ban, I feel there is a strong argument that vegetables and other home produce should be excluded from this.
Grantham Ecology 
Hello. I’ve never commented on your blog before, although I’ve been reading since you started it. I must say that I disagree with this post, and in fact think you’ve used a circular argument in your argument for the use of hosepipes in veg growing.
A hosepipe uses 10-20 litres of water a minute. Using your facts above, assuming tomatoes need 1.8 litres of water a day, most get drowned when watered with a hosepipe, and lots of water will be wasted. If they’re getting watered every day during the summer, for 20 secs each, that’s 3L of water per plant (assuming an efficient hose at 10L/min and rounded down). If we assume that there are 25 rainy days in the summer months (which is the east of England average) and that the plants are kept outside, one plant will be watered by hand on 67 days through June-August. That’s 201 litres of water used already, before you include April and May growing, lots of tomatoes are grown inside to keep them warm (so don’t get the 25 natural watering days), most hoses will use more than the 10L/min figure used here, most gardeners will leave their hoses on a plant for more than 20 seconds and some may water twice a day.
I never water my veg with a hosepipe, and I do think it’s wasteful to do so. Obviously I’m not including farmers in that, since they have huge areas to farm, but allotments and gardens should be watered with watering cans. Using a hosepipe is simply not necessary for these smaller growing projects.
(I’m ignoring the fact that hosepipes are easier, as did you in your post! Obviously if you can’t carry a full watering can then the arguments for using a hosepipe are different!).
Anyway, sorry that my first comment is an argumentative one! This is an issue close to my heart (and interests) and I couldn’t resist.
Thanks for your comment and an argumentative comment is most welcome! I meant really to pose a question… although it may have come across a little more strongly than that!
I think my fundamental point is that you NEED less water to grow something like a tomato at home in comparison to a commercial operation, and I do think that my figure of 90l is about right because it assumes three months of watering which would be sufficient even for a plant grown inside (according to the table of figures I found and linked to in the post).
But I do agree with you; that there is a difference between how much water a plant empirically needs and how much the average gardener might bestow upon it. In this sense, a gardener with an aching arm from carrying a watering can is more likely to water it correctly than a trigger-happy hoser. But then, even if we gave each plant 4x the amount of water it needed every day, that would still come in at around 60l less than is required to grow the crop commercially.
I do still agree that flower beds, lawns etc. should remain excluded would also hope that, if the average gardener knew that there was a hosepipe ban on the rest of their gardens, they would take that extra bit of care to make sure they weren’t overwatering their vegetables. Perhaps a little optimistic…
But to say that vegetables should always be watered with a watering can does make some assumptions about the size of vegetable growing and the distance to the tap – our 50m hose is at full stretch to get to the vegetables (it has to loop around the house) and I would estimate that all of the veg we grew last year needs around 25l of water (tomatoes, runner beans, mange tout, lettuce, spinach etc. etc.) on a warm day. This would mean half a kilometre of walking to fill five 5l watering cans which is quite an additional burden on a daily basis after work etc. I’m quite happy to do it, and intend to, but some people I know have been put off growing this year due to this scale of extra work required to keep them alive and healthy.
I think the point is, people should be encouraged to grow their own as this will save the UK’s water supplies at a faster rate than making people dependent upon buying supermarket vegetables grown with excessive water use because of the scale at which they are produced.
But then I do also agree that the vegetables are more likely to be watered correctly under a hosepipe ban. I suppose the question is where the balance lies between encouraging people not to over-water their vegetables but at the same time, not put people off growing them altogether as this really is more efficient, if done properly.
Thanks again for the comment, I hope it has balanced the argument a little!
Thank you for your reply 🙂 in my garden, the tap is at most 4m away from my veg, so I don’t have to walk very far. At the allotments though, hose pipes are not allowed anyway so we have to walk what feels like miles (it’s not really, it’s 10-50m depending on which trough has water) to water the veg. The clever gardeners use their wheelbarrow and put lots of watering cans in it so they don’t have to do so many journeys. I’m not clever and I just carry two cans at a time!
I agree with you that veg gardeners should be trusted to look after their veg and not waste water on flowers etc in times of drought, but I can just imagine the arguments that would ensue if the government valued someone’s tomato plant over someone else’s prize roses! For now, I think hose pipe bans are the best plan we have for saving water, at least until water butts and veg patches become compulsory in all gardens!