Gardening Tips: How to Grow Dahlias in Melbourne

by Deb Collett

EWHA member and Dahlia expert Deb Collett shows us how to get the most out of our Dahlias here in the Melbourne climate. Deb is a long-time grower, exhibitor and judge of Dahlias. You may have seen her perfect blooms at Dahlia shows and the Melbourne International Flower & Garden Show.

Dahlias – Diva or Workhorse?

Whatever your opinion of dahlias is, dahlias are certainly having ‘a moment’ right now. They seem to be everywhere!

As a gardener who grows quite a few of these plants and someone who also likes to get into the competitive side of horticulture and exhibit them, I think they are generally a great, easy-care plant giving abundant flowers during their season, which can last at least five months. The more you pick them, the more flowers you will get, and this is where their workhorse attributes shine brightest. Their bounty doesn’t stop with just the flowers, they are typically generous producers of tubers too.

So, what are my recommendations for growing them? I’ll try to keep it simple, but I have found from experience that for every directive to do something a specific way, there does seem to be evidence that you can do the complete opposite and still have success. We’ve all had that plant that we have stringently followed the growing advice only to face failure. We have, conversely completely ignored plants and expected the worst, to find them performing magnificently. Dahlias are no different but are generally much more resilient that we think.

Therefore, my ultimate and overriding tip – read the advice and then do what feels right to you in your own circumstances.

Dahlias want sunshine, to be fed and to be kept hydrated. A bit like us on a summer holiday. Do this and you’ll be well rewarded. The trickier part of the equation is what to do when they are dormant, so I hope the following points are helpful.

• Lift in June if you want to grow something else in that spot for winter.
• Rot is the enemy but if the area is well draining and you don’t get severe frosts (where basically your ground freezes as it can in parts of Europe and the USA) you can leave the plants in.
• If you lift, you will need to store and again there are so many options. The risk of rot remains with the added risks of losing them to the rats or contrarily they dry out.
• A caveat – if your dahlias have been in the ground for several years and you don’t think they are as vigorous as they once were, they are probably overcrowded and lifting and dividing will improve the situation and the bonus is you will have tubers to plant in other parts of the garden or to give away. This can be done as late as October/early November which is considered the typical time for planting in Melbourne. At this time the plants will have started to shoot, so this step could be done in September.
• You can lift and divide, by simply cutting the clump in half or quarters if you don’t want to divide down to the tuber – leave for several hours or a day or more for the cut to heal/dry out and then replant. There just needs to be at least one eye with each division, and these are found near the crown of a tuber.
• At planting it is a good time to add a tonic to the soil.
• Plants don’t generally need supplementary water until they are established (four/five sets of leaves), remember rot can also be the enemy at this time.
• If your soil is really pumping you may not need to feed but early in their growth they are looking for nitrogen to get the plant established.
• Mulching helps keep the soil moist and things like pea-straw or lucerne will break down and feed the soil.
• Again, if you have great soil you may not need to feed – but potassium as they come into flower will boost production (if you are asking a lot of the plants as I do, liquid feeding on a “weak weekly” basis really keeps them blooming).
• Most importantly keep cutting the flowers to give away or enjoy indoors. Or keep up the deadheading if you like to enjoy you flowers in the garden. Both of these actions will encourage more blooms and don’t be afraid to cut deep into the plant for a nice long stem, they will soon spring back with more buds.
• Let them die back naturally if you can (this will generally happen from April).
• Make sure you mark where your plant is and what variety it is before it dies down, you don’t want to inadvertently dig it up while it is dormant and once dormant all tubers look very, very similar.

These simple steps should set your dahlias up for success.  However, as I’ve already alluded to, there are always exceptions to the rule and a small percentage of varieties are much more of a diva.  Fingers crossed, you’ve not set your heart on growing a diva.

If you don’t have dahlias growing, do think about sourcing some tubers this year. There are a myriad of small flower farmers, mostly female, all-over Victoria that sell tubers. Many have been affected by the ban that other states have applied to certain plants (including dahlias as a potential carrier plant) due to the Tomato Potato Psyllid (TPP) outbreak here and most are now only shipping to Victoria. It’d be a great time to support them.

For more info dahliasocietyofvictoria.org.au/Monthly-Guide

PS: Have you also spotted dahlias on your mail recently? Like I said, they really are having a moment and I’d encourage you to buy some dahlia stamps from your local post office to brighten up the winter months when the real plants are dormant.