What To Do With Over-Wintered Dahlia Plants?
Winter of 2020-2021, I over-wintered some tubers in the ground for the first time. And— I really learned some things. Fast forward a few years and I decided to do it again this past year. I wanted a chance to fix the mistakes I made.
We still dig 95% of our tubers since we sell them each year. However, over-wintering in the ground really helps my perspective when talking dahlias with a lot of you. Most of the home gardeners in my area leave their tubers in the ground. We don’t freeze hard enough for the ground to freeze solid. As long as you have good drainage, your tubers will do just fine in the ground. (Zone 7b-8a, South Carolina) In fact, I recommend most people leave them in unless they have a temperature and humidity control storage environment.
A Bed of Dahlias From mid April 2021
Overwintering in the ground works pretty reliably in Zone 7 and above. Some zone 6 can do it. Occasionally I hear about a zone 5 but that takes some work and I wouldn’t risk it.
So when you overwinter, your tubers will begin to sprout once your ground gets warm enough. We overwintered in 2 different environments- on our farm in a cooler than average spot. The second was our off farm plot that sits high and very open to the wind. In early March I began checking to see if they were resprouting. I found our off farm plot was already greening up when I removed the tarp. This location gets full sun all day so the soil is a bit warmer even though it is more exposed. It runs warmer when the suns out but much colder on a freezing night than our home farm.
The home farm area sits between 2 hoop houses so has wind protection but that also means a bit of shade and gets enough sun to grow dahlias but not 100% all day full sun. So in early March, those tuber clumps were still slumbering when we removed the tarp. I noticed that this week (3 weeks after removing the cover) they were beginning to sprout.
*** Side Note— Do you have to use a tarp to cover during the winter? No- We used one for several reasons: weed control. We needed to kill off some weed pressure on the off farm plot. We also needed to be able to control how much water was getting in because that plot doesn’t have as good of drainage as our on farm plot. (in fact, we lost about 50% of one variety on that plot) As long as you planted in an area with good drainage, I’d recommend a bit of mulch and that will work just fine in the home garden. ***
Now- you’ve probably already thought— It’s March- do you really want your tubers sprouting then? Well no- but it’s not the end of the world and when you leave them in the ground, you have to roll with the punches. So I’ve been taking pictures over the past few weeks of what’s been happening:
The above pictures are from right after we removed the tarp from the off farm plot. You can see how the tips got a bit burned from not getting the tarp off sooner. But I didn’t worry about it because I knew we had a frost coming.
after an early Spring Frost
When you let your tubers sprout naturally, you are probably going to have a frost that knocks them back at some point. So I just let it happen because I knew they’d resprout.
Resprouted tuber after a spring frost
This picture above is about 8-10 days after the frost picture. It doesn’t take long. They may go frosty again- we are still 3 weeks from our last frost date. But it’s okay because I know they’ll resprout again.
The first time I over-wintered, I covered with frost cloth each time we got a Spring frost. But I learned that was just extra work- they are going to do what the weather tells them. And once we level off temperature wise, they will grow like crazy!
So what do we do with these dahlias once they sprout and stay sprouted? Fertilize!!! This was a major mistake I made the first time I over-wintered. I didn’t fertilize early enough. Once they are sprouted, begin your fertilization. They need food- they are hungry after that long winter’s nap!
Also make sure to re-install any support structures if you removed them throughout the winter. They will need them sooner than you think.
Lastly- the question I always get: So if I over-winter in the ground, should I divide my tubers and if so how often?
For years, leaving tubers in and rarely dividing was the norm. However— in this day and age of virus potential in dahlias, I think it’s good to check your tubers often. So I recommend digging up your tubers at least every other year to check for gall diseases (crown and leafy). It’s hard to tell above the surface if you have these. You can then divide or just put the clump back into the ground. If you are introducing a lot of new varieties each year, I would check more often- I’d dig your clumps each spring, inspect and then replant.
Yes- I know this is extra work but it will go a long way to keeping your plants healthy!
So go check those clumps— hopefully you’ve got some green sprouts! If you need help dividing your tubers, come join our workshop on April 13- Dahlia Dividing and Planting. It’ll be a morning of exploring the beauty of Spring on a flower farm and learning how to divide your tubers like a pro! Sign up Here!
