How to grow Dahlias

After consulting a few experts here are our tips on the best way to grow dahlias. Firstly Dahlia season in in summer, and flowers come in a range of colours from white through to deep reds, some small, some as big as dinner plates.

Dahlias are grown from Tubers or Bulbs and flowers come in many colors and forms. They are simple to plant and grow and do well in many areas.

They are a favourite flower and varieties are readily available for sale online from specialist Dahlia Nurseries.
Many questions are asked about how to grow Dahlias, when to plant, location soil requirements and how to grow them from cuttings.

Dahlia flowers vary greatly from complex decorative types to simple varieties. A list of classifications appears below.

Dahlia Care

Planting Dahlia tubers

Dahlia tubers are best planted after the risk of frosts is over. With most varieties

Dahlias will need staking, so stake first and then plant the tuber close to the stake, at around 4 inches (20cm) deep.
When you look at the tuber you will see the growing point or ‘eye’ at one end, this end should be a little higher.
Do not apply fertilizer to the tuber directly, this can cause burning.
Dahlias can be planted in a cottage garden among other perennials if you wish
In wet areas we suggest raising the garden bed a little to ensure drainage is good.
As for selecting tubers, big is not always better. Smaller tubers tend to develop more quickly than larger ones.

Watering

A drip irrigation system is ideal for large plantings, however in a well prepared soil with lots of water retentive material and protection from hot afternoon sun you will find Dahlias are fairly hardy.

Water in the evening to give the plants a chance to recover from the heat and also prevent evaporation. Mulch is great….

Digging Dahlias

The reason we dig dahlias is to prevent the tubers rotting over winter.

So technically if you can guarantee good drainage you may get away without digging.

HOWEVER, if you do not dig and divide you will find that the plants become smaller and the flowers are fewer and smaller.

Digging every year is best, every 2 years is essential.

Dig, Divide and then Store.

When you do dig its time to divide the clump. Look for the new tubers and look for the ‘eye’ on the neck or stalk. Each division needs a tuber with neck and eyes. And leave the tail as well.

We use trays, however many gardeners use polystyrene boxes lined with newspaper.

The tubers are laid on the paper and covered with sawdust, potting soil or coco peat.
You can do 2 – 3 layers. A cool dry position is needed over winter.
Some gardeners just divide them and place them in an onion sack and then in a canvas bag, a cheap recyclable shopping bag will do the job, again store in a cool dry dark place.

Propagation

Easy by division, or splitting of tubers when dormant. However we have two schools of thought on this subject.

Divide when you dig them in fall. This way its done and they are ready to plant.
Divide them in spring as they begin to show signs of growth when the ‘eyes’ swell and are easier to see.
You basically need a tuber to provide energy for the new shoot, so a sharp knife will be needed to divide them properly.

Basic Dahlia Care Summary

Water once a week, or more often in dry conditions.
Mulch well.
Liquid fertilise every 3-4 weeks and provide protection form snails (especially new shoots)
Pinch back growth to provide a more bushy form.
Remove spent dahlia flower heads.
For best results, dig and divide or separate dahlia tubers and store in a cool dry place over winter. (Although in well drained milder climates tubers may be left in the ground if desired)

Planting Summary

Dahlia Bulbs should be planted about 4 inches (20 cm) deep.
Dahlias prefer full sun to part shade to produce the best flowers.
Plant Dahlia Bulbs after the danger of frost has passed.
Plant Dahlia bulbs or tubers with the eye pointing upwards
With Tall Growing varieties place a stake in the ground before planting the Dahlia Tuber. This can help prevent damage to dahlia flowers when in bloom.
Water in well.
Separating Dahlia bulbs when dormant is fairly easy, simply use a garden fork to lift and seperate bulbs.

Where to plant Dahlias

Ideally you will find a position with good morning sun and dappled or filtered afternoon shade, this works well for most home gardeners.

For those looking to grow those exhibition quality flowers then a 50% shade cloth will be beneficial. This not only controls the light but will also protect flowers from any heavy rain.

Soil Preparation

Dahlias are actually fairly tolerant of soil conditions, as long as drainage is good. However a humus rich soil with added well rotted animal manure will certainly give better results.

Many grower sow a green manure crop and dig this back into the soil with extra manure in early spring before planting out the dahlia tubers.

Do Dahlias require any extra fertilizer ?

If you want big healthy plants, yes !

We suggest an application of a general garden fettilizer as soon as the first buds begin to appear.

This should be a balanced fertilizer NOT a high nitrogen type, we are after flowers not leaf growth.

An application of sulphate of potash when new growth first commences is also beneficial

Dahlia Varieties

Dahlias come in many flower forms and colors ranging from white through to deep red, forms or varieties include those listed below.

The Watererlily variety pictured right is one of the best dahlia varieties of all.

Single-flowered Dahlias
Anemone-flowered Dahlias
Collerette Dahlias
Paeony Dahlias or Peony Dahlias
Formal Decorative Dahlias
Miniature Decorative Dahlias
Ball Dahlias
Pompon Dahlias
Cactus Dahlias
Semi-Cactus Dahlias
Fimbriated Dahlias
Single Orchid Dahlias
Double Orchid Dahlias
Waterlily Dahlias
Informal Flowered Decorative Dahlias
Large Pompon Dahlias
Stellar and Dark Foliage Dahlias
Tiny Tot, Dwarf and Baby Dahlias

Where to Buy

Readily available from specialist growers.