Dozen hues from one dahlia

It started as a bit of a joke, persuading a colleague to enter the Dunedin Dahlia Circle’s show two years ago.

To her delight, she scored a third prize with a flower grown from seed and the red-and-yellow bloom was nicknamed Brenda’s Pride.

I admit I got a bit carried away by her success and scrounged a ripe seedhead of Brenda’s Pride, then sowed the seeds in spring.

Incredibly, that sole seedhead produced 40 seedlings, most of which I gave away. Only a couple of those I kept flowered the first summer — one red, one lavender — but this season (2022-23), a kaleidoscope of colours appeared, ranging from off-white and pale pink to deep purple and vivid citrus yellow. Nearly all were singles but a couple were semi-double and one a collerette.

My favourite was the creamy-lemon collerette, with its two layers of petals, short near the centre then framed with longer ones, A red, tipped with yellow, also appealed.

I had done something similar about a decade earlier and got six colours, which I thought rather impressive, so it was amazing to get a dozen hues from one Brenda’s Pride. As a free means of getting more plants to give ongoing late colour, it couldn’t have worked better.

The singles didn’t seem to interest the earwigs, another plus for the homegrown collection. Neither are the insects very impressed by the tree dahlias, Dahlia apiculate, D. excelsa, D. imperialis and D. tenuicaulis. Maybe the earwigs can’t be bothered crawling 3m-4m to get to the single pink flowers.

Dahlias are most useful flowers because they bloom from early summer through until hit by frost. They will even flower into winter if you live in a frost-free coastal spot, although there will tend to be fewer, smaller flowers at the end of the season.

The first record of them being grown in Europe is of dahlia seeds arriving in Spain in 1789 from their Mexican colony. Seedlings bloomed the following year and they have been garden favourites ever since.

The first flowers were single but a century later, doubles appeared and these still dominate the show varieties, from tiny pompons to giant decoratives as big as dinner plates.

Dahlias last only three or four days when picked but look striking in indoor arrangements and are increasingly popular as wedding flowers. The newer variety Cafe au Lait is already a florists’ favourite for its medium-sized buff blooms.

Being greedy, dahlia tubers need very rich soil enriched with plenty of sheep pellets or rotted horse manure to ensure they perform well.

If earwigs are an issue, a small zap of rose spray on the buds when the first hint of colour shows keeps them away. Unfortunately, such sprays are toxic to bees, so you may prefer to crumple newspaper into balls and tuck them into the stems below the buds. Every day or two, remove the paper and drop it into a bucket of boiling water to kill the earwigs lurking inside. When the water cools, toss it and the earwigs into the compost bin.

Dahlias can be lifted in autumn and stored under cover in damp sawdust. This is not essential but is an opportunity to enrich the ground where they grew and damaged and rotten pieces of tuber can be cut off before replanting in spring.

Keep plants moist during the growing season and deadhead frequently to keep new flowers coming.

And don’t forget to save a seedhead or two to create your own unique variety.