How to Grow Dahlias

Your dahlias are in and starting to sprout green leaves above the ground- yay! So now what?! Here are some tips to get you growing.

If you’re looking for info on how to plant your dahlia tubers, go to our post “Planting Dahlias”


Once the plant is sprouted and growing, dahlias need regular, consistent watering. We use multiple lines of drip tape to be sure that they receive sufficient water and usually water 2-3 times per week. Check the soil moisture not just at surface, but at 6 inches down to see if your  irrigation is penetrating and providing sufficient moisture.


Keeping your plants well fertilized is an important task throughout the season. As we’ve said before, healthy soil grows healthy plants! Often people want a specific fertilizer recipe and regime to follow, but every garden and climate is different and you’ll need to tailor your program to your particular space. (Keep in mind that over fertilizing isn’t good either! It can be detrimental to our environment as well as your plants.) One important thing to know is that once your plants are established, you don’t want to give them fertilizer that is too high in nitrogen. This can cause plants to rapidly put on lots of green lanky growth and result in small blooms or low flower production. According to Swan Island Dahlias, it can also be a cause of tubers shriveling in storage.

Although we typically add in some organic, balanced granular fertilizer when planting, we also fertilize our dahlias on a regular schedule throughout the growing season. We like to water our plants regularly with an organic blend of fish and kelp fertilizer. Our philosophy is to use a very diluted mixture, but to do it more often. If your garden is small, it’s as simple as adding the concentrate to a watering can, mixing it thoroughly and watering your plants and the soil around the base with the mix. On a larger scale here at the farm, we use a fertilizer “dosatron” which allows us to mix in the concentrate on whatever dilution level we choose and then irrigate, or “fertigate” our plants through our drip irrigation system.

Keep the weeds at bay!

To control weeds, a good method is to mulch your plants. Quality straw, that is free of weed or grain seeds, works as well as decomposed leaf mulch. Often it is advised to wait to apply mulch until your plants have emerged and the weather has warmed up so that you don’t unintentionally cool the soil and slow growth. You can also top-dress your plants with a thick layer of well aged, quality compost to help prevent weeds- the thick layer of compost acts like a mulch. If you don’t have access to mulch, you can also just weed your plants by hand or with a hoe- the old fashioned way! Any way you cut, you’ll want to eliminate competition for nutrients and water by keeping your dahlia bed tidy.


To encourage branching and a bushier plant, pinch your dahlias when they are approximately 12 inches tall. Simply snip (or pinch!) the central growing stem just above a set of leaves, leaving at least 3 sets of leaves on the plant. Although it sometimes feels like it’s the wrong thing to do (why am I chopping of 4 good inches of my plant?!), you’ll be glad you did! It encourages the plant to branch out and essentially make more flowers with better, longer stems for cutting. Even if you don’t plan to cut your flowers for the vase, it still encourages the plant to put out more blooms. Check for other posts on how we pinch our plants.

Staking or Trellising

Dahlias will also benefit from staking. There is nothing worse than watching your beautiful plant that was just about to flower topple over in a rain or wind storm! Home gardeners can just use a wood or bamboo stake pounded in the ground next to the plants and then tie the main stalk to the stake as they grow. We pound in posts at the ends, and spaced about 7 ft apart along each side of, our beds. We then tie and run sturdy twine down the sides, wrapping in around each post to create a corralling effect.


Depending on your climate and the variety of dahlia, some early flowering types can start to start flowering as quickly as 75-80 days. But most seem to be closer to 90 days.  Remember that every variety is different and some take much longer to flower than others. Generally, smaller flowering types will be quicker to bloom.

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