How to Grow Delphiniums in Pots or Containers

Are you thinking of growing delphiniums in containers this season but aren't quite sure where to start? Container grown delphiniums are a great option for gardeners that have limited space. In this article, certified master gardener Laura Elsner walks through eight simple steps to grow beautiful delphiniums in pots or containers this season!

Container Grown Delphinium

Delphiniums are one of my all-time favorite garden flowers. These tall blooming perennials have beautiful blue, purple and white flowers. Their tall and colorful blooms are a sure sign of summer. I normally plant them in the back of garden beds, providing a glorious floral backdrop to the rest of the garden.

But, if you are short on space, delphiniums can also be successfully planted in pots or containers. Because they grow upwards and don’t have a rapid spreading rate, they make a great option for container gardens if you live in the right hardiness zone for the variety you’ve chosen.

If you’ve decided you’d like to add some delphiniums to your space limited garden, you’ve come to the right place. Follow along as I outline how to grow delphiniums in pots or containers in eight simple steps!

Step 1: Choose Your Container

Terracotta containers on the wood table in the garden
Pick a large pot that provides decent drainage.

Choosing a container for a potted delphinium will take some thought. First, make sure whatever pot you choose, it has drainage. Delphiniums do not like sitting in water. They like to be evenly moist and never dry, but sitting in  water will cause them to turn yellow and die.

Second, get a pot of substantial size. They do not like being smooshed into a pot. Their roots need some room to spread out. Another reason for a larger pot is that they also do not like drying out.

They will dry out much faster if they are in a small pot. And finally, delphiniums are a tall narrow flower, a bigger pot will provide some stability to the flowers, so they don’t tip over in every gust of wind.

Step 2: Use The Right Soil

gardener holding soil for planting in pots
Use a moisture-retaining potting mix when planting.

Delphiniums like nice loose free draining garden soil with lots of organic matter. But, this does not mean you can just dig up the soil in your garden and put it in a pot and be successful.

Containers require extra drainage for success. I recommend using an all purpose potting mix for all container plants, including delphinium. This allows for nice drainage so the plant does not sit in water. A moisture retaining potting mix is even better.

Delphinium do not like drying out completely, so having a moisture retaining mix will really help on days you forget to water.

Step 3: Pick The Right Variety

Variety 'Summer Nights'
The popular ‘Summer Nights’ variety is excellent for planting in containers.

Not all varieties of delphinium are suited for containers. There are hundreds of varieties.  The taller varieties will bend and snap. Or they need staking, which doesn’t look great in a container on the patio.

Also a tall variety in a container that is near a seating area will be too tall to enjoy, you want the flowers at eye level. Tall varieties are better suited for in the garden, or in a large pot placed farther away from seating areas.

I recommend a dwarf variety for container growing. These varieties only grow about a foot tall. It makes them less likely to snap off, and gives a nice bushy lush look to containers.

Give Delphinium Grandiflorum ‘Summer Nights’ a try. It features delicate lacey foliage and small sprays of a dark indigo blue color. It grows about a foot high and flowers for a longer period than some of the taller varieties.

Step 4: Start Planting

Garden planted sprouts
Place the delphinium in the center of the pot up to the crown of the plant.

Planting into your container properly is key to its success. Make sure you have the proper soil, as mentioned in step number 2.

Make a hole in the container in the place you want the delphinium. Place in the back of a container for room for other smaller plants in a mixed container. Or plant in the center if it will be the only plant in the container.

Gently squeeze the plant out of its plastic nursery container. If it is really really root bound ( the roots are in the shape of the container) make sure to break up the root ball.

Now plant the plant in the potting soil up to the crown of the plant. Make sure the soil line is level with the container. Not mounded over or sunken under. Over mounded soil will spill dirt all over when it is watered. It will make a mess and the water won’t seep to the roots. If the plant is sunken into the container,  it leaves the stem vulnerable to crown and stem rot.

