Flower Spotlight: Dahlias

Dahlias have a way of capturing our hearts. With every shape, size and color imaginable it is every flower lover’s dream! On our last property, we always had a small patch designated to dahlias. Having twenty dahlias was a huge deal to us! They are heavy producers but who can ever have enough dahlias? Definitely not me! Eager for summer, last fall I went a little nuts on ordering tubers. Definitely not as many as bigger growers but over 600 is a ton for us and we have given them nearly half of our growing space for this year. Watching all of them coming up healthy and happy has me counting down until we are are harvesting hundreds and hundreds of dahlia flowers a week! Fortunately, at the new property earwigs have not become a problem, unlike our last property! What we do have is a golden retriever puppy who thinks dahlia tubers are a tasty treat. He has since been banned from the garden the little rascal, fortunately for him the tubers are not toxic and didn’t make him ill.

Dahlias may not have a sweet fragrance like a rose or peony, but what they lack in fragrance, they more than make up with their magnificent beauty.  With numerous varieties, it is easy to find oneself quite the hoarder of these amazing flowers.  They give us a spectacular show at the end of summer and help us to greet fall. Besides, with some yummy scented geraniums as filler, who needs a scented dahlia?  

While out in the garden, my daughters skip and sing behind me.  My oldest daughter, Emma, stays by my side, hopeful of a treasured dahlia bloom.  Whether there are too many nibble marks from an earwig or a stem is simply too short, she is there in great anticipation.  Rejected dahlia blooms quickly are added to their hair to be like a princess, or are used as a sword on the battlefield, or become a cupcake that pairs wonderfully with their afternoon tea.    Even at such young ages, the girls realize the splendor and magic of these wonderful flowers.

 

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Dahlias do not originate from English gardens of European princesses but rather come from Mexico and were believed to be cultivated and used by the Aztecs. Their tubers used and eaten similar to potatoes- could you imagine?!  Dahlias made their journey over the leaping seas a mere two centuries ago by a botanist to make a new home in Spain.  From there, they have been cultivated and bred in any shape and color you can imagine! These days they are grown more for the eye candy they are and a little less for cuisine.  

Don't let their magnificance intimidate you.  They are hardier than they look and their beauty makes them a worthy candidate in your cut flower garden!  Dahlias can be grown from seed or from a tuber.  From seed, they most likely won't be true to the mother plant but can make for a fun experiment and surprise at blooming time.  And... what's a tuber?  It looks like a scrawny yam.  Kind of like growing potatoes, growing from a tuber will give you a dahlia true to the mother plant.  Actually, their tubers are edible and at one point it dahlias were commonly grown as food!  I can't personally imagine wasting a future dinner plate dahlia on my dinner plate but dahlias can produce five to ten tubers from a single tuber in one season.  They are prolific, so if you decide to experiment and cook one, please let me know how it goes!  I think I'm going to stick to sweet potatoes or carrots and leave the dahlias to march on in all their glory in the garden and vases.

The tubers don't look like anything super special, but patience will be rewarded!  Dahlias can be grown as a perennial in some areas, but like most things- not in Northern Nevada!  We grow them as an annual.  In the fall or winter we place our order in for the tubers and these guys came into the mail late April- early May.  It was way better than Christmas!  These tubers came while the weather (especially this last year!) was on and off bleak.  As I opened the box the hope of summer sat in there.  Some of the more specialty varieties were potted up. As the crates and crates of the wholesale tubers flooded in, those were tucked into the cool spare room until it was time to plant out in the field. Our greenhouse is too tiny for that haul!

