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Cosmos x Dahlia Mexican Star

Cosmos x Dahlia Mexican Star
Cosmos - Dahlia Hybrid

4,2/5
10 reviews
3 reviews
0 reviews
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1 reviews

The bulb arrived in pieces and was broken. One piece is starting to sprout, and I have put all of them in damp sphagnum to encourage more sprouts before planting. I can't see any growing points on the other pieces, but just in case I'm surprised, I will give them an opportunity to show their viability.

Erik, 02/06/2023

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More information

This curious tuberous plant is a hybrid between Cosmos atrosanguineus and Dahlia coccinea. It bears single flowers, 6cm (2in) in diameter, made up of a collar of dark purple-brown petals surrounding a beautiful golden yellow centre. This flowering bushy plant, reaching a height of 75cm (30in), also develops a mound of divided, dark green foliage. It should be grown like a dahlia.
Flower size
6 cm
Height at maturity
70 cm
Spread at maturity
50 cm
Exposure
Sun, Partial shade
Hardiness
Hardy down to -4°C
Soil moisture
Moist soil
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Best planting time April to May
Recommended planting time March to May
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Flowering time August to October
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Description

Cosmos x Dahlia 'Mexican Black' is a rather curious tuberous plant, apparently discovered in a wild area in Mexico. It is said to be the result of a cross-breeding between Cosmos atrosanguineus and Dahlia coccinea, with which it shares various morphological traits. This rare and unique plant produces single, slightly scented flowers, 6cm (2in) in diameter. They are made up of a collar of dark purple-brown petals surrounding a beautiful golden yellow centre. They bloom in late summer and autumn, above an elegant mound of dark green foliage. It is not very hardy, so it should be grown like a dahlia, in full sun and in light soil.

 

Cosmos x Dahlia 'Mexican Black' is an herbaceous tuberous plant that belongs to the Asteraceae family. It resembles a dahlia more than a cosmos, both in the scent of its foliage and its mode of growth. Primarily obtained through vegetative propagation, it develops from a frost-sensitive fleshy tuber. From spring, it quickly forms a clump of foliage measuring 40 to 50cm (16 to 20in) in all directions, and 70 to 80cm (28 to 32in) when in flower. The foliage is cut into narrow lobes, and somewhat resembles that of peonies. It is composed of dark green leaves, slightly tinged with a dull purple, and remains low. The floral stems, tinged with purple-brown, appear in August-September, and last until October if faded flowers are regularly removed. The flowers are grouped in heads and consist of slightly wrinkled ligulate florets on the periphery. They are dark purple-brown with a heart of golden yellow tubular florets. These heads emit a slight chocolatey aroma, especially in warm weather. According to molecular studies conducted in 2012, the dark colour of the heads cannot be attributed to a cross-breeding with Cosmos atrosanguineus, as it is found in at least 14 cultivars of dahlias.

 

Cosmos x Dahlia 'Mexican Black' is a relatively rare variety. It will not go unnoticed! It is sublime when paired with grey and silver foliage. It will wonderfully accompany artemisias, lamb's ears, or Cineraria maritima in flower beds or pots. The warm tone of its flowers brings out pastel colours, like the pink or blue of asters, or the azure of 'Indigo Spires' sage. It stands out nicely against the acidic green foliage of bipinnate cosmos or Alchemilla mollis.

 

Cosmos x Dahlia Mexican Star in pictures

Cosmos x Dahlia Mexican Star (Flowering) Flowering
Cosmos x Dahlia Mexican Star (Foliage) Foliage

Plant habit

Height at maturity 70 cm
Spread at maturity 50 cm
Growth rate fast

Flowering

Flower colour red
Flowering time August to October
Inflorescence Flower head
Flower size 6 cm
Fragrance slightly scented, Chocolate.
Bee-friendly Attracts pollinators
Good for cut flowers Cut flower blooms
Flowering description The flowers are grouped in solitary heads (capitules) measuring 6cm (2in) in diameter. The capitule is the typical inflorescence of the Asteraceae family, simulating a corolla that, instead of being composed of simple petals, corresponds to ligulate female flowers. The "false stamen heart" in the centre corresponds to a multitude of hermaphrodite tubular flowers.

Foliage

Foliage persistence Deciduous
Foliage colour green

Botanical data

Genus

Cosmos x Dahlia

Cultivar

Mexican Star

Family

Asteraceae

Other common names

Cosmos - Dahlia Hybrid

Origin

Cultivar or hybrid

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Planting and care

Plant in spring, once the frosts have passed. Plant in light, humus-rich and well-drained soil. It prefers sunny situations, which will better reveal its fragrance, but tolerates partial shade. Once well established, it withstands drought and heat. It can be grown like a dahlia, by lifting the tubers before the frosts and storing them in a cool place.

It also performs very well in pots. This cultivation method allows the pots to be stored during winter in a cool and bright place. Under these conditions, it will flower for a good part of the year. Regularly remove faded flowers to encourage new blooms.

Planting period

Best planting time April to May
Recommended planting time March to May
Planting depth 15 cm

Intended location

Suitable for Meadow
Type of use Border, Container
Hardiness Hardy down to -4°C (USDA zone 9b) Show map
Ease of cultivation Amateur
Planting density 4 per m2
Exposure Sun, Partial shade
Soil pH Any
Soil moisture Moist soil, Well-draining, humus-bearing.

Care

Pruning instructions Regularly remove faded flowers to encourage new blooms.
Pruning Pruning recommended once a year
Pruning time August to September
Soil moisture Moist soil
Disease resistance Good
Overwinter Needs to be stored
4,2/5

Dahlias

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