And so the La Niña blues roll on
And you thought (hoped)! we had seen the last of her. With the little girl still hanging around I figured these two very common problems of this season deserved sharing.
Hi Glen,
I have a 28-year-old walnut tree in the back garden. This year it has barely come into leaf and is looking sick. I am wondering if it is due to being a wet winter and the fact it was heavily watered last summer. Do you think it would benefit from a trim back? Or could I dig a trench out from the trunk and fill it with Seasol or something similar? I don’t want to lose the tree. Do you have any suggestions?
I also have had difficulty getting rid of the cherry slug by using copper spray at leaf burst, lime sulphur, and pest oil – to the extent that I have lost young trees including a weeping flowering cherry. I would value your opinion.
Thank you in advance, Marg

1 The Walnut tree

Walnuts grow best in deep, well-drained loam and do appreciate compost, organic manures etc. They are best planted on the high side of sloping gardens, not down the bottom where, in heavier-type soil, water tends to lie.
I can tell you that damned interloper Ms Niña’s re-appearance causing this awful, miserable and overly wet, and not to mention, violent weather, has caused my deciduous fruiting trees similar grief to yours. I only hope the rest of summer is a little benign, at least for long enough for everything to recover.
Hopefully your walnut’s roots didn’t suffer any great damage. The best course of action would be to dig a few shallow channels radiating from the trunk out to just past the “drip-line’ (just past the branch ends) making sure you don’t damage any shallow roots.
Don’t put any fertiliser around until you see positive signs of young growth, so you know it’s ready to get going again. Then you can let fly with the manures, Seasol etc.
Walnuts aren’t all that fond of pruning so wait until you see some real movement before you trim off any damaged or weakened growths.

2 Pear/cherry slugs

These little monsters are as persistent as blowflies around a picnic and will take constant action to clear up. So it’s useful to know their life cycle to understand the several remedies needed.
Pear/cherry slugs are larvae of one species of insect commonly called sawfly. The adult fly lays her eggs on the back of the selected tree’s leaves and dies. The eggs hatch and become the slugs, which gorge themselves on your tree’s succulent leaves, then head south to dig themselves a cosy spot in the ground at the foot of the tree to mutate into flies…which then proceed up to the next season’s succulent leaves to continue the life cycle.
So you have several chances of stopping them, as well as physically removing and killing the slugs – spray the pest oil as soon as the leaves are fully opened to get the eggs before they hatch.
Hit the slugs with the oil or water to knock them off the tree, and stop them either going down, or coming back up to eat, by placing a barrier ring of pest oil-soaked rag about 5-10cm above the ground. This not only deters the little blighters, if you regularly repeat dousing the rag and completely break the life cycle, you could be lucky enough to rid your garden of them – and maybe a few of their cousins for at least a couple of seasons.
Happy Hunting!
Got a gardening query? Email glenzgarden@gmail.com