Purchasing Dahlia Tubers

For the last few years, due to limited spacing we invested in single tubers from other flower farmers. Let me tell you, getting those coveted tubers is like a race for your life! Its intense! When you are setting your alarm up in the dead of winter at 4:30am to purchase some dahlia tubers- family begin to think you are insane. Really, do your customers really care if you have peaches n cream dahlias? Probably not… but I do! The quick sell outs that the small suppliers have is one downside to purchasing the tubers from individual growers compared to the big suppliers/wholesalers. Tubers from smaller growers are also incredibly pricey. Knowing we wanted to really focus on dahlias and grow a lot more volume, this year we bought them through a wholesaler. There are pros and cons to purchasing tubers from a small farmer or a wholesaler. First off, I prefer supporting the smaller farms. The dahlias are lovingly grown, divided, packaged and overall are healthy tubers without indication of disease. As a small-scale grower myself, I know the love that goes into it! We have never gotten diseased tubers from the smaller growers, have had minimal rot and viable eyes. Also, the tubers don’t tend to be mislabeled as often. The drawback? You are looking at a minimum four to five dollars per tuber and upwards of twenty dollars for the more sought out varieties and that’s before shipping. When you want to start growing dahlias by the hundreds or thousands and want to do it NOW… that’s when you go to the wholesaler. If you are patient (unlike me) and the idea of starting off with a few dahlia tubers and propagating your own sounds better: go for it! Support the smaller guys!

Through a wholesaler, you get a way bigger price break. Unfortunately, that price break comes with a.. price. There is a greater chance that you don’t end up with the exact varieties you ordered. Mislabeled tubers is something you need to prepare yourself for if you are going to purchase wholesale. If you are depending on the tubers purchased from the wholesaler… well, I wouldn’t be making any promises until you see them start to bloom! I chucked tons and tons of clumps of questionable tubers, I suspected crown gall and leaf gall. Some varieties seemed more susceptible than others. When I reached out to the wholesaler, he suggested tossing the suspicious tubers but said unless I got the tuber sampled to confirm, there was no way of knowing for certain they were diseased. The underlying tone is- what do you expect kid? Plan on having some tubers/clumps of tuber from large wholesalers , I had ordered more than I needed so I wasn’t too worried. Except for the risk of introducing diseased tubers into my new plot of land. Don’t bank on every single clump or tuber ordered to be viable, because of disease or rot or broken necks or tons of other scenarios. These guys are plucked from the field and tossed in a bag. End of story, they are not lovingly divided and not closely inspected. I know, I am making wholesalers sound awful! These are just some things to know upfront before ordering, it sets your expectations and allows you to order backups from another supplier or keep you from making promises you can’t keep to brides and florists. The up side? Once fall hits and it’s time to dig those clumps up- you will have tubers going out your ears to quickly grow your dahlia stock pile. The mislabels? Yeah, those suck but you may come across a variety you didn’t expect and now find swoon worthy!

No matter who you decide to source dahlia tubers from be sure to open the tubers and inspect upon arrival. Cut off any rot, take photos and if damage is excessive reach out with the photos to the supplier. Be kind, you catch more flies with honey right? If you are not going to be able to plant the dahlia tubers, keep them in a cool/dark place that stays at about fifty to sixty degrees Fahrenheit and will not freeze. Inspect them every week or so to make sure that the tubers are shriveling up on you too bad (honestly, even a shriveled dahlia tuber with viable eyes will still grow just fine). If the dahlia tubers go crazy sprouting before they get in the ground, don’t panic! Not all is lost. Simply snip off the sprout if it is too long, it will grow back healthier and happier.

If purchasing tubers seems too expensive or there’s been a tuber crop failure for a specific variety (it happens!) or you just want dahlias and don’t care the shape or color purchasing seeds or cuttings can be a great options. Purchasing cutting is an option growing in popularity for the more sought out varieties when you can’t get a tuber but still want the dahlia true to the mother plant. Starting dahlias from seed are for the more adventurous. You will have no clue the color or shapes you’ll wind up with and my understanding is you may end up with a lot more single petal varieties of dahlias than you may hope for. Starting dahlias from seed, though the resulting flowers will be a surprise, can give you some amazing varieties and even new ones (if you start saving seed yourself even better!). From cutting or seed, both ways will result in tubers by the end of the year. This will allow you to save the tubers of the ones you love and start increasing your own tuber stock. Don’t tell Graham we could start dahlias from seed… I like my tubers! I am not the adventurous type when it comes to dahlias- I like what I like!

