Care and Cultivation of Dahlias
Flowers for your garden
With a blast 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 Dahlias allow you to use them in many different aspects of your landscape design, from low growing border plants to stately background plantings which may reach six feet in height.
Dahlias make excellent cut flowers, which typically last about a week in the house.
These tender tubers bloom best in full sun and will tolerate most soil types, but prefer a sandy, well draining soil with a pH of 6.2- 6.5. If you have a heavy clay soil, try adding sand or peat moss to lighten it.
Dahlias are summer blooming tubers which are generally only hardy in USDA zones 7-11. In the majority of the country, they must be planted each spring and then cut back and dug each fall after the first killing frost.
There are literally thousands of cultivated varieties of Dahlias which 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 and 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 to grow in subsequent years.
Dahlias should not be planted until all danger of frost has passed, and the soil temperature reaches 58-60 degrees 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 which was removed.
Fill the planting hole with the soil mixture until it is about six inches deep. Then place the tuber horizontally in the bottom of the hole with the eye pointing upward. Tall varieties 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 which can result if it is added after the tuber has begin 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 the plant 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.) Add more ties as the stem grows until the plant is supported approximately 24 inches below the eventual top of the plant.
A Dahlia in bloom is a heavy feeder, so you may want to consider using a water soluble "bloom type" fertilizer about a month before the plants begin to bloom.
Dahlias which have been started in pots may be planted in the prepared hole following the same procedures you would for any other perennial plant.
Dahlias from Seed
Generally, dwarf 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 may 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 may 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 the seeds about 1 inch apart in a seedling tray or individually in 4 inch pots, and cover them with about 1/4 inch of fine soil. The seeds will germinate best at between 70-85 degrees F. Keep the soil damp, but not soggy. Typically the seeds will sprout in 7-21 days. When the young plants (in the trays) have two or more sets of true leaves (about five weeks) carefully transplant them into 4 inch pots. Grow them in bright light, but not direct sunlight until it is time to move them into the garden.
General Care of Dahlias
Water established Dahlias thoroughly and deeply once a week. Water more frequently if it's very hot.
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 a favorite entree 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 are first opened. Place them in water which has set for 24 hours to allow any chlorine to dissipate, and change the water daily. Cut Dahlias will last from 5-7 days.
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.The tubers will be 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 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 your tubers periodically during the winter for signs of shriveling (moisten the storage medium), or mildew (treat with a dry fungicide such as Captan)
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