Dahlia Growing Tips for Hot Climates
The best gardening tips I ever learned came from failure—ideally, failure followed by success. Growing dahlias in Southern California comes with its own set of challenges, but it hasn’t stopped me from truly enjoying these flowers and being fascinated by their behavior in the garden. I hope that sharing my dahlia growing tips will make your experience more enjoyable as well!
My own dahlia growing journey has been filled with breathtaking success and complete failure. The very first dahlia I ever planted in my garden was a ‘café au lait’ and it knocked my socks off! For a beginner, having such immediate success with dahlias gave me a little bit of a false sense of security back then…..’dahlias must be so easy to grow!’ I thought. While I’m thankful that early success encouraged me enough to catapult me into learning all about dahlias, I’m also thankful for the failures I’ve had with my dahlias as well. If you stay tuned, I’ll tell you the story about how I lost all my dahlia tubers one year…..
I’ve been growing dahlias for many years. I first started out with tubers, which I highly recommend for anyone looking to start. As I grew more and more, I became interested in dahlia breeding and experimenting with growing from seed. All the dahlias I’m holding here were grown from my own harvested seed. It’s so fun to see what each offspring will look like! I’ve written about growing from seed here on the blog as well.
Keep Soil Cool to Beat The Heat
Maybe this isn’t a concern in other climates, but I found that it’s totally possible to fry your dahlias both above ground and under the soil. Soil temperature is not a dahlia growing tip you see very often, but I learned the hard way. Last year I tried a new dahlia growing bed. It was short (about 8-12 inches tall) and surrounded by stone/boulders. The growing medium I used was also an extremely well-draining potting/raised bed mix. This was a recipe for disaster, as I quite literally fried my dahlias into crisps! There was nothing to save, I lost all my tubers. Granted, the whole point of this new bed was to condense down my dahlia collection because I was planning to grow fewer dahlias in favor of edible plants. Well, the collection got condensed for sure…..
In hotter climates especially , it’s necessary to consider soil temperatures if you want to grow dahlias successfully. So, what will keep the roots cool in the soil? For hot climates, mulching and having deeper garden beds/in-ground beds to start with. I won’t give an ideal bed depth because I think it’s just something to consider and try to make as large as you can. Imagine how hot my stone-built, short, well-draining garden beds would get on a 110 degree day?! I’m melting just thinking about it! Keeping in mind your soil volume (more volume, less dramatic fluctuations) will help keep your dahlias happy.
Also, mulch! This goes the same for all kinds of crops we grow—-mulch does wonders for regulating soil temperature, decreasing evaporation, and protecting root systems. You can find some information on types of organic mulches I use HERE.
Here’s a little peak at how I planted my dahlias this year. It has worked out great, and I’ve even decided that I will be growing dahlias in one Birdies Bed from now on.
Pinching Your Dahlias
Speaking of soil temperatures, I’ve learned that pinching your dahlias produces a result that may actually help your dahlias beat the heat! I should note that I’ve got an entire “beginner’s guide to dahlias” already on the blog, so today’s post is a more in-depth look at what my growing experiences have taught me. Truth be told, pinching is not necessary to dahlia survival in general BUT— the more compact, robust, and shorter plants that pinching can produce seems to really help dahlias band together to survive hotter summer temperatures.
For example, a pinched dahlia plant will create more lateral stems and foliage that is bushy and lower to the ground. My non-pinched dahlias can get a little tall and lanky—sometimes the stems will flop over, thus exposing the fragile stems to the harsh sun. Lower, bushier plants will also help keep the soil covered like a “live mulch” which circles us back to the idea that keeping our soil as cool as possible will help the dahlias survive hotter temperatures.
Supporting your dahlias
Unfortunately, it’s rare that I come upon a dahlia that doesn’t need some support. Personally, there are some I’ve grown that I haven’t supported, but it’s best to be prepared to give your dahlias something to help them stay upright. Luckily, supporting or staking dahlias is quite simple and doesn’t require anything complicated.
I’ve used everything from tomato cages to a bamboo stake with some string to support each plant. This year, as you can see in my Dahlia Growing Tips video (also linked above), I took some large pruned branches and set one at each end of my dahlia bed. From there, I took some garden twine/string and strung it between the two branches to support my dahlias. This has worked just fine. Is it an incredible, permanent installation? No. But It’s practically free and works for the season.
Either way, supporting your dahlias will help you avoid what we talked about before (lanky stems flopping over and exposing your dahlias to sunburn) and make your dahlia bed more organized as well.
Cut Dahlia Stems Deep When Picking
One of the best dahlia growing tips I’ve picked up over the years is the important of cutting long stems in your dahlia patch. Cutting long stems serves a few purposes: first, your cut flowers will last longer than dahlias on puny stems (and be better for bouquets) and second, cutting deep will create more lateral stems and growth for more dahlia buds!