Now perhaps buying online or from a wholesaler is not your cup of tea. Perhaps you snagged some off a Costco shelf or even the plant itself from a garden center. Dahlias are great in the landscape and not all dahlias are meant to be cut flowers. There are many varieties that should stay in the landscape. If you are looking for dahlias specific for cutting, research. Research the varieties that specialty cut flower growers are focusing on growing. If you are just looking for something pretty in the yard, garden centers can be the resource for you!

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Planting Dahlia Tubers

As just hinted at there are a couple options in planting dahlia tubers: potting them up and pre-sprouting or planting directly in the grown- preferably before they start sprouting too much.  You can take cuttings from the dahlia sprouts and root them, then you get even more dahlia plants!  I dropped the ball and did not take on this experiment, plus I only had one row to designate to them (now we have more like six fifty foot rows!).  Next year, taking cuttings of our favorite ones to make more dahlia babies is definitely on the to-do-list.  To start dahlias indoors, plant them in a decent size container (I used a one gallon but have also just stuck them in a tray).  Have the soil ever-so-slightly moist but don't water again until you see a sprout.  If over watered, they can rot.  Let me warn you- a mushy tuber is not only sad but kind of gross too.

Since we keep dropping the ball when it comes to actually taking cuttings for propagating, why bother pre-sprouting? The lame answer is that I am just itching to grow them in the dreadful winter/early spring months! The more responsible answer, it gives us a little head start to begin getting some dahlia flowers here and there by early summer. Not a huge amount, and the field planted ones are quick to surpass, just a nice glimpse of the dahlia season to come and we get some blooms a few weeks earlier than the directly planted tubers. What we also get? A crop trap to start knocking out those pesky pests!

When the weather begins to warm, and the nights stay above freezing, the tubers or the started plants can be planted out into the garden.  It is good to keep track of the nighttime temperatures, especially when planting out pre-sprouted tubers, they will be more susceptible to nips of frost since they have been growing in ideal conditions and well, have leaves! This is one reason, even though we pre-sprout some tubers in the greenhouse, we prefer to plant the tubers directly (the other reason? The directly planted tubers grow more robust plants!). Don’t go off the temperature highs and lows themselves. We also use a soil thermometer to check on the soil temperature. You are good to plant once the soil is maintaining seventy degrees Fahrenheit. I get paranoid in our volatile climate and like to see that consistency for about five days. Since the tubers will be buried about four inches below the surface, as long as the soil is warm enough you will have some happy plants! Along with temperatures, we watch the weather forecast like hawks. Not incredibly reliable but if there’s rain predictions in the future, we hold off. We do have clay soil after all.

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With more dahlia tubers than we ever had, we were inspired to try the trench planting method this year, rather than digging a hole for every. single. tuber. I loved the trench method, Graham still feels I ended up planting too crooked. I told him, he can plant them next year- let’s see how perfect he does it in a wind storm using strung up baling twine as a guide! Besides, he dug the trenches… I was following his lead! Let’s just say the conclusion to that? I didn’t plant that crooked. Anyways, we planted the entire clump about four inches down. With as many clumps we had and the fragility of the clumps (lots of broken necks) we did not find it worth the effort to divide them. The priority was to get them run the ground and growing. Even though I am bundled up and the winds were freezing, the soil itself had been more than ready! In our area, we aim to get these guys in the ground once May hits. Each year is a different story. Between having to break new ground, the harsh winter and odd ball spring rains, they got in a couple weeks later than I had hoped. Though later, it is more than worth the wait to evade the tubers becoming waterlogged. Next year, we may experiment using a post hole digger and the trench method since we will not be planting entire clumps. See which one we prefer!

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Dahlias like elbow room, give the larger varieties (dinnerplates, informal decorative, ball) a minimum eighteen inch spacing. Some of the smaller varieties you can get away with planting twelve inches apart if you are looking to pack more in (such as poms, perhaps ball varieties if you want to push it). We are in a very dry climate. Like, if you are not used to it your skin will crack kind of dry. This has its good and bad points. One good point is that we have the legacy of planting things closer with minimal concern for powdery mildew, which dahlias are prone to. Still want to pack them in close? I would keep a bottle of Serenade on hand to help combat that, especially is you are not in an arid climate (more on that in a bit).

