Care of Dahlia From Seed (Complete Guide)

Care of Dahlia From Seed (Complete Guide)


Dahlias are one of the most popular and versatile flowers to grow in your garden. They come in a wide range of colors and they bloom from summer to fall.

Growing dahlias from seeds is a rewarding and cheap way to add more beauty and variety to your landscape.

In this article, we will show you how to care for dahlia seeds from sowing to harvesting. We will also share some tips and tricks to help you get the best results from your dahlia seeds. Whether you are a beginner or an expert gardener, you will find this guide useful and informative.

How Many Varieties of Dahlias Are There?

There are over 70,000 named varieties and 42 species of Dahlias as a result of centuries of cultivation.

Dahlias flowers can range from less than 50mm to giant dahlias with a diameter of over 250mm.

Some of the flower types include:

  1. Decorative
  2. Pompon
  3. Ball
  4. Cactus
  5. Semi-cactus
  6. Anemone
  7. Collarette
  8. Mignon
  9. Single
  10. Peony
  11. Orchid
  12. Waterlily.

Each flower type has its own characteristics and charm.

Some examples of dahlia varieties are:

  • A La Mode, which has orange flowers with white tips
  • Kelvin Floodlight, which has huge yellow blooms
  • Magenta Star, which has dark purple petals with white tips
  • Arabian Nights, which has red cactus flowers.

Where to Buy Dahlia Seeds?

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Dahlia Bulbs – Antique Blush Mix – 5 Bulbs…

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Dahlia Bulbs (Decorative) – Brown Sugar – …

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Dahlia Bulbs (Dinnerplate) – Mystery Day -…

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Dahlia Seed Planting (Germination Instructions)

Step 1: Sow your seeds

The best time to sow your dahlia seeds is between February and April.

The ideal temperature for germination is between 15°C and 20°C (60°F and 68°F). You may need to sow them indoors or in a greenhouse if the temperature outside is too cold.

You can use seed trays or small pots filled with moist potting mix or seed starting mix. Sow the seeds about 0.5 cm (1/4 inch) deep and 2.5 cm (1 inch) apart, and cover them with soil. Water them well and place them in a warm spot with bright light, such as a windowsill or under grow lights. Keep the soil moist but not soggy.

Things You May Need

Step 2: Transplant your seedlings

Transplant your seedlings into individual pots when you see their first true leaves. This will give them more room to grow and prevent overcrowding.

Lift the seedlings out of the soil by holding them by their leaves, not their stems. Tease apart their roots if they look tangled.

Fill small pots with fresh potting mix and make a hole in the center for each seedling. Place the seedling in the hole and firm the soil around it. Water well and label your pots with the name and date of transplanting.

Step 3: Harden off your plants

Before planting your dahlias outside, they need to first harden to outdoor conditions. This prevents shocks by sudden changes in temperature, light, or wind.

Start hardening about two weeks before your last frost date in spring.

Place your pots outside in a sheltered spot for a few hours each day. Increase the exposure time until they can stay outside all day and night.

Avoid exposing them to direct sun, strong wind, or frost during this process.

Step 4: Plant Your Dahlias Outside

Once your dahlias have hardened, you can plant them outside in their final location.

Choose a spot that gets at least six hours of sun per day, has well-drained soil, and is not exposed to strong winds. Space your dahlias about 30 inches apart.

Soil Requirements for Dahlia

The ideal soil for dahlias is well-drained, fertile, and acidic.

Dahlias do not like soggy or waterlogged soil, as this can cause root rot and fungal diseases. Avoid planting dahlias in clay or compacted soil that retains too much moisture.

Instead, choose sandy or loamy soil that allows excess water to drain away.

Add organic matter such as compost, manure, or peat moss before planting. This helps to improve the fertility and structure of the soil.

The optimal pH range for dahlias is between 6.0 and 6.5, which is acidic.

You can use lime to raise the pH or sulfur to lower it.

You should apply a 2-3 inch layer of mulch around your dahlias after planting and replenish it as needed.

What is Mulch?

Mulch is a layer of organic material that covers the soil surface around the plants. It can be things like straw, bark, or leaves.

Mulch will help conserve moisture, suppress weeds, regulate temperature, and prevent erosion.

Things You May Need

Where to plant dahlia

Dahlia loves the sun and needs at least six hours of direct sunlight per day to produce abundant blooms. Yet, too much sun can also cause problems, such as scorching the petals or wilting the stems.

It is best to plant dahlia in a location that gets morning sun and afternoon shade. If not, choose a spot that gets filtered sunlight throughout the day.

Avoid planting dahlia in areas that have strong winds or frost.

If you live in a hot climate, you may need to provide some extra shade for your dahlia during the peak hours of summer.

You can use a shade cloth, an umbrella, or a nearby tree to protect your plants from the harsh sun.

