A spectacular addition to a colourful garden.
Dahlias make for excellent long lasting, bold cut flowers with their long, sturdy, contrasting stems and lush green foliage to dark shades of bronze and maroon, almost black leaves, that you can reap for months.
Dahlia plants flourish the more you prune, deadhead or harvest. The large blooms and plethora of striking colours and eye catching shapes make them attractive exhibition and vase flowers. Dahlias flowers do not significantly open after cutting, pick them when they are nearly our fully mature.
Dahlias are perennials in warm climates similar to USDA Zone 8 and above, they are native to Mexico, Central America and northern South America. Their natural habitat includes uplands and mountains, at elevations between 1 500m and 3 700 m, in the pine oak woodland vegetative zone. Most Dahlia species have limited ranges scattered throughout many mountain ranges in Mexico. Only D. australis, D. coccinea and Pseudodendron D. imperialis occur outside Mexico.
Planted as annuals in regions of the world that experience sub zero temperatures, they produce countless flowers in an average of 75 to 120 days, depending on the cultivar, right up until first frost in late fall. They can be planted outside after all danger of frost has passed, or when soil temperature reaches 15°C/ 60ºF, as confirmed by The Old Farmer's Almanac. Pull the tuberous roots from the ground in autumn to save the plants for next year and grow your collection.
When grown from seeds, dahlias can blossom in only 4 months.
Members of the floriferous Asteraceae family, dahlias are very easily propagated and grown from rooted cuttings, tuber division and hand pollinated or insect pollinated seeds. Open centred dahlias offer more access to pollinators, increasing pollination, seed quality and germination rate.
The huge variation of garden dahlias is due to them being octoploids, they have eight sets of homologous chromosomes, and contain many transposons, genetic pieces that move from place to place upon an allele, contributing to manifesting their great diversity.
- New dahlia cultivars are developed and supplemented annually.
- There are 42 accepted species in the genus Dahlia, and further new species continue to be described.
- Within the species are sections defined by native geographical distribution and chromosome numbers, namely Pseudodendron (the tree dahlias), Epiphytum (the vine dahlia) and two herbaceous sections defined by their pinnules, Dahlia (opposing pinnules) and Entemophyllon (alternating pinnules).
- Horticulturally, dahlias are classified by their flower type by numerous national agricultural societies. The Royal Horticultural Society lists 14 groups its publication of The International Dahlia Register.
- Dahlia groups are further subdivided by flower size but this is not standardized. The RHS describes the Dwarf Bedder and Liliput dahlias. The National Dahlia Society of New Zealand better describes dahlia bloom sizes as Giant (over 250 mm), Large (200 to 250 mm), Medium (155 to 350 mm), Small (115 to 155 mm), Miniature (50 to 115 mm) and Pompom (under 50mm) flowered cultivars. Words like mignon or dinner plate may also be featured to convey the flower size.
- Single flowered dahlia.
Flower has a central disc with a single outer ring of florets, which may overlap, encircling it, and which may be rounded or pointed.
- Anemone flowered dahlia.
The centre of the flower consists of dense elongated tubular florets, longer than the disc florets of Single dahlias, while the outer parts have one or more rings of flatter ray florets. Disc absent.
- Colerette dahlia.
Large flat florets forming a single outer ring around a central disc and which may overlap a smaller circle of florets closer to the centre, which have the appearance of a collar.
- Waterlily dahlia.
Double blooms, broad sparse curved, slightly curved or flat florets and very shallow in depth compared with other dahlias. Depth less than half the diameter of the bloom.
- Decorative dahlia.
Double blooms, ray florets broad, flat, involute no more than seventy five per cent of the longitudinal axis, slightly twisted and usually bluntly pointed. No visible central disc.
- Ball dahlia.
Double blooms that are ball shaped or slightly flattened. Ray florets blunt or rounded at the tips, margins arranged spirally, involute for at least seventy five percent of the length of the florets. Larger than Pompons.
- Pompon dahlia.
Double spherical miniature flowers made up entirely from florets that are involute, curved inwards,) for their entire longitudinal axis.
- Cactus dahlia.
