How are gardens set to change?
With changing temperature and rainfall patterns predicted by climate change, how might our gardens and vegetable patches have to adapt in the future? Ross Cameron is a landscape horticulturalist at Sheffield University and works on climate change mitigation; he’s co-authored a report for the Royal Horticultural Society on this topic, and he spoke to Chris Smith...
Ross - It's about extremes. It's about, generally speaking, drier summers and wetter winters, in a nutshell. There's some variation - Northwest Scotland, for example, might also have slightly wetter summers. But it's about pulling apart those weather conditions. So we're going to see drier spells for longer, but also wetter spells for longer. I guess one of the worrying aspects of it is it's not going to be a smooth ride. We're going to see a little bit more turbulence in the system. So we're going to see more oscillations, more extremes coming sometimes quite quickly after each other. So a very dry period followed by possibly a very wet period.
Chris - Of course, the plants that we are very fond of growing, and those plants that feed us very well, are not necessarily as fond of those sorts of changeable conditions as a weather person is. So what might be the implications for the plants we can grow? Do we expect that some things are just not going to be viable anymore? Is this the end of the English country garden?
Ross - We can deal with the weather by putting on a coat, taking the coat off sort of thing, but plants can't. Plants are very much in tune to their environment and the seasons. So they go through periods of acclimation so they can adapt to drought if they're given a bit of a chance to run up to that drought beforehand. So these conditions are quite challenging. We're going to see plants that are traditionally grown in warmer climates. They may adapt. They may be useful in the garden. We may see more of those types of plants. At the same time I think we're also going to see plants who are just kind of generally speaking more resilient, more tolerant to stresses in general, and trying to bring in that sort of resilience. Unfortunately, that often means the plants that are quite competitive, quite successful already. So things we might sometimes define as slightly weedy, they'll be the ones that are the survivors in some ways.
Chris - So in my case, lots of stinging nettles. When you were talking there I was thinking about the fact that if we do see a lot of rain all at once, we get these big deluges. Is there a risk that you could end up with leaching? So the rain comes down on the soil, it washes out nutrients. They go into the river, not good news for silting up rivers, but also not good news for the soil. So gardeners are then attempted to put more fertilizer on and that gets leached as well. There could be a vicious cycle there.
Ross - Yeah. So we're going to be careful about how we manage our gardens, not putting too many chemicals onto the system. We have some allies in that - we have things like organic matter. So the more we can recycle compost, recycle horse manure, all those sorts of things that have been traditionally useful for improving the soil. They're actually quite beneficial here because that soil organic matter helps act as a sponge and hold water when there's too much. But also it helps keep that water up when it gets dry and provide it to the plants. So all gardeners always say, feed the soil to feed the plants. And that adage is still quite true, I think.
Chris - And you mentioned water and keeping water in the soil, but what about keeping water not in the soil, but in things like water butts? Is this all going to be about better water stewardship? If we anticipate we're going to have a long run of dry days and we want to grow the same plants, we just need to make sure we store up water for the bad times when we've got the good times as it were.
Ross - That's right. If rain comes in bigger dollops, then we want to capture that and reuse it really for garden use. Rain butts are a great idea, but we're also seeing interventions in places like Australia and North America, particularly, in things like rain gardens. So you actually sculpt out some of the landscape where water can be held. That water runs off very quickly. You avoid it going into the houses and the roads and you collect it in certain places, and then that can then be pumped out to actually irrigate farms and gardens later or itself becomes a feature in the landscape. So it can be quite small scale things, or it can actually be almost at a community level that you're trying to capture and hold water.
Chris - Well, more on that sort of thing in just a second because I'd just like to play you, Ross, a little clip we recorded at a special dry garden that's being developed at the Cambridge University Botanic Garden.
Chantal - It's called the dry garden, because there's a permanent hosepipe ban in here.
Katie - There is no water in this garden?
Chantal - No irrigation, no watering. That's really the idea. It's surrounded on all sides with these quite tall hedges. Those can provide shade as well. Enclosed reduces impacts of wind. So if you can reduce that wind and you can provide the shade, then you are providing some sort of micro climate that allows some of the plants that may be less drought adapted to survive. But then you need to think about the plantings. And this comes back to selection of those kinds of plants that have that adaptations to the dry environment. But the practical activities to ensure that water doesn't get lost in this garden are things like mulching, so mulching often. Having this surface layer of organic material, bark cuttings, or minerals like gravel, all of that will reduce moisture loss from the soil surface. No lawn, permeable paving that allows the water to move through the landscape and doesn't result in if there is a heavy rainfall - now we're predicting more rainfall in winter on the other hand to drought in the summer - so you want to make sure that your surfaces are permeable, you're not going to increase your flooding.
Chris - So basically it's more sympathetic planting and a bit of forward thought.
Ross - Yes, indeed. Yeah. It's the right plant for the right sort of situation. And I think that will vary slightly in the different areas of the country. So the areas that are wet at the minute and get wetter you might be thinking of certain types of intervention and planting. Somewhere like East Anglia, the east side of the country, then you're thinking about things like scree gardens, where you're using dry adapted species more effectively. And you can get the balance right. You can keep these guys going quite happily in the summer, but keep the roots above any water table that might appear in the winter through slight changes of level in the garden and using things like was mentioned there - shale, and other sort of mulch systems.
Chris - Is it all bad news? Are there any silver linings to this longer growing season et cetera because the temperature's a bit different? Are there any things we can look forward to?
Ross - From the personal point of view, us, we will enjoy the garden more. We'll be outdoors more often. I think we will be using the garden as that outdoor room. And we will always obviously still grow plants and containers where you can, to some extent, mollycoddle them and look after them. So we will still have our special plants, our pets, but it may well be that we're actually having more time and using the garden more effectively just because we are having these longer summer dry periods.