The Art of Watering

29th July 2006

Tracy Wilson on how to help your plants to survive

Depending on which bit of the country you’re in, you’ve either been suffering from drought restrictions for over twelve months now, or, like us in the south west you don’t actually have drought orders yet but the plants themselves are starting to suffer from what has been one of the best – or, depending on how you look at it, the worst– summers that we’ve had for some considerable time. The rainfall, certainly down here in Cornwall, up until the end of May was quite high. Since then, we’ve had very low rainfall and increasingly hot weather, although nowhere as hot as in the south-east – which I’ve experienced at first hand and was quite debilitating.

When to water

If you can imagine how you feel in the hot weather, it’s pretty much exactly how your plants are feeling. People panic and dash out at midday when they see a plant flagging, looking all faint and weak and wibbly, and they dash out to throw water at it. Well, the chances are that it’s not actually lack of moisture at the root which is the cause of the problem: it is that the plant is actually expiring moisture faster than it can take moisture up from the ground and the best thing you can do for it is to shade it from the sun and that will probably give it the best level of protection you can offer it. You can – and this is when people tend to run off to have a screaming abdab when I say this – mist the foliage because it stops them from expiring moisture through the foliage. Everybody panics at the thought of putting any water at all on plants during the daytime because they’re worried that they’re going to get burning of the foliage. Well, I can only tell you that from my own personal experience, if I didn’t water 24-hours a day I’d have an awful lot of very dead plants at the nursery. Water on the foliage doesn’t make a hoot of difference, you make get the occasional bit of refraction happening through a water droplet that might cause a smidget of burning, but believe me that is an awful lot more preferable to the whole plant keeling over because you haven’t watered it at all! It doesn’t matter two hoots! You think of all the times you have a summer shower and then the sun’s out ten minutes later – nobody goes round drying all the leaves off. So it doesn’t really matter at all. The main reason for watering at the beginning of the day and in the evening is that the plants can make more use of it and the soil can absorb the moisture without it all literally evaporating from the soil due to the sheer heat of the day, so that’s the main advantage of watering in the cooler hours. Without doubt it is better, the plants have got longer to take the moisture up. But if it’s a matter of life-and-death, I know which I’d go for: so don’t worry.

How often to water

There are a lot of myths surrounding watering, and these can cause your best-est and precious-est plant to take quite a setback. I was talking to a lady only earlier this week. She rang me up to say that a plant she'd bought wasn't looking very good, the leaves were quite yellow although she’d been watering it every day. I said ‘Is it in the ground?’ and she said, ‘Yes, it is.’ I said, ‘Ah…’ She said ‘What do you mean, “ah…”?’ I explained that the chances are she was killing it with kindness. A lot of people seem to think that they have to go out every day with a lance on the end of their hose and sprinkle some water round the garden, and they’re out there for hours. In fact they’re probably playing water on any given square inch of soil for less than a couple of seconds – that does nothing. All it does, in fact, is to bring roots to the surface of the soil. This will encourage plants to become more dependant on the water you put on them and less resistant to drought conditions, more susceptible to drying out during the middle of the day. So it’s really not a good idea.

If you think of normal summer weather patterns, you would go several days with no rainfall at all, then you get a good shower, then you go maybe a couple of weeks with no rain, and you get a good shower. That’s what plants need during the summer: they need to have those periods of slightly drier, bright, warm and sunny conditions and then a good drink of rain. I nearly always advocate that with newly-planted stock, or plants you may have planted last year that are still dependent on you for water,) it’s better to go out once a week or once a fortnight depending on the weather conditions and give them a really good drink – I mean, two or three or four cans of water depending on the size of the plant – and really soak the soil. And then leave it alone again for another couple of weeks. The plant itself will be an awful lot happier. But there’s a fascination people have for going out and giving them a little bit of water every day. For plants in the garden, it‘s absolutely unnecessary and in fact can act very much to the detriment of the plant. With pots, it’s a very different issue and they are solely dependent on you for their water, they can’t access it from surrounding soil. In those cases at this time of year (late July) in this sort of weather (dry and hot) unless they’re in very big containers the chances are that you’ll need to be watering every day, unless of course you’ve been very astute and only planted drought-tolerant plants in your containers, in which case you may be able to cut the watering down a bit.

