Dahlias: The Number 1 Care, Propagation, and Watering Guide For Your Garden Flowers

Garden flowers that give colorful and mesmerizing blooms are one of the priceless gems every plant lover goes for. Pop of colors would add nothing but beauty and grace to any living space you have. Plus, they give a hint of freshness and would definitely uplift your well-being, making your day brighter and livelier. In this dahlias growing guide, you will learn the best methods on how to grow these beautiful plants.

dahlias growing guide

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A perfect addition to make your green garden colorful are the ever-famous Dahlia flowers. With their vast range of colors, sizes, patterns, and forms of flowers, surely they will bring new life to your space.

 This is especially for you if you want the addition of bright, vibrant colors to your green garden. If you are interested, learn more about this gorgeous plant’s care and propagation by reading this article.

Dahlias Profile

Colorful dahlias

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General Information

Dahlia flowers may sound familiar to you because it’s probably in the family of the flowers you already own. It is a member of the family Asteraceae, just like your daisies, sunflowers and chrysanthemums. They usually grow up to 3-4 feet tall and are grown as herbaceous perennials. However, if you are located in a colder climate, you can consider growing the Dahlia plants as annuals.

They are known to be native to tropical America (Central and South), mainly Mexico in South America, typically at places with higher elevations. They are also known to be traditionally used as medicine by indigenous peoples, specifically by the Aztecs. No surprise, it became Mexico’s national flower as early as 1963.

There are a lot of reasons why you should consider planting Dahlias. These stunning plants have a wide range of varieties that will fit any of your preferences. They can thrive in most zones and have blossoms that can last for months. Plus, they are frequently visited by hummingbirds and butterflies!

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Dahlia Varieties

dahlias growing guide

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The Royal Horticultural Society (RHS) has grouped different varieties of Dahlias into 14 distinct groups, namely:

  1. Group 1 – (Sin) – Single-flowered Dahlias 
  2. Group 2 – (Anem) – Anemone-flowered Dahlias
  3. Group 3 – (Col) – Collerette Dahlias
  4. Group 4 – (WL) – Waterlily Dahlias
  5. Group 5 – (D) – Decorative Dahlias
  6. Group 6 – (Ba) – Ball Dahlias
  7. Group 7 – (Pom) – Pompon Dahlias
  8. Group 8 – ( C) – Cactus-flowered Dahlias
  9. Group 9 – (S-c) – Semi-Cactus Dahlias
  10. Group 10 – (Misc) – Miscellaneous Dahlias
  11. Group 11 – (Fim) – Fimbriated Dahlias
  12. Group 12 – (SinO) – Single Orchid (Star) Dahlias
  13. Group 13 – (DblO) – Double Orchid Dahlias
  14. Group 14 – (P) – Peony-flowered Dahlias

On the other hand, the New Zealand Society has its own Dahlia groupings, based solely on the diameter of the flowers. Specifically, the groups are:

  1. Giant-flowered cultivars: over 250 mm.
  2. Large-flowered cultivars: 200-250 mm.
  3. Medium-flowered cultivars: 155-350 mm.
  4. Small-flowered cultivars: 115-155 mm.
  5. Miniature-flowered cultivars: 50 – 115 mm.
  6. Pompom-flowered cultivars: less than 50 mm.

The American Dahlia Society, on the contrary, grouped Dahlias according to purpose: (1) garden type, (2) exhibition dahlias, and (3) container or border dahlia plant.

As of the present, there are a total of over 57,000 cultivars registered in RHS. Here are some Dahlia varieties that you may consider planting in your garden:

  1. Dahlia “Pianella” – A pink-colored variety that is also known as “cactus Dahlia”. This variety has double-flowered blooms and petals that are long and rolled, resembling spines.
  2. Dahlia “Kelvin Floodlight” – A yellow-colored variety that has flat and broad petals that have tips that are slightly rolled
  3. Dahlia “Magenta Star” – A magenta-colored variety with only one row of overlapped petals.
  4. Dahlia “Moor Place” – A variety that has tiny, double-flowered blossoms. The petals of this variety are round, resembling a pompom, thus the common name “pompon dahlias.”
  5. Black Satin Dahlias – A variety with deep red wine flowers. The name “Black Satin” refers to the luminous sheen of the flower petals.

