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Dahlia Growing Tips

Dahlia Growing Tips

We moved to Braidwood a few years ago, and shortly afterwards I was gifted a few mystery dahlia tubers. We basically just planted them in the ground and were surprised by the results. Since then, I've been reading and watching everything out there about dahlias.. and our dahlia patches have grown year on year. Here are some tips I’ve collected along the way.

Storing until Planting

When your tubers arrive, store them in a cool, dry place if it’s a while before you’ll be ready to plant (they will arrive in saw dust). Check when you’re able to pop them in the ground for your climate zone. For us, in our cool climate, we wait until after the last frost. 

Soil Preparation

Once you have chosen a sunny spot with well-drained soil for your dahlia patch, it’s important to check the soil’s condition and improve your soil as required. We have a few cows, so it’s easy for us to add well composted cow manure to our dahlia beds. I also add our own compost, plus Seamungus, lime and multi grow. I top the beds with sugar cane or pea straw mulch. There are crops you can plant to suppress weeds and improve the soil in between the growing months – I haven’t experimented in this space yet. Everyone’s soil will be different. I had grown a few dahlias initially to test my location, and then kept planting nearby my test patch. I sent soil away for testing in each area of our farm we planned to grow certain things for some expert advice on what to add in which location. Depending on how many dahlias you plan to grow, it could be worth testing your soil and adjusting your soil conditions to suit. Our soil beds are built up to a good 25cm or so, with lovely loose soil containing good organic matter.

Planting

To plant dahlia tubers (also called bulbs), wait until the danger of frost has passed and the soil has warmed, this is usually in late spring. Dig a hole about 10-15cm deep and lay the tuber horizontally with the "eye" (a small bump where sprouts emerge) facing up. You want this top part of the tuber to be sitting about 8cm below the ground. Space tubers about 30-40cm apart to allow room for growth and cover with soil. Label your dahlias well if you are planning to divide or pass on tubers or keep track of your own dahlia collection. I have quite a few mystery tubers this season as I decided permanent marker on bamboo forks would be a great system for labelling some of my dahlias – turns out, no – you need to use a garden marker on plastic markers or gardeners tape around the stem and you need to check your labelling system is holding up well.

Watering & Staking

Do not water your dahlia bulbs heavily until they start sprouting and reach around 10cm in height, as excess moisture can cause rot. Once the plant is growing, you’ll need to water regularly. We set up a drip watering system for our dahlias – we adjust this depending on the weather, but generally we have our drip system on initially twice a day, for 10 minutes each time. We check the effectiveness of this and adjust as needed. As the weather warms up, we have increased this to three times a day. We have also switched our watering system off during period of good rainfall to save overwatering. Prepare stakes or a system for supporting your dahlias as they grow, quickly and tall. There are a lot

Follow the Dahlia Community

There is so much information out there – many You Tube instructional videos and dahlia blogs that have many and different answers to your dahlia growing questions. I have enjoyed learning as I go and trialling different approaches to storing, dividing and growing dahlias

Enjoy your Flowers

You may like to experiment with clipping, or pinching, out the centre stems of your dahlias to encourage more flowers. The best time to do this is when your dahlia plant is about 40cm tall with three to four sets of leaves. Last year we enjoyed dahlia flowers from December through to early April. Regularly picking the flowers helps the plants to keep on blooming, so cut them and enjoy them and cut back any flower heads that you didn't manage to pick while at their best.

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My Dahlia Timeline (Cool Climate Zone)

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September: Soil Preparation & Watering System Set Up
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  • Consider having your soil tested to prepare for the planting of your dahlia tubers.

  • Improve your dahlia bed’s soil with organic matter such as cow manure, compost and multi-grow. Our soil testing recommended we add lime. Give it all a good mix with a garden fork, loosening the soil as you go. It’s a good idea to do this a few weeks prior to planting.

  • Prior to planting is the ideal time to set up any watering system if you are planning to install one (we have a drip system for our dahlias)

  • Have a supply of mulch ready to apply after planting your dahlia tubers.

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October: Planting
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  • If you are planting more than one variety of dahlia, I recommend labelling. I have a spreadsheet and map to identify where each variety will be planted. I will also place a garden marker scribed plant label in the ground next to the dahlia, and once December comes, I’ll attach a ribbon tag label around each central stem.

  • Keep an eye on your local weather reports and note any upcoming frosts. As tempting as it is to get your dahlias going, wait until the danger of frost has passed and the soil has warmed, to plant your dahlia tubers, this is usually in late spring. I’ll be waiting until the last week of October here in Braidwood. The Bureau of Meteorology has some data around no. of days of frost per region, but I’d simply check with other gardeners in your area or your local gardening club or nursery on their experience of final frost dates.

  • Dig a hole about 10-15cm deep and lay the tuber horizontally with the "eye" (a small bump where sprouts emerge) facing up. You want this top part of the tuber (the crown) to be sitting about 8cm below the ground. Space tubers about 30-40cm apart to allow room for growth and cover with soil.

  • Do not water your dahlia bed until the plants are shooting about 10cm above the ground.

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November: Watering & Staking

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  • Start watering your dahlia bed once your dahlia plants are 10cm tall. You want your soil to be moist but not too soggy, so play with timing that works best for your location. 

  • Set up a staking system ready for a big growth spurt. I would look at online tutorials to find a staking solution that works for you and the number of plants you have.

  • Cut centres out for bushier growth once 40cm tall.

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Late December: Cut Flowers

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  • Flowers should start to appear mid to late December. This will vary depending on soil conditions, hours of sunlight and watering. And once they come, you will be surprised by how they just keep growing. Pick your gorgeous blooms and enjoy them as this helps more dahlias to come.

  • Any flowers that wilt before you’ve had a chance to pick them, should be cut as though you are picking them and added to your compost pile to create mulch.

  • When I cut my dahlias, I cut them with a long stem and trim off any side shoots – I’ll post a video of this during growing season. I have buckets of fresh cold water ready to place them in while they wait to be arranged.

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January / February & March: Enjoy your dahlia blooms
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  • Play with different arrangements and enjoy gifting bunches to family and friends – the more you cut your dahlia patch the better.

  • Add extra fertiliser to give your dahlia bed soil a boost during its peak growing period. Take plenty of photos and tag your images with each dahlia’s name.

  • Work on building up your compost pile, ready for next spring.

 

April: Before Frosts Arrive

  • Lift your bulbs in clumps before the first frost appears (this could be late March or early April). Keep on eye on your local forecast.

 

May through to August: Dividing and Storing Tubers

  • There’s a lot to cover here, so please subscribe and I’ll send out further details on this topic as this time approaches.

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