Dahlias will grow well in sun or shade but you will get more flowers and a stronger plant if they are growing in at least 6 hours of sunlight. Dahlias grown in shade will flower well as long as they get morning sun, are growing in good quality, well-draining soil and are watered regularly.
Dahlias will grow and open flowers within a week after they appear if they are in full sun. They can last for up to 2 weeks and can be picked and kept successfully in a vase with water.
This article will explore what you need to know about growing dahlias in the sun and shade, what you can expect and tips for growing in each light condition.
Growing dahlias in the sun
Here are a few tips and what you can expect if you grow dahlias in the sun. This is what you can expect and what you can do to get the most flowers and best growth in this position.
1. Dahlias flower earlier in full sun
The benefit of growing dahlias in full sun, at least 6 hours is that you will get flowers earlier. If you get your dahlias in the ground in spring you can have them flowering as early as possible.
2. Larger plants
Dahlias growing in full sun will give you larger and heathier plants. They will be able to photosynthesize efficiently, taking in the sunlight and converting it with carbon dioxide into carbohydrates. Dahlias growing in full sun will grow healthy, green leaves and a healthy root system.
3. Surround them with mulch
Dahlias growing in a position that gets full sun will grow best if they are surrounded with mulch. This will help to hold water in the soil for longer and stop it from evaporating as quickly. I like to use bark mulch but you could also use straw, hay or even fall leaves.
Make sure the mulch is around 2 inches thick, which is enough to keep moisture in the soil, to stop weeds from growing through and will protect worms in the soil. The worms will feel safe to dig their way up, start to break down the organic matter making the nutrients available to the plant roots.
4. Plant in good quality soil
It is essential to grow dahlias in good quality soil when they are growing in full sun. Dahlias need free draining soil to avoid root rot, but soil high in organic matter will help to hold enough moisture in the soil to keep the plant happy.
Dig through compost and aged cow manure to help to improve the sol before planting. This will encourage worms, improve your soil bacteria population and allow the roots to get the oxygen they need.
5. Water regularly
Dahlias growing in full sun will grow best if they are watered regularly. They like consistent water however the soil can dry out fast in the full sun. Mulching the soil helps to reduce the water evaporation but watering is also essential.
I live in a sub-tropical area that gets lots of rain over spring and summer. I can usually get away with minimal watering over this time but always check the soil. Water the soil when it has dried out 1-2 inches below the surface.
Growing dahlias in the shade
Dahlias will still grow well in part shade. If they get at least 6 hours of morning sunlight, then they will still grow strong and flower. Here are the top things to know if you plant to grow dahlias in the shade.
1. They will take longer to flower
Dahlias growing in part shade will take longer to flower than those growing in 8 hours of full sun. They will eventually get there and open up their beautiful blooms. If you only have a part shade position available you can still have beautiful dahlias, you might just have to wait a little longer.
2. You may get less flowers
Dahlias are going to produce less flowers if they are growing in shade. Generally, the more shade they get, the less flowers they will grow. Dahlias that are getting morning sun and at least 6 hours of full sun or dappled shade you will still have success.
3. Aim for morning sun
If your dahlias can only be planted in part sun, aim for morning sun if you can. This gentle sun is great for dahlias to grow well. Afternoon sun only can be too hot for dahlias if they have had shade all morning.
My dahlias get around 6 hours of morning light, from around 8am to around 2pm. Their flowers have popped up fast and are getting ready to open and bloom. My dahlias are soft pink this year, and they have prime position near my lemon tree in my front yard.
When dahlias flower and deadheading
Dahlia flowers will flower from spring all the way through summer and into fall. To get them to continue to flower throughout this time, deadheading them is essential. Grab some sharp, clean secateurs and trim the long stem down as close to the base of the plant as possible.
The old flowers can be put in your compost to break down. Add some flower promoting fertilizer after around 8 weeks to replace any lost nutrients. Dahlias will continue to grow and bloom for your beautifully during the warmer weather.
Check out how to plant dahlia tubers in the video below.
Do Dahlias Like Sun or Shade? | Summary
Dahlias will grow best in full sun growing faster, bigger and growing more flowers. Dahlias will still succeed in the shade but will not produced flowers as fast or as well. Dahlias are a great spring and summer flower to add a fun and bright feature in your garden. They can flower all the way through fall and keep your garden looking bright.
Happy growing.
I am an accredited practicing dietitian, experienced gardener and a dedicated cook. I love writing and sharing my experience so you can learn from my successes and mistakes.