Staking or netting them is essential, especially in our area with the crazy Carson Valley winds.  Personally, we prefer the corral method. It’s easy and less hassle than using hortonova. Hortonova trellising has its merits but can be a hassle to harvest dahlias with.

Dahlias are not fans of the cold. Have I mentioned that yet? The good news is even if the plant itself gets nipped by a frost, as long as the tuber hasn’t gotten frozen, isn’t mushy- the plant has a big chance of bouncing back! This doesn’t mean we don’t take precautions. After all, just because a plant will bounce back does not mean that flowering will not be delayed.

 This last year was frigid, we even suffered major freezes in June! Okay, okay we’ve had snow here in July. True story, it snowed the week of mine and Graham’s wedding- our wedding was mid July!  To keep the dahlias from not missing a beat, we keep frost cloth and plastic on hand.  We are prepared to toss a low tunnel over a row and have gotten quite speedy, not to brag or anything.


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Now let’s chat watering your dahlias. A rookie mistake is overwatering. It is easy to over love our plants, especially our summer ones! Just like in pre-sprouting the tubers in the greenhouse, the tubers in the ground are susceptible to rot. Ick. Another rookie mistake for us? Actually, under watering. I know- the complete opposite of what I just said! Remember, we are in an incredibly dry climate. We also have clay loamy soil at the new property. It’s a tough balance! The clay makes you think that the beds are being waterlogged but what we found is the new garden beds are actually shedding water better than we thought! It’s also difficult to get the soil to get hydrated to begin with. We increased water slightly, just overhead watering not drips (until we saw them coming up from the ground). Once they are up above ground, the drips are turned on and we gain some freedom from dragging a garden hose around! On the new property, we are still tweaking the drips to not over or under water the dahlias. It takes observation and patience, fortunately the critical time of where overwatering is a huge risk has now passed. The dahlias are a little more forgiving now that they are growing like crazy.

Dealing with Pests, Disease and Mildew

If the cold and overwatering didn't take these guys down- the earwigs have sure been trying to get their punches in!  Along with setting some traps (which I go into detail about in "The Nitty Gritty on Battling Earwigs”, I made some mesh bags to go over the blooms, though you can totally snag them on Amazon as well.  Earwigs have a habit of taking beautiful flowers and making them ugly.  Chew holes are the worst!  We are gaining a better control on the earwig population (finally!) and the bags are not needed as much, which is good.  The bags are not the most attractive and can create for some tedious, time consuming work, but they served their purpose.  They allowed the dahlia to evade the terrible earwigs.  We haven’t experienced problems with Japanese beetles but we have plenty of flea beetles, stink bugs and thrips! The bags seem to help with those guys too. Well, thrips… yellow stick traps and pyganic when the population is out of control. I hate it when I have to bust out the Pyganic but it works fast to knock down the population. At the new property, the thrips are completely out of control! I thought we’d at least have one season before they found us. That was a big nope. Thrips are terrible and brown the light colored flowers making them hideous but lovely for two little girls wanting to play princesses. If you have slugs and snails in your growing area, be aware that they find dahlia plants scrumptious! Putting down Sluggo plus is a great OMRI product to use that will also help if you are having troubles with earwigs and pill bugs. Even using organic or OMRI pesticides is not my favorite. We will continue to work on building a healthy ecosystem in the field, where the plants are healthy enough to combat them and beneficial insects are there to finish the battle for us. Something I am looking forward to researching a ton about this winter is using biologicals instead of sprays. Beneficial nematodes, insects, fungi and bacterias sound much more enticing to me.

Moving away from the creepy crawlies: be aware that rabbits will also go for the dahlias. Though, I don’t think they are in love with the taste, they will still feast on tender new growth. Grow dahlias in a bunny proof area. Blood meal broadcasted along with weekly sprayings of fish emulsion also helps to repel these adorable little jerks.