Etymology

The name Dahlia is actually modern Latin that came from the name Andreas Dahl. Anders Dahl was a Swedish botanist in the mid-1700s, and this flower was named in honor of him.

Flowering

The bloom time for dahlias usually takes around 120 days. Usually, they start blooming in mid-July if the environment is favorable, and you can expect to enjoy them fully through mid-November. In some locations, the blooms can last longer than four months.

They usually bloom during summer and fall.

Season of Interest and Purchasing

You might want to start purchasing and planting them in the late spring when the last frost has come and gone. They usually bloom around eight weeks after you plant them. Usually, you can already see their petals opening in your garden by mid-July.

Growth

Dahlias grow in the Americas, mainly in Central America. But due to its popular demand, it has reached many places in the world like Australia, Europe, Asia, and Africa. Ensure they get sun and are protected every winter to ensure their full growth potential.

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Dahlias Overview

Scientific nameDahlia spp.
Common name/sDahlia, Garden Dahlia
FamilyAsteraceae
Growth HabitHerbaceous 
Height and SpreadOne to six feet tall, and one to three feet wide
Classification based on life cyclePerennial
Origin and DistributionCentral and South America
Climate ZoneGenerally mild to warmer climate
USDA Plant Hardiness ZoneUSDA Zone 8-10
ColorGreen foliage with a wide variety of flower colors (red, orange, yellow, pink, white, purple)

Care Tips

Light Requirement

These stunners love sunlight. Ideally, they should be given 6-8 hours of full sunlight every day. The more sun they get, the more blossoms they’ll be able to give. 

Temperature Requirement

Dahlias thrive best in moist, moderately warm climates. Even though they are not suited for extremely hot environmental conditions such as in Florida, they lighten up any sunlit garden during the growing season. They grow at ideal temperatures of 38 to 45 degrees Fahrenheit. 

Dahlias are actually tubers, and they are winter hardy, especially in hardiness zones 8-11. But, plant lovers in zones 6 and 7 may also have luck in keeping them underneath the ground. Just make sure that they are not in close contact with fans, ACs, and winds, as they are sensitive to strong winds and drifts.

Water Requirement

These stunners require regular watering and moist soil. However, you do not want the soil to get soggy. Make sure the soil is draining adequately and that you are not watering too often or too much. Overwatering can cause root rot and loosening of the tubers.

Humidity Requirement

Since this plant prefers high moisture environments. Ideally, they should be stored in 75-85% relative humidity environments. If the humidity is too low, your dahlias might get dehydrated, causing them to shrivel. On the other hand, too much humidity can get their tubers rotting or moldy.

Soil Requirement

Dahlias need moist, well-draining soil, pH 6.5-7.0, and at least 60 degrees Fahrenheit. The soil should also be rich, as they do not do well in poor soil. Do not plant them in dense soils such as clay, as it can get muddy and stuck. Try mixing in the sand, manure, or peat moss for a homemade mix.

Fertilizer Requirement

Fertilizing Dahlias is not optional. Aside from the fertile soil, they require additional nourishment. When choosing a fertilizer, choose one that is low in nitrogen. The best time to fertilize them is a month after you plant them and the subsequent month after that. Roughly half a cup should be adequate for them to be healthy. 

Space Requirement

The space requirement depends on the type of Dahlia you are growing. For the bedding varieties, nine to twelve inches would be sufficient. They should be at least one to three feet apart for ideal growing conditions and avoid hedges’ formation. The critical tip is that the larger the plant, the more space it will need.

Growing and Planting Tips

Growing dahlias

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Propagation

Dahlias can be planted directly as tubers or started indoors in pots from seeds.

