Dahlia Growing Stages: Everything You Need to Know

Dahlia flowers are bright and abundant.

Of course, you must take good care of the plant if you want them to grow healthy and provide you with beautiful blooms. 

The Dahlia is a perennial plant, which means that it begins to form flowers at the end of its first year and will be more abundant in the following years.

Like any other plant, growing Dahlias will undergo the stages of germination, seedling stage, vegetative growth, flowering state, etc. This article will describe how to grow dahlias from seed up until they are harvested.

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Stage 1: Planting and Germination

Dahlia growing stage


The first stage of growth for a dahlia flowers begins when seeds have been planted in a warm environment (around 70º Fahrenheit). 

This entails the germination process, which involves developing an embryonic root system within the seed’s shell and can take anywhere from 10 – 21 days.  

During this period, water and nutrients should be regularly supplied, and access to sunlight should be limited to shock the plant into producing a strong taproot. 

If grown under normal conditions, the young plant may produce leaves that grow out, but no true root system will develop. These floppy dahlia Flowers seedlings should only be considered a last resort, as they are unlikely to survive transplanting.

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Stage 2: Vegetative growth

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The next stage of dahlia flowers growth occurs during the vegetative phase before flowers or buds appear. 

During this stage, the plant takes on its distinctive vertical form and builds up an extensive root system; it is also when leaves start to grow and mature.

This period can last anywhere from 3 – 8 weeks, depending on environmental factors (such as temperature) and genetic factors (such as variety). 

However, for optimal flowering, many growers will opt to limit the vegetative phase by preventing their plants from growing beyond 10″ tall; at 12″ tall, most varieties will begin to flower.

Normal dahlias will grow 1-2″ per week during the vegetative phase, but some flowering varieties will double this rate.

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Stage 3: Reproductive stage

The third stage of dahlia growth is the reproductive stage, just before the plant begins to produce its flowers. During this period, the plant switches its energy source from producing leaves to developing buds and blooms. 

It should be noted that pale green petals are not considered flowers since they do not contain pollen or pistils (male reproductive organs) required for reproduction. 

Unfortunately, environmental factors can take their toll on your plants; if temperatures become too cold, fading petals may occur throughout the plant; if temperatures become too hot, the plant may experience bud drop.

Stage 4: Harvest

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Once your dahlias have finished flowering, the aforementioned stage slowly transitions into harvest – which takes place after all of the petals have fallen off. At this point, both roots and leaves can be used for their respective purposes.”

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Tips for Growing Better Dahlias

1). Planting Method  

Sow seeds in spring in pots or trays of seed compost. Keep the temperature around 72°F (22°C). Cover with a plastic sheet to retain moisture and humidity. Water the surface daily, but not allow it to become waterlogged. 

Tubers can be planted one inch apart with a six-inch spacing between rows after raking the soil smooth of all weeds and pebbles.  

The tubers should not be covered or surrounded by the soil until shoots appear because this causes rot and decay problems for your plants before they have a chance to survive on their root systems.

Seeds should germinate after 8 – 10 days. If no germination occurs after 15 days, discard the seed tray/pots and start with fresh compost in new pots or trays. 

When seedlings are large enough to handle, pot them up individually in 9cm (3in) pots using a good quality multi-purpose compost. Harden off and plant out in the garden after all chance of frost has passed.

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2). Transplanting Method  

The best time to transplant Dahlia tubers is in spring, just as new growth appears. Dig a hole that will accommodate the tuber, retaining at least 1in (2.5cm) from the top of the tuber to the soil surface. 

Place each tuber with its ‘eye’ facing upwards, cover with loose soil and tread down gently. Water well and ensure plants receive adequate moisture during dry spells to allow tubers to swell fully before winter sets in. 

Tubers should be left undisturbed while they develop roots and shoots; your dahlias may require staking to support wind and rain if planted late in the growing season.

3). Spacing  

Plant tubers about 6in (15cm) apart, in rows 18in (45cm) apart. Grow single or double flowers, depending on the variety you choose to grow, but if you want to create a spectacular show of brightly-colored blooms, grow them in multiples of one color per clump.

4). Height control  

Dahlias are long-flowering plants; however, shortness is also an essential trait for garden use. 

It enables flowers and leaves to be packed together without causing interference with each other when the flower stem elongates during blossom development. This trait can be improved by removing all side shoots below 6″ high (15 cm) after planting. 

