The Beginner’s Guide to Dahlia Cuttings

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By Ted & Margaret Kennedy (teddahlia) on February 10, 2015

Dahlias can easily be grown from rooted cuttings.

The Beginner’s Guide to Dahlia Cuttings
by Ted J. Kennedy

Dahlias can easily be grown from rooted cuttings. Experienced dahlia growers grow many of their plants from cuttings for several reasons. First, several plants can be grown from just one tuber and that makes economic sense when one can pay upwards of $25.00 for a new variety. Another benefit is that the plants will bloom a few weeks earlier than those grown from tubers.

Dahlia cuttings can easily be rooted without the use of any chemical rooting compounds. The process takes about 2 weeks from the removal of the cutting material until the plant has roots. The plants need an additional 2 weeks or more to be large enough to be planted in the garden.

Tubers or pot tubers are placed in potting soil in 4-6 inch pots with the eyes just underneath the soil level. The pots are moistened and placed under florescent lights attached to a plastic shelf unit. The proper temperature for rooting cuttings is 72 degrees and warmer or cooler temps slow down the process. When the tubers sprout and the length of the sprout is 2 to 3 inches long, the sprout is removed from the tuber by using a very sharp knife or a small scalpel. It is cut from the tuber 1/16th of an inch above the tuber. This leaves eye material on the tuber so that more sprouts will grow. It is important to do this exactly, as the plant material that will produce the roots is located just above the tuber.

The cuttings must be rooted in some kind of sterile medium. Many people root the cuttings in germination mix, a peat moss based product that has no pathogens that affect plants. Regular potting mix generally should not be used, especially those mixes that fertilizer in them. Baled peat moss products such as Sunshine mix #3 or 4 work well also. Many other people use Oasis foam products as the medium while others use rock wool. If you use germination mix, it is important that all the pots and flats used be sterilized in a weak bleach solution to kill fungus spores.

The cuttings are inserted into the medium for about one half of their length. I use small 2.5 inch pots and 36 of them fit into a flat. Enough water is added so the soil is very damp but not wet. Each plant should be labeled using a 5 or 6 inch plant tag. I place the flats of pots of cuttings into a plastic bag(clear or white 13 gallon kitchen bag). The potted cuttings are now placed under the florescent lights at about 2 inches or so from the bulbs. If you do not place the pots into a plastic bag they need to be watered during the 14 day stay under the lights. If you use Oasis cubes, there is little watering that needs to be done.
Dahlias root in about 10 -16 days and my definition of rooted means that the white root can be seen in the weep hole of the pot. Some may take longer. Once rooted, a very weak liquid(1/4 strength) fertilizer such as Miracle Gro or 20-20-20 greenhouse fertilizer can be used. Note that no fertilizer is given to them during the rooting process.
I move the plants to a green house a week or two after they root and grow them to about 8 to 10 inches tall before planting in the garden. Plants as short as 6 inches can be planted in good conditions(not too hot) and plants that are taller than 10 inches can be planted a bit deeper.

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About Ted & Margaret Kennedy
We have been growing dahlias since 1988 and began breeding new ones in 1995. We call our small nursery in Oregon City, Oregon, Hollyhill Dahlias. We grow about 3500 dahlia plants each year and about 1500 of those are grown from rooted cuttings. We enjoy entering dahlia shows and attend about six of them each year. Margaret specializes in showing flower arrangements and baskets and bouquets. I am a Senior dahlia judge and Margaret is now an Honorary Senior judge.

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Enlightening! starlight1153 Mar 20, 2019 9:37 AM 15

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