Apply a mulch

But again, with any of these plants you can save yourself a lot of work by a little bit of careful planning and forethought. With plants that are in the garden, at any time when the surrounding soil is really well soaked, that is an ideal time to put a mulch on to the ground so that it retains the moisture in there and it allows more moisture to carry on flowing through the mulch, whatever form you decide to use. The whole plant will stay much wetter much longer and will be a much happier bunny. You haven’t got to water artificially and the plants will be generally much happier. You can do the same thing in pots, but obviously a lot of people think of ‘mulch’ as being farmyard manure, coco shells or something like that, but anything that breaks the contact between the sun and the soil is a mulch. So, decorative pebbles on top of your pots are a mulch, gravel is a mulch, even seashells are a mulch. Vermiculite is fine. Anything like that which you can dress the top of the soil with: if it reflects the sun it’ll work very nicely. Even slate, whilst that itself gets quite warm, still stops the moisture from evaporating off the soil so easily. Anything like that is advantageous, particularly on long-term plants in pots, things like Camellias, Azaleas, even Bananas or Alpines. If you dress the tops with gravel , it keeps them clean, keeps weeds down and helps to keep the moisture in.

You’ll be keeping your plants happier for much longer, particularly if you’re out at work all day. And sometimes, when you get home at night, really the last thing you’re in the mood to do is to go out and start watering, at least if you’re like me and you’ve been outdoors watering anyway! So anything that means you only have to do it every other day or every Thursday, or whatever it may be, makes life easier and it’s better for the plants – they’re not getting soaked every day, they’re not going to get so much disease. It’s an ongoing solution to a problem, if you like. So I strongly advocate doing that and also mulching plants in the garden.

Don't forget hedges and trees

I strongly advocate mulching both plants in pots and plants in the garden. In particular, we’re dreadful at neglecting our hedges. If you think about it, you’re growing a lot of plants cheek-by-jowl, you’re going to be growing them usually up to a reasonable height, so they’re going to be under slightly stressed conditions anyway – and then we don’t even bother to give them a feed or water – it’s really like adding insult to injury. All these things need to be fed to be fed earlier on, but you need to feed them at a time of year when the soil’s moist and the fertiliser can get in. And then mulch them. What I do very often with hedges is to mulch them with my lawn clippings – and yes, it does take some Nitrogen out of the soil but the benefits which the hedge reaps in terms moisture retention far outweigh what it loses in Nitrogen. It’s very easy to put an extra-nitrogenous feed down: it’s a pain in the neck trying to put extra moisture in.

The effects of heat

In these conditions we have now, plants suffer badly. We’ve got a cracking batch of Hydrangeas at the nursery but the colours are getting marked – it’s nothing to do with not being watered, it’s because they’re physically getting cooked – ‘ready roasted’ plants! We’re getting damn near ‘ready-roasted people’ so it’s hardly surprising! A lot of the plants in this country aren’t designed for this heat, unfortunately. We’re a temperate climate here and we’re suddenly developing Mediterranean temperatures, and whilst it isn’t the first time it’s happened, it won’t be the last time it’ll happen. It doesn’t mean the plants are any happier about it. And the polytunnel temperatures are through the ceiling. To give you an idea of how temperatures will change around the country: when I was up at Hampton Court, building up, the temperatures there reached 37°C. I wasn’t working in the shade, as a consequence of which, it was rather hot and sticky! The marquees reached 32°C. The canvas acted as a sort of shade although there wasn’t much air movement on the whole site. Last week, when we again had the two hottest days of the summer so far, where was I? In London again… in an un-airconditioned minibus going to visit a garden centre in N1, and it was just unspeakably evil. So we’re feeling like that, how are the trees and plants feeling?

So many plants, particularly trees, are shallow-rooted – things like Beech and Birch – and they are really starting to suffer now. We’re starting to see a real downward spiral with them – they’re going to get more disease and get more stressed. It will look as if they’re succumbing to disease rather than anything else, but disease is a symptom of the problem and is not the problem itself, which is drought. We’re going to find that Beech won’t be growing in the south of the country much longer, they’ll all be moving north (mind you, I have visions of this phantom-like forest of Beech all wandering their way north!) . Birch will be growing less in the south of the country, you’ll find that we’ll be growing more Sweet Chestnuts and Oaks because these are tap-rooted or are more flexible as to the range of temperatures in which they’ll grow.

Do your bit

I think it’s probably all these knock-on effects of drought that we just don’t think about: we see our own little patch and the worries that we have with it. What we are really missing out on is the bigger picture and what’s happening to the planet in terms of global warming. So you really do need just to be aware, I suppose, of what is happening with the rest of the planet and try not to think too selfishly.

As a consequence of this I think it’s very important that we all do what we can to recycle water – I know it’s something I’ve banged on about before – but every time I see a house without a water butt on a downpipe, I feel there should be a ‘name and shame’ campaign going on to try to make them recycle what water they can. Of course, this is all assuming that they do actually have a garden and do do some watering: if they don’t, fair enough. But I think that as far as possible we should be looking at recycling water by all means that we can. If we can’t recycle, then we should conserve – this is where the mulches and different gardening practices come into play and they’ll start to have a bigger effect.

Tracy Wilson