Personally, I tend to use the time I spend cutting dahlias for bouquets to “shape” or prune my plant. I keep an eye out for leaf nodes that are low and possibly sprouting, and try to cut my stems above that node. Unfortunately, cutting your dahlias deep can mean that the occasional bud gets cut as well (it won’t open), but I still find this method of cutting dahlias worth it. Each plant is so generous during the growing season anyway! If you need a little more insight into what I mean by “leaf nodes” and where to cut your dahlias, definitely make sure you check out my YouTube video as well.
Overwintering Dahlias Will Help Them Establish
In mild climates you can overwinter your dahlias in-ground. Did your dahlias get started late this Summer and suffer in the heat? That’s okay! If you let your dahlias overwinter, they will have a much earlier start in Spring and have time to grow larger before the heat arrives. It’s a common struggle for us Southern California gardeners to get our dahlia tubers at a good time in the Spring. Honestly, many providers send them out much later than we need, so it can be tough to get an early start. Overwintering dahlias can really allow the dahlias to start sprouting when they feel ready in the Spring.
If you are able, you can get an early start on your dahlias and by planting them in pots like I did HERE, and keeping them sheltered and safe from frost. Either way, it’s important for us mild climate gardeners to get our dahlias sprouting and growing early so that they can be as large and established as possible before our intense heat.
For many mild climate gardeners it is difficult to receive tubers early enough to plant in Spring. That’s okay. I still plant my tubers as soon as possible.
Fall Planting Dahlias?
There is a school of thought that says dahlias can be planted in mild climates in Fall. I’ve seen gardeners in Texas and Florida talk about this before, and it’s very interesting. Essentially, the idea is that you can plant in Fall for a bloom in the cooler months and then cut back your dahlias (and mulch) to prepare them for an early Spring sprouting. This concept also embraces a “summer dormancy” because it’s just so darn hot for them. If you’ve truly struggled maybe give this a try, but my personal experiences haven’t supported the idea that this would be more ideal for me. Besides, after the first season, overwintering your dahlias in-ground means you don’t need to worry about planting anymore.
For example, both my mom and I leave our dahlias in the ground all year round. If they sprout, I let them. But they really don’t look good or bloom profusely at all from Winter to Early Spring. I get a Fall bloom for sure, but the same effect can be accomplished by simply planting in Spring and just letting the dahlias do their thing. So….I guess I’m saying that, in hot climates, simply just keeping your dahlias in the ground year-round can help you assess the best patterns for their growth. Fall planting can indeed be an option, but dahlias have also worked out just fine for me when planted in early Spring after the dangers of frost.
Choose Specific Dahlia Varieties for your Climate
My last tip for growing dahlias (in hot climates especially) is to keep an eye out for those varieties that simply LOVE your climate. This year, growing eight dahlias side by side, I can really see a difference in the vigor and disease-resistance of certain dahlias. For example, my Danny’s Girl dahlia has gotten powdery mildew twice, is more lanky, and just hasn’t been as vigorous as my Diva dahlia. Oh my! The Diva dahlia has been vigorous, bushy, healthy, and the flowers have had the longest vase life compared to all the others. Whenever you notice these types of characteristics in a dahlia, note it!
Admittedly, I’m intentionally going to keep my dahlia collection minimal. It’s not that I don’t LOOOOVE dahlias, but it’s more because I have a lot of plants I need to grow in my space and have to prioritize. Therefore, I’ll be getting rid of any varieties this year that don’t seem great for inland Orange County and replacing them with new ones next year. Think of this process as curating the “perfect” dahlia collection for your space. As the years go by, your dahlias will naturally be better and less maintenance. Isn’t that amazing?!
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Meet Randi
I was just thinking today that I give up on Dahlias. I bought several different types of bulbs two years in a row from the same company but they were dud. Only one grew a stem and the Rollie pollies went insane on it… I surrounded it with a clear plastic pot and it started growing again. And then it just died completely. Once the storm passes I might dig down to see if there’s anything worth saving. I don’t know if the bulb will produce next year if this year it didn’t get to leaf out and collect energy?? Even a tiny bit of success would have been encouraging! I did plant them in the garden in a somewhat shaded area. So I still don’t know what to do differently. Where do you buy your bulbs? (I’m in Orange County too).
Hi! If you love dahlias, don’t give up on them! I would highly recommend giving them a full sun spot because that’s really where mine thrive. In terms of vendors to buy from, there’s a list of tuber sources in the “where to buy seeds” section—I’ve purchased from all those places with success. Hope all these tips will help!
When is best time to dig up dahlias in Southern CA?
