Growing guide
Where do I start?
Open your package and check your tubers! Make sure that nothing broke in transit and that the tubers arrived in good condition.
When can I plant my tubers?
You want to plant your dahlia tubers outside after all danger of frost has passed and your soil temperature is around 60 degrees. You can find your area’s last frost date with a quick Google search.
I can’t plant my dahlia tubers yet, what do I do?
If you’re not able to plant the tubers outside immediately, then crack open the tuber bags and store them in a cool dry spot between 40-50 degrees (garages and basements work best!).
Check on the tubers now and then to make sure that they aren’t getting too much moisture or that they are drying out. If you’re noticing excess moisture or condensation, you can open the bag more, and if they’re too dry (starting to shrivel) give them a light spray of water.
GETTING A JUMP START
How do I start tubers in containers indoors?
If you are planting only a few dahlias I would recommend starting them in a container so you can get a jump start on their growth. You can start this up to a month before you plan to plant them outside.
Find a container that is 8-10 inches tall. Place about 2 inches of dirt at the bottom of the pot. Place the tuber horizontally (on its side) with its eye (pink or purple swollen growth) facing up. Cover with 4-6 inches of dirt. Water once, but not again until growth emerges. Place in a sunny spot in your home.
What is hardening off and why do I need to do it?
Once you are ready to plant your sprouted dahlia containers outside, you will need to “harden off” your plants. This means that you start to bring your plants outside for a short amount of time each day, slowly increasing their exposure to the elements over a week. If you don’t do this you are going to shock the plant and it will be hard for it to bounce back, if it can at all.
PLANTING INSTRUCTIONS
Where do I plant dahlias?
Dahlias need to be planted in an area with well-draining soil that gets at least 6 hours of direct sunlight daily.
What kind of soil do I need?
Dahlias need good fertile soil to grow abundantly. I like to add a few inches of compost and organic fertilizer to my beds every year. If you want the best results, send a sample of your soil to a soil testing company so you know exactly what you need.
How far apart should I plant my dahlias?
Dahlia should have 12” of space in between plants.
How deep do I plant my tubers?
Dig a hole 4-6” deep and place the tuber horizontally (on its side) with the eye (swollen growth) facing up. Cover with soil. Don’t water until growth emerges. Growth can take up to a month to emerge from the soil so be patient! Some varieties are fast, some are slow.
CARE & HARVESTING
How much water do dahlias need?
When you see growth emerge from your dahlias you can start to water them. Younger dahlia plants require less water than when they are in their mature state. You want the soil to be moist, not waterlogged.
Once the plant is between 8-12” tall you can water more regularly. It depends on your climate and the weather. Simply put, if it’s hot, you’ll need to water the plants more. If you’re ever unsure of how often to water, you can check the top few cm of soil to see if it’s dry or moist.
When watering, make sure that you’re saturating the base of the plant and into the soil instead of giving the foliage and flowers a bath (which often causes damage to blooms).
Do I need to stake dahlias?
Dahlia tubers need staking when they get to their mature height, otherwise, they could be easily damaged by weather or the heaviness of their blooms. When you are planting your dahlia tubers outside it’s a good idea to place a supporting stake where you dug your hole so that when the plants grow you can tie the branches for support. Of course, you can add these once they become mature, but you run the risk of piercing some of your tubers underground while placing the stake.
What is pinching, and why do I need to do it?
When dahlias reach 8-12” tall, cut the top 3-4” off of the plant above a set of leaves. Although this seems counterintuitive, this will promote multiple branches to grow from where you placed the cut. If you want a lot of strong long stems do not skip this step!
When do I harvest dahlias?
You want to harvest dahlias when they are almost fully open but not all the way. You can check the back of their heads to make sure their petals aren’t damaged or starting to fade. Try to harvest your blooms at the coolest parts of the day when your plants aren’t in direct sunlight.
Remove any foliage from the stem that will be submerged in water.
For a good stem length, you can measure from the tips of your fingers to your elbow. Make sure you cut about a set of leaves on the plant.
Harvest and deadhead dahlias daily to promote growth and prevent the plant from going to seed.
How long will my dahlias last in a vase?
Dahlias will last 3-5 days in a vase if taken care of properly. Use a hydrating solution or flower food to extend their vase life. Recutting stems and changing water daily is recommended.
DIGGING DAHLIAS
Unless you live in a very warm climate (USDA Zone 8 or higher) you need to dig up your dahlias in the fall and store them inside over the winter. If left outside they will freeze and rot.
When do I dig up my tubers?
Wait until 10-14 days after your first killing frost in the fall (one that kills your dahlia foliage and other annuals).
If you live in an area that doesn’t freeze, you can cut your dahlias down to the ground and let them sit for 2 weeks before you dig them. This tricks them into starting to enter their dormant stage.
How do I dig up my tubers?
Cut down the plant’s foliage, and leave about 6 inches of the stalk so you have something to hold on to when you are digging.
Be careful when digging to try and not pierce any of the tubers with your shovel or pitchfork. Dig about 2-3 times bigger than the circumference of the plant, slowly lifting the soil to loosen the tubers.
Gently pull the clump out of the ground and carefully shake off dirt clumps. If you’re planning on storing and dividing later then keep a thin layer of dirt on the tubers.
DIVIDING DAHLIAS
Dividing dahlias is the process of taking your dahlia tuber clumps and cutting (dividing) them into individual tubers.
When do I divide tubers?
First, you need to decide when you want to divide your tubers. If you are working with small quantities then most growers will do this immediately after digging up their tubers. If you are busy in the fall and can’t get to this task then you can store them as clumps over the winter and divide them in the spring. It depends what works best for you!
How do I divide tubers?
When you’re ready to divide you will want to wash your clumps of their excess soil. Try to get the crown of the plant as clean as possible so you’ll be able to see clearly what you are dividing.
Let the clumps dry for 1-2 days before you divide, but don’t let them sit out for longer than that otherwise, they’ll start to shrivel (the dirt helps them keep their moisture).
Take a tuber clump and cut it in half (with pruners) so they’re more manageable. Discard any with broken necks or any other visible damage.
A dahlia tuber should have a body, neck, and at least one eye present. Eyes will be found near the crown of the plant.
Using pruners, cut each tuber off the clump making sure they have a body, neck, and at least one eye present. Not every tuber will have an eye, and that’s ok! Just make sure you discard them since they will not grow any flowers.
STORING DAHLIAS
Where and how do I store them?
Whether you are storing dahlia clumps (and are waiting to divide) or if you just finished dividing and need to now store your dahlias, the process is the same. Dahlias need to be kept in a dark place that is between 40-50 degrees with 85-90% humidity.
As long as you keep the temperature and humidity at those levels it doesn’t matter how you store them. You could put them in cardboard boxes, paper bags, or if you’re storing in a dryer space you might need plastic bins with vermiculite.
Everyone has a different way of storing tubers. Just make sure you’re checking them frequently to see if you need to change your method. If the air is too wet the tubers will start to mold and rot, but if it’s too dry they will start to shrivel. You’ll need to experiment with what works best for your setup!