Plant of the Month: October 2021

Dahlias

by Judith Ladley

I suppose strictly speaking the dahlia does not fall into the category of a hardy plant but for the purpose of this article I am claiming “horticultural licence”

The garden dahlia, Dahlia x variabilis, is a cultivated plant derived from wild relatives found growing in Mexico.  As far back as 1651 reports were published in Rome, originally in Latin, from a Spaniard who had spent several years in Mexico.   

The first seeds to arrive in Spain were sent by the Director of the Mexican Botanical Gardens to the Madrid Botanic Gardens, these being grown and named as D.pinnata, D.coccinea and D.rosea (possibly Merckii).

     

For many years it was believed that the dahlia had been introduced into Britain in 1789.  The story of how this came about is complicated, involving Lady Bute, wife of the then Ambassador from England to the Court of Spain. (See ‘The Gardener’s Guide to Growing Dahlias’ by Gareth Rowlands – well worth reading and available from the RHS library at Harlow Carr.)

The advent of the double dahlia is thought to have occurred when the explorer Alexander von Humboldt sent seeds from Mexico to Paris and Berlin in 1804.  It is thought that these seeds were not collected in the wild but came from garden plants grown by the Aztecs, who were great gardeners.

The development of decorative dahlias

During the early part of the nineteenth century regular consignments of tubers arrived in England from France and English nurserymen had started to develop new types.  By 1836 the Royal Horticultural Society published the Dahlia Register, listing more than 700 varieties.   The dahlia had become a popular flower with the wealthy and tubers of new varieties were known to change hands at a guinea a time, a lot of money in those days.   A total of 45 Dahlia Shows were held in England in 1835 (a far cry from today’s shows, although it was good to see the flowers exhibited at the “Autumn Chelsea”).

Dahlia Classifications at Newby Show, 2021

Propagation and Cultivation (The words ‘Grandmother’ and ‘Eggs’ spring to mind)

Dahlias are grown from seed (as originally) and from tubers.  Young seedlings develop a mass of fibrous roots which will eventually become the tubers that overwinter.

Many amateur growers prefer to leave their plants to overwinter outside and as our climate appears to be changing the tubers will often survive.  I find the setback to this method is that new growth does not appear until quite late in the season and the grower needs to be watchful for the ever-present pests that eat the new young shoots.    I prefer to dig up my tubers and dry them off to enable me to store them in a frost-free place.   Over time the tubers become quite large and this is the time to obtain new plants by taking cuttings from the old tuber.

Another method of growing dahlias is to raise them from seed, which usually germinates very easily.   I particularly enjoy growing ‘Bishop’s Children’ seeds and waiting to see which colours arise.

Some of my favourite dahlias

D. ‘Murdoch’

D. ‘Murdoch’ This dahlia came into my possession via Pat Clarke, a much liked and respected Chairman of our Group.  It is a very strong grower and I always think of Pat when I see it in bloom.

D. ‘Flaxton’

My gardening friends have named this dahlia ‘Flaxton’.  Pat bought it many years ago at a little nursery in Flaxton, near York.  It had belonged to the owner’s mother but the name had been lost. 

D. ‘Totally Tangerine’
  • D. Totally Tangerine  I particularly like the anemone-flowered dahlias and orange is one of my go-to colours.
D. ‘Blue Bayou’
  • D. ‘Blue Bayou‘ Of course it is not blue – there are no blue dahlias, but I love purple so it definitely gets a place in my garden.

Images courtesy of Judith Ladley and the HPS Image Library


Judith Ladley

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