 For direct planting:

  1. Prepare the soil with the minimum requirements. Dig down at least 6-8 inches to accommodate the root ball. 
  2. Put the dahlia tuber into a hole.
  3. Make sure the sprout will emerge from the conditions. The eyes should face upward while the tail with roots should be pointing downwards.
  4. Cover the Dahlia tuber partially with soil. Anywhere from 1-4 inches will do.
  5. Keep an eye on your tuber. When it sprouts, fill the rest of the hole with soil.
  6. Only water your tuber after it sprouts. 

Starting from seeds indoors:

  1. Put Dahlia seeds in a seed pot/tray and make sure it is damp.
  2. Create holes for the plant seeds, approximately an inch between each hole and half an each deep.
  3. Insert seed into each of the hole.
  4. Add seedling mix until the seeds are covered fully.
  5. Place the seed pot or tray where it can get plenty of sunlight. 
  6. Give water to the seeds daily until it germinates (~2 weeks)
  7. When the seeds are two to three inches tall, they may be transferred to pots. Acclimate them by bringing them outdoors once in a while until they can be outdoors permanently. After this step, you may now transplant them.

Pruning

Pruning Dahlias can be done through deadheading, pinching and disbudding. Pinching is something you have to do during the spring. Pinching is done to encourage lower branching of the plant that will make it stronger and make more blooms at the top. 

Now disbudding might be difficult for some owners as it means removing potential flowers. But this is necessary in order to channel sufficient food to a select number of flowers. 

Lastly, deadheading. These are very important to prolong flowering. Just make sure and take time to see the difference between buds and spent flower heads. Buds are round while spent flower heads are more pointed. Make sure only to remove the latter ones. 

Potting and Repotting

Regardless of how they were grown, they should be transplanted outside before they reach one foot in height. Make sure your pot or garden bed has the soil, environmental and space requirements before you transplant them. Also, protect them against strong winds and rains during this transitioning phase. 

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Dahlias Care

LightFull sunlight, six to eight hours a day
TemperatureIntermediate to warm, 38-45 degrees Fahrenheit
WaterOnce a week, increased in summer, decreased in winter
SoilLoamy, well-draining mix
FertilizationRegular household fertilizer, once a month
SpaceDepends, 9-12 inches bedding, 1-3 feet apart
PropagationVia tuber propagation or seeds
BloomingBlooms during summer and fall
PruningThrough deadheading, pinching, disbudding
PottingRegular potting mix with parts of sand, manure, and peat moss

Problems and Troubleshooting

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Overwatering

Overwatering may cause root rotting and molding of the tubers, which can manifest as a specific smell [of rotting tissue], especially on the base of the plant. 

To avoid overwatering, make sure that your Dahlia is being watered correctly. It is also important to note that it is getting its minimum requirements such as a well-draining moist soil, plenty of sunlight and a specific moisture level. 

Underwatering

Dry leaves, brown tips, leaf drops, wilting, and leaf curling are all symptoms of underwatering. Also, you will notice that the soil is drying out. To avoid such issues, you must water the plant on a regular basis.

Some ideas for dealing with underwatering:

  • Consider watering more frequently or more thoroughly. 
  • Remove any dead growth. 
  • Check for dampness. If the soil is excessively dry, stick your finger into it 
  • Daily Plant inspection

Nutrient Deficiency

Nutrient deficiency occurs when a plant does not have an adequate supply of an essential nutrient necessary for development. A nutritional deficiency can also cause yellowing and stunted growth.

To ensure that your plants get all their nutrients, use organic materials and feed them, especially during the growing season. Also, use the proper fertilizer ratio.

Flowering Problem

A lack of light is one of the most common issues with flowering Dahlias. To ensure that your Dahlias produce flowers, give them the best possible care and attention. Sufficient water and light are also required for optimum flowering.

Diseases

Root rot is still the most common disease that Dahlias face. To avoid this, make sure your soil is well-draining and that the pots have drainage holes. You might also want to check on your watering habits. Your plant may be receiving more water than it should. Overwater makes your Dahlia plants wilt.