Things You May Need

When to Plant Dahlia Tubers for Beautiful Blooms

Dahlias are native to Central America and need warm soil and sunny conditions to thrive. They are not frost-hardy and will die if exposed to freezing temperatures.

You should plant dahlia tubers when the soil temperature reaches at least 60°F (15°C).

How Far Apart to Plant Dahlias

Generally, the larger the dahlia, the more space it needs to thrive. A good rule of thumb is to plant dahlias at least half their mature height apart from each other.

For example, if you have a dahlia that grows 1 m tall, you should plant it at least 50 cm away from its neighbors.

How Often Do Dahlias Need to Be Watered

Dahlias need regular watering, especially during hot and dry weather.

A general rule of thumb is to water dahlias once or twice a week, giving them about an inch of water each time. You can use a rain gauge or a finger test to check if the soil is moist enough. The soil should feel damp but not soggy at a depth of two inches.

How often do dahlias bloom

Some varieties of dahlia will only bloom once a year, while others may bloom several times.

In general, dahlias will rebloom every 4-6 weeks during the summer months. The blooming period can range from 3 months in cold climates to 5 months in hot climates.

Pinching & Staking Dahlias for Bushier Blooms

Pinching and staking your dahlias will make them more compact and bushy.

Pinching is the process of removing the main stem tip of the dahlia plant when it reaches about 12 inches tall.

This encourages the plant to bear more flowers by producing more lateral branches.

Staking is the process of using a stake or a cage to support the plant. This helps to prevent it from flopping over due to its heavy blooms.

Staking also helps to keep the plant upright and exposes it to more sunlight.

Best fertilisers for dahlias

Fertilizer is another important factor for dahlia growth and flowering.

Dahlias are heavy feeders. They need regular doses of nutrients to produce large and colorful blooms.

Use a balanced fertilizer that contains equal amounts of (N-P-K):

  1. Nitrogen
  2. Phosphorus
  3. Potassium

Apply fertilizer every 2-4 weeks during the growing season.

Over-fertilizing or using high-nitrogen fertilizers is bad. They can cause excessive foliage growth at the expense of flowers.

Dahlia Care Over Winter

Dahlias cannot withstand freezing temperatures especially if the soil is wet.

If you leave your dahlias in the ground over winter, they may rot or become food for rodents or insects.

What is Overwintering?

When the weather gets cold and snowy, some flowers die. They cannot survive the winter. That is sad.

But some flowers are very smart. They have a special way to stay alive in the winter. They go to sleep under the ground.

They hide their roots and stems and leaves in a ball of dirt. They do not need sun or water or warm air when they sleep. They wait for spring to come. Then they wake up and grow and bloom again. This process is overwintering.

Dahlias can overwinter in places where the winter is not too cold. But if the winter is very cold, they need some help from us.

We can help dahlias overwinter by digging them up from the ground before the frost comes.

Even in a mild climate, it is safer to lift and store your dahlias indoors. This helps to protect them from frost damage and disease.

How to Overwinter Dahlias in Pots

If you have grown your dahlias in pots, overwintering them is easy. Here are the steps you need to follow:

  • Cut back the entire plant to 4 – 6 inches above the soil level after the first frost has blackened the foliage.
  • Keep the dahlias in their pots over winter. Do not water them or fertilize them during this time.
  • Store the pots in a cool, dry, dark place that does not freeze, such as a basement, garage, or shed.
  • Check on your dahlias and remove any rotten or shriveled tubers.

How to Overwinter Dahlias in the Ground

If you have grown your dahlias in the ground, overwintering them requires a bit more work. Here are the steps you need to follow:

  • Wait until a frost has blackened the foliage, then cut back the plant to 4 – 6 inches above the ground.
  • Dig up the tubers with a garden fork, avoiding damaging them with the spikes. Shake off as much soil as you can.
  • Rinse the tubers to remove any remaining soil. Stand them upside down to drain and dry them for a couple of days.
  • Pack your tubers in a box or a container filled with dry compost, peat moss, sawdust, or vermiculite. Make sure they are not touching each other and have been completely covered.
  • Store the box or container in a cool, dry, dark place that does not freeze, such as a basement, garage, or shed.
  • Check on your tubers and remove any rotten or shriveled ones.

How to Prepare Your Dahlias for Replanting

In spring, when all risk of frost has passed, you can replant your dahlias outdoors. Here are some tips on how to prepare them for planting:

  • If you have kept your dahlias in pots, bring them into a warm and bright place about a month before planting. Water them every week until you see some growth.
  • If you have stored your dahlias in boxes or containers, inspect them for signs of sprouting. If they have sprouted, pot them in fresh compost and place them in a warm and bright place. Water them every week until they establish. Do this a month before planting.
  • If your tubers have not sprouted yet, soak them overnight in water. You can then either pot them up as above or plant them in the ground.

Choose a sunny and sheltered spot for your dahlias. Enrich the soil with organic matter such as compost or well-rotted manure. Plant your tubers about 4 – 6 inches deep and 18 – 24 inches apart, depending on their size.