Step 5: Start Your Watering Schedule

Purple flower with water drops
Delphinium needs regular and abundant watering, especially those planted in a container.

Container grown delphinium will require more water than those grown in the garden. Especially if it is grown in a smaller container. When it is hot out they may require water everyday.

Do not let the pot dry out completely. Under watered flowers will get droopy and sulk. Water it and it will perk back up. Don’t let it get to the crispy point of no return.

When watering try and aim only for the soil line. Try an avoid spraying the leaves and water at the base. Constantly wet leaves makes them more susceptible to pest and diseases such as aphids and powdery mildew.

Step 6: Pick Your Location

Wild flowers blooming in full sun
Partial morning sun is recommended while avoiding afternoon sun.

Make sure you place you delphinium container in a location that gets full sun. Ideally, it would get full morning and/or late afternoon early evening sun, with a bit of protection from the extremely hot afternoon rays. This will help the flowers last longer, and prevent the leaves from getting crispy.

Do not place your container in too much shade. The plants will get long and straggly and will have few blooms.

To prolong your their blooms in a container, try and place it in a protected location. Ideally, I would also try and plant it under a covered porch or eaves.

If you are in control of the watering, you can aim it at the soil line of the plants. If the delphinium is not pummeled with rain, the blooms will last longer. Since they only bloom once a season, protecting those blossoms should be top priority.

Also, try and place it in an area away from harsh winds. Having a newly blooming stalk snap in the wind is a garden tragedy.

Step 7: Regular Maintenance

Blue flowers in garden
Trim off yellow leaves and faded delphinium buds to keep it looking neat.

Luckily delphiniums are fairly low maintenance perennials. Especially if you get the soil, water, and sun conditions just right.

You may have to cage or stake them depending on the height of the plant and size of the pot. Try and stake it early on. It is easier to place the cages and stakes on with less risk of bending and snapping the stalks of flowers.

Also for container grown delphinium try and find green stakes or cages, or natural bamboo stakes. Since the containers are usually up close to seating areas you will want them to look natural and nice.  You can also find stakes with decorations and adornments on them to add a touch of whimsy into containers.

Deadhead flowers after they finish blooming. If you live in an area with a long growing season you can cut them right back and you should get another flush of flowers late in the season.

Prune any yellowing leaves off. I don’t spend much time doing this, since they usually are far off in the background and nobody can see the yellow leaves near the bottom of the plant. But for containers that are close to view, I always take the time to prune out any brown or yellowing leaves.

Step 8: Combine With Other Flowers

Flowers in hanging pots
These popular flowers typically bloom in summer for 2-4 weeks.

Delphiniums are a perennial that only bloom for a 2-4 week window in the summer. Keep this in mind when you are planting. It won’t bloom all summer long like a geranium will. It still has delicate lacy foliage with a nice green color and some height the rest of the season. But the vibrant flowers only have a small window of time.

You have some options to add color the rest of the season.

Plant your delphinium in a mixed container of other flowering annuals to add all season flowers. I like have a delphinium in a pot that will bloom and remain green the rest of the season. I will pair this with trailing petunias, or geraniums to compliment the flowers and then to keep flowering after the delphinium is done.

You can also plant in a mixed container with other flowering perennials that have different bloom times.

An example of this would be a large container with a peony, delphinium, and brown eyed Susan. The peony will bloom first, followed by the delphinium and finally the brown-eyed Susan. The foliage of the other plants will still provide interest in the container even when they’re not in bloom.

Another option is to plant in a pot and have other plants planted in separate pots. Then just move them in and out of the arrangement based on their blooms. This is great if you have a large yard. You can swap things out and place the pots of things no longer in bloom somewhere out of view (where they still get sun and water). Then swap in other plants that are blooming.

Final Thoughts

Growing delphiniums in containers is easier than you think! They can add height to container arrangements, and their distinct flowers are hard to beat. They are also great for gardeners that are a bit short on space. With these eight simple steps, you should be growing them effortlessly in containers all season long.

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