Dahlia tips and facts to entertain and educate so you can more easily grow beautiful blooms and amuse others with your Dahlia knowledge. This blog may help you when choosing which of the hundreds of Dahlia tubers you should buy this year. There again, if it merely amuses you to know these dahlia anecdotes that’s equally valid. Either way, enjoy!
Firstly a bit of Botany
Dahlias are tuberous perennials as the flower grows from a swollen root which is called a tuber. However, they are also referred to as herbaceous perennials as the foliage dies back over winter. As a gardener, one of the most important thing to remember is that Dahlias are tender tuberous perennial plants. Which mean that they do not reliably survive in the cold, wet, winter soils of Great Britain and the northern USA.
And of course, if they’re tender, then obviously they’re not one of our native plant species! Dahlias originated in central and southern America, including Mexico. They were known and cultivated by the Aztecs, who possibly used parts of the plant for culinary or medicinal purposes. The Aztec name for Dahlia was ‘acocotl’.
Dahlia Tips and Facts – a bit of History
The earliest drawings of Dahlias date from the late 16th century and come from a Spanish ‘fact finding team’. But these are not the herbaceous Dahlias we grow. The drawings show that the Spaniards had discovered what we know as the Tree Dahlia, Dahlia imperialis, which has hollow stems and grows to 20 feet.
However, despite this finding, it wasn’t until the 18th century that Dahlias were brought from Mexico to the Botanical Gardens in Madrid. Dahlia coccinea was one of the first species to be introduced in 1789. Although these were mainly single flowered types, horticulturalists soon realised that when grown from seed Dahlias naturally hybridise. Which led to double Dahlias being bred in Germany as early as 1808. The pace grew rapidly and by 1840 an incredible 2000 different Dahlia varieties had been cultivated.
The National Dahlia Society was formed in 1881 and is still going strong.
By 1936, there were some 14,000 recognised dahlia cultivars. To date, the number has risen to over 50,000! And if you really want to be amazed, then get this. All of these dahlia hybrids and cultivars have been developed from just 2 or 3 of the original dahlia species that came from Mexico.
Dahlia Pests
Slugs and snails can decimate your young plants overnight. Two tips that often reduce the severity of the issue are –
- Watering in nematodes on pot grown Dahlias, as early as you can
- Planting them out when the Dahlias are larger plants
However, if there are no slime trails alongside your holey leaves and flowers, then the problem is probably caterpillars. Whereas tattered petals are caused by earwigs. There are more, but these are probably the most common – along with aphids… Bring on the helpful garden predators like Ladybirds and Leopard slugs please!
Autumn Gardens
One question I’m regularly asked is whether you have to dig up Dahlias in the autumn. I go into more detail with those face to face answers, but briefly, dear Reader, you have these options:-
Firstly, in well drained soils in mild areas, Dahlias stand a good chance of overwintering in the ground. Cover the soil with a mulch for extra protection. There is always a risk that the tubers might rot in wet winters, but that sort of leads us to
The second option, which is to treat Dahlias as annuals. You can dig them up and compost them or leave them in the ground. If they survive, great if not, buy new.
These two options presume that your plants are in the borders. If your Dahlias are in pots, then you have the option of placing pots in a frost free shed. Remove top growth. Water lightly to prevent the tubers from drying out but not so wet that they’ll rot.
The catch with this is that you can’t be sure what condition the tubers are in. Which is why many gardeners dig up their Dahlia tubers as soon as the frost blackens the foliage. Some do this as soon as the foliage fully dies back. Then one of two options –
- The tubers are then cleaned of soil and hung up to dry. They’re then stored in a frost free dry shed.
- Other gardeners store tubers in shallow trays in contact with soil either encased in soil, ie not washed, still in a frost free place.
Dahlia Tips and Facts – they’re edible
Whilst the Europeans focussed on the floral attributes of the newly introduced tuberous plant, Mexicans continued to eat them. However, there may be a turn in the fortunes of dahlias as a food crop.
Land pressure means many of us have small gardens, so the plants we grow have to work hard to justify their inclusion. Now a plant which can provide us with lots of colourful drama in the late summer and autumn, provide us a few meals for our family, and still have a bit left over that we can propagate for the following year has to be worth giving space to!
And of course you can compost all the spent flowers and stems to provide soil food for your garden! NB Do Not eat the dahlia tuber you buy in the spring, it is likely to have been treated with chemicals. Six months in the soil seems to resolve that issue.
Dahlia flower petals are edible as well as the tubers. As regards taste, those early Dahlias, such as D. coccinea and D. variabilis, tend to be flavoursome. The former is the one most frequently used in cooking in Mexico and they ought to know. It’s also worth bearing in mind that in Europe and North America the focus has been hybridising for stunning blooms so ‘trial and error’ before success is likely where taste is concerned. As for the flavour, somewhere between carrot, celery and potatoes with a water chestnut type crunchiness.
Plant Heritage National Collection of Dahlias is in Cornwall
The collection was originally established near Penzance, Cornwall in the 1980s by David Brown, a leading expert on Dahlia in the UK and internationally. This National Plant Collection has been, and still is, the largest recorded collection of Dahlia in the UK. There are currently more than 1700 cultivars from 22 different species of Dahlia within the collection .
However, due to changing circumstances, it had to be moved. Louise Danks, now the accredited Collection Holder, wanted to ensure that the collection would remain in Cornwall, where it had become an integral part of Cornish horticultural heritage. And so the entire National Plant Collection of Dahlia was relocated. Some 2000 individual plants were moved from Varfell Farm to the Kehelland Trust near Camborne during autumn 2020 and early spring 2021. And in May 2021 the first Dahlia was replanted. They were closed for visitors for essential maintenance of the Colelction but will be open again for the 2025 Dahlia season.
and finally…
Hopefully, these Dahlia tips and facts have inspired you to grow a few in your own garden. And you may even like to think about exhibiting some at your local flower show. This can be great fun and you’ll find the garden club members helpful and supportive of newcomers.
Of course if you’d like some personal help with a planting design for a mixed ornamental border of bulbs, herbaceous perennials and shrubs filled with colour and bees year round, then do please get in touch to ask about our design and consultancy services.
For further gardening advice and inspiration, check out Plews Potting Shed blogs, including the selection below and our monthly Tipsheet – You could come and find us on Instagram Pinterest and Facebook too.
If you’d prefer hands-on personal help from yours truly to learn more about your garden and gardening, why not ask about our bespoke Gardening Lessons, where your classroom is actually your own garden. We can help you learn gardening basics, and also show you how to plan an ornamental border or kitchen garden. Have a read through this pdf download for info
And on that note, you can have a peek at the progress of my garden renovation, Spitfires and Slow Worms, on Instagram and Facebook You’ll get to see it in person if you come to the Plews Gardening Workshops, I’m at the finalising of dates stage for weekday and weekend slots for January – April, so keep an eye on the website for updates.
Plus get your local garden club, allotment, WI, U3A or other group to ask me along to give a talk (and bring plants 😉)
Related Gardening articles you may enjoy from our Award winning blog
What is an Ornamental Edible Garden?
Edible Gardens Ornamental food
Autumn Planting Ideas for Your Garden
Edible flowers – Eating your Flower Garden
Autumn Borders – Colourful Planting Ideas
Autumn Garden Visits for Design Inspiration
