How to Choose, Plant, and Take Care of Your Dahlias

Anybody who loves flowers and colour would love dahlias.

There are so many varieties of dahlias to choose from, whether you prefer tiny, dainty, and cute blooms or large, flashy displays of bright colours.

Dahlias Flowers
Dahlias Flowers

The Basics of Dahlias

Dahlia is a genus made up of about 42 species of herbaceous perennial plants. These bushy and tuberous plants are native to Central America and Mexico. It is also Mexico’s floral emblem.

Known for their bright colours, dahlia flowers can be as small as 2 inches (5 cm) or as gargantuan as 12 inches (30 cm).

Dahlia flowers are usually not scented, but they do come in a wide variety of colours with the exception of blue. Its stem can be as short as 12 inches (30 cm) or as tall as 6 to 8 feet (1.8 to 2.4 m).

The dahlia’s flower head is actually a composite—ray florets surround the central disc florets. Dahlia florets are not petals as some would call them, because each floret is an actual flower in itself.

The dahlia’s mid to dark green leaves are pinnate, growing in pairs of opposite leaves on the stem.

Dahlias are considered as perennial plants but are grown as annuals in areas with frigid winters.

This plant has tuberous roots, and some have herbaceous stems. The dahlia’s tuberous roots allow it to survive winter dormancy.

Other species of dahlias have stems that lignify (become rigid or woody) in the absence of secondary tissue, which allows them to resprout after dormancy in winter.

Dahlias Flowers
Dahlias Flowers

Planting Your Dahlia

Dahlias will naturally grow in places with no frost because they are not adapted to survive very low temperatures. However, it is still possible to grow dahlias in colder regions, with proper care.

The same as too cold, too hot climate also has some challenges for growing dahlias as you would need to water it more.

The ideal time for planting dahlias is in late spring to early summer. Check that the soil is warm enough before planting.

You can plant dahlias about two weeks after the last frost, and it is best if the soil is not wet and is above 60 °F (15 °C).

Dahlias like the sun, so plant it where it could get around 8 hours (at least 6) of sunshine.

Plant dahlias in rich and well-draining soil, with a pH of around 6.5

If planting dahlias in containers, mix in 1/3 garden soil to the potting soil for better moisture retention.

If you are planting with tubers, plant it about 6 to 8 inches (15 to 20 cm) deep for large ones, and about 3 to 4 inches (7.5 to 10 cm) for smaller varieties.

Large dahlia varieties need space to grow, so give them about 20 to 24 inches (50 to 60 cm) between each plant. Large dahlias may also need staking for support as they grow.

Dahlias Flowers
Dahlias Flowers

Caring for Your Dahlias

Make sure to keep the soil of your dahlias moist until the roots are established. Mulching the ground will help keep your dahlia’s soil moist, especially because dahlias have shallow root systems which are prone to drying out.

Feed your dahlias in summer with low nitrogen ratio to help them through the winter. Do not fertilise later than mid-summer.

Pinch the growing tip to encourage multiple stem growth. But keep in mind that this method will keep the dahlias from growing taller.

Another option is to remove the first flower bud. Cut the flowers for arrangements and deadhead regularly to ensure more active blooming.

To store dahlias during winter, dig them up after the frost and the dahlias’ leaves blacken. You can then store the bulbs for winter to plant in the spring after the frost.

Common Problems with Dahlias

Dahlias, like most vegetations, are prone to pest infestations such as slugs and snails. Earwigs can also cause problems and even disfigure the blooms.

Aphids can be found on young dahlia stems and immature flower buds.

Capsid bugs can cause holes and contortions at the dahlia’s growing tips.

Red spider mite, which is a worse issue in hot and dry conditions, can cause the mottling and discolouration of the dahlia’s foliage.

Larvae of some insects such as common swift, angle shades, large yellow underwing, and ghost moth will consume dahlias for food. Some diseases can affect dahlias such as powdery mildew, verticillium wilt, grey mould or Botrytis cinerea, phytophthora, dahlia smut or Entyloma calendulae f. dahliae, and some plant viruses.

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