When I first joined the Plants2Gardens team my plant knowledge was, let's say, a tad limited, and rhododendrons scared me a little. I'd always thought they were tricky. How wrong I was! They're one of the easiest shrubs I grow now, so if you're feeling a bit nervous too, please don't worry.
We get asked lots of questions about our rhododendrons, so I've gathered up the ones that come up most (with a little help from the team, of course).
The short version
- Rhododendrons need acid soil: ericaceous compost in pots, Sulphur Soil in the border.
- Plant somewhere sheltered with shade from the midday sun.
- Keep watering through late summer and autumn, when next year's buds form.
- Use rainwater where you can, and deadhead after flowering.
What soil do rhododendrons need?
Rhododendrons are ericaceous plants, which simply means they like acidic, lime free soil. Azaleas, camellias, heathers and blueberries are the same. The pH of your soil tells you whether it's acid, alkaline or neutral, and rhodos are happiest at around pH 5 to 6.
You can buy a little kit to test your garden soil if you're not sure. If it turns out to be on the alkaline side, don't give up on planting in the border (I was surprised by this one). Sulphur Soil granules can be forked into the soil to bring the pH down and unlock nutrients for the plant. Churn them in once every six months and your rhodo will be very happy.
You'll find it in our soil improvers.
Can rhododendrons grow in pots?
Yes, and this is exactly how I started. Pick a compact or dwarf variety, fill a good sized pot with ericaceous compost and you're away, no soil testing needed. Result! A taller planter is lovely as it lifts the plant up so you can enjoy the leaves as well as the flowers.
Plants in pots dry out much faster, so they need more watering than those in the ground (more on that below).
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Join the Garden ClubCan I use multi-purpose compost?
You can, as long as you sort out the pH. Mix in some Sulphur Soil when you plant and top it up every six months and a good quality multi-purpose compost will do the job.
Where is the best place to plant a rhododendron?
Somewhere sheltered from the wind with a bit of shade from the midday sun. Next to a fence or wall, or under a tree canopy with dappled light, is perfect. Full, baking sun all day isn't their favourite, and a sheltered spot helps the flowers last longer too.
When is the best time to plant rhododendrons?
Autumn and spring are ideal, when the soil is moist and not too cold. Avoid planting when the ground is frozen or waterlogged. Plant at the same depth as the pot (they don't like being buried deep), water well and add a mulch around the base.
How often should I water a rhododendron?
Regularly, especially in pots, and this is the one that surprised me most. Keep watering through late summer and autumn as well as the warmer months, because that's when next year's flower buds are forming. Let them go dry then and you could lose the display. The same goes for camellias and azaleas.
Use rainwater whenever you can. Tap water often contains a lot of calcium (lime), which slowly makes the soil less acidic. A drink from the tap now and again is fine though, so don't panic.
How do I feed a rhododendron?
A slow release ericaceous feed in spring and again in autumn is plenty. We use Fed N Done Ericaceous, which you'll find with our plant food. A mulch of leaf mould or bark is very much appreciated too.
Do I need to prune my rhododendron?
Hardly at all. Rhodos don't need regular pruning unless you want to reduce the size or tidy the shape. If you do, wait until just after flowering, as cutting earlier takes off the buds. Take out any dead or damaged stems at the same time. Be warned though, a heavy prune can mean fewer flowers the following year.
The one job worth doing every year is deadheading. Gently snap off the faded flower heads with your fingers, taking care not to knock the new buds forming just underneath.
A little inspiration from Brian
I have to finish with a couple of customer photos. Brian has been a loyal customer and friend of ours for many years and is a self-confessed rhododendron addict. He's our "Rhododendron Man" and knows everything about these splendid plants, as you can see from his beautiful garden. Thank you Brian for sharing, absolutely gorgeous.
If you fancy giving one a go, have a browse of our rhododendrons. I promise they're not as scary as they look (not all superheroes wear capes, but they do grow rhodos).
Take care,
Lins x
