Hot Stuff in the Garden

As I’m writing this in July, the UK has recently achieved a new record high temperature, breaking the 40°C barrier for the first time. This year has been dry since spring, April showers seem to be a thing of the past, and there are news stories about a potential hosepipe ban. We’ve had hot dry summers in the UK before, but there is a definite trend towards more extreme conditions.

What’s a gardener to do? For the rest of this summer the only answer is to try to do the best you can. All of the usual advice still holds: watering early in the morning or later in the evening, properly soaking those plants you do water, grouping plants in pots to create humid microclimates, and so on and so forth.

But this summer is not a one off, and it seems we need to change our gardening habits to cope with whatever extremes come in the future. So what new and exciting gardening solutions will we adopt to take us forward into this brave new gardening world?

My suggestion is nothing. Nothing new at all. Not a sausage.

I think that we already know how to deal with these conditions, and that traditional British garden-craft can provide (most of) the answers. But it may need a little tweaking.

Drought tolerant Romneya coulteri.

Consider the happy occasion of planting a new plant. Traditionally we have always tended to make new permanent plantings in the spring or autumn, and many of us probably act as if either season is equally fine. Both ends of the year tend to be cooler than the summer, so plants are less likely to dry out. Springtime tends to be when plants start growing, and so are ready to put down roots. During the autumn, most plants are heading towards dormancy but the roots tend to keep growing later into the season, this allows a new plant to establish a little before winter. It’s a case of horticultural swings and roundabouts.

But there’s also some psychology here. Springtime is all about new starts and fresh beginnings, buds bursting into growth and all that. It’s natural for gardeners to want to join in with the general vernal ebullience. Conversely, planting things in autumn does not have quite the same feel. It’s a less optimistic time of the year. Anything you plant probably looks half dead. It’s a season of shutting down and hibernating. So, on balance, we probably tend to favour springtime. Conventional wisdom tells us that this is totally fine.

But the fact remains that autumn is a sensible time to start planting new plants, and I think it may become the only time to plant new plants, maybe we should ditch springtime planting. In autumn the soil is warmer than in the spring, but there is (hopefully) a little more moisture around than in the summer. Autumnally lowering air temperatures mean drying out is less of an issue for any plant whose leaves haven’t already fallen.

A plant put in the ground in the autumn has a head start on one planted in the spring. The autumn plant will have done a bit of extra growing, sinking roots into the warm soil before going to sleep; after winter it wakes up and continues to establish itself from an already advanced position. By contrast, the spring plant is bunged into chilly soil, and is only just starting into growth, so those roots are not growing super fast. Obviously the autumn plants’ roots will have grown further by, for example, mid spring. So which one will cope better if another spring dry spell comes along, or if a dryish spring is followed by a dry summer? Clearly it’s the autumn plant for the win all the way.

Ornamental grasses: handle with care.

None of this particularly radical, all of the above is based on ‘ye olde garden wisdom’. But that same garden wisdom would also point out that there are problems with my call to abandon spring planting.

For example, it’s often said that deciduous trees and shrubs are best planted in the autumn, for all the reasons I’ve just mentioned. However, the generally accepted rule is that evergreens are far better planted in the spring. The reasoning is that the leaves of evergreens make them susceptible to drying out in freezing winter temperatures; the ever-present leaves are still losing water, but their newly planted roots cannot pull water from the frozen ground. Deciduous or herbaceous plants don’t have this problem as they have no leaves to lose water during winter. This has been gardening wisdom for a long time, but I don’t think we get the same freezing winter weather that used to be commonplace. My suspicion is that over much (if not all) of Britain, autumn planted evergreens would be just fine. Even if they did get a little scorching on their leaves, I suspect they would still establish better than those planted in the spring, just before driest time of year.

So far I’ve only been talking about planting new plants. Lifting and dividing existing plants, by and large, follows the same logic in terms of timing. But not always.

The big exception (and there are probably others) to my autumnal planting extravaganza idea are the ornamental grasses. Received wisdom is that grasses should only be lifted and divided in the spring. This is because they tend to stop active growth during summer, and so don’t re-establish well if you chop them up and replant in the autumn. This response is not likely to change. A plant that shuts down as day length shortens will never cope well with being dug up and divided in the autumn, no matter how mild the following winter. It’s the climate that’s changing, not the innate behaviour of our plants.

This raises an important point. If our winters are getting increasingly wet and mild some “rule” breaking (like autumn planting of evergreens) will be very successful. On the other hand, some gardening commandments (like springtime grass dividing) will remain relevant. As I said at the beginning, we need to tweak our gardening methods, but not completely alter them.

I’ve talked a lot about autumn planting versus spring planting. It goes without saying that planting in the middle summer is at best tricky, and always has been. Equally obviously we may need to think about changing the types of plant we grow in our gardens. The old gardening adage of “right plant, right place” is as true now as it’s ever been. No amount of autumn planting will make a water hungry plant thrive in the middle of a summer drought. Also remember that a newly planted specimen will likely need extra water during at least the first summer after planting. Watering also needs to be done the right way, if it’s to be effective; a really good soaking once a month is far better than a sprinkling once a week.

So what do you do in springtime if (almost) all of your planting has been done in the autumn? One word: mulching! Another piece of good old fashioned gardening advice that still makes sense.

Happy gardening.