Introduction: There are probably as many ways to propagate dahlia cuttings, as there are dahlia growers. We grow Dahlias for cut flowers and we need flowers early in the season. We have found that dahlias grown from cuttings serve our needs very well. We have been taking cuttings for many years now and wish to share some of our methods with you. Our success rate in the cutting process is about 95% to 97%.
Why not just grow dahlias from tubers? Why go to the bother of taking cuttings?
Advantages to cuttings:
(1) Economy: One tuber can produce 3,4 or as many as 5 to 10 plants from cuttings. If you only were able to save one tuber or paid lots of money for a new variety, taking cuttings is very cost effective.
(2) Early flowers: Cuttings taken in February and March and grown in the green house can be planted outside at the same date you plant tubers. They will flower weeks ahead of your dahlias grown from tubers.
(3) Disease detection: Cuttings that show signs of virus or other disease can easily be discarded. A tuber will have been in the ground for as much as a month before you can see the leaves. By that time it may be too late to replant with another tuber (if you have one).
(4) Pest detection: Plants grown from cuttings will be planted when they are 6" to 12" tall. Slugs are a real problem in our area. After planting, you can immediately see any damage from slugs and bait accordingly. A tuber sends up its sprout and slugs eat them as they come through the soil. You may not even realize that the slugs ate your prized dahlia. Also slugs often dig into the ground and eat the sprouts right on the tuber.
(5) Rotten Tubers: Many tubers rot in the ground before producing a viable plant. Cuttings do not have a tuber that can affect the plant.
Disadvantages:
(1) Not as many tubers: Dahlias grown from cuttings do not produce as many tubers as those grown from tubers. However a good tuber making dahlia variety will have lots of viable tubers from cuttings. Ironically, the varieties that are poor tuber makers are the ones that many expert growers propagate from cuttings. Probably the best way to grow these varieties is to grow them from cuttings and save some of the cuttings for pot tubers which are used the next year to produce cuttings.
(2) Will not send up another shoot: A cutting will not send up another shoot if the plant is broken off or destroyed by a pest. Tubers will most probably send up another shoot. The solution is to grow extra plants, just in case.
(3) Pot bound tubers. The tubers that do develop will quite probably be contorted and difficult to divide because of the "pot bound" effect of growing roots while in the pot. If you are good at dividing clumps this may not be a problem for you.
(4) Time and equipment: You need some lights and shelves and perhaps a green house or cold frame, and lots of pots and flats. It does take time to tend to your plants.
Outline of the Cutting Process
(1) Tubers or pot tubers need to be potted in a soil medium in sterile 4-inch pots.
(2) The watered pots are placed on a shelf or bench about 6 inches from a florescent light source.
(3) The temperature should be room temperature 68 to 72 degrees.
(4) In about 2 to 3 weeks the tubers will have 2 to 3 inch shoots.
(5) Cuttings are taken from the tubers and dipped in Woods's hormone solution.
(6) Cuttings are inserted into 2.5" pots filled with sterile germination soil mix.
(7) The pots are watered and placed into a sterile flat.
(8) The flat, full of cuttings, is inserted into a 13 gallon kitchen bag and tied shut.
(9) The flat is placed on the shelf or bench 4 to 6 inches under the florescent lights.
(10) After 9-11 days, open the bag and check the pots for roots.
(11) Remove the plastic bag from the cuttings and leave the flat under the lights for 3 to 7 days.
(12) Water cuttings as necessary; do not fertilize yet.
(13) Move cuttings to the green house or cold flat or lighted window.
(14) When watering use 20-20-20 greenhouse fertilizer diluted to one-third strength.
(15) After two weeks or so, replant to four inch pots using a good soil mix.
(16) After two to three weeks re-plant in gallon pots or plant in garden.
(17) Plant in garden and bury plants deeper than they were in the pots.
(18) Control for slugs or other pests as needed.
(19) Grow as you would a dahlia grown from a tuber.
(20) Enjoy the wonderful flowers, weeks earlier than plants grown from tubers.
Materials and Equipment List
Pots and flats: Lots of 2.5 inch, 4 inch pots and flats to match. A box of about 1000 2.5 " pots cost about $32.00. The 4 inch pots come in a case of 560 and cost $38-. Plastic flats come in different quality levels and can be purchased for as little as 60 cents but the heavier ones are better and cost closer to $1- or so. Four-inch pots can be purchased in a case with matching flats included.
Shelf Unit: A plastic shelf unit that is about 6 feet tall, 40 inches wide and about 16 inches deep, with five shelves. Cost is about $35 to $40- at Target or K-Mart.