Waking Up Your Tubers
For some reason, the beginning and end of dahlia season seem to be the most confusing for new dahlia growers. I get so many questions about what to do with tubers to get them started and what to do with them during the winter. Well- let’s talk about Spring stuff since we are almost there- only a few days!
If you need a quick refresher about what to do when your tubers arrive- Click here for last week’s post.
OK— So— Waking those tubers up from their winter nap:
First thing: Do you have to wake up your tubers? No- they will be perfectly fine if you unpack them from storage and plant. This process is not necessary but does have some advantages.
Advantages- If you live in a short season climate, waking tubers up gives you a bit of a jump and makes sure you have blooms before it frosts.
If you have a small garden, waking tubers up makes sure you take advantage of every space and you don’t plant a dud. This applies to commercial growers too- we don’t plant anything we don’t see a viable eye on b/c we need every spot to be productive!
So how do you it? It’s very simple- Take your tubers from their storage location and move them to a frost free place that’s around 65-70 degrees. A little warmer is okay but not too much. You still need to be paying attention to humidity b/c if not, it’s possible for your tubers to shrivel at this point. So keep that humidity high 80-90% if possible.
Keep checking on your tubers regularly and within about 2 weeks you’ll see a few starting to swell at the eyes- there will be green or purple (occasionally white) nubbins which will turn into sprouts. Once you see these, you can plant if you are past your last frost date. This process is called “eyeing” up your tubers. Eyeing up your tubers can help them to sprout a little quicker when you plant.
Few more questions I get — Do you need to remove them from the storage medium? Maybe— The medium can help you control humidity. This is why you need to monitor them. We remove ours from the storage medium and we usually put a lid on our container for a few days. BUT— I always check in after 2-3 days. If I see any sign of condensation on the container, I will crack the lid.
Do I need to pot them up into containers with potting soil? This is not required for the “eyeing up/waking up” process. The only need to pot up would be if you desire to take cuttings or really need to get a head start on growing them. Potting up with soil is going to be like planting them- so you’ll need lights and a place for them to grow and will actually mean you are looking after them for much longer (6-8 weeks) before planting out. So you only need to do this if you have a very short season or need a super early bloom.
Now you may be thinking, this is too much trouble- Can’t I just plant them when I receive them? Well that depends- if you are past your last frost date, then most likely you’ll be fine to plant. Why do I say most likely? B/c ideally you need your ground to be warm, 55-65 degrees to really get the tuber going. A last frost date by definition is just when you have a 50% chance or greater of not having a frost. But what really matters is your soil temps. So it never hurts to wait a bit. Or if you get impatient (like I often do), lay a black tarp/plastic over the area a few weeks before last frost and it will warm your soil up!
I know this has been a post with a lot of caveats- but that’s just growing anything. Everyone’s climate is a bit different. Microclimates play a big role in how well things grow. So remember- There’s no set way to start a dahlia- you have options. Pick the one that’s best for you!
What to do when your tubers arrive?
Tubers are arriving! I love this time of year because it really feels like Christmas- new plants and tubers arriving almost every week!!
So what do you do when that long awaited box shows up at your door?
Well- You open the box! I’m not trying to be sarcastic here but seriously— Open the Box! People get busy and leave them for a day or two in the box. This is not good. Remember tubers are dormant but they are still living things. So Open the Box!
Then remove them from their packaging. This will vary according to seller. (This shipment is from Eagle Dahlia Farm by the way. First time I’ve ordered from them and the tubers look great!) I remove mine from the plastic bags. Let’s just say I’ve had bad experiences — moldy tubers from leaving them in a closed plastic bag. Kudos to this farm for cutting a slit in the plastic bag to give the tuber some air. I think that’s a great idea. You could also leave the tuber in the bag and make sure the top is wide open.
After removing from the bag— Label them right away! I use an abbreviation system. So for example, this tuber was labeled HHCC. I’ll record it on my spread sheet as Hollyhill Cotton Candy= HHCC. You can write the whole name on there if you like.