Thanks
Hi! Well, I don’t typically dig up my dahlias. But when they do start looking tattered, yellow/browning, wilty I trim them down. This usually happens once the nights start to get cold (after Thanksgiving). It’s rare that we get cold enough to truly kill the dahlias off with frost, so it’s more flexible here. You can stop watering for a bit to let the tubers build up a thicker skin for storage and then dig up. I don’t have much experience digging and storing because I just leave them in the garden most years. Our home is so small I’d have no place to store the tubers anyway!
Where do you buy seeds. I live southern california close to beach
Hello! I have a list of my favorite seed sources here: https://freckledcalifornian.com/where-to-buy-seeds/
I left mine in from last year, I had also purchased a few from a major supplier in Washington. I realized when I received the new ones that I had a total of 50. I live in Ventura County (coastal weather, rarely reaches 85 degrees) it does not get too hot. For the first time this year I had a mildew, and beetles….this is my 4th year to grow dahlias and the first time that I am happy to cut them down and have them come next spring. It was a lot of work and the mildew went all the way down the row of dahlias, and was impossible to contain, I tried a variety of fungicides and spent a fortune trying to get it under control. The flowers looked great but the rest of the plant looked really bad. The ones that did well received 3-4 hours of sun and the others had about 6 -8 hours. I will see what happens next spring before I completely throw in the towel.
This is really interesting, and thanks for providing your experience! I’m sorry you dealt with so much powdery mildew and I hope it was more about this specific year and won’t be as bad in the future.
Thanks for the post! I planted 4 different varieties this year in different soil types in my garden. Cafe au lait was the first to come up in early summer but infested with bugs. Cornell and burlesca are doing great. Thomas Edison is barely sprouting up in late summer now, but I’m not sure it’s going to make it. None are mulched but I’m somewhat experimenting with them this season and seeing how they grow in my 10a garden.
Hello! Thanks for sharing your experiences in zone 10a. The friends I know who grow Thomas Edison have had the most success with that one blooming later in the season (like Fall), and one friend even had hers blooming in winter! It wasn’t profusely blooming, but it was pretty. Keep going with the cafe au lait! The older mine got, the hardier and more magnificent it got. I really do love that one!
Thank you so much for sharing these invaluable tips on growing dahlias in hot climates. As a fellow gardener battling scorching temperatures, I can’t express how timely and helpful your post is. Dahlias have always been a favorite of mine, and your insights have given me renewed hope to cultivate these beauties successfully.
Your emphasis on soil preparation truly resonated with me. It’s often underestimated how much of an impact proper soil conditioning can have on plant health. The suggestion of incorporating organic matter and maintaining adequate moisture levels is a game-changer. I can already envision my dahlias thriving with the enhanced care they deserve.
Thank you for your dedication to spreading knowledge and nurturing a community of passionate gardeners. I’m excited to put your tips into practice and watch my dahlias flourish like never before!
Dahlias are a warm-season crop and should not be planted until the soil has warmed up to at least 60 degrees Fahrenheit.
Fantastic post Randi! I remember your ‘café au lait’, they were gorgeous! I’ve tried two of the dinner plate dahlias from a nursery and unfortunately I ended up drowning the tubers and they rotted so I will be trying the dwarf dahlias from seeds this next go around… can’t wait! I’ll definitely brush up on the post for beginners but will keep this one at the ready as well.
When is best time to dig up Dahlias in Carlsbad CA as I need to make room for spring blooming bulbs?
Thanks
Hello! That’s a good question, although I don’t usually dig up my tubers, so have less experience. From what I understand, you don’t need a frost necessarily, but you should cut back the plant halfway and then stop watering for a week or so to help the tubers develop more of a skin. Then dig them up! It might be a little early still for us, but I understand the need to get spring bulbs in soon.
I wish I’d found your site sooner! I’ve been going through the same trial-and-error learning process (I’m in zone 10 San Diego) and I could have saved myself soooo much time! I grew up in New England and learned all the classic garden “rules” which…just don’t apply here. The seed packets especially drive me crazy as they never have the right information for our zone. For instance, for years I couldn’t keep a Zinnia alive to save my life. Seed packets led me to believe they loved hot summer weather so I sowed them in March-April and they started off great but died in July or August. Now I sow them in September and they do great. Also, I’m so tired of seed companies describing some perennials as “annuals” simply because they’re frost tender. I shake my fist at the skies and shout “That’s not what ‘annual’ means!” lol My biggest gardening dilemma is when to remove skanky-looking plants that are well past their prime but refuse to die due to the lack of frost. I hate euthanizing plants even when I should.
“I’m new to gardening, and I’ve heard that dahlias are both stunning and versatile. Could you share some tips on how to successfully grow and care for dahlias? Are there specific soil and climate requirements I should be aware of? Thanks for your guidance!”