Dahlia Gardens: A Guide to Planning and Cultivating Stunning Displays

In the world of flowers, dahlias are the leading ladies, caparisoned in Haute couture for a grand ball.

Big as dinner plates and available in almost every color of the rainbow, dahlias stand out among flowers. And if you’re into the arts, you’ll find resonance in the repeating fractals of dahlias petals as being emblematic of the sacred geometry of life.

Dahlias are beautiful flowers, shooting skyward on pliant stalks – the perfect companions on days that feel less bright. Here’s how you can court these vivid, vivacious blooms in your own garden. 

Varieties

Dahlia season begins in July and reaches its height in September before slowing.

Native to Mesoamerica, particularly the high plains of Mexico, dahlias were introduced to the Botanical Gardens in Spain towards the end of the 18th century.

Today, there are many variants of dahlias available for sale, from the spherical Pompon Dahlias to the quill-shaped Cactus Dahlia.

Of all colors, true blue remains the most elusive, evading gardeners and florists for centuries. Their petals can range from spidery whorls to honey-combed, but are all iconic in their own right.

Below are a few stunning varieties of dahlias to cull your fancy.

Dahlia Crazy Love: White, luminescent petals edged with rosy magenta, reminiscent of moon-lit gardens; lends a subtle elegance to the garden. 

Arlequin Decorative Dahlia: A striking variety known for its unusual coloring, this dahlia features blush pink petals stippled with red. 

Nuit D'ete Cactus Dahlia: Derived from French for ‘summer night’, this flower’s dramatic burgundy petals speak for itself; an exotic flower with a dark heart. 

Dahlia Franz Kafka: Avid book readers will know that the term ‘Kafkaesque’ refers to a situation that is nightmarishly complex; luckily, this flower is a delight to all, its florid pink blooms ideal for borders.

Dahlia ‘Verrone’s Obsidian’: An intriguing variety with a pin-wheel like appearance, this petal’s sunny center contrasts with its dark, cabaret color; ideal for goth gardens or as a counterbalance for more pastel color settings. 

Plan your dahlia garden

Dahlias are commonly grown from tubers, not seeds

A liberal planting of dahlias along a border or walkway can create a dramatic architectural effect. Smaller and less stately flowers can be interspersed among other flowers in raised beds.

As you may already know, dahlias are commonly grown from tubers rather than seeds. Dahlias are sun-loving flowers and will not tolerate frost. They are best grown when the soil is 60º F and all dangers of frost has passed. The best time to sow dahlia bulbs is late spring, around the month of May. 

Choose a site that:

• Has full sun
• Has organically rich soil
• Has good drainage properties
• Is free from deer and other pests

Planting your dahlia garden

Purchase dahlia tubers and choose your method of growing: If you’re a freeform gardener, you just plunk things down and leave it to nature. But if you’re more thought-out and tend to stress over the littlest things, then garden planning can help.

Despite its flamboyant appearance, dahlias are relatively easy to grow. However, they are tender perennials, and those that live in a cold climate may need to dig out the tubers and store them for the winter. A rolling planter allows you to forego the process of digging them out – all you need to do is wheel them inside. 

Growing dahlias in containers

Some gardeners will start dahlias indoors in pots filled with an organic potting mix.

Otherwise, raised beds are recommended for dahlias, both for their elevated designs and optimal growing conditions. Planting in raised beds will allow you to circumnavigate cumbersome tree roots common in backyards and hem in untidy growers. While deer do not typically bother dahlias, they will occasionally munch on them, so it’s better to place physical barriers  if you encounter frequent foot traffic.

Planting dahlias

Dahlias are generally spaced 12 to18-inches apart, one tuber per square feet, with dinner-plate varieties requiring wider spacing.

Before you begin, the location should be prepared with high-quality soil and cleared of debris. Once you are done preparing the planting site, begin placing the tubers in the hole, 5 to 6-inches deep, leaving the ‘eyes’ facing up.

When planting dahlias, wait until sprouts have appeared before watering – otherwise, the tubers can suffer from root rot. Normally, you do not need to fertilize at planting, but a handful of bone-meal or other slow-release fertilizers can remedy sub-par soils. 

Pinching and staking dahlias

Border dahlias and other diminutive varieties do not need to be staked, but larger cultivars will benefit from some support. Long-stemmed dahlias are usually staked with hardwood stakes, though bamboo poles or metal trellises are another population option. As the dahlia plant grows, tie one to wood or metal pole, allotting one stake per plant. When dahlias are 12-inches tall, they can be pinched to promote fuller growth. A detailed demonstration on how to pinch dahlias can be found here. 

Caring for your dahlias

Deadheading spent dahlias will keep your garden neat and tidy while ensuring flower production.

To deadhead dahlias, use a pair of pruning shears or a Hori Hori knife and cut off the flowers – preferably back to the main stem to stimulate new growth. Dahlia flowers make lovely bouquets, and the same implements can be used to snip off stems for floral arrangements. 

Dahlias are exotic flowers and will not tolerate cold. Unless you live in zones 8 to 10, then it’s unlikely that they will survive the cold. When the dahlia foliage starts to blacken, it is a sign to start digging out the tubers.

Using a pitchfork or Hori Hori knife, carefully dig around the tubers and then retrieve them from the dirt. Shake off excess dirt, rinse them, and remove any rotten parts. Dry them for several weeks in a well-ventilated spot before storing them in containers.

Remember the beauties' basics

• Light: Full sun
• Soil type: Well drained
• Water: Medium
• Bloom time: July to September
• Type of dahlias: Cactus, pompom, anemone, orchid, waterlily