If you are adding dahlias to your summer garden, make sure to consider planting tips and techniques for best blooming results. Providing the right care from the start makes all the difference in the growth of dahlia plants. Learn how to plant dahlia tubers, for beautiful summer blooms.
Dahlias are stunning flowers which bloom from mid-summer through to the first frost, offering late season beauty when other flowers might wane. In fact they are some of the last flowers to bloom in our garden.
Planting tubers is the best method for growing dahlias because it ensures stronger, healthier plants with more robust blooms. Compared to other growing methods, such as starting from seed or cuttings, tubers are a faster and more reliable way to grow your chosen dahlias.

Understanding Dahlia Tubers
Dahlia tubers are thick, fleshy root structures that store the energy and nutrients that a dahlia plant needs to grow. It’s amazing to see the plants develop from such a small but very important structure.
Each tuber contains the necessary resources to sprout into a full, thriving plant, when conditions are right.
The tubers typically have small “eyes,” similar to those on a potato. These are growth points where new shoots emerge in spring. The eyes are located on the crown of the tubers, and are generally more easily visible in spring.
Any tubers without eyes can be discarded, because they will not grow.
Tuber size does not reflect on the size of the final plant. This is determined by the cultivar or variety of dahlia. Growing conditions of course will also have an impact on size.
Preparing To Plant
Where and how you plant your dahlia tubers will make a big difference in the success of your plants, and can affect on the whole growing season.
If you plant too early, the plants can freeze. Plant too late, and you may not have blooms in time.
Planting too shallow can cause heavy plants to tip over.
As well, I’ve seen vast differences in dahlia plants when grown in very fertile soil, as opposed to those grown in less fertile ground. If the soil is not fertile, plants will not grow as well, and are much more vulnerable to disease and insect infestation.
1. Plant At The Right Time
Dahlia tubers should be planted in the spring, once the soil has warmed to at least 60°F (15°C) and all danger of frost has passed.
Dahlias are frost sensitive. The exact timing depends on your climate.
Check your last frost date with this calculator to determine the best time for your growing zone.
Be careful not to wait too late for planting however, especially in colder climates. One year I planted a full month after the last frost date, and the dahlias had just started to bloom when they were killed off by the first fall frost.
In colder climates, you can get a head start by potting up your tubers a little earlier, and then planting out the plants when the soil warms up, once the risk of frost has passed. Consider starting dahlia tubers indoors in pots 4–6 weeks before the last frost, to give them a head start.
Avoid planting during prolonged wet periods, as excess moisture can also cause tubers to rot before sprouting.
Check that the soil temperature is consistently warm. Cold soil can delay growth or cause tubers to rot.
Plants can also be protected in case of a late spring frost by application of a frost cover.
2. Choose The Right Location
Sunlight Requirements
- Dahlias thrive best in full sun, which means they need at least 6–8 hours of direct sunlight daily. Morning sunlight is especially beneficial, as it helps dry off dew, reducing the risk of fungal diseases.
- In extremely hot locations, some afternoon shade can help prevent the flowers and foliage from scorching.
Soil Preference
- Choose a location with well-drained soil. Dahlias are prone to tuber rot in soggy soil, so good drainage is essential.
- They do best in slightly acidic to neutral soil, with a pH between 6.0 and 7.0
- Fertile soil will make a big difference in the growth of your plants. Dahlia plants prefer nutrient rich soil that supports healthy growth.
3. Prepare The Soil
- Incorporate compost or well-rotted manure before planting, to boost fertility. We have clay soil, and amend with a thick layer of compost every season.
- A mix of sand, silt, and clay creates an ideal loamy texture that retains moisture while also allowing excess water to drain.
Step By Step Planting Guide
1. Prep The Tubers
- In spring you can begin to prep your tubers for planting.
- Many gardeners divide their tubers in fall, although some will do this task in spring. In spring the eyes are generally more visible, and will appear as small bumps or nodes, where new shoots will emerge.
- You can also leave the tubers in a clump if this is manageable. I prefer however to divide the clumps if possible, to remove any rot or damage, and to get a good visual on what I am working with.
- If you do divide in spring, allow at least 24 to 48 hours for the wounds to heal over from cutting, and callous, before planting.
- For tubers that have been stored and wrapped in plastic wrap, you will need to remove the wrapping, which can be somewhat time consuming. It’s easier to remove by cutting the plastic with sharp scissors, which will save a lot of time.
- Check for damage as you remove the tubers from storage. Look for signs of rot, mold, or shrivelled areas, and discard.
- Remove any damaged sections with a clean, sharp knife or pruners.
- I find that the eyes tend to grow and sprout in spring, if exposed to any light and warmth.
- If this happens, don’t panic. Keep the tubers in a darkened space if possible, and they can remain there until you are ready to plant them, even if they have sprouted.
- Harden off any potted dahlia plants that have been planted up early, before transplanting out.
2. Planting Depth And Spacing
By planting at the correct depth and with proper spacing, you ensure your dahlias have enough room to grow, and produce stunning summer blooms.
Tubers can be planted in a number of different ways. They can be planted into containers, into the garden setting, or set out in rows if you are planting many.
Some gardeners will use landscape fabric to cut down on weeds, however it can be difficult to dig holes through the fabric for planting the tubers, unless you burn larger sized holes. Also, it can be difficult to lift the tubers at the end of the season, with the fabric in place.
I have used fabric for planting dahlia seedlings, however not for planting tubers.
