Want to get your dahlia plants ready for the season ahead of time? Need to make sure your tubers will grow? A pre-sprout test is the way to go.
First, I will talk about the fastest way to test for tuber viability. Perform a pre-sprout test for viability if you are not sure that your tuber has eyes. I basically never do this on the farm. This is simply because I can tell which tubers are going to grow, just by inspecting their eyes. Of course, this takes some practice. You can learn how to identify eyes on your dahlia tuber, here. But you’re still not sure? A pre-sprout test is the best way to let the dahlia show what it can do.
Second, I will share a great way to get a head start on your dahlias for the year. Start dahlias in pots in a protected space. Then, transplant them out into the garden. You could get blooms around 4-6 weeks earlier than otherwise.
Keep in mind that when you do any kind of pre-sprout test on your tubers, you start the growth of their eyes. This means you can no longer return them to storage in a cool dark place. In other words, they must be planted and cared for. This is a pretty good reason to not start this process too early. Not unless you want to keep some dahlias inside or in a greenhouse until your “last spring frost date” that is.
As a gardener who grows dahlias I was disappointed when I discovered my carefully stored dahlia tubers already sprouting in early spring. Dahlia tubers are not supposed to sprout until planting time! After researching the issue I learned why tubers sprout early and how to handle premature sprouting.
Why Dahlia Tubers Sprout in Storage
Dahlia tubers are living organisms that go dormant for the winter. They produce sprouts and leaves when conditions are right for growth. Tubers left in warm temperatures can mistake the conditions for spring and begin growing
Dahlia tubers require cool storage below 50°F to remain dormant. Temperatures above 60°F encourage sprouting. High humidity around the tubers also prompts premature growth. The tubers think spring has arrived early!
Signs of Growth on Stored Dahlia Tubers
I stored my dahlia tubers in their pots in my basement, layered with peat moss. When I checked on them after a month, I found:
- Small green shoots emerging from the tubers’ eyes
- Short stems and leaves growing from the main tubers
- Tiny white roots visible on some tubers
This growth meant my basement was too warm and humid for proper storage. I had to take action to stop further sprouting.
Should You Remove Dahlia Sprouts in Storage?
Seeing sprouts on stored dahlia tubers can be worrying. Are the tubers still viable? Should you remove the sprouts?
The good news is that early sprouting won’t harm the tubers. The sprouts can be removed, but this isn’t necessary. Nipping off sprouts now won’t affect the tuber’s ability to grow come spring.
However, any growth at this point takes energy away from the tuber’s food reserves. The tuber needs that stored energy to grow a strong, healthy plant later on. Leaving sprouts to grow will weaken the dahlia plant once planted.
Stopping Further Sprouting of Dahlia Tubers
If your stored dahlia tubers have started into premature growth, take steps to stop continued sprouting:
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Move tubers to a colder area – Get the tubers into temperatures below 50°F. A garage, shed, or unheated basement area works well.
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Separate and inspect tubers – Divide clumps and discard any rotten tubers. Check for disease and insect damage.
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Dry tubers & use fresh storage medium – Dry off any moisture on tubers before re-storage. Use new peat moss, vermiculite, sawdust, etc.
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Store tubers in paper bags – Paper bags allow air circulation while preventing light exposure. Plastic encourages moisture buildup.
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Add apple cider vinegar to storage medium – The acidic ACV inhibits sprouting at 1 part vinegar to 10 parts storage material.
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Try a cardboard box – A box lined with paper bags keeps tubers cooler, drier, and in the dark.
When to Pot Up and Force Dahlia Tubers
Potting dahlia tubers early indoors can give you a head start on spring planting. But tubers forced to sprout too early will stretch and weaken. Wait until 6-8 weeks before your outdoor planting date before starting tubers.
Check sprouted tubers daily and plant outdoors promptly when the weather warms. Avoid shocking young plants by hardening them off first. Cover new growth if cold temperatures threaten.
Emergency Action for Dahlias Sprouted Too Early
What if your dahlia tubers have already gone too far, sprouting long stems and abundant roots in storage? Take these emergency measures:
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Immediately move tubers to the coldest area available – even a refrigerator works temporarily.
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Prune off all growth down to the main tuber. Remove shriveled tubers.
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Dry tubers thoroughly before re-storage in a cooler spot.
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Pot up only the healthiest sprouted tubers to grow as backups. Discard potted plants after planting dahlia garden.
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Mark sprouted tubers to plant first when spring arrives. Use the others as backups.
With quick action, you can salvage overeager dahlia tubers. Just provide ideal storage conditions going forward to prevent recurrent sprouting. Come spring, even tubers with early growth should thrive when properly planted.
Avoiding Premature Sprouting Next Year
I learned some lessons from my dahlias’ premature awakening. Here are tips to keep tubers dormant for winter storage:
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Harvest tubers after the first fall frost when all foliage has died back.
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Cure harvested tubers for 1-2 weeks in a warm, dry area before storage.
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Select a storage spot that maintains 40-50°F temperatures, such as a cool basement, unheated garage, or crawl space.
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Use peat moss, vermiculite, sawdust, or wood shavings as storage mediums. Newsprint or coffee filters work for wrapping.
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Inspect tubers every 2-3 weeks. Check for sprouting, rotting, or drying out.
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Repack tubers in fresh medium if any show growth. Move to a colder area right away.
With proper harvesting, curing, and storage conditions, dahlia tubers stay dormant until spring planting time. A yearly review of storage methods can prevent next year’s tubers from awakening too early.