As briefly mentioned dahlias have their fair share of diseases and viruses to watch out for. “When in doubt, throw it out” needs to be followed. As in my experience where tubers from the wholesaler looked mighty suspicious, they were tossed. If I planted a tuber with leaf or crown gall, not only would I not have flowers but I risk introducing the pathogen to my field that would risk future dahlia crops for years. Dahlias are not fans of moisture sitting on their leaves, therefore drip irrigation is best. If you live in a more humid climate, along with being prepared with some Serenade, you are going to want to consider planting them two to three feet apart to increase air flow which will help cut down on leaf spots and mildews.

Harvesting and Post-harvesting Care of Dahlias 

Talking dahlia vase life gets tricky. It really depends on numerous variables one especially being the type of dahlia. The ball type dahlias have a better vase life and can handle the heat (such as at the farmer's market) than some of the fancy dinner plate dahlias.  Dinner plate dahlias are huge and glorious but with their fragility and size are better suited for design work, to enjoy in the garden or saved special for those customers who can embrace their ethereal beauty (which honestly, I find a lot of customers are good with that!).

Dahlias have a hollow stem, therefore harvest and then recut the stems under water then straight into the cooler they go that’s set at about forty to forty two degrees Fahrenheit.  I prefer to harvest my dahlias early in the morning. This helps give an optimal vase life.  

There’s different opinions on the stage the dahlia needs to be at harvest. I’ve tried about all of them: when they are fairly open but before the back petals feel “papery” was the main advice I followed. Personally, I felt that was too late or I was just not understanding the wording. That’s great for dahlias for event work but the vase life wasn’t as good as it could be for my subscription and market customers, in my opinion. That’s when I finally purchased the Postharvest Handling of Cut Flowers and Greens published by the ASCFG that was written by a ton of flower farming gurus. I highly recommend this book and I will attempt to word harvesting stages of dahlias without hacking. Basically, harvest the dahlias when the first two outer rim of petals is fully opened for ball, pom, informal decorative and dinner plate varieties. Basically your fluffy fellas. The book also suggests that some single varieties can be harvested when the first petals are lifting off the bud, like the harvesting stage of a sunflower. Some have said that is too early and the dahlias will not open. This is where you how you decide how to post handle the flowers: store them, flower food (or no flower food), etc all have to be experimented with for your specific operation. I will say, that unknowingly I accidentally harvested dahlias at more closed stages and have watched them open. I’m not the biggest fan of commercial flower food but with dahlias I see an increased vase life. Depending on variety a vase life can be anywhere from three to seven days. Perhaps more if you are including the additional few days it takes the dahlia to continue to open.

As fall approaches, the dahlia’s season comes to an end, do not be shocked when they begin showing their centers before you even get a chance to harvest! Though it is preferable not to harvest once the center is shown, this is the nature of late season dahlias. Personally, I find they still have a decent vase life and are still swoon worthy. Since they are protected by the mesh bags, they haven’t been pollinated. The dahlias simply know their season is coming to an end and they need to make seeds! Bottom line: don’t panic about it! Embrace it. Sip some hot apple cider, since by then it will be perfect for that fall treat!

Fall Clean Up

In our area, the winter is too cold to safely overwinter the tubers in the ground. Dahlias are hardy down to hardiness zone 8 (we are 6b). Though, there are many tricks to be able to overwinter them in colder zones, we don’t find it worth the risk. Besides, we are big believers in crop rotation to help keep pest and pathogen problems to a minimum.  

In the fall, the tubers are dug up and stored for planting the next spring.  If that seems like too much effort, mulching the dahlias heavily may protect them enough to overwinter.  Either way has risks.  Digging up and storing can result in some tuber rot, if not stored correctly or some just rot in general and no fault of our own.  Storing properly will help.  Be on the look out for our blog post on which tuber storage method works for our arid climate. Hint: we learned the hard way that the dry air makes us have to work much faster than others that are in slightly more humid climates.

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I can keep rambling about these summer favorites. At some point: I should cut myself off and save some ramblings for another post! Whether you are a dahlia enthusiast, a farmer, florist or home gardener I hope you enjoyed learning a little about what it takes to grow these amazing blooms (and are now inspired to grow some in your own cut flower garden!).



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I am looking forward to handing you blooms soon!

- Jessica


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Here are some products we find must haves when growing dahlias!