Garden School:


Garden School:
Teaching this week: "Putting the garden to bed for the winter"

Saturday, 7 July 2018

Salix Kilmarnock: suffering in the heat

A nice lady called Wendy sent me this picture of her Salix Kilmarnock:

...along with the comment that some of the leaves had started to go yellow and drop off and - worryingly - she could see a lot of what looked like tiny black eggs on the undersides of some of the leaves.

First things first, the dropping of the leaves: this is nothing to worry about in early July 2018, after three weeks of solid sun and no rain, with no rain forecast for at least another week.

All it means is that the tree - along with the rest of us - is getting a bit stressed by the continued heat, and is probably a wee bit short of water.

During periods of drought, many trees shed their leaves to conserve water, then when the rains come again, they put out a whole batch of lovely new ones.

So that's the leaves, now what about the things that look like tiny black eggs? Well, they are probably tiny black eggs... *laughs*... and they are probably from aphids. If you have time, they can be removed: either you can jet-blast them off with the hosepipe (a perfectly valid way of cooling down, as there will be a lot of back-splashing, ha!ha!), or you can gently wipe each leaf individually, squashing the eggs and destroying them. It is perfectly permissible to wear gloves to do this.

Whether you manually remove them or not, it is best to give the tree a going-over with the bug spray.

There are two main types: organic ones using “fatty acids” and non-organic systemic ones using chemicals. There is a difference in the way they work, and the way in which they are applied, so it's worth checking which one you have.

Organic bug sprays, using those odd-sounding “fatty acids”, work on contact by smothering the bug. So it's very important to get it all over the plant, including the undersides of the leaves. Yes, I know we all read those instructions, then blithely spray from above - but if you don't wet the entire surface, top and bottom, then you are leaving safe havens for the little buggers bugs to live and breed.

So be prepared to get the spray all up your sleeves, down the back of your neck, and all over the place - but it's worth it, to get rid of the pests.

Non-organic bug sprays are "systemic", which means that they are absorbed by the plant, then when the sap-sucking insects arrive, and bite the plant, they are poisoned. This means that the damage is often done before the bugs die... but it does at least mean that each insect only gets one sip!

Systemic sprays don't need to be applied to every part of the leaf in quite the same way that organic ones do, but you do need to ensure that the leaves are well wetted. And do bear in mind that it takes a day or so for the “poison” to work its way through the plant, hence the instructions on the packs to spray at the first sign of pests - that is, don't leave it until your plant is a heaving mass of aphids before applying it!

And in all cases, read the instructions on the pack, and follow them: they will tell you how to apply it, and when to re-apply it. There is no point spraying the same plant five times in one day - follow the instructions.

Right, that's the dropping leaves, and the aphids: what else is there to mention? Oh yes, take a look at the top of the pot: it seems to have a few weeds and mossy bits growing there. Always best to remove them: a tree in a small pot like this needs all the water and nutrients it can get, so don't make it fight the competition.

Clear out the top layer of soil along with all those weeds, and then add some fresh soil or compost: this is what is called “top dressing”. It's a chance to get rid of weeds along with the tired old top layer of soil. When I top dress, I take the opportunity to drop in a handful of granulated balanced feed such as Growmore, underneath the new layer of soil.

If you don't like the look of bare soil around the base of your potted plant, you can add a mulch of gravel, shingle, stones, slate chips, anything you like: these hard mulches have another advantage, in that they allow the water to soak straight in to the soil when you water it, rather than pouring over the sides of the container.

The disadvantage is that once a year or so, you will need to scrape them all off so that you can top-dress the soil underneath. This is a good time to wash the hard mulch to get rid of moss, algae, lichen etc. You'll usually find that, over time, the mulch becomes incorporated with the top layer of soil, which makes it look untidy, and allows weeds to grow - so it's a good exercise once a year, to clean it all off. It's also a good time to check that nothing has taken up residence in among the hard mulch - they can be a haven for slugs, snails, ants, woodlice, you name it!

Going back to the pot, Wendy's pot is a good shaped one: straight sides are far and away the best, they give the biggest amount of soil and are the most stable.

Second from worst (bear with me!) are pots with wide tops which slope elegantly in at the base, such as this one - left.

They look lovely but as the roots grow downwards, they are in less and less soil: and these pots tend to tip over quite easily. They don't hold as much water as a square-sided one, and have a higher ration of "side" to content, as it were, so the roots get baked by the sun all the way down.






Worst of all are those lovely Ali-baba style pots:

...this one (right) looks lovely, but it combines the top-heavy wrongness of the narrow base with a narrow neck, which makes it impossible to get the plant inside it out, if you need to repot it.

Well, I say "impossible", nothing is impossible, but it took me the best part of a whole morning to wrestle this particular fig out of this exact pot, a few years before this photo was taken, in order to straighten it up.

So, squat and square-ish are the best shapes for a pot in which you are growing a tree, and as always, the larger the better in order to give the tree the most amount of soil, and the best possible "water bank", ie the amount of water that remains in the soil between watering.

Wendy's tree is in a pot that is just about big enough; if it were mine, I would probably get a pot that was a couple of inches bigger all round, but I like to give trees room to stretch a little.

Bearing in mind that these Salix Kilmarnock trees are top-grafted, they won't get any bigger, just stouter: so you might think that by keeping it in a smallish pot, you are restricting its size, but that's not the case. I've written about these trees here, here and here (and several other times! ), so if you want more details about the intricacies of top-grafted Salix Kilmarnocks, check those articles, and you can also use the "search" facility at the top left of the page.

And finally, a general point for all pot-grown trees, we are expecting them to do a lot of work for us, for not much payment: so if you grow a tree in a small pot, remember to give it a feed every few weeks through the summer. Top-dressing in spring, with the addition of a small fistful of granulated feed, will get it going nicely: and add some liquid feed to the watering can from time to time through the summer: I use liquid seaweed, but any liquid feed will be better than nothing.

Oh, one other point:  during a hot, hot spell like the one we're having currently (in a couple of weeks' time, when the clouds come back, and we're sitting indoors glumly looking at the raindrops splashing in the paddling pool we rushed out and bought, we'll no doubt be wondering if we dreamt about five weeks of endless sunshine), you can make life easier for your potted tree by putting a large saucer underneath it: if it's up on feet, take the feet away, and let it sit directly on the saucer.

This means that when you water it, the water will go through the pot and will collect in the saucer, where it can gradually be re-absorbed. This is particularly helpful if you've accidentally allowed the plant to dry out too much: you know that horrible situation where you pour on the water only to see it gallop straight through the pot and out the bottom. By putting the pot on a saucer, that wasted water has a chance to get back inside the pot.

I wrote about re-watering over-dry pots at length here,  so check it out for more details.

1 comment:

  1. Your Salix Kilmarnock posts are invariably killers!

    ReplyDelete

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