Florescent Light Fixtures: The cheapest 4-foot shop lights that sell for as little as $10.00 are just fine.
Electric Strip to plug in Lights: A cheap grounded strip with 5 plug in slots is fine. Nice to have a switch to turn all of the lights at once.
Florescent Tubes: The cheapest ones work just as well as the expensive ones. We use 40-watt tubes. 25-watt tubes will probably work fine also. "Grow Lights" are a waste of money.
Hormone Dipping Solution: We use Woods Rooting Compound, available in a 4 ounce bottle for less than $7-. It will last you several years.
Scalpel or knife: A small stainless steel scalpel can be purchased at a farm supply store for less than $2- Or use any sharp knife.
Plastic 30-Gallon Garbage Can: Used to soak the pots and flats in bleach solution to sterilize them. The kind with wheels is better.
Plastic Kitchen Bags: The cheapest clear or white 13-gallon bags work great. The white ones let through all the light that is needed for cuttings, so don't spend much time looking for clear bags.
Bleach: Laundry Bleach. Use a half a gallon in the 30 gallon can to sterilize pots and flats.
Pot Labels: We use 5 or 6 inch nursery pot labels that come in several colors. Cost about $14- per thousand.
Sharpie Marking Pens: Black Sharpie marking pens work fine.
Germination Soil Mix: We use Growers Gold (Used to be Black Gold?) Germination Mix by Sun Grow Horticulture. It comes in 3 cubic foot bags and costs about $8-. We have used Sunshine Mix numbers 3 or 4 with success also, but it is more expensive. Others use Whitney Farms products. All are based on peat moss with vermiculite and/or perlite and lime and most importantly a wetting agent so it will absorb water quickly. All are also sterile so that the cuttings will not suffer from diseases such as damping off. Germination mix is a much higher-grade product than a standard potting mix, which is too coarse for cuttings.
Green House Fertilizer: We use 20-20-20 green house fertilizer with trace elements. Numerous brands are available including Plantex, Fusion, Peters. Cost is about $22- for 20 pounds.
Instructions
Before you start: It is imperative that all pots and flats need to be clean and sterile. We soak the pots and flats in a bleach solution for a day or so. We use 30-gallon plastic garbage cans that have about a half of gallon of laundry bleach added to the 30 gallons of water. New pots or flats do not have to be sterilized (but it never hurts). Knives and scalpels can be soaked in a bleach solution but remember that if they are left in the bleach solution for longer than a day or so, the bleach will corrode stainless steel. The key to success in successfully growing cuttings is using sterile pots and flats, and sterile potting mix.
(1) Tubers or pot tubers need to be potted in a soil medium in sterile 4-inch pots. It is not necessary to use expensive potting soil for the pots but the soil mix must be sterile. The tubers should be placed in the pot with the neck slightly above the soil level. All should be labeled. It is handy to have some larger pots for large tubers. Some people place the tubers horizontally in flats but we find that it is harder to label the tubers and also harder to water them. Also if you desire to plant the tuber in the garden after taking cuttings it is more difficult to do so when using flats. There may be some controversy about whether a tuber that has produced cuttings should be planted in the garden. We have done so with few problems.
(2) The watered pots are placed on a shelf or bench about 6 inches from a florescent light source. We grow the cuttings in our heated basement. We use plastic shelf units on which we have attached the florescent lights. The pots need to be watered regularly and most of them will sprout in 2 to 3 weeks at 70 degrees or so.
(4) In about 2 to 3 weeks the tubers will have 2 to 3 inch shoots. We like to take cuttings when the sprouts are about 2.5 inches long. We have accidentally broken off a 1-inch sprout and were successful in getting it to grow roots. Sprouts as long as 6 inches or so can also be rooted but they do not fit easily into the plastic bags that we use to keep the cuttings moist. Another type of cutting material is the so-called "white cutting" which is a cutting taken off a tuber that sprouted in storage. They will work if they are not too long and convoluted. They seem to take longer to form roots. This is probably because they do not have any chlorophyll to produce energy for the development of roots.
Another type of cutting is a leaf cutting, which is taken from a long sprout that has leaves or from an adult plant. The stalk is split carefully and the portion of the stalk where the leaf attaches to it is placed into the potting medium. Leaf cuttings take longer to root and longer to develop into a full size plant. The plant that develops is very small it takes weeks longer to grow than a regular cutting.