Remove weak flower stems that appear at the base of the plant after flowering, allowing only one strong stem to remain.

5). Hardiness  

Hardy in most parts of Ireland when planted out in spring. However, protect against late frosts until the plants are established. 

Dahlias are fully hardy and can be left in situ during winter if well mulched or taken up tubers by early autumn and stored overwinter in a frost-free place. Cutting back spent blooms encourages reblooming for later seasons. 

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When shoots emerge        

As the dahlia shoots emerge, they should be thinned to six inches apart.  Most gardeners choose to remove extra plants to help ensure that the remaining plants have plenty of room for further growth later in the season.        

During summer    

As new stems and blooms appear on your plants, it is important to deadhead spent flowers immediately after they fade so that energy can produce more buds and flowers instead of seed pods that will sap strength from your plants as autumn approaches.     


The most common pest problem associated with a dahlia is damage caused by slugs and snails during the early summer months when their leaves are tender and young enough to be eaten by these creatures.  

In addition, slugs have been known to eat holes through flower buds, leaving them open for diseases to enter.  

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Before you start growing dahlias, there are a few essential facts you should know

1). Dahlias need full sun – at least six hours of direct sunlight per day. If they do not receive enough light, their blooms will be smaller and paler than they otherwise would have been.

 2). Dahlias require fertile, well-drained soil – They prefer moist but not wet soil. 

3). The plants can grow very large – so think carefully before deciding where you want them to grow in your garden. 

4). It is best to plant dahlias when they are dormant – usually November through March, depending on the region of the country. This will help ensure that they grow strong and healthy before winter sets in, so they can withstand cold temperatures. 

5). Mulching – Dahlias should be mulched with a three-inch-thick layer of bark or pine needles to protect against frost. 

6). Avoid planting them next to each other – Dahlias can get very tall, so if you’re planting more than one variety, it’s best to avoid planting them next to each other unless you want them all to tower above your head.

7). Deadhead – Once dahlias begin blooming, deadhead the spent flowers regularly (just pinch off the stem right at the base where it meets the plant). If you do not remove old flowers regularly, they will take energy away from the plant and produce as many blooms. 

8). Dahlias are very hardy –  If you live in an area that experiences extreme heat or cold, they may benefit from being planted in a sheltered area.

9). It’s easiest to start new dahlia plants by planting tubers – If you’re looking for flowers sooner than four months, it’s easier to start them by growing from seed.

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How to Plant Dahlias?

When planting dahlia tubers, it is best to put two or three tubers together for each group of plants, as long as one tuber is twice as big as the others, so they will grow at different rates. 

When planting dahlia seeds, place one seed per pot and plant them about half an inch deep. They can be planted outside in your garden when the soil is at least 60 degrees Fahrenheit.

When planting a dahlia, use a fertilizer that is high in phosphorus to promote blooming. 

When buying tubers or seeds, look for varieties bred specifically for blooming in summer instead of spring. These will have longer growing seasons with more opportunities to produce flowers before frost sets in.

How Long Does it Take Until Dahlias Bloom?

The dahlias should start flowering between 80 and 120 days after planting if you’re growing from seed. If you’re growing from tubers, they may take up to six months to flower unless you’ve purchased a variety bred to flower in less time.

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How Long Do Dahlias Live?

Most dahlias live between 3 and 5 years. New varieties are developed every year to produce more flowers quickly, but they will still need to be replaced after three or four years.

Common NameDahlia
Life CycleHalf-hardy perennial is usually grown as a hardy annual by gardeners.
Height12 to 60 inches (30 to 180 cm)
NativeSouth and Central America
Growing RegionZones 3 to 10. As a perennial in zones 9 and 10


It’s best not to fertilize newly planted tubers until growth begins; usually, two weeks before the first shoots appear above ground.

It’s also important to keep the soil moist by watering it regularly (about once a week) during times of drought or extreme heat.

Don’t worry if the dias begin turning yellow; this is a natural part of the blooming process. However, if you want to give them a boost, try spraying them with a fertilizer designed for flowering plants.

Dahlias can become very large plants, so that they will need plenty of room in your garden. They also need regular pruning to keep their appearance tidy and encourage more blooms.

Propagating new dahlia plants from cuttings is easy to replace tired-looking flowers with many healthy new ones.

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