Shading Dahlias?

steve22802(7a VA)March 10, 2013

Does anyone have any experience to share regarding shading dahlias from intense summer sun to improve coloration and form? I have a lot of problems each season with dahlias fading and showing bad form due to high heat and intense sun here in the Shenandoah Valley during the hottest months of summer. I've seen a few pictures on the web of shade cloth and even umbrellas being used to improve bloom quality. Can anyone share any success (or failure) experiences using shading with dahlias? What percent shade cloth might be most appropriate? I'm thinking maybe 30% black. One company sells 50% white shade cloth. I wonder how that would compare to 30% black. It would be nice to get more ambient light but less heat. I wonder too if a mist system might help.

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50% is best. Make sure it is about 10 feet above the dahlias as dahlias grow much taller under shade cloth.

    Bookmark   March 10, 2013 at 10:26PM
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steve22802(7a VA)

Thanks Ted, I appreciate the info. I'm growing them to use as cut flowers so it sounds like the shade will help give me better stem length too. I've had some issues with stems that are too fat with too much branching. I suspect that some aggressive early season pruning would help with this as well.

    Bookmark   March 11, 2013 at 8:51AM
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Topping(removing the central bud) dahlias when they are about a foot or so tall encourages more stems to take over and gives you more "laterals" for flowers. It is done quite scientifically by show people who want perfect flowers. Larger flowers get fewer side branches; smaller flowers get more. Cut flower people usually grow so many plants that they usually just top everything the same way when the plants are about 12 inches tall or do nothing. Smaller flowered varieties send up lots of laterals after you start picking flowers.

    Bookmark   March 26, 2013 at 9:12AM
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steve22802(7a VA)

Thanks for the tips Ted. I think I'll probably need to top my potted dahlias at least once while they are still in my greenhouse this year. I'm hoping to transplant them out into the ground just as they are starting to set buds so that I can start harvesting flowers soon after my last frost (usually around May 10-15.)

    Bookmark   March 26, 2013 at 3:00PM
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It is really hard to get dahlias to bloom outside until July. It is difficult to get plants big enough in pots and if you do, they suffer tremendous transplanting shock for about a week or more. A well grown cutting that is no more than 12 inches tall will have little transplant shock and take off very quickly in the garden. You can gain about 3 weeks over tubers planted in the garden with cuttings. At our trial garden, I am banned(there are no judges available for early blooms) from planting my rooted cuttings until at least 2 weeks after the tubers are planted and even then they bloom over a week earlier. .

    Bookmark   March 27, 2013 at 11:38AM
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steve22802(7a VA)

I started about 15 dahlias early in my (newly built) greenhouse in pots last year and it definitely helped me get early blooms. I had several plants in full bloom by the end of June and lots of flowers to use for a wedding on July 7th, 2012. My biggest problem last year was not getting dahlias to bloom early but rather to keep them producing high quality blooms during July and August with frequent highs in the 90s. I think there is a significant climate difference between our regions. Are you (Ted) in the Pacific Northwest?

Here's a picture of the bridal bouquet I arranged for the wedding using flowers from my gardens.

The dahlias are Onesta, Arabian Night, and Taboo. The other flowers are white Calla lilies, Echinops, Sedums, perennial statice and variegated Euonymous.

    Bookmark   March 27, 2013 at 2:09PM
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Dahlias bloom non stop during the summers in the Northwest . Our highs are typically in the low 80s with some days over 90. We can get a heat wave with temps above 100 but the evening temps are always in the 60s even during these hot days. It is the warm temps in the night that hold back the dahlias. Shade cloth would help. Moving to the NW is best.

    Bookmark   March 28, 2013 at 12:03PM
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steve22802(7a VA)

We do sometimes have warm night temperatures in midsummer. Maybe it would help for me to spray them with water after sunset so that evaporative cooling would lower their temperature at night.

I've visited the northwest and it's very nice there but I have too many family and friends here and that's important too. I could move out to the Piedmont of VA to get to zone 8 but I would still have warm nights.

    Bookmark   March 29, 2013 at 8:15AM
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Hey Steve - beautiful Bouquet! The Dahlias and the Callas are a great textural contrast.

    Bookmark   March 30, 2013 at 7:22AM
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steve22802(7a VA)

>> Hey Steve - beautiful Bouquet! The Dahlias
>> and the Callas are a great textural contrast.

Thanks! I love using callas and dahlias together but so far I've only had a few weeks when both are blooming at once. Normally I have calla lilies throughout most of June but I have to get my dahlias off to the earliest start possible in order to get any overlap. To have callas for this July 7th wedding I had to refrigerate lots of them in advance. Callas can be held for up to 2 weeks in wet refrigeration but they can be quite tall (36 inches+) so you really need dedicated space for them. I've been potting dahlias up since the beginning of March so I'm hopeful that some of the first one's will be blooming by the beginning of June. I've got two nice Le Baron's that are strong stocky leafy 6 inch plants, they will probably be the earliest. I expect I'll top them once or twice while they are still in the greenhouse.

    Bookmark   March 30, 2013 at 9:33AM
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I've got nothing to add to the shading discussion; but I agree that the bridal bouquet that you made is fantastic. I tried calla lilies a couple times with no luck. What variety do you grow?

    Bookmark   March 31, 2013 at 11:06PM
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steve22802(7a VA)

The vast majority of my callas are straight species white Zantedeschia albomaculata. I have propagated them over the years by both division and from seeds. Growing them from seed will get you nice disease free rhizomes but you can't count on getting blooming sized bulbs until the third season. I've tried some of the miniature colored hybrids but they seem to be more susceptible to both rot and frost damage. Picasso and Blackstar have done pretty good for me. The rhizomes cannot be allowed to freeze and must be protected by heavy mulch in a borderline climate or by lifting them out of the ground for the winter and storing them in a cool basement or root cellar. Storing callas in sawdust in my unheated basement has worked well for me.

    Bookmark   March 31, 2013 at 11:34PM
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