(5) Cuttings are taken from the tubers and dipped in Woods's hormone solution. We use a small disposable surgical scalpel to cut the sprout of the tuber. You should cut as close as possible to the tuber but not cut into the tuber. This is because the next sprouts will appear from the site where you removed the cutting. Usually two sprouts grow from that spot. We dip the sprouts into Woods Rooting Compound at the softwood concentration, which is 20 to 1. We dip only the bottom half inch or so of the cutting. This stuff is toxic so we use a paper cup for the solution and toss it after using. Margaret likes to wear rubber gloves when dipping cuttings.
(6) Cuttings are inserted into 2.5" pots filled with sterile germination soil mix .We prepare an entire flat of 2.5 inch pots and fill them with moistened germination mix. The cutting is planted into the pot by first inserting your finger into the soil to make a small hole and the cutting is placed into the hole. The leaves of the cutting should be above soil by about .25 inches.
(7) The pots are watered and placed into a sterile flat. We then water each of the pots with an additional tablespoon of water. Be sure that the plastic flat is clean and sterile. Our flats hold 36 pots. Don't forget to label each cutting with a 5" pot label.
(8) The flat, full of cuttings, is inserted into a 13-gallon kitchen bag and tied shut. A regular plastic 13-gallon bag fits the flat just right. Even though the bag may be white, plenty of light gets through to the cuttings. The plastic bag keeps the cuttings moist. This replaces the method of misting the plants many times per day. Since everything in the bag is sterile there is little chance that the cuttings will rot or get fungus.
(9) The flat is placed on the shelf or bench 4 to 6 inches under the florescent lights. The lights are left on 24 hours a day. I have been told that 12 hours is sufficient but I know that 24 hours works really well. Again, the temperature should be 68 to 72 degrees. We use a sharpie pen to mark the plastic bag with the date we took the cuttings.
(10) After 9-11 days, open the bag and check the pots for roots. At our house nearly all of the cuttings have roots at 11 days. You can determine if they have roots by looking at the weep hole on the bottom of the pot. A white root can be seen. If there is none, carefully remove the plant and soil from the pot by putting the pot upside down in one hand with the cutting between your fingers and tap the bottom of the pot with your other hand. The soil and plant will fall into your hand and the pot can be removed to inspect the soil for evidence of roots. We remove the flats from the plastic bags at about 11 to 15 days.
(11) Remove the plastic bag from the cuttings and leave the flat under the lights for 3 to 7 days. This step allows the plants to get used to being in the open but still in the even temperatures of the house. After this period, they are ready to go to the green house.
(12) Water cuttings as necessary; do not fertilize yet. There is a small amount of fertilizer in the germination mix and the plants really cannot handle fertilizer yet.
(13) Move cuttings to the green house or cold flat or lighted window. Our green house is not really well heated. I have one 8-foot long heat pad that works really well to give cuttings some bottom heat.
(14) When watering use 20-20-20 greenhouse fertilizer diluted to one-third strength. We have used different brands of green house fertilizer including Peters, Fusion and Plantex. It comes in 20-pound bags. We use the 20-20-20 formula that has trace elements. It turns the water blue when you mix it. We find that is easy enough to water the cuttings with a one third concentration every time you water. The plants love the continuous availability of nutrients and they grow very evenly.
(15) After two weeks or so, replant to four inch pots using a good soil mix. This step is necessary to keep the plants from getting too root bound. Also it is difficult to keep a large plant watered in small pot.
16) After two to three weeks replant in gallon pots or plant in garden. Plants grown in gallon pots can get very large in the green house. I have had some of them bloom there.
(17) Plant in garden and bury plants deeper than they were in the pots. Dahlias are like tomatoes in that they will produce roots from any stem that is buried. You may get more tubers if they form on the buried stem. Also the plant will be less likely to fall over in the wind. Be sure to water in the plants very well. The dilute greenhouse fertilizer can be used to water them in.
(18) Control for slugs or other pests as needed. A wise gardener will check for slug damage right away. Newly planted dahlias will start growing again after a week or so. During this first week, you need to watch your plants carefully and control any damage from pests.
(19) Grow as you would a dahlia grown from a tuber. Once the cutting is planted in the garden, it grows pretty much like a plant grown from a tuber. Some varieties seem to grow more vigorously from cuttings. Some plants seem to send up more stalks than those grown from tubers. We believe that plants grown from cuttings produce more flowers.
20) Enjoy the wonderful flowers, weeks earlier than plants grown from tubers. This is part that we like. We can count on having enough flowers to sell by about July 15th. Customers begin knocking on our doors in June wanting bouquets. We have had our sign out as early as the first week in July. And we nearly always have a few flowers for our table in June.
