How to Grow and Care for Dahlia Plants
Big and Beautiful Dahlias for your Garden
With a multitude of different colors, shapes and sizes, Dahlias bring life and beauty
back to your landscape in late summer and into the fall months.
The diversity of the Dahlia allow you to use them in many different aspects of your landscape design,
from low growing border plants to stately background plantings that may reach six feet in height!
Dahlias make excellent cut flowers, which will typically last about a week in the house.
Growing Requirements of Dahlia Plants
Dahlias are summer blooming tubers that are generally only hardy in USDA zones 7-11.
In the majority of the country, Dahlias must be planted each spring
and then cut back and dug each fall after the first killing frost.
Dahlia plants grow and bloom best in full sun.
Dahlias tolerate most soil types, but prefer a sandy,
well drained, slightly acidic soil with a pH of 6.2- 6.5.
If your soil is heavy or clay, adding sand and peat moss will help to lighten it.
Water established Dahlias thoroughly and deeply once a week.
Water more frequently if it's very hot.
Dahlias in bud or bloom are heavy feeders, so you should begin feeding them monthly, beginning a month
they begin to set buds using a water soluble, 'bloom' type fertilizer
Planting Your Dahlias
Dahlia tubers should not be planted until all danger of frost has passed,
and the soil temperature reaches 58°-60° F. Excessively wet soil may cause the tubers to rot, so if your weather
has been wet and stormy, you may want to wait for a drying trend.
Dig and prepare a 12 inch diameter by 12 inch deep planting hole.
Mix a shovel full of compost, a handful of bone meal, and a little Dolomite lime to the soil that was removed.
Fill the planting hole with the soil mixture until it is about six inches deep.
Then place the Dahlia tuber horizontally in the bottom of the hole
with the eye pointing upward.
Tall varieties of Dahlias will need staking, so this is a good time to set an appropriate size
stake into the ground next to the tuber, near the eye. This will prevent damage to the tuber
which can result if it is added after the tuber has begun to grow.
Cover the tuber with about two inches of your soil mixture and water thoroughly. When the sprout
begins to emerge from the soil, gradually add more soil mix until the hole is entirely filled.
Once your Dahlia attains sufficient height, secure it loosely to the stake.
I recommend using a length of an old nylon stocking because it will stretch as the plant grows,
rather than cutting into the stem, as string will do.
Loop each tie into a figure 8, with the crossed portion between the stem and the stake
to keep stems from rubbing or being choked. Add more ties as the stem grows until the plant
is supported approximately 24 inches below the eventual top of the plant.
Dahlia Growing Tips
Dahlias that have been grown in pots can be planted in the garden following
the same procedures you would for planting any other perennial plant.
To promote a compact, bushy growing habit, with more flowers,
pinch back the new growth when your dahlia is about a foot high.
If your goal is to produce massive sized flowers, remove all of the side buds at the end of each branch throughout the growing season. If you want your Dahlia to provide a continuous, extended flower show, you will need to remove the spent buds promptly.
The tender new growth of a Dahlia is one of the favorite entrees of slugs and snails. Take the necessary precautions to protect your plants from these evil lawn prawns.
If the identity of your Dahlia is important to you, be sure to add a tag to the stake at planting time. This will be an invaluable help when it is time to dig your tubers in the fall.
For the finest cut flowers, cut them early in the day, when they first open.
Place them in water which has set for 24 hours to allow any chlorine to dissipate
Change the water daily. Cut Dahlias will last from 5-7 days.
Growing Dahlias from Seed
Generally, seed grown varieties of Dahlias are started as bedding plants and then treated as annual plants. They will produce tubers during their first year of growth which can be dug and replanted in the same way as larger Dahlias, but because of the ease of growing them from seed, most gardeners prefer to discard the old plants and start fresh the following year.
Growing dwarf Dahlias from seed can also reward you with surprising new hybrid varieties and colors.
In warm regions of the country, Dahlia seeds can be sown directly into the garden where they will grow.
In the majority of the country however, the seeds should be sown indoors
6-8 weeks prior to planting outdoors.
Sow Dahlia seeds about 1" apart in a seedling tray or individually in 4" pots,
and cover them with about ¼" of fine soil. Maintain a temperature in the growing medium
of 70°-85° until germination which takes from 7-21 days.
Keep the soil evenly moist, but never soggy.
When the seedlings have two or more sets of true leaves at about five weeks,
carefully thin and transplant them into individual 4" pots.
Grow them on in bright light, but not direct sunlight until it is time to move them into the garden.
Digging, Dividing and Storing Dahlia Tubers
Some gardeners choose to leave their Dahlia tubers in the ground over the winter.
In certain regions, this can be very risky but if you have decided to follow this path,
make sure that your Dahlias are growing in very well drained soil and apply a minimum
of 6"-12" inches of mulch to the planting area before the ground freezes.
The best plan is to dig the tubers and store them in a cool, dry place for the winter.
Prior to digging, your Dahlias will need about a week to produce new sprouts on the tuber.
The production of these new eyes can be stimulated by cutting the stem back to a 6" stub,
or will occur naturally when the majority of the plant has died back due to frost.
Dahlia tubers are easiest to divide if they are harvested after this one week period.
Using a garden fork to prevent damage, dig a circle about 12 inches around the plant stub,
and lift the clump carefully out of the ground. (Be careful not to damage the tender new sprouts)
Use a gentle spray from your hose to clean and remove the remaining soil from the clump.
Allow the clump to dry for a day in a cool dry place. You are now ready to divide the clump,
then store the individual tubers or store the clump and do your dividing in the spring.
To produce a new plant, each Dahlia tuber must have an eye (the new growth bud)
which appears at the point where the tuber connects to the main stalk.
(Each tuber on the clump will not necessarily have an eye.)
Using a sharp clean knife carefully separate tubers.
Discard any damaged tubers and any that don't contain an eye.
Place the tubers in a bed of sawdust or vermiculite, inside a cardboard or wooden box.
Store them in a dry area where the temperature will remain at about 40 degrees F.
Check Dahlia tubers periodically during the winter, for signs of shriveling (moisten the storage medium),
or mildew (treat with a dry fungicide such as Captan)
Characteristics of Different Dahlia Hybrids
Gallery of Identified Dahlia Cultivars
There are literally thousands of cultivated varieties of Dahlias
that have been hybridized throughout the years.
Dahlia plants range in height from as low as 12 inches to as tall as 6-8 feet.
The flowers can be as small as 2 inches or up to a foot in diameter.
You should therefore consider the ultimate goal of your endeavor, as well as your available space
in choosing the varieties you wish to grow. Some specimens may provide an abundance of cut flowers
for the home, while others give you the opportunity to make a bold statement in your landscape
by pruning, disbudding and ultimately forcing the plant to create a few single, gigantic blooms.
Novice Dahlia growers may want to start by selecting a few plants of varying colors,
sizes and types. Most Dahlia gardeners will be happy to share their thoughts and
experiences with you regarding their successes, failures and favorites.
They may even be willing to share a few tubers with you.
Once you've grown your first crop of these beauties,
you will have a much better idea of which types of Dahlias to grow in subsequent years.