How to Grow Dahlias

Dahlias - what can I say? Flamboyant, gasp-worthy and just downright gorgeous

They come in so many shapes and sizes (here are the ones I'm growing this year), but despite looking like you need a horticultural qualification to create such beauty in your garden - they are actually incredibly easy for beginners.

Here's how to grow them - you might want to make a note of some of these dates in your diary - add a link to this post so you can come back and refresh your memory - plus I'll add additional tips and pictures for you as we grow together.

Early March

If you've ordered dahlias, they will start to arrive about now - looking, I have to say, mainly like a cock and balls and there is no denying it.

Don't worry, they haven't sent you a cock and balls (imagine!) - this is actually a dahlia tuber. Who knew such un-pretty things could turn into such beautiful ones.

Apologies if you've just snorted tea all over your phone.

Just make sure they are either in brown paper bags - or if in plastic, tear a small hole in the bag to allow in air and store them somewhere dry and cool - in a shed or unheated room if possible. Don't rush.

Late March/ Early April

If and only if you have a greenhouse or somewhere frost free can you begin now to start your dahlias - they can't handle any frost.

I'll be doing this on 21st March this year if you want to join me.

Take your tubers and pot them up into ....um.....pots!

Use 2LT or 3LT pots, put a layer of compost (mixed with horticultural grit if you have it) into the bottom of the pot, place your tuber on top with the old stalk upwards and add compost to the base of the old stalk. It's the eyes (seen below), not the old stalk where your new shoots will come from.

Water but make sure the soil isn't too damp and place into a frost-free area - I'll be using my greenhouse - and throwing horticultural fleece over them if frosts are expected overnight.

Add slug pellets to the floor away from your pots to entice them in the opposite direction.

April

Shoots should begin to appear on each tuber - but don't give up too early on them - some can surprise you weeks later.

Don't poke or prod them looking for shoots as the eyes the shoots come from are delicate and you'll probably snap them off by mistake.

When they are a few cm high, slice off all but 5-7 shoots - the pieces you cut off can be used as cuttings to create new plants (will share that when we get there!).

Keep moist but not damp and keep fighting slugs.

May

Once they have started shoot, you can take cuttings and make even more dahlias from the ones you already have :)

 

This is the time you might need to pot your dahlias on into bigger pots if their roots have filled the smaller ones you started them in. Bumping them up to 5L pots at this stage gives them more room to spread their tubers and also refreshes the compost, which by now will be stale and deprived of nutrients.

In the middle of May you can start the Dahlia dance. This involves putting them out during the day and putting them back in at night so they can harden off before being planted out.

Keep the horticultural fleece handy in case of surprise frosts - right up until 25 May where I am here in Surrey.

In late May, if your last frost date has passed and you haven't done a thing with your tubers yet, you can plant them directly into the ground now.

1 June

Block off the date in your diary! Or as soon as possible afterwards.

Plant out your Dahlias. For my spacing I'm using that recommended by Erin at Floret and planting intensively in two rows with plants 45 cm apart with 30 cms between rows - see below.

 

Dig a hole and add grit to the bottom if you have poor drainage, then plant.

You'll also want to stake your plants at some point this month - sooner is better than later as there's less risk of damaging the tubers as they grow. I do this with bamboo canes and twine - but you can also just create a criss cross of twine across the bed to support them or one big solid stake and tie them in as they grow.

Fail to do this and you WILL lose your dahlias in the wind.

When they get to about 30cm high, pinch out the main growing tip to encourage bushier growth, avoid a broomstick thickness stem (!) and more flowers.

July

You can expect the first flowers from July (although my garden is always about a month behind everyone else on instagram!)  and they will keep going all the way through to October and the first frosts.

Feed them every two weeks with a liquid seaweed feed and be prepared to water them weekly - they are thirsty things.

July to October

Unlike most flowers where you would cut them before they are in full bloom, ONLY pick your dahlias when they are in full flower and deadhead regularly to maintain flowering.

If you're giving them as part of The Floral Project, you can mix them up with all the other beautiful flowers you have in your garden, or I found just handfuls of dahlias all on their own were perfect.

 

October/November 

The start of October is a great time to 'rogue' your dahlias which simply means to take a close look at each one and evaluate how it did. Any that failed to flower well, are showing signs of disease or you just didn't like the look of  - now is the time to pull them up and chuck them out.

This is also the time I go to my absolute favourites and add a special bit of string to their bamboo canes - a gold star if you like - just so they know how much I appreciate them.

When the first frost comes, the leaves on your dahlias will blacken and that's the end of dahlia season! Literally overnight. And you'll have no idea which you liked and which you didn't if you haven't 'rogued' them before this happens. Again, make a note in your diary - you'll kick yourself if you forget.

If you live somewhere where your soil stays relatively dry and you have good drainage over the winter, you can simply mulch over the top of the dahlias and leave them in the ground to overwinter.

Where my dahlia beds are situated turns into a swamp in the winter, so mine are carefully dug up, washed off, dried out and stored in brown paper in the shed over winter until we begin the whole thing all over again.

You can also split your dahlias in Autumn or Spring (I'll do a video when I do that myself) and because your original dahlias will grow again next year, because you can take cuttings to propagate them and because you can split them to create new plants, every investment you make in a dahlia tuber is so worthwhile.

December

It's time to get organised and start ordering your dahlia tubers for next year if you'd like to add to your collection - the most popular sell out quickly so order now and then forget about it until they arrive on your doorstep next March - by which time they feel like free surprise gifts from the flower fairies as you unwrap each one and discover all over again which ones you fell in love with.

Before you know it, you're hooked and growing about a million different varieties:)

I hope this has persuaded you to sow, grow and give your own dahlias.

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