We plant dahlia tubers into uncovered soil.
- Start by digging holes approximately 4 to 6 inches deep. Add some bonemeal and compost to the holes prior to planting.
- Space tubers 12–18 inches (30–45 cm) apart for compact varieties, and 18–24 inches (45–60 cm) apart for larger varieties, to give them room to spread.
- If growing in rows you may choose to plant the dahlias closer together than recommended, such as 12 inches apart. This can help to contain the plants, as they tend to provide support to each other on either side.
3. Position The Tubers
- Place dahlia tubers horizontally 4–6 inches (10–15 cm) deep in the soil. Planting deeply allows the soil covering the tuber to hold the plant down, and helps to prevent tipping as the plant grows.
- Set the tubers into the hole with the eyes or sprouts facing up. Don’t worry however if they get planted upside down, the sprouts will find their way!
- Gently cover the tubers with soil, being careful not to break the sprout if it has already started growing. You can cover the sprouting tip, it will eventually make it through the soil.
- If any sprouts break off during the planting process, it’s okay. They will likely regrow when planted.
4. Label Your Dahlias
- Make sure to place a stake in the ground to accurately label the dahlias that you have just planted. A wooden stake with a waterproof marker or paint works well.
- Identification is key, especially if you are going to lift and divide the tubers at the end of the season.
Caring For The Dahlias After Planting
Moisture Requirements
- Water in after planting, then do not water again until the sprouts are above soil level, unless the soil is extremely dry. Overwatering at this stage can cause the tubers to rot before they sprout.
- Begin watering once sprouts appear above the soil, typically 1–2 weeks after planting.
- Water deeply 1–2 times per week, depending on your climate and soil conditions. This encourages deep root growth which can support the plant.
- Using a drip line is very helpful, as it prevents water on the foliage and flowers, reducing the risk for mildew development.
- If possible, water in the morning to allow foliage to dry before nightfall, reducing the risk of fungal diseases.
Staking Your Plants
- Staking is an important step for growing healthy dahlia plants, and ensuring their stunning and often heavy blooms are well supported throughout the growing season.
- This support anchors the plant, and helps to prevent tipping as they get top heavy. Without any support, the stems may struggle to remain upright, especially in windy or rainy conditions.
- For taller varieties, place a stake or support structure in the soil at planting time to avoid disturbing the tuber later. Make sure that the stake is tall enough to support the full-grown height of the dahlia.
- Secure the plant to the stake as it grows.
- Alternatively, rows of plants can also be corralled, by placing stakes along the outer edges of the rows and running twine between the stakes.
- Corralling can be quite effective, although will not always prevent the plants from tipping in a strong wind. It will however catch the plants from falling completely over.
Mulching And Weed Control
- Once the plants sprout, add a layer of mulch to retain moisture, reduce evaporation, and minimize weed growth.
Pinching
- Pinching is a technique that can be used on dahlias to encourage branching out, leading to more flowering stems.
- If you choose to pinch, do so when the central stem of your dahlia plant is about 12 inches tall. Cut off the top 1 to 2 inches of the stem, to promote more growth.
Fertilizing
- Dahlias grow well with an application of fertilizer once a month, throughout the growing season. This includes dahlias grown in pots, as well as those growing in the ground.
- Look for formulas with lower first numbers in the N-P-K ratio (e.g., 5-10-10 or 10-20-20). These encourage root and flower production.
- Higher nitrogen amounts will produce more foliage growth, and less flowering.
- Bone meal, compost tea, or fish emulsion can be excellent choices for a natural approach.
Deadheading
- Deadheading and pruning are important techniques for keeping your dahlias blooming abundantly throughout the growing season.
- Removing spent dahlia blooms is easy, and will promote more flowering. This practice will also help to tidy up the plant’s appearance.
- To deadhead, look for flowers that are wilting, browning, or losing their petals. You can also check on the back of the blooms for telltale signs that the flower is past it’s prime.
- Using sharp, clean pruning shears or scissors, cut the stem back to a set of healthy leaves or the next branching point. This encourages the plant to focus on developing new flower buds at these nodes.
- Check your dahlias for spent flowers every few days, especially during peak blooming season. Removing those faded blooms promptly helps maximize the plant’s flowering potential.
Frequently Asked Questions
Do I need to soak dahlia tubers before planting?
You don’t need to soak dahlia tubers, and it is not advised to do so due to the risk for rot.
Can I grow dahlias in pots?
Absolutely, dahlias can thrive in pots as long as the container is large enough (at least 12–16 inches deep) and has good drainage. A heavy pot is recommended, to prevent tipping as the dahlia gets top heavy with growth.
Do dahlias come back every year?
In frost-free climates, dahlias are perennials and will return each year. In colder climates, you’ll need to dig up and store the tubers over winter to replant in spring.
Enjoying Your Dahlias!
Dahlias are prized for their presence as a garden flower, as well as for their use as cut flowers, due to their wide range of colors, shapes, and sizes.
As a cut flower, they are not typically long lasting, with a vase life of approximately 5 days. However their beauty packs a punch, and the flowers are exquisite for event work.
Whether enjoyed in the garden or as part of a stunning bouquet, dahlias are versatile flowers that can bring joy in many forms.
Make sure to plant the tubers at the right time, and give plenty of time for growth. With proper planting, care and attention, dahlias will reward you with a spectacular display that lasts until the first frost.
Have you ever planted dahlia tubers in spring, for beautiful summer blooms? Be sure to leave a comment below to share your experience!
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