Dahlia Growing Guides
How to Grow Dahlias in South Africa
Growing dahlias successfully starts with understanding what they need at each stage of the season — from choosing and planting your first tuber to caring for your plants, cutting flowers and preparing your dahlias for winter.
We grow dahlias on our farm in Douglas in the Northern Cape, and over the years I have learnt that much of the dahlia growing advice available online is written for gardeners in the Northern Hemisphere.
Our seasons, temperatures and growing conditions in South Africa are different.
That is why I created these Dahlia Growing Guides for South African gardeners.
I have arranged the guides in the same order that you would grow your dahlias through the season. If you are completely new to dahlias, start at the beginning and work your way down. If you already have dahlias growing, simply jump to the stage you need help with.
1. Getting to Know Dahlias
Before you plant your first tuber, it helps to understand a little about the plant you are about to grow.
Dahlias come in an extraordinary range of flower shapes, sizes and colours. They can also be grown from seed or tubers — but there are important differences between the two.
Dahlia Seeds vs Tubers
Dahlias can be grown from both seed and tubers, but they don't necessarily give you the same result.
This guide explains the difference and why named dahlia varieties are propagated from tubers rather than grown from seed.
[Read: Dahlia Seeds vs Tubers]
Dahlia Classifications Made Easy
Ball, pompon, decorative, cactus, waterlily... what does it all mean?
Dahlias are classified according to characteristics such as their flower form and size. Once you understand the basic classifications, it becomes much easier to identify flowers and choose the types of dahlias you would like to grow.
[Read: Dahlia Classifications Made Easy]
2. Preparing to Plant Your Dahlias
A successful dahlia season starts before the tuber ever goes into the ground.
Dahlias need plenty of sunshine, good drainage and soil that allows their roots and tubers to develop well.
Before planting, choose your growing position carefully and prepare your soil so that your tubers have the best possible start.
When to Plant Dahlias in South Africa
Planting time varies across South Africa.
Rather than simply planting according to a date on the calendar, it is important to consider your local climate, frost and soil temperature.
[Coming Guide: When to Plant Dahlias in South Africa]
Preparing Your Soil for Dahlias
Healthy dahlia plants begin below the ground.
Good soil preparation and drainage are especially important because dahlia tubers do not enjoy sitting in cold, waterlogged soil.
[Coming Guide: Preparing Your Soil for Dahlias]
3. Planting Your Dahlia Tubers
Now it is time to get those tubers into the ground.
One of the most common mistakes new growers make is loving their newly planted dahlia tubers a little too much — particularly with the watering can.
Your tuber already contains the energy it needs to begin growing.
How to Plant Dahlias Step by Step in South Africa
This is your complete planting guide.
Learn how we plant our dahlia tubers, including planting depth, positioning, spacing and what to do during those important first weeks while you wait for your new shoots to appear.
[Read: How to Plant Dahlias Step by Step in South Africa]
4. Caring for Growing Dahlia Plants
Once those first shoots emerge from the soil, your dahlia season really begins.
As the plants grow, they will need water, nutrients, sunshine and eventually support. The aim during this stage is to build a strong, healthy plant capable of producing plenty of flowers.
Watering Dahlias
When should you start watering? How much water does a dahlia need? And how does that change during a hot South African summer?
[Coming Guide: How to Water Dahlias in South Africa]
Feeding and Fertilising Dahlias
Dahlias are vigorous plants and their nutritional needs change as they move from early leafy growth towards flower production.
[Coming Guide: Feeding and Fertilising Dahlias]
To Pinch or Not to Pinch Dahlias?
Pinching is one of the simplest techniques we use to encourage our dahlias to branch and produce more usable flowering stems.
But when should you pinch? Where should you make the cut? And do all dahlias need to be pinched?
[Read: To Pinch or Not to Pinch Dahlias?]
Supporting and Staking Dahlias
Don't wait until a summer storm teaches you this lesson.
Dahlia plants can become surprisingly large and heavy. Supporting them early helps protect the plant and those precious flowering stems later in the season.
[Coming Guide: How to Stake and Support Dahlias]
5. Growing Dahlias for Cut Flowers
And then comes the part we have all been waiting for — the flowers.
If you are growing dahlias for cutting, you are looking for more than a beautiful bloom. Stem length, plant productivity, flower form and how well a variety performs in the vase all become important.
Top 10 Best Dahlia Varieties for Cutting
Some dahlias are particularly good cut-flower varieties.
In this guide I share some of my favourites and what I look for when choosing dahlias to grow for cutting.
[Read: Top 10 Best Dahlia Varieties for Cutting]
How to Grow Dahlias with Longer Stems
Pinching, plant spacing, harvesting and the way you manage your plants can all influence the stems your dahlias produce.
[Coming Guide: How to Grow Dahlias with Long Stems]
When and How to Cut Dahlia Flowers
Knowing when to cut a dahlia makes a difference — both to the flower you take inside and to the plant you leave behind.
[Coming Guide: When and How to Cut Dahlias]
6. Dahlia Problems, Pests and Diseases
At some point in the season, almost every grower walks into the garden, looks at a plant and thinks:
What on earth is THAT?
