How much sun do Dahlias REALLY need to do well?

12 years ago

I initially read on the internet that Dahlias need AT LEAST 8 hours of direct sun per day, no less..

When I got my tubers in from Swan Island this year, and read their catalog's instructions on how to grow them, they once again said that dahlias need AT LEAST 8 hours of full sun, or they will not flower well if at all.

Then I called Swan Island to ask a question, and while I had the lady on the phone(who didnt seem to want to be bothered with any questions), I asked her if less than 8 hours of full sun would be enough, and she very sternly reiterated that dahlias need AT LEAST 8 hours if not more!

The reason I was concerned is that we live on a 1.25 acre, heavily wooded lot with only 2 clearings that get limited sun. But if we move from one spot in the clearing to another spot just 10 feet away, the amount of sunlight in the new spot drops about 1.5 -2 hours per day. So we cannot just grow in any spot in the clearing.

The area where I grew my large Dahlias and large Zinnias is the sunniest spot, in that it gets about 6-8 hours of sun in high June, depending upon which area within that spot we planted. The dahlia at the top of the rows gets 7.5 - 8 hours in June, and the Dahlia at the bottom of the rows just 9 feet away gets 6 hours. But as the months go by, and we get into sept and October(prime Dahlia blooming months), the amount of daily sun is down to like 2-4 hours per day, or less! Then by late October, none are getting more than 1.5 - 2.5 hours per day.

I planted later than I wanted too. Half were planted as dormant tubers on May 25, and the other half as dormant tubers on June 11. So they were just starting to come up at the height of the summer solstice, when they were getting the most sun they'd get all season. From there on, the sun began to sink down in the sky(beginning in mid July or so).

However, the only problem I seemed to have related to lack of sun was the fact that all but 1 plant grew taller than advertised. They were supposed to be all 4 feet tall, with only 1 plant, Vassio Meggos at 4.5 feet tall.

Well, most grew between 5 - 6.5 feet tall, with Vassio Meggos growing it's tallest flowers almost 8 feet tall!

But, I pruned them all at the 3rd leaf level initially, and they ALL grew nice, thick, healty, strong stems, which were only trellised by the upside down tomato cages which were only 30" tall, so the top 2/3 of each plant really didnt need trellising, except for during 2 hurricanes when I temporarily tied the stems together so they wouldnt blow around too much.

But as far as flower productivity, they were GREAT! In fact, most of them became most productive later in the season, once the amount of sun had plummeted, and half were producing a glut of flowers in mid-late October!

Out of only 6 large dahlia plants and 2 smaller ones, we were swamped with cut flowers from my dahlias to the point where I had at least 15-40 flowers inside in vases at any given time once flowering, and I was also constantly giving bunches away to friends, family and customers as well!

So, I question the claim that dahlias need AT LEAST 8 hours of sun or more or they wont flower well at all......

Featured Answer

keriann_lakegeneva

12 years ago

last modified: 9 years ago

I plant mine in 4-10 hours of sunlight. I get blooms faster in more sun, but they all still bloom for me. The biggest difference is that the ones in less sun, get so leggy as they reach for the sun. The plants get HUGE! Over 10ft tall for some! I think it is really pretty but it makes cutting them pretty comical.

Keri~

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Comments (11)

redmond_phyllis
12 years ago
last modified: 9 years ago
Is that why some get so huge! Last year, I had a row of plants that every one was really tall. And did they ever bloom on that row! It makes sense, but I never thought of that!
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highlandernorth
Original Author
12 years ago
last modified: 9 years ago
Yep.....

It seems that a lack of sun will make many plants grow tall...

However, my tomatoes also grew tall due to lack of sun, but their stems were pencil thin, and wanted to fall over, but my dahlias were thick, strong and healthy, and need very little support.

They also bloomed VERY well even though they didnt get the 8+ hours of sun they allegedly desperately needed.
redmond_phyllis
12 years ago
last modified: 9 years ago
But Highlander . . I've had it go the other way too. I've also had plants in shadier spots be short, late, and sickly. So . . . less sun is okay, but next to no sun doesn't work perhaps?
Laurel Zito
12 years ago
last modified: 9 years ago
I think it has to do with fungal diseases like white powder mildew. Plant in shade the plant stays wet longer.
Ellen Gladney
6 years ago
I got some yellow dahlias for mother's day 2017. They were in a pot but appeared to get too much sun or rain. The tag said partial sun so that is where I planted them in partial sun. They still have buds on them but we are getting a lot of rain so they may be water logged. I see I have to cover with much during the winter (NJ) so we will see what happens.
cntrylady
6 years ago
I had six new plants that started as tubers. Planted them along a fence and they get 5 hours of sun per day, plus the heat off the wood fence is a plus. . This is their second year with slow start due to the bad NW Spring, too much rain and little sun, but last year they all performed beautifully. I had blooms into October. We'll see this year. One plant didn't come up, but the rest are growing. My old gardens got about 7 hours and I had 20 plants. All did beautiful. Key is to deadhead old blooms and water regularly. Don't stress dahlia or they will not due well, like overwatering or competing with weeds, and not desdhesding. Happy growing!
Rachel Cross- Harder
6 years ago
I have 7 dahlias in pots on my back lanai - all get NO DIRECT SUN - all are blooming well but I'm in fla -
dianekmueller
5 years ago
I live between the Mississippi River and a wooded state park. We have 9 large old oak trees and many other trees. You can imagine that sun is hard to come by in our yard. My best sun is 4 hours and our dahlias bloomed great last year. I use lots of Cowsmo compost and vegetative compost and water whenever needed. I think even those of us with less sun can enjoy the beauty of dahlias if we give them good soil and care.
Mariel Richards
5 years ago
Hello from London! I'm very tempted to start growing Dahlias, but worried that I am in a North facing garden and my flowerbeds don't get *any* direct sunshine at all - the only spot I have free gets light, but no sun. Is it worth it? I'm loving the idea of tall leggy blossoms - but worried that my garden is slightly impossible...
cicivacation
5 years ago
Mariel, there are a lot of dahlia growers in England, with many in small city gardens between tightly spaced cottages. One thing I've found about English cultivars is that they tend to grow shorter than ones hybridized in the United States. So, if they don't get enough sun and stretch a bit to optimize the available light to their leaves, you shouldn't be overwhelmed by a monster bush.

Treat dahlias like annuals for the first couple years, don't worry about overwintering, and PLAY! There are so many different forms to try, and at their small price-point, it is worth trying.

Cheers!
-CiCi