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Growing Dahlias

Dahlias are one of the most rewarding annual garden plants. A dahlia starts as a tuber; their size doesn’t matter as long as they are bigger than your thumb. Once planted properly it will sprout into a plant in a few short weeks/months and then will continue to grow for several more months producing some of the most well loved cut flowers. Their amazing blooms come in a large variety of colors, shapes, sizes and they have the most fantastic personalities in the garden. They flower in most regions from mid summer until the first frost. What is better yet, while the plant is in the ground all season long, it is making an abundance of new tubers in the soil that can be shared for next season when dug and stored properly.


Please read “Getting started with Dahlias”, then continue with the instructions below. If you have done that already, terrific, you are ready for the next part which is below….. GROWING DAHLIAS!!   


       Growing Dahlias


  • Once a Dahlia has reached 6”-12” tall and the plant has 3-4 sets of leaves, their roots have begun to be established and it’s unlikely the tuber will rot when the plant is watered. Dahlias need at least six-eight hours of direct sun. Dahlias like to be deeply watered 2-3 times a week at the base of the plant depending on your climate and soil. I have found that my dahlias have benefitted from some overhead watering very early in the morning when the temperatures were forecasted to reach over 90 degrees. Caution: watering later in the day can lead to diseases if the leaves are wet heading into the evening hours.


  • Mulching dahlias with weed and seed free mulch is an excellent way to retain moisture in the soil. Keep the mulch from touching the main stalk of the plant.  The mulch will also help with weed suppression. Commercial mulches with dye are not recommended for dahlias.


  • If you would like to have a bushier plant with more blooms you can  “pinch” or cut back the plant once it has over 4 sets of leaves (usually about 12-16”). To do this, find the center stalk and remove the top sets of leaves with your clippers. The center stalk will scab over in time. Pinching encourages the plant to branch out, thus creating more stems for more blooms. If you choose not to pinch, the plant will use its energy to create one large center stalk. This is fine too; it is your choice.


  • Once the plant has begun to grow taller it will be necessary to tie the plant to the stake to keep it upright. Once the plant starts to bloom, the plant will be unstable due to the nature of the large flowers. If the plant is not properly tied to the stake, you risk the stalks breaking. (If a stalk does break, simply cut it back to the next set of leaves, it will be fine.) If you grow many dahlias there are other techniques for supporting the plants such as the corral method or horizontal netting.


  • Dahlias are easy to care for once they get going. Fertilizing is always something to consider that helps the plant throughout the growing season.  Dahlias are hungry for food all the time, but it needs to be the right kind of food (fertilizer). Amending the soil at the beginning of Spring is a fantastic practice in successful gardening. Many plants, including dahlias like an extra boost of food. Please make sure to take a soil test before adding any additional amendments in the soil. In general dahlias don’t need extra nitrogen (N) after they start blooming but rather more Phosphorus(P) and Potassium (K). Find an all-natural fertilizer that is higher in Phosphorus and Potassium- something like a 10-20-20 or a 5-10-10. Everyone’s soil is different; please do some additional reading. This is simply a reminder to find a fertilizer that will work for your garden and your dahlia plants. Also, follow the instructions on the packaging, “more is not necessarily better”.


  • Now let’s talk about pests: large and small. Deer do not normally bother dahlias.  Snails and slugs can be damaging to your young dahlia shoots, I recommend reading up on this. Insects like Japanese beetles, earwigs, thrip, aphids cucumber beetles, spider mites and saw flies are common pests too. There are numerous methods for treating these pests. If you are new to gardening contact your local Extension agent and they will help you learn what are the best natural and conventional methods for dealing with these kinds of insects. In general, greater soil health will lessen insect damage. This practice of creating better soil is a whole other concept and I am diving deeper into learning more about it myself even after gardening for 30 years.


  • Harvesting the dahlias flowers is the fun part!! I recommend you cut your dahlias as long stemmed as possible early in the morning. Cut the bloom when it’s not quite fully opened. Dahlias will open a little bit more after they are cut. Once you have cut the dahlia stem place it in a bucket of cool water. Dahlia stems are hollow and need fresh clean water to keep them vibrant and healthy. There are many philosophies on how to preserve a dahlia bloom for the longest vase life. Feel free to read up on those suggestions. I personally keep my dahlias in clean water in a cool dark place until I am ready to use them. Normal vase life for a dahlia bloom is 3-8 days depending on the bloom size. In general, large dinner plate dahlias usually last the least amount of time in a vase, while the smaller ball and formal shaped dahlias last longer.


  • One last thing, the more you pick dahlia blooms, the more they will produce more flowers. It is good practice to dead head the blooms that are spent and not useable. This encourages new growth and more buds!




If you have read to this point, Congratulations!!!!! If you are feeling a little overwhelmed my advice to you is….go for it. Dig a nice fluffy hole when it’s warm enough and hammer a stake into the hole and plant your tuber. My odds to you- 98% success!! I would say that’s an awesome start to a new hobby!! (Don’t worry about the other 2%- that’s simply Mother Nature). Gardening is supposed to be fun, relaxing and rewarding. As time goes by you will learn more about dahlias and how to improve your soil and your growing techniques. Dahlias are a highly rewarding  and I will warn you now, you will be addicted to Dahlias in no time…. In my world, that’s a fantastic addiction to have!!!!!

Go back to read about Getting Started or continue on to Dividing/Storage.

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