Water well after planting and mulch them to conserve moisture and suppress weeds.

Stake your dahlias as they grow taller and use a loose knot to tie them to support their stems. Pinch out the growing tips when they reach about 12 inches high. This helps to encourage bushier growth and more flowers.

Use a balanced liquid fertilizer every two weeks during the flowering season. Deadhead them every three weeks to prolong their blooming period.

Common Problems When Overwintering

1. Rotting

This can happen when tubers are in a damp place with poor ventilation. To prevent rotting, you should dig up your dahlias after the first frost and cut off the stems and foliage. Wash off any soil and let them dry for a few days in a cool and airy place. Pack them in boxes or crates filled with dry peat moss, sawdust, or vermiculite. Store them in a dark and cool place with a temperature between 4°C and 10°C.

2. Sprouting

Another common problem when overwintering dahlias is sprouting. This happens if the tubers receive light or warmth during storage. To prevent this, keep your dahlias in a dark place and avoid temperature fluctuations.

You should wait until the last frost has passed before planting them out in the garden. If your dahlias have sprouted during storage, you can still plant them out. Be careful not to break off the shoots when doing this.

3. Shrivelling

A third common problem when overwintering dahlias is shriveling. This can happen if the tubers lose too much moisture during storage, or if they are growing in a dry or windy spot. To prevent this, make sure your dahlias are well-hydrated before digging them up.

Common Reasons Why Your Dahlia is Not Flowering

1. Not Enough Sunlight

Dahlias need at least six hours of full sun per day to produce abundant and vibrant blooms. If your dahlias are in a shady spot, or under a tree, they may not get enough sun to flower well.

2. Improper Watering

Dahlias need regular and deep watering, especially during hot and dry weather. If your dahlias are too dry, they may not bloom at all, or produce small and weak flowers. But if your dahlias are too wet, they may rot or get fungal diseases that affect their flowering.

Check the soil moisture around your dahlias and only water them when the top inch of the soil feels dry. You can also mulch your dahlias to conserve moisture and prevent weeds.

3. Wrong Timing

Dahlias are tender tubers that cannot tolerate frost or cold temperatures.

If you plant your dahlias too early in spring, they may not sprout or get damaged by frost.

If you plant your dahlias too late in summer, they may not have enough time to grow before the first frost in fall.

The best time to plant your dahlias is after the last frost date in your area when the soil temperature is above 60°F.

4. Not Pruning Them Enough

Pruning your dahlias helps to encourage branching and more blooms. If you do not prune your dahlias, they may grow tall and spindly, with fewer and smaller flowers.

You should prune your dahlias when they are about 12 inches tall, by pinching off the top 3 to 4 inches of growth. You can also prune your dahlias throughout the season. Do it by removing dead or faded flowers (deadheading), as well as any weak or diseased stems.

5. Over Fertilizing

A fifth common reason is giving them too much nitrogen fertilizer. Too much nitrogen can cause excessive leafy growth at the expense of flowers. Dahlias need a balanced fertilizer that contains phosphorus and potassium.

Common Pests & Diseases for Dahlias


Some of the most common pests that attack dahlias are:

  • Aphids
  • Spider mites
  • Thrips
  • Slugs
  • Snails.

These pests can damage the plant by sucking its sap or chewing its tissues. They can also spread viruses and other diseases that can weaken the plant.

To prevent pest infestations, keep your dahlias healthy and well-watered. Inspect your plants every two weeks and remove any pests by hand or with a blast of water.

In severe cases, you can use organic or chemical insecticides to control the pests. Be careful not to harm beneficial insects such as bees and ladybugs. These insects can help to pollinate your flowers.


Some of the most common diseases that affect dahlias are:

  • Powdery mildew
  • Botrytis blight
  • Bacterial wilt
  • Mosaic virus.

These diseases can cause various symptoms such as:

  • White or gray patches on the leaves
  • Brown spots on the petals
  • Wilting or yellowing of the stems and leaves
  • Distorted or mottled flowers.

To prevent disease outbreaks, practice good hygiene and sanitation in your garden:

  • Removing any dead or diseased plant material from your garden
  • Avoid overhead watering that can splash water on the leaves and flowers
  • Spacing your plants wide enough to allow good air circulation.
  • Using disease-resistant varieties of dahlias
  • Rotate your crops every year to avoid soil-borne diseases.


Are dahlia plants deer resistant?

Generally, dahlias are not very attractive to deer, as they have a bitter taste and a strong scent. Yet, this does not mean that deer will never eat them, especially if they are hungry or curious.

If you want to protect your dahlias from deer damage, you may need to take some preventive measures. Consider planting deer-resistant companion plants, building a fence, or using repellents.

How many dahlia seeds per pot?

Two to three dahlia seeds per pot to ensure ample space for growth.

Do dahlias self-seed?

Dahlias do not self-seed easily.


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