Starving rhododendrons

While we’re on the subject of miserable plants, the two rhododendrons on either side of the front gate are also looking poorly.



The foliage is yellow, curling and sickly, and the flowers half-hearted and few. I have been comparing our rhododendrons with the multitude of rhododendrons in the gardens of Southside Edinburgh (if there’s one thing a Southsider likes almost as much as a clematis it’s a rhododendron). Ours are three weeks behind everyone else’s as usual, and looking far less wholesome.

IMG_0364I found a website that suggests, given the symptoms, that the rhododendrons are ‘starved’ of water, nutrients, ions, air about the roots. Rhodadendrons aren’t fussy, but they need the basics that all plants need. And when I gave consideration as to why ours might be starved, the answer wasn’t hard to deduce.

You see, each rhododendron is growing out of a small square between the concrete slabs that cover the surface of our front garden. The soil around the base of the trunks is hard, compacted and gravelly. Water poured on to it runs straight off as easily as it runs off the concrete. These concrete slabs are the bane of the garden. With the earth covered and compacted in this way, how can water and nutrients ever drain in to the soil? How can nutritious, soil-conditioning vegetable matter ever get through to the earth? How can the soil beneath harbour insects and worms that aerate and process it? Think how much energy and creation is stored in a large shrub. It all has to come from the soil. Once the nutrients in the soil have been used up, that’s it. Rhodadendrons starved?
You bet.

IMG_0363I can’t do anything about the concrete. We’re tenants and not in a position to lift the concrete slabs, so I have to do what I can to improve the small square foot of earth at the base of each rhododendron trunk. The first thing to go was the evil anti-weed netting lying an inch below the surface. I felt a bit guilty about this, as the landlords probably put it there to make life easier for non-gardening tenants. However, it’s clearly partly to blame for the atrocious soil quality; besides that, rhododendrons do not like their roots too submerged. Therefore I’d argue that if the netting stays the landlords are going to lose their rhododendrons altogether (and their roses too). So up it came.

IMG_0366Next I mixed in to the soil some all-purpose granulated fertiliser and big dose of coffee grounds, which the thoughtful ladies in the hospital cafe save for me in huge quantities. Coffee grounds are a decent (and free) mulcher and soil conditioner, providing potassium and acidity to the soil. Rhododendrons like a soil with a pH of 5.0 to 6.0. Finally I gave the rhododendrons a good watering with instant fertiliser.

IMG_0361Now, I have to admit that I am not wholly fond of rhododendrons. They are not native to the UK, but they are extremely invasive. I was shocked when I went to Glen Coe a fortnight ago to see whole hillsides of the things. Their big, showy flowers are not attractive to bees (or to me, for that matter), and they are altogether too common, too obvious, too ubiquitous. Nonetheless, they are here to stay, and if I must have rhododendrons in the front garden they’d better be healthy ones.

2 thoughts on “Starving rhododendrons

  1. It’s a pity rhododendrons are so invasive. I have admired them since early childhood. Although they are rather stiff and large for a small garden they can be magnificent in the right setting. Also when they are mature the tunnels underneath are very good play value.
    I like your bud, it looks as though the flower will be a good rich purple. I also love the honeysuckle on your home page, a lovely colour combination and if I may say so, a super photo.

    1. The honeysuckle is the healthiest thing in the garden, and loved by all. I’ll let you in to its secret… the boiler exhaust pipe comes out of the wall right in the middle of it, letting out huge wafts of CO2 all over it. It’s the plant equivalent of an athlete on EPO.

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