Double blooms, ray florets pointed, with majority revolute over more than fifty percent of their longitudinal axis, and straight or incurved. Narrower than Semi Cactus.
- Semi Cactus dahlia.
Double blooms, very pointed ray florets, revolute for greater than twenty five percent and less than fifty percent of their longitudinal axis. Broad at the base and straight or incurved, almost spiky in appearance.
- Miscellaneous dahlias.
Not described in any other group, used for unique, intermediate or hybrid forms.
- Fimbriated or Laciniated dahlia.
Ray florets evenly split or notched into two or more divisions, uniformly throughout the bloom, creating a fimbriated, or fringed, effect. The petals may be flat, involute, revolute, straight, incurving or twisted.
- Single Orchid or Star dahlia.
Single outer ring of florets surround a central disc. The ray florets are either involute or revolute.
- Double Orchid dahlia.
Double blooms with triangular centres. The ray florets are narrowly lanceolate and are either involute or revolute. The central disc is absent.
- Peony flowered dahlia.
Large flowers with three or four rows of rays that are flattened and expanded and arranged irregularly. The rays surround a golden disc similar to that of Single dahlias.
You may also come across these groupings:
- Formal Decorative dahlia.
Fully double flowers with broad, flat petals that are arranged in a precise, symmetrical and uniform manner. These petals gradually recurve backward toward the stem and often feature rounded or slightly pointed petal tips.
- Informal Decorative dahlia.
Large, fully double blooms with a loose, relaxed appearance. Unlike formal types, their broad, flat petals are irregularly arranged, appearing wavy, twisted or curled.
- Stellar dahlia.
Fully double blooms with narrow, pointed ray florets that are partially involute, curled inward, and recurve toward the stem. The centre is conical, closed and high, with petals decreasing in size toward the centre.
- Incurved Cactus dahlia.
Fully double blooms with narrow, pointed petals that roll and curve inward toward the stem, often creating a swirling appearance.
- Novelty dahlia.
Classification for varieties with unique, distinctive features that do not fit into standard categories. Novelty dahlias can be fully double with a tight, symmetrical centre or open centered, featuring unique, irregular, or distinctively formed petals. They are characterized by unconventional petal shapes like collars, involute, twisted, curved, curled, split or laciniated, creating a unique textural look and often combine traits from other forms. They display distinct colour patterns, or, in the case of Novelty Open types, a prominent centre.
- Species dahlia.
Original species, rather than modern bred hybrids.
For those new to planting dahlias, space these fast growing large plants 30 cm to 60 cm apart. 1.5 m row spacing gives an ample walking aisle and allows for adequate air flow.
Place the tubers horizontally, laid flat on their length, about 10 cm deep, with the eyes facing up.
Do not water exceedingly before the shoots poke out of the ground.
Seeds will germinate in 7 to 14 days with constant adequate soil humidity.
You can start them indoors for 6 to 8 weeks at temperatures of 18 °C to 21 °C, not exceeding 24°C.
Sown dahlia seedlings germinate sporadically, be patient.
Tubers and tuber clumps can be started indoors 4 to 6 weeks before the last spring frost as well.
Dahlia cuttings can be taken as shoots from sprouted tubers or stems. They will root in 2 to 3 weeks in moist soil.
Pinch your plants early to encourage branching low on the plant, leading to a bushier plant, more flowers and longer stems.
Full sun, at least 6 hours daily, with protection from the afternoon sun in equatorial regions, and consistent irrigation throughout the season will allow dahlia plants to thrive and yield abundantly for months.
Deadhead often if you are not picking often for arrangements, bunches and bouquets.
Dahlias are highly productive, continuous blooming cut and come again flowers. Dahlia blooms last 5 to 7 days in the vase.
One dahlia plant will give you 20 to 100 cut flowers in a single season. Prolific smaller flowered varieties produce more blooms than very large ones. Expect a safe, conservative 1 to 2 long stems per week so you can plan ahead accordingly.
We strive to bring to you the largest worldwide selection of dahlias out of the 5700 registered cultivars, including heritage heirloom varieties, wild species and newer hybrids to suit your needs as cut flower growers, home gardeners, plant breeders, large scale propagation farmers, landscape artists and floriculture enthusiasts. Happy planting!