Category - Nature

This article was written in the hot summer of 2018. It applies equally to the one in 2022.

My article about early leaf drop in Silver Birch trees is very popular – but it has really peaked this year (2018).

My own trees started going yellow this time around in mid-June. After a lot of research, I concluded that it was due to heat stress as a result of the prolonged warm weather and low rainfall we have experienced. I know that some places have had torrential downpours, but it isn’t enough. The temperature has remained pretty much in double digits the whole time, and has been in the mid-20s and low-30s most days for almost two solid months, and with no end in sight.

I commenced deep watering right after I found it as a remedy in June, and it has worked like magic. Right now, I simply set the sprinkler going for about an hour in each of three separate locations, and I do this each night (next year, I’m going to install deep-watering spikes to help the water get deeper into the soil). I have also found a way of watering and fertilizing at the same time.

When trees are stressed as a result of high humidity and low rainfall, they can’t get enough water and begin to shut down just as they do in the Autumn. It doesn’t kill them unless it happens year after a year, but obviously you can take steps to deal with it once you notice it.

One thing I have noticed with the benefit of hindsight is that the foliage on virtually every Silver Birch I have seen this year is thinner than in previous years (that’s also true for a lot of other trees I’ve seen). The leaves are actually smaller. The reason I say “hindsight” is that about a month into deep-watering and my tree has put out some significant new growth and the leaves on that new growth are much larger, and just like the photo I took last year.

Note that we have no hosepipe ban, and I wouldn’t be doing this if we did.

Once I commenced the watering, the yellowed leaves all fell over the next week or so, but no more were produced. Right now, not a single leaf has fallen in the last month at least and the whole tree is green with the aforementioned new growth. It is also producing fat catkins.

Will a Birch recover from drought?

It depends on whether the drought killed it or not. A reader wrote to me last year, mentioning that his tree had lost its leaves, and I advised that the only thing he could do right then was to feed and water – and hope for the best. He wrote to me recently to tell me the tree had started to rock in the wind, and that a tree surgeon had subsequently declared it dead, and had had to remove it. Apparently, the roots were rotten.

There’s no way of knowing if it was just the drought that did the damage. The tree may have been weakened by not feeding and watering over previous years, and the drought was just the final nail in the coffin. But last year’s drought certainly caused problems.

By now – early April 2019 – Birches are showing profuse growth of leaves and catkins (mine is). If yours is still completely bare then it doesn’t look good. Last year’s drought did a lot of damage, and since not many people do the feeding ritual that I have covered in the main leaf drop article, trees may already have been struggling.

That said, mine has certainly recovered from last year’s drought, although I did catch on very early and stopped it becoming a major issue.

All I can say is: water (if it’s not raining much) and feed.

One of the most popular posts on the blog is the one about Silver Birch Trees shedding leaves in the middle of summer as a result of nutrient deficiency in the soil. The remedy involves applying fertilizer and watering it in so the trees can get at it.

In 2018, though, another cause of premature yellowing has surfaced. The prolonged hot weather has stressed many trees, and the remedy for that is deep watering.

Ever since I found the solution to the nutrient problem I had toyed with the idea of semi-automating the fertilizer/watering process by combining the two and applying it via a sprinkler system. Indeed, I toyed to the extent that I bought a cheap Venturi mixer – which should have worked, but didn’t. I concluded that my water pressure was not sufficient to provide the necessary lift in the Venturi, because I just couldn’t get it to suck anything up. So I gave up on the idea for a year or two until 2018, when watering became such an issue in its own right.

I started Googling and many things came up, but they were all on a small scale – watering plants in greenhouses or by drip-feeders. But there was an American dilutor which apparently did exactly what I was after. You put your fertilizer in the mixer container, connected it to a tap, connected the other side to a hosepipe, and let it do the mixing before sending it down to your sprinkler or spray nozzle. The problem was availability in the UK. It came in various sizes, and the only one carried by any UK-based seller had a capacity of one pint (damned American units), which is no bloody use at all except for window boxes or greenhouses. The next size up was only available from American suppliers, so apart from the $100+ price tag, there was also the $100+ shipping fee – not to mention whatever UK Customs & Excise (who have become very sharp of late) slapped on it when it came into the country.