Don't panic.
Some dahlia problems are caused by weather, watering, nutrition or pests and can be corrected. Others may indicate disease and need to be taken much more seriously.
Learning to recognise the difference is an important part of growing dahlias.
Dahlia Problems and Troubleshooting
Yellow leaves? Poor growth? Strange-looking foliage? Flowers that aren't developing properly?
Start here.
This practical troubleshooting guide will help you work through some of the common problems you may encounter while growing dahlias.
[Read: Dahlia Problems and Troubleshooting]
The Dark Side of Dahlias – Leafy Gall
This is the elephant in the room.
Leafy gall is something I believe dahlia growers need to talk about openly.
Knowing what suspicious growth looks like, what to do when you find it and why potentially infected planting material should not be ignored helps protect your own garden as well as other growers.
[Read: The Dark Side of Dahlias – Leafy Gall]
Root-Knot Nematodes and Dahlia Tubers
Sometimes the problem isn't above the ground at all.
Learning to inspect your roots and tubers when you dig them is an important part of preventing unhealthy planting material from being kept, shared or sold.
[Coming Guide: Root-Knot Nematodes and Dahlias]
7. The End of the Dahlia Growing Season
Eventually the flowers slow down, temperatures drop and your dahlias begin moving towards dormancy.
But your dahlia season isn't quite finished.
What you do now has an enormous influence on the tubers you will have for next season.
What to Do with Dahlias After the First Frost
Should you cut them down immediately? Should you keep watering? And how long should the tubers remain undisturbed?
[Coming Guide: What to Do with Dahlias After the First Frost]
8. Overwintering Dahlias in South Africa
This is one area where South African growers should be particularly careful about blindly following Northern Hemisphere advice.
Growers in very cold climates often have to dig their tubers before the ground freezes and store them indoors for winter.
That doesn't necessarily apply everywhere in South Africa.
Here in Douglas, our winters are very dry and mild enough for us to leave our dahlia clumps in the soil through winter without watering them.
Your climate should determine how you overwinter your dahlias.
How to Overwinter Dahlias in South Africa
This guide looks at the different options available to South African growers and helps you decide whether your dahlias can remain in the ground or should be lifted and stored.
[Coming Guide: How to Overwinter Dahlias in South Africa]
How to Store Dahlia Tubers
If you do need to lift your tubers, how you store them matters.
There are different ways to protect dormant tubers from drying out, rotting or being damaged before the next growing season.
[Coming Guide: How to Store Dahlia Tubers]
9. Digging and Dividing Dahlia Tubers
This is where the magic of growing dahlias really becomes apparent.
That single tuber you planted at the beginning of the season may now have become an entire clump of tubers.
Learning how to dig and divide those clumps means you can keep your favourite dahlias growing from one season to the next — and eventually turn one plant into many.
When to Dig and Divide Dahlia Tubers
You don't necessarily have to rush to dig your dahlias as soon as they become dormant.
Timing, your climate and the way you intend to store or divide the clumps all matter.
[Coming Guide: When to Dig and Divide Dahlia Tubers]
How to Divide Dahlia Tubers
Learn how to identify the crown, neck and body of the tuber and how to divide a clump while keeping what each tuber needs to grow again.
[Coming Guide: How to Divide Dahlia Tubers]
What Does a Dahlia Eye Look Like?
This is probably one of the biggest mysteries for a new dahlia grower.
Once you know where to look, it becomes much easier.
[Coming Guide: How to Find Eyes on Dahlia Tubers]
Can You Divide Dahlia Tubers Before They Sprout?
Visible sprouts can make dividing a clump much easier, particularly when you are still learning, but you don't necessarily have to wait for every tuber to start growing.
[Coming Guide: Can You Divide Dahlia Tubers Before They Sprout?]
What Happens if a Dahlia Sprout Breaks Off?
Don't throw away a perfectly good tuber because you accidentally knocked off its new shoot.
A broken sprout doesn't necessarily mean the end of that dahlia.
[Coming Guide: What Happens if a Dahlia Sprout Breaks Off?]
10. And Then We Start Again
That is the wonderful thing about dahlias.
You plant one tuber in spring. You watch the first shoot push through the soil. You grow the plant, pinch it, care for it and eventually cut armfuls of flowers.
Then winter arrives.
The plant goes dormant, you dig or overwinter the clump, divide your tubers...
…and before you know it, spring arrives and we start all over again.
These Dahlia Growing Guides are based on what I have learnt growing dahlias here in South Africa — including the successes, the mistakes and the lessons that only really make sense once you have grown a lot of plants.
I will continue adding new guides as we move through each growing season, so bookmark this page and come back whenever you have a question.
You don't need to know everything before you plant your first tuber.
Sometimes the best way to learn how to grow a dahlia is simply to grow one.
Ready to Grow Your Own Dahlias?
Explore our Dahlia Tuber Collection to discover the varieties we grow here at Love Dahlias.
Our dahlia tubers are grown on our farm in South Africa and are available seasonally as planting stock.
[Shop Dahlia Tubers]
Happy growing!
She who loves dahlias,
Mareli
Love Dahlias