Next up- inspect the tuber. It should be firm, slightly soft is okay but not squishy. Some tubers store better than others. Also it’s not unusual to see the end cut off like this. A lot of growers do it to inspect for rot inside the tuber. The cut will be healed over by the time you receive it.
This tuber already has an eye sprouting. This is great! Sometimes tubers will be “eyed up”— showing the beginnings of sprouting. But they don’t have to be. It depends on if the grower took the tubers out of cold storage a few weeks before shipping. Either way, if a tuber is planted or potted up, it should begin to eye in 3-7 weeks. Most will eye in 3-4 but some take as long as 8 weeks- so don’t give up on them.
If you want to take cuttings from your tuber, pot it up right away. If you are going to hold the tubers until time to plant, hold them in a 40-45 degree area and at about 80-90% humidity (if you have more than 3-4 weeks until planting time). If you are within 3-4 weeks of your planting time when they arrive, you can usually leave them at room temp. Make sure they can breathe. Also check on them weekly to make sure they aren’t shriveling. If they begin to shrivel, pot them up so that they get a bit of moisture from the damp soil. This will help preserve the tuber until time to plant out. A single tuber or potted up— either gives the same result. I’m going to be taking cuttings from these so they’ll get potted up right away.
Tuber size can vary a lot. It varies by variety- some produce long skinny tubers (looking at you Rip City!), some big fat round ones (like Cornel or Diva). As long as the tuber is firm and has a viable eye- it’s going to grow. So don’t worry if you get a smaller tuber. Pictured below is a clump of Blizzard tubers. The small tuber in front was the original tuber planted (often called the Mother tuber). Blizzard is a great tuber producer but usually produces smaller tubers. As you can see, it doesn’t take much to get a good clump!
**Originally published March 2022, updated March 2024.
Dahlia Game Plan: Harvest and Post- Harvest Care of your Dahlias
You’ve planned, worked hard and now your dahlias are finally in bloom! We’ve come to the last section of our Dahlia Game Plan for this winter. Let’s talk about how/when to harvest your dahlias and how to care for them once cut!
Hilltop Lost Treasure
Harvesting your Flowers:
When cutting stems for cut flowers, you want to cut deep into the plant. Every time I show a new employee how long to cut, there is always an expression of surprise on their face. We use our arms as a measure and cut between the elbow and mid-bicep - kinda’ depends on how long your arms are! Cutting deep into the plant like this encourages the plant to produce more long stems. If you cut shorty stems, then the new stems are going to be shorter than what you cut. So although it may feel like you are taking a lot- you gotta cut deep for continued long stems.
(This is why we’ve spent time setting up that fertilizer regimen- we need to give back to the plants b/c we are expecting a lot out of them. Don’t forget to Feed!!)
Stage of harvest: It varies for different forms but here’s some basic tips-
Ball/Rounded Shapes - 2/3 open, when petals have begun to curve backwards
Decoratives- 50% open
If pollen is already pushing out of the center, then you’ve waited too late.
Blooms will continue to open about another 20%, some more than this.
When to harvest: Cut stems early in the morning- plants are higher in sugars and hydration during that time. Cut before you hit 85 degrees if possible. Place cut stem into water after cutting. If you have to wait more than a few minutes after cutting before getting them into water, recut the stems.
Where to harvest: Cut above a leaf node- this will encourage regrowth for more stems/blooms and keep your plant tidy as you go, remove any foliage that will be below the water line.
Omega
After Harvesting Your Flowers (Post-Harvest Care):
For the home grower:
Cutting into water with flower food helps extend vase life. Place bucket or vase in a cool dark room for a few hours to let blooms hydrate before using or displaying. Chrysal and Floralife are great brands and are easy to find for flower food.
Using an old refrigerator as a cooler and conditioning blooms over night at around 40-45 degrees will add 1-2 days to your average vase life.
Change your water at least every other day, add more flower food. Keep in a cooler spot and away from heat or high direct light.
For the commercial grower:
Harvest early in the morning
Cut into buckets with water and hydrating solution. (Chrysal Professional #2 Transport and Display Solution or Floralife 200)
Once blooms are dry, place into flower cooler for at least overnight, preferably 24 hours.