I was just steeling myself to order the American product, but while I was searching for the best price I accidentally came across the Access Irrigation Static Dilutor. It hadn’t come up on any of my previous searches over the last three years, and even when it did this time it hardly stood out until I followed the link and read the specification sheet and user manual. As an aside, whoever designed the Access Irrigation website decided to use images of text for product titles instead of just plain old searchable text. As a result, Google isn’t indexing them and normal search terms like  “inline fertilizer dispenser” or “fertilizer dispenser using sprinkler” don’t stand a chance.

Access Irrigation were very helpful with my pre-order questions, so I went ahead an ordered it. It came next day.

I’ve also recently bought a new sprinkler – a Gardena ZoomMaxx. Depending on water pressure it can water over a range of between 3m and 18m, or an area between 9m² and 216m² in an almost circular pattern (though the pattern is adjustable). In my case, with a water flow rate of 7L per minute (which is classed as “low pressure”), it was able to cover an area of around 80-90m² – which is about 5 times what my old bar sprinkler could manage.

The Access Dilutor consists of a thick plastic bottle which can hold about 9L of liquid. A screw-fit head assembly consists of a Venturi unit with a choice of Hozelock or GEKA fittings (Hozelock fitted as standard, but both types supplied).

For anyone who is interested, a Venturi is so-called because of the Venturi Effect. This is where a fluid flowing through a constriction in a tube creates a pressure drop, and this can be used for various effects. I became familiar with it when I was still at school, because we used small Venturi devices connected to laboratory taps to produce a partial vacuum when filtering liquids using conical flasks. In the case of the Dilutor, water flowing from your tap goes via the Venturi and down to the sprinkler head, and the pressure drop created inside the Venturi is used to pull liquid fertilizer from the bottle and into the main water flow. There is a bit more to the device than that, though, because as the fertilizer is removed, it is replaced by clean water to keep the bottle completely full. Since the fertilizer solution is more dense than water, this clean water sits on top, so you have a distinct border between fertilizer and water. Access Irrigation says you should use food dye if your fertilizer is colourless so that you can see when it is all used up. In my case, my mixture contains chelated iron, so it is almost black. Incidentally, this is why they call it the “static” dilutor, because you mustn’t move it when you’re using it, otherwise the divided liquids get all mixed up.

Until I tried it I was sceptical, but it really does work. The Dilutor is supplied with a range of nozzles which fit on the end of the dip-tube that carries the fertilizer. This allows you to control how quickly the fertilizer is used up. In my case, since I wanted to irrigate for an hour at each of several locations, and since my water flow was 7L/min – or 420L/hour – I used the light blue nozzle corresponding to this volume of water (edit: I have since changed to the grey nozzle, which uses the fertiliser more quickly, my logic being that I want to get the fertiliser on the lawn, then make sure it is watered in properly). I was doing my first run in the dark – literally – and using a torch the border between the black solution and clean water was dramatic. It was all used up in slightly more than one hour.

Previously, and as I have pointed out in my article about summer leaf drop, I was dissolving solid ericaceous fertilizer in water (which takes a couple of hours), and using this as a concentrate in five watering cans-full each liberally spread over 10-20m² (about half an hour overall), then watered in using a bar sprinkler for about half an hour in each of five locations to get the coverage. Overall, it was maybe 8 hours involving frequent interventions by me.

Now, using a liquid version of the same ericaceous fertilizer, I can make up a full batch in the Dilutor in about three minutes, and just set the sprinkler running for an hour. Then, I make another batch, move the sprinkler, and repeat. It only takes a couple of hours now to get the same coverage – and I’m doing a lot more irrigation because of the heat stress problem this year.

What are the different nozzle colours?

I don’t want to state what the colours are (though I did mention a couple, above), because Access Irrigation might change them at some stage, and then whatever I’ve written would be wrong (one of mine was not quite the colour the instructions said, anyway). However, four of these are supplied, and they give you a 10:1, 25:1, 50:1, or 100:1 dilution ratio.

Obviously, the 100:1 jet will be the smallest, and the 10:1 jet will be the widest. So you can work it out from there just by looking at them. The lowest ratio jet (widest) will use up whatever you’re spreading quicker than the highest ratio (narrowest) jet.

To be honest, unless you’re doing something really strange, the best thing is not to overthink these numbers. In my case, for example, I use a jet which empties my feed in about 45-60 minutes. That’s long enough to get an even spread and deliver an effective watering over about 100m².