How to grow dahlias:
The American Dahlia Society provides comprehensive growing information here: https://dahlia.org/growing/fundamentals-of-growing-dahlias/ Just click the link above.
Lee's notes on growing dahlias
HERE ARE A FEW THINGS I'VE FIGURED OUT ALONG THE WAY:
I have found dahlia tubers to be sensitive to day length and my tubers are acclimated to our LATITUDE: 36.15 N. If they are sent north and receive shorter days, they may take longer to wake up. If you must have them early and want them to wake up, provide supplemental lighting.
Tubers are stored on the high end of ideal storage range 50F here and brought in to about 60-65F before shipping, so don’t hold them in a colder environment.
DO NOT OVERWATER!! Tubers will rot in a pot or in the ground if they are overwatered before growing shoots emerge. Tubers don’t drink water, fibrous roots do. If there aren’t roots, they don’t need water. During the winter months, I do pot up dahlia tubers in a greenhouse to force for cuttings but until they show green growth, I never, ever give them any more moisture than a fine mist and ONLY on extremely sunny days to maintain humidity, not to soak the growing medium. Once they have begun to grow, they still only require minimal water. If the growing medium is saturated and there are not enough roots to drink the water, they still have a very good chance of rotting, so just avoid it.
GET YOUR SOIL FERTILITY RIGHT!
#1!!! FEED YOUR SOIL. THE MOST CHALLENGING CLASS I TOOK IN COLLEGE WAS 'PLANT NUTRITION'. MY PROFESSOR LITERALLY WROTE THE BOOK AND I STILL FREQUENTLY REFER TO IT OVER 20 YEARS LATER. HE TRAVELLED THE WORLD CONSULTING LARGE FLOWER FARMS AND GREENHOUSE VEGETABLE OPERATIONS AND MADE THE VALID POINT THAT IF YOUR NUTRIENTS ARE OFF TO BEGIN WITH, YOU WILL NOT REALIZE THE CROPS FULL POTENTIAL.
BOOK INFO: HARRY A MILLS, J. BENTON JONES, JR 1991 PLANT ANALYSIS HANDBOOK II (REVISED 1996) MICROMACRO PUBLISHING ATHENS, GEORGIA
IF YOU ARE UNSURE OF WHAT YOUR SOIL NEEDS, GET IT ANALYZED THROUGH YOUR LOCAL AG EXTENSION AGENCY. AMMEND AS NECESSARY. DAHLIAS PREFER RICH WELL DRAINED SOIL. THEY ARE HEAVY FEEDERS.
HERE'S AN EXAMPLE: MY AREA SOIL IS COMMONLY DEFICIENT OF PHOSPHORUS. PHOSPHOROUS IS EXTREMELY IMPORTANT FOR DAHLIAS AND IF THEY LACK IT, SHORT PLANTS & STEMS AS WELL AS OFTEN MISFORMED FLOWERS RESULT. PHOSPHOROUS IS NOT MOBILE IN THE SOIL AND THE SUPPLY OF IT NEEDS TO BE CLOSE TO THE ROOTS. THEREFORE, THE 'DIG A HOLE AND STICK IT IN' METHOD, RATHER THAN TOP DRESSING, IS IMPORTANT.
TOO MUCH NITROGEN WILL RESULT IN ABUNDANT GROWTH OF FOLIAGE AND FEWER FLOWERS.
EVERY REGION DIFFERS IN SOIL STRUCTURE & FERTILITY, GROWING CONDITIONS SUCH AS LIGHT, HUMIDITY AND TEMPERATURE. IT IS UP TO YOU TO LEARN ABOUT YOUR GARDEN'S PARTICULAR NEEDS! WHEN I AM PREPPING MY SOIL, I LIKE TO COMPARE IT TO BAKING A CAKE: ADD ALL OF THE RIGHT INGREDIENTS, AND IT WILL RISE TO IT'S FULL SWEET POTENTIAL. IGNORE IT, AND YOU GET A FLOP.
SOMETIMES IT TAKES A COUPLE OF YEARS TO REALLY GET THE HANG OF GROWING A PARTICULAR PLANT. THE GOOD THING ABOUT DAHLIAS IS THAT THOSE TUBERS REPRODUCE. DIG AND DIVIDE IN THE FALL AND YOU WILL HAVE PLENTY MORE FOR THE NEXT SEASON. YOU WILL HAVE THE OPPORTUNITY TO TWEAK YOUR GROWING METHODS YEAR AFTER YEAR.
PLANTING:
I MAKE LONG BEDS ABOUT 4' WIDE AND THEN DIG LONG ROWS OF TRENCHES SPACED 18-24 INCHES APART. DROP TUBERS IN 1-2 FEET APART DOWN THE ROWS. MAKE SURE THAT TOU ARE PLANTING DAHLIAS THAT HAVE SIMILAR GROWING HEIGHTS TOGETHER, OR THE TALL ONES WILL CROWD OUT THE SHORT ONES AND YOU WON'T GET BLOOMS ON THE SHORTIES. I START AT THE BOTTOM OF THE BED WITH THE TALLEST AND WORK MY WAY UP DESCENDING IN HEIGHT AS I GO. THIS ALSO HELPS WITH YOUR SUPPORT SYSTEM.
SUPPORT THOSE THINGS!:
IF YOU WANT STRAIGHT STEMS, YOU HAVE TO PROVIDE SUPPORT- EVEN FOR THE 2' SHORTIES. Although there are many different methods, I USE 4' WIDE HORIZONTAL NETTING PURCHASED IN ROLLS FROM JOHNNY'S SEEDS. YOU CAN USE IT YEAR AFTER YEAR. SINK IN T-POSTS IN PAIRS 4' APART EVERY 8' DOWN THE BED. ROLL OUT THE NETTING AND EITHER SECURE IT DIRECTLY INTO THE POSTS OR USE ZIP TIES. MAKE SURE THE NETTING IS TAUGHT BUT NOT TO THE POINT OF BREAKING THE MATERIAL. AS THE PLANTS GROW, YOU CAN MOVE THE NETTING HIGHER FOR THE PLANTS UP TO 4' OR ADD A SECOND LAYER FOR THE TALLER ONES.
DON'T LOSE TRACK OF WHAT YOU ARE PLANTING!:
MAKE A HAND WRITTEN GRAPH WITH EVERY TUBER YOU PUT IN THE GROUND AS YOU GO. COLLEGE RULED NOTEBOOK PAPER WORKS GREAT. TAKE A PICTURE OF THOSE GRAPHS BECAUSE THEY WILL GET WORN OUT AND YOU WILL PROBABLY LOSE THEM IF YOU ARE LIKE ME. WHEN I HAVE TIME,
Once the dahlias start to bloom, we tag EVERY SINGLE PLANT with the correct name at the base of the plant so the tags are not lost when the plant is cut down and dug.
DIGGING and STORING DAHLIA TUBERS
ALTHOUGH EVERY GROWER HAS THEIR OWN SPECIAL METHODS, THE BASICS REMAIN THE SAME. IF THIS IS YOUR FIRST TIME DOING IT, YOU’LL FIND THE FOLLOWING LINK FULL OF HELPFUL INFORMATION.
https://www.dahlia.org/tubers-2/
Usda Plant hardiness zone map
FOLLOW THE LINK BELOW TO VIEW THE PLANT HARDINESS ZONE MAP. YOU NEED TO KNOW THIS FOR PLANTING AND SHIPPING INFO.
http://planthardiness.ars.usda.gov/PHZMWeb/