Vertical garden with dead plants: where they die tells you why

The end of September is when a vertical garden presents the summer’s bill. Almost all of them have casualties: a gap here, a brown clump there, a row that isn’t what it was in June. And the natural reaction is to buy the same plants, put them in the same gaps and hope they last this time.

They almost never do, because the plant wasn’t the problem. In a vertical garden, where a plant dies says more than the plant does, and before replacing anything it’s worth reading it.

Why the spot matters more than the plant

In the ground, each plant has its own soil and its own hole, and if one dies the natural thing is to look for the cause in the plant: the species, the spot, the sun it gets. Not on a wall. They all share the same watering, which comes in at the same point, and the same wall, which gives them all the same heat from behind.

So when the losses have a shape — a row, a strip, one side — you shouldn’t look at the plants, but at the system. And the system has a property hardly anyone has in mind: water isn’t shared out, it runs down.

The controller gives the whole wall the same minutes, and from that people assume the whole wall gets the same. It doesn’t. The top gets the water first, but it’s also the first to drain. The bottom gets its own share plus everything left over from above, and often doesn’t get to dry out between one watering and the next.

Where it rains in summer, the odd storm evens that out now and then. Not here. The wall has spent four months living on irrigation alone, so any imbalance isn’t corrected: it builds up, week after week, until in September it shows.

Four patterns and what each one says

The top row has dried out

It’s the most common and the most misread. At the top there isn’t a shortage of water overall: there’s a shortage of water there. The top row drains before any other and is usually also the most exposed, with nothing to shade it or shelter it from the wind.

The temptation is to add minutes to the watering. That rescues the top plants a little and waterlogs the bottom ones completely, which is the third pattern. What really fixes it is putting plants at the top that cope with being drier and, on tall walls, adding a second irrigation line lower down rather than more time on the top one.

A dry strip from top to bottom

A whole column, from the first row to the last, while the ones either side are fine. That isn’t the plant or the sun: it’s a dripper that isn’t dripping. The water that should run down that column doesn’t get in, and everything below lives on the little that reaches it from the side.

Drippers get blocked with dirt and, above all, with limescale. There’s a simple way to tell whether that’s your case without testing anything: if your shower screen gets covered in limescale, so do the drippers on the wall. Before replacing that column you have to clean or change the dripper, or the new plant will die just the same and for the same reason.

At the bottom, yellow, soft plants

If the losses at the bottom aren’t dry but discoloured and soft, or the pocket smells, the problem is the opposite: too much water. The bottom row gets everything that drains from the wall, and if the collecting channel doesn’t drain properly as well, its roots spend the summer soaking.

It’s very typical on walls where someone turned up the watering in July to save the top plants. You can check by pushing a finger into a bottom pocket a couple of days after watering: if it’s still soaked, nobody in that row is short of water.

Everything at once, or a whole side

If the whole wall has gone brown in one go, there’s nothing to diagnose in the plants: the watering failed. A pump that stopped, a controller that reset itself after a power cut, or an empty house in August with nobody to spot it in time.

If it’s a whole side, look at what that side gets. The edge of the wall that catches the afternoon sun or the wind takes the worst of it. In and around Málaga you also have to reckon with the terral, the hot, dry wind that comes down off the mountains and hits hardest the face of the wall that’s turned towards it.

In every case, before you pull anything out, check that the brown is dead. A pocket holds far less in reserve than the ground and it usually is, but the test takes a minute. It’s explained in how to tell whether a dried-up plant is dead or just dormant.

What to do now, and why now

The end of September and October are the time, for the same reason as in the rest of the garden: here the enemy is July, not winter. That’s why on the Costa del Sol you plant in autumn, not in spring. A plant that goes in now has the whole autumn and winter to root before next summer, and in a pocket, rooting well is the only reserve it’s going to have.

You replace gap by gap, not the whole wall. Each gap is a pocket with a handful of soil, and it’s enough to change what has failed.

A real pocket wall, halfway through its life. The empty pockets show how little soil each plant has; alongside, newly replaced plugs sit next to established clumps, and at the top are the remains of one that dried out where it stood. That’s how you replace: gap by gap.

And with three things in order:

• First, the cause. A blocked dripper, a channel that doesn’t drain or watering turned up too far are fixed before planting. Otherwise the new plant dies where the old one died.
• Each plant at its height. At the top, the ones that cope with being drier, which tend to be those with small, fleshy or silvery leaves. At the bottom, the ones that want more moisture. Moving plants around costs nothing and, with the same watering, gives a different result.
• The watering, in sections if need be. On a tall wall, two lines at different heights share it out better than a single one at the top with more minutes.

And if the house is going to spend another August empty, that’s also sorted out now and not in July: a failure alert on the controller, or someone to check on it. Why a vertical garden has no margin for a failure like that is covered on the vertical gardens on the Costa del Sol page.

In short

In a vertical garden all the plants drink from the same watering, and water isn’t shared out: it runs down. That’s why the losses don’t fall at random, and the pattern they leave tells you what happened. A dry top row is distribution, not lack of water. A strip is a dripper. Yellow and soft at the bottom is too much water. The whole wall at once is the watering that stopped.

Once you’ve read that, replacing is the easy part: first the cause, then each plant at the height it can cope with, and in October, which is when you plant here. And if what you’re thinking about is extending the wall or putting up another, what comes before choosing plants is in what to check before a vertical garden on a community terrace.