Store for 3-4 days, no more before selling/delivering to customer. Try to move blooms within 2-3 days of harvest, especially for larger blooms.
Recommend customers use flower food to extend vase life.
Try to ascertain end use to determine when to cut for best results.
Gerrie Hoek
Vase Life: Average vase life on a dahlia is around 5 days. Some varieties/forms last longer, some less. Also blooms last longer when it’s cooler outside and the plants are well-hydrated. Warm temps mean lower vase life unfortunately. But it’s good to know what to expect!
And the positive thing is that— You can just go to your beautiful dahlia garden and cut some more!!
Dahlia Game Plan 2024: Choosing Varieties
What dahlias should I grow? What will thrive in this hot humid climate?
I can’t tell you how many times I’ve been asked that question. Often people assume that I just pick what I think is pretty. And yes- looks play into it. But the longer I grow in a hot climate, I understand that it takes more than just good looks to thrive here!
So what factors do I consider when choosing varieties for our trial gardens?
Customer preference: I grow a lot of flowers for florists who do very fancy weddings so that influences my color choices- white (always white!), pinks, peaches, neutral blending colors and a few burgundies mostly. Maybe you grow for a farmers market- that would influence your color choices - brights and fun colors!
If you have a home garden, this would mean you choose a color you like or that fits in your garden color scheme. Thankfully there are tons of dahlias out there so you can choose several in your color and then see if they fit the rest of the characteristics.
Heat tolerance: You hear this term thrown around a lot in the dahlia world- especially down South here. But what does it mean? Well that may depend on who you ask. But for me it means a few things:
The center of the dahlia stays closed in high temperatures.
The plant stays healthy with minimal maintenance through high temps
The bloom has a decent (4-6 days) vase life in high temps. Some dahlias will bloom in high heat but then will only last 2-3 days.
Peaches N Cream is an excellent example of a highly heat tolerant variety
Classification: There are lots of classes of dahlias but mainly I’m concerned with balls, decorative, waterlily, and formal to semi-formal types. Those work well as cut flowers and are also what my customers prefer.
Size: I do love the WOW factor of a 12” bloom but the reality is that my customers have no use for it. So I grow a few large blooms but mostly stick to things in the 3-6” size range.
One nice thing about growing in the South is that larger varieties do tend to shrink a bit here. Cafes are regularly more 6-7” in size than their normal dinner plate scale you may see elsewhere.
Orientation: Dahlia blooms can sit several different ways on a stem and that plays a bit factor in how you arrange/design with the bloom. Some face upwards, some face forwards (often called “clock facing”) and some sit at a 45 degree angle. The 45 angle is probably the most desirable and what I try to find. But I’m not going to turn down Cafe Au Lait just because she’s usually clock facing!
Petal Density: I’ve learned through many years of observation that dahlias with higher petal densities hold their shapes better. Ball dahlias with high density of petals tend to not blow their centers as quickly. You do have to let these open up a little longer to get a really full look but it’s worth the extra day or two.
Height: For me, I tend to choose varieties under 5’ because I live in an area that can get strong tropical storms. I cut out all the super tall dahlias (looking at you Lady Nathalie) because they always blew over no matter how many layers of netting we used!
Bloom time: I really like dahlias that bloom early. One- because I’m impatient to see them but also because I grow in a long climate area and I can usually get 2 strong flushes out of early blooming varieties. On the flip side, our long climate gives us a chance to grow varieties that take 120+ days to bloom (looking at you Nicholas) My favorite early varieties are Peaches N Cream, Sweet Fabienne, and Linda’s Baby.
Bred in the right climate: Years ago you couldn’t find dahlias that were bred in hot climates, but these days there are a few places you can get them. I really do think the breeding climate makes a difference. I see dahlias from hot climate breeders thrive from year one. Whereas sometimes I have to grow a dahlia from elsewhere a few years to get it acclimated to our climate. So look around and find out who’s breeding close by.
We all have different things we are looking for in our dahlias. But over the years the above characteristics are what I have found that attribute to varieties that are successful in my field.