Troubleshooting Prematurely Sprouted Tubers
If your dahlia tubers start into growth before you are ready to plant them, don’t panic! With these troubleshooting tips, you can get sprouted tubers back on track:
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Ask gardening experts online for their advice about your situation. There are helpful forums like GardenHelper.com to connect with experienced dahlia growers.
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Consult reference articles about dahlia storage problems. Sites like GardenMaking.com offer science-based guidance.
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Check tubers regularly during storage to catch early sprouting right away. Frequent inspections let you take action before growth advances too far.
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Review the conditions of your storage area. Does it remain cool and dry enough? Are tubers exposed to light or excessive warmth anywhere?
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Reassess your storage methods. Peat moss and vermiculite hold moisture. Switching to cardboard boxes or paper bags allows more airflow.
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Consider trying commercial storage products made for dormant bulbs and tubers. Some contain sprout inhibitors that discourage premature growth.
With attentive storage practices and quick response to any sprouting, you can keep dahlia tubers dormant until spring planting time. Don’t let surprise sprouts ruin your dahlia garden plans.
Frequently Asked Questions About Dahlias Sprouting Early
If you’ve had dahlia tubers start growing too soon, you likely have many questions. Here are answers to some frequently asked questions:
Why are my stored dahlia tubers sprouting when it’s weeks before planting time?
Dahlia tubers require cool temperatures around 40-50°F to stay dormant. Warmer conditions trick them into thinking spring has arrived early. High humidity also encourages premature sprouting.
What should I do with sprouts on dahlia tubers in storage?
You can remove the sprouts, but this is not necessary. Just be sure to stop further sprouting by moving tubers to a colder space right away. Ongoing growth will deplete the tuber’s resources.
Is it okay to pot up dahlia tubers that have sprouted early?
You can force sprouted tubers, but wait until 2-3 months before planting outdoors. Tubers started too early will become leggy and weak by planting time. Grow lights and warmth encourage rapid growth.
Can dahlia tubers that have sprouted and resprouted in storage still grow okay when planted?
Yes, tubers that sprouted repeatedly can still thrive when planted at the right time. Just be sure to prune off excess growth and select only the healthiest tubers. Prioritize sprouted tubers to plant first.
How can I prevent my stored dahlia tubers from sprouting early next year?
Proper harvesting, curing, temperature, humidity, storage containers, and medium selection will help tubers stay dormant. Check tubers regularly and act quickly if any sprouting occurs.
What’s the ideal way to store dahlia tubers over winter?
Cure freshly dug tubers for 1-2 weeks in a warm spot. Store in a 40-50°F location like an unheated basement or garage. Use vermiculite, peat moss, sawdust, or cardboard boxes to discourage premature sprouting.
With the right troubleshooting approach, premature sprouting doesn’t have to spell disaster for stored dahlia tubers. A little extra care and planning goes a long way to keeping tubers fresh for spring planting!
To Get a Head Start on Your Dahlia Season
If you want to get a head start on your dahlias, consider planting your dahlias into small pots. I use one gallon pots. Larger will work well too. Dahlias need to be planted in a place where the soil will stay at least 60 °F (16 °C) all the time. They also need access to sunlight as soon as they begin to sprout out of the ground. A greenhouse, hoop house, or sunny windowsill are great places.
It takes dahlias about two to four weeks to start coming up from the ground. Start this process five to seven weeks before you want to plant them outside.
Because this is a lot of extra work for the dahlia farmer, this method works best for people who only have a few dahlias. The benefit is that you will get blooms typically 4-6 weeks earlier. Planting in raised beds, under floating row covers, or in hoop houses are some other ways to get flowers earlier.
Start with about two inches of damp soil. Again, remember not to use soil that is too wet. Otherwise, your tubers will rot before they establish a root system. Plant the tuber horizontally with the eye facing up toward the sky.
Cover in five inches of soil. Do not water until greens begin to appear.
Moving your happy dahlia plants to your garden is possible once the ground outside has warmed to 60 °F/16 °C.
To Test Your Tubers for Viability
First, find a tray or container that will hold about six inches of soil. Put this tray in a place where the soil temperature will not drop below 60 °F/ 16 °C. Next, spread about two inches of lightly dampened soil along the bottom. Be sure that the soil is not too wet, otherwise the tubers will rot.
Then, line up all of your tubers horizontally. Be sure to label and keep track of which tuber is which. At this point, space does not matter, because the tubers will be transplanted. So, you can put a ton of tubers into this container.
Cover them with the remaining soil so there is about an inch on top. Do not water, assuming you started with damp soil. Remember, dahlia tubers are very prone to rotting. It is better for the soil to be on the dry side than the wet side. Of course, once you have a plant that is growing, you will need to water it often.
Your dahlia tubers will quickly begin to sprout. In a week, dig out the tubers and see what’s happening. Bury the ones that haven’t sprouted eyes. Give them another week, and check again. Give up on tubers after 3 weeks of no sprouts. Eyes can be white, pink, or purple.
Immediately transplant the sprouting to deeper pots, so the tubers are covered in about five inches of soil. Be sure to time this correctly. They won’t grow healthy plants if they aren’t moved to a more permanent spot, like the garden or a deeper container that is planted 5 inches deep. The leaves will grow at a shallow depth. Remember, when you transplant them, use lightly damp soil and do not water until growth begins to appear. Plant the sprouting tuber 5 inches deep, horizontally. Once the leaves pop out of the soil surface, begin watering regularly.