Pests

The most common problems of Dahlias are slugs, snails, caterpillars, aphids, earwigs and beetles. They eat dahlias and, in turn, leave holes and fewer nutrients for the plant. To prevent this, be attentive to your plant. Once an infestation is apparent, you might try using natural insecticides that would keep them away from your plant. 

You may also want to place them near plants such as anise, coriander and onions, which keep aphids away, and wormwood, which keeps slugs away. 

Drooping and yellowing of leaves

If you start to notice your plant is drooping and the leaves are turning yellow, you might consider lessening the fertilizer. Drooping and yellowing are often signs of overfertilizing your Dahlias.

Common Pests/DiseasesSymptomsTreatment and Prevention
Common diseases include crown rot, stem rot, root rot, leaf spot, fungal diseases, and Xanthomonas infection
Yellowish rimming around black or dark brown spots on leaves

Avoid overwatering. Keep soil dry. Avoid too high humidity.Proper ventilation is needed around the plant. Remove infected parts of fungal infections to avoid spreading.




Common pests include mealybugs, spider mites, aphids, and scales


Visible insects on the surface
Spray plant with warm, soapy water. If infestation is present, use insecticide or neem oil. Use diatomaceous earth. 

Problems with People and Animals

Toxicity

Although seemingly beautiful and safe, Dahlias are unfortunately not safe for pets. Unlike other plants, they do not have high toxicity, but they can cause your pets to experience mild gastrointestinal signs and dermatitis. Make sure they are kept away and far from reach from your fur babies.

Dahlia Plants Meaning and Symbolism

dahlias growing guide - meaning and symbolism

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Dahlias stand for wealth, elegance as well as love and involvement. For the Aztecs and indigenous people, they were used as medicine and religious symbols in types of ceremonies. It’s a perfect flower to express your priceless love!

General MeaningWealth, elegance, love, involvement
SymbolismTo express a priceless love
Cultural SignificanceIn Aztec culture and other indigenous tribes, they are used as medicines and religious symbols in ceremonies

Landscaping and Gardening Ideas

Dahlia landscaping

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Companion Plants

Fall-blooming and late-season plants go well with Dahlias. Some of the plants on top of the list are purple asters, wormwood, New England asters, and Salvia to attract more butterflies. Geraniums are also pretty, but not if you are having issues with Japanese beetles around your area. 

Landscaping Ideas

Dahlias are usually planted to create beautiful borders, such as along walkways or by your front porch. They may also be placed as focal points in some gardens, significantly taller Dahlias. 

What to plant withPurple Asters, Wormwood, New England Asters, Salvia, Geraniums
What NOT to plant withBasically nothing

Conclusion

Dahlia flowers

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Dahlia tubers are quite pricey, but claiming and dividing it once it grows will definitely have a big payback. Over time, they become more of an adorable and affordable addition to your collection. After all, who doesn’t want a little more color in their gardens and in their lives?

FAQS

  1. Is Dahlia a perennial or an annual plant?

Dahlia plants are perennials; thus, they come back every year. The tubers underneath the ground are unharmed during the winter season and will grow back year after year.

  1. Do Dahlias like sun or shade?

Dahlias are sun plants and love a full sun for six to eight hours a day. The more sunlight they receive, the more Dahlia flowers they will give. That is why it is important to give your Dahlia plants the sunniest location that you have.

  1. Can you leave Dahlias in the ground over winter?

In Zones 8 and above, Dahlia tubers can be kept in the ground over winter. However, in other Zones, they will rot during winter. Therefore, it is a must to dig them from the ground and keep them indoors.

  1. Where is the best place to plant Dahlias?

Dahlias thrive the best when they are placed under full sun and with a loamy, well-draining soil. They thrive best in USDA Zones 8-12. However, you can also grow them in other zones, provided that you keep them indoors during the winter season to prevent winter frost.

  1. Should you deadhead Dahlias?

Deadheading your Dahlia plants are important in order to prolong your Dahlia blooms.

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