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Past Articles Library | How to Grow and Care for Delphinium

As a child, I took many trips to my Great Grandmother’s garden.  It was a magical place for me that was filled of plant material from faraway places and stories.  While my grandmother was not formally educated in horticulture or botany, she could really make a twig grow with just a 9th grade education. 

One of my fondest memories of my Great Grandmother’s garden was her delphinium plants.  While there are several different varieties today, in my Great Grandmother’s time the only kind was the standard, which required staking.  Today, you can find the standard variety along with semi-dwarf, and dwarf.

If you have interest in this perennial, keep in mind that it only grows well in USDA Plant Hardiness Zones 3 through 7 but can grow in other areas as an annual.

Prior to planting your delphinium, you will need to select the best location.  Delphiniums like areas that receive full sun to slight shade.  They also prefer to be planted in areas that are protected since they do not do well with sudden wind and/or rain.

While planting seeds is going to be covered, they are notorious hard to grow from seed.  If you are a beginning gardener, consider buying plants.

Prior to moving on to the seed planting process, you will need to pull out your calendar.  Delphinium seeds will need to be planted 8 weeks before you local frost free date.  Once you have that date, you are ready to move on to the seed propagation process.

To begin the seed planting process starts with preparing the seed tray.  This is easily done by cleaning and sterilizing the tray.  To do this, fill a basin with water and a capful of bleach.  Once that is done, place the tray inside the basin and soak.  Yes, I know that the whole tray will not fit into the basin.  In doing so, this process will need to be repeated.

After you get the seed tray in the basin, allow the tray to soak for 5 to 10 minutes.  Once that time period has passed, scrub the seed tray to remove dirt, and pests.  Repeat the process with the other side of the tray and then rinse in clear water.  Allow the seed tray to set out to dry.

Once the seed tray has dried, the next step is to prepare the planting medium.  To do this, mix 1 part sterilized all purpose potting soil to 1 part sterilized compost.  Next, fill the seed tray to ½ inch from the top.  After that is done, moisten the planting medium until it is evenly moist.  Let the moistened soil set for 5 minutes before moving on to planting the seed. 

To begin the seed planting process starts off with pulling out a ruler.  Using a ruler will allow you to get the most out of your seed since it will allow you to properly space your seeds.  Delphinium seeds need to be spaced 1 inch apart.  As you begin the seed planting process, simply drop one seed at 1 inch intervals.  Once that is done, cover the seeds with ¼ inch of the planting medium created.  Mist the soil surface and move the seed tray to a sunny room that is kept between 65 and 75 degrees Fahrenheit.

Continue to monitor the moisture of the soil and water accordingly.  Do not allow the soil to complete dry out.  In about 10 to 20 days, you should begin to see little dots appear.  These are the germinated seeds or delphinium seedlings. 

Keep your delphinium seedlings in their seed tray until they are 1 inch in height and have their second set of true leaves.  After the seedlings have met these requirements, the next step is to move them to their individual 3 inch containers.

Monitor the soil moisture and feed your delphinium seedlings a balanced fertilizer.  This fertilizer formulation needs to be 12-12-12, which needs to be diluted by ¼ and given once a month.

About a week prior to your planting date, it is time to harden off your seedlings.  What is hardening off?  Well, it is a process by which you gradually expose your plant material to their new environment.  In this case, you will need to slow expose the delphinium to a sunny or slight shade location.

While you are hardening off your plants, you can begin preparing the garden space for your new addition.  If the garden space is new, remove all the plant material and loosen up at least 6 inches down.  Next, add 3 inches of well seasoned compost and 1 inch of seasoned manure to the soil surface.  Mix these ingredients down into the soil and smooth the soil surface.

If you are using an existing garden space, simply add the seasoned compost and manure, turn the soil over, and smooth the surface.

Planting the delphinium starts off with pulling out the ruler and powdered milk.  Delphiniums need to be planted so that there is 20 to 25 inches between plants.  Once you have the space measured off, make sure to mark the space with powdered milk.

The next step is to dig a hole that is the same depth as the container that the plant is in and twice the width.  After this step has been completed, remove the plant from its container.  Do not simply pull out the plant.  The best approach is to tip the plant upside down and gently squeeze the sides of the pot.  The plant should then simply fall into your hands.

Once you have the plant in your hands; gently tease the roots by loosening them up.  Next, place the plant in the hole that you have prepared and fill in.  When doing this step, make sure that the crown of the plant is even with the surrounding soil.

After all the plants have been planted, water in the delphinium and cover with a 4 inch layer of mulch.

If you are growing standard delphinium, go ahead and set up your support system so that you can tie them up as they grow. 

During the growing season, apply a powdered balanced fertilizer once a month but do not just sprinkle it on top of the mulch.  To get the most out of your fertilizer, move the mulch away from the base of the plant and sprinkle the fertilizer.  Replace the mulch and water in.

To keep your delphinium looking its best, cut the flower stalks just below the last flower after the blooms are spent. 

When the first killing frost hits your area, cut down the dead foliage and cover the plant with 6 inches of hay or shredded leaves.  Keep this mulch on until about a week prior to your local frost free date.  At that time, remove the mulch so that new growth can break through.


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Purple Knight Alternanthera

This ground cover likes partial sun to full sun.

It grows 16 to 20 inches (40-50 cm) tall, and 2 to 3 feet (60-90 cm) wide. It is very heat tolerant.

Its beautiful purple leaves make an excellent accent plant in the garden.

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