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Potted Dahlias

Words | Dr Clare Gleeson, NZ Gardener Magazine October 2022

Nothing can stop a true dahlia lover from growing their favourite bloom, not a lack of space nor the prevalence of wind.

How to grow dahlias in pots.jpg

Charlotte Matthews with some of the potted dahlias grown by her mother Rachael.

For the past two years Rachael Matthews has been on a dahlia quest.  She is looking to grow 20 dahlia varieties for her design customers – in pots.


Rachael runs Hedge Garden Design & Nursery in Khandallah, and although structure and form are the basis of her projects, “I have flowery customers who love flowery gardens” she smiles.


To get her top 20 Rachael has been experimenting with dahlia varieties and different ways of propagating them over the past two years. 


Hedge Garden Design is run from Rachael’s home, so every inch of space is precious.  “I’ve been very disciplined with what dahlias I’ll grow next season and what I will order.  I have been working out which ones I wanted, and I’m now getting rid of some and ordering new ones.  I’m going to limit myself to 20, which is two full rows, and I’ll grow 20 as parent plants.  It was lovely having more flowers during the season, but I really do need the space”.


To help her decide on which ones to keep growing – and also to tantalise those who follow her on Instagram ( – Rachael photographs the flowering dahlias constantly. “I’m out here in the weekends in my pjs and gumboots catching the light and trying to get good pictures”. 


Rachael grows all her dahlias in plastic pots and recommends 13L pots or larger.  Apart from anything else, in Wellington the pots need to be that big so they don’t topple over in the wind, she explains.   These larger pots hold the “parents”, the dahlias grown from the tubers Rachael has bought.  She also has dahlia “children” in smaller pots.   The “children” are potted up and placed in a line near their parents. 


Rachael grows her dahlias from cuttings as opposed to cutting up tubers. Dahlia breeder Dr Keith Hammett has “been very generous with his knowledge” about this.  “You have to pinch the dahlias anyway to improve the structure and get a nice multibranched plant” says Rachael. “The pinched sections are perfect to use as cuttings”. 


“Tt’s easy to grow dahlias from cuttings, as opposed to cutting up the tubers.  You need to have a growing eye on a tuber, which can be a little tricky to identify; so if you cut and don’t get a tuber with a growing eye, that’s a waste of a tuber.”


Once potted up the dahlias grow and flower, with the tubers developing beneath the soil.  To make sure the tubers are fed for their next season’s growth the foliage must be allowed to die down fully.  Once the dahlias have gone brown and completely died away Rachael cuts them off at ground level and stacks the pots up, with the tubers still in them.   The frees up space will be used for something else until it’s time to bring out the pots and replant the tubers for the next season.  Rachael gives the tubers she no longer wants to friends.


Rachael and her customers reflect the changes in dahlia growing and dahlia varieties that have taken place over the past few years. “There’s a whole new wave of independent flower growers and people who just love this type of flower,” she says.


The new growers are “all about the flower” and not so concerned with perfection.  “These days in gardening you don’t have to be pristine and perfect, you can be wild and natural.” 


The new dahlia fans are looking for a different type of dahlia to the more traditional varieties.  Strong colours are still popular, but blush tones are the new craze, she says.  These newer dahlias are popular with the flower farm, backyard type of grower and the younger gardener. 


Rachael is a fan of American flower grower and author Erin Benzakein of Floret Flower.  Erin is incredibly generous with her knowhow.


In New Zealand, dahlia sellers such as Susie Ripley Gardening and Petal Plants in Auckland can’t keep up with demand.  It’s the fierce competition for their tubers that initially led Rachael to grow her own, so she can supply her clients with the dahlia tubers they want. 


However, Rachael is not cultivating dahlias for retail sale either as tubers or cut flowers.  The gorgeous bunches she cuts to put in vases around her house and give to friends are a bonus.


She also likes to share her tips on how to grow them in pots and gives detailed instructions on how to do this on her website.

Rachael’s top 20 dahlias for pots

Top 20 Dahlias by garden designer Rachael Matthews.JPG
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