Name: 'Penhill Watermelon' giant dahlia
Brand: Van Noort
SKU: VAN-327-414-20
Price: 9.99 CAD
Availability: InStock

Sale Sold out

Emballage Florissa du dahlia géant ‘Penhill Watermelon’, montrant une fleur rose pêche aux pétales ondulés.

Tuber Asteraceae

Van Noort

Dahlia × pinnata

From bulb to bloom

Common nameGiant Dahlia ‘Penhill Watermelon’

FamilyAsteraceae

GenusDahlia

SpeciesHybride horticole

CultivarPenhill Watermelon

Bulb typeTubercule de dahlia géant

Botanical nameDahlia

Quantity per pack1 tubercule

Bulb sizeNo 1

'Penhill Watermelon' Giant Dahlia (Dahlia × pinnata). 'Penhill Watermelon' Giant Dahlia (Dahlia) The 'Penhill Watermelon' giant dahlia displays large, double flowers with petals shifting from coral pink to pale mauve. Wide, wavy, and twisted, the florets curl in multiple directions, giving the flower head a supple, almost aquatic movement. The dark green, bronze-tinted foliage provides a rich contrast. The Van Noort No. 1 tuber produces an upright clump that can reach approximately 150 cm (59 in.) in height and 50 cm (20 in.) in spread. From mid-summer until the first frost, the flowers bloom continuously on stems perfect for flower beds, cutting gardens, and large containers.

Their nuanced palette shifts with the light, creating a romantic focal point without appearing uniform. Plant 'Penhill Watermelon' in the spring after the last frost, once the soil has warmed. For the 'Penhill Watermelon' giant dahlia, lay the tuber 10 cm (4 in.) deep, bud side up, in fertile, humus-rich, moist, and well-draining soil. For the 'Penhill Watermelon' giant dahlia, leave 50 cm (20 in.) of space around the crown, choose a full-sun location, and protect the plant from strong winds. Install a sturdy support at planting time, as the clump can reach 150 cm (59 in.) and the large flowers retain rainwater.

For the 'Penhill Watermelon' giant dahlia, pinch the young shoot when it is 20 to 30 cm (8 to 12 in.) tall to encourage branching. Mature compost and moderate fertilization—higher in potassium once buds appear—support firm stems without excess nitrogen. Pair 'Penhill Watermelon' with violet-blue sage, white gaura, chocolate cosmos, and coppery grasses. These companions highlight the coral pink and pale mauve tones while allowing the wavy petals to breathe. Harvest stems when nearly open early in the morning, and continually deadhead spent blooms.

Light and life cycle

In the garden

Exposure: Sun
Life cycle: Tender perennial
Hardiness: Zone 8

Planting and establishment

Planting guide

Planting & establishment

Planting depth

10 cm (4 po)

Spacing / density

50 cm (20 po) entre les plants

Establishment temperature

Sol à environ 16 °C ou plus

Rooting time

Environ 3 semaines en pot; variable selon les conditions

Planting period

Printemps, après les derniers gels

Propagation

Division of tubers, each bearing a viable bud

Growing method

Plantez au printemps en sol réchauffé, au soleil et à l’abri du vent. Installez un tuteur solide, arrosez régulièrement après la levée et déterrez la souche après le premier gel pour la conserver hors gel.

Soil and care

Soil & care

Soil pH

Slightly acidic to neutral

Moisture

Sol frais pendant la croissance, sans eau stagnante.

Minimum temperature

5 °C (41 °F)

Care level

Easy

Watering

Régulier pendant la croissance, sans détremper le sol; arrosez au pied lorsque la surface sèche.

Soil type

Fertile, meuble et bien drainé

Fertilization

Incorporate mature compost before planting. At the start, use a balanced formula low to moderate in nitrogen, then favor more potassium when buds appear. Follow the recommended dosage and then water. Too much nitrogen produces tender stems and fewer flowers. The coral pink to pale mauve contrast remains sharper when the plant receives at least six hours of direct sun and regular feeding without excess nitrogen.

Seasonal care

In spring, inspect the tuber, remove only rotten tissue, and plant after the last frost in warmed soil. Install support immediately. Until sprouting, avoid repeated watering. In early summer, pinch the shoot back to 20 or 30 cm (8 to 12 in), tie new stems, and keep the soil moist without saturation. Once buds appear, fertilize moderately with more potassium. In summer, water deeply at the base during dry periods, harvest flowers when almost open, and continuously remove faded flower heads. Watch for slugs, aphids, earwigs, spider mites, and gray mold. After the first frost, cut back stems, gently lift the tuber, let its surface dry, label it Penhill Watermelon, and store it in the dark, in a cool, dry, and frost-free place. Check it monthly during winter. The coral pink to pale mauve contrast remains sharper when the plant receives at least six hours of direct sun and regular feeding without excess nitrogen. An early-installed stake supports the 18 cm (7 in) flower heads after rain without compressing stems or damaging active roots. Remove faded flowers before seed formation so the clump directs its energy towards new buds until the first frost. Always water slowly at the base, then allow the top layer to breathe to maintain a balance of moisture, oxygen, and drainage. The coral pink to pale mauve hues pair particularly well with blue, white, and purple perennials, and light grasses.

Growing in containers

Container growing

Recommended pot size

Capacity of 40 to 50 L, deep and very stable

For the 'Penhill Watermelon' giant dahlia, container growing requires planning for the volume needed by the roots and the plant's final height. Choose a stable pot with drainage holes and a suitable potting substrate. Allow enough space to respect the recommended depth and spacing, rather than crowding the plants to fill the pot immediately. Place the container in the indicated exposure and check moisture regularly, especially in hot or windy weather. A pot is more exposed to temperature fluctuations than planting in the ground. Therefore, plan ahead for a wintering location compatible with the plant's needs and your region's climate. Plant in spring once all risk of frost has passed and the soil has warmed up sufficiently. Choose a sunny spot, sheltered from strong winds, in fertile, well-drained soil. Position the tuberous roots with their neck and buds facing upward, without breaking the fragile attachments. Install a stake at planting time if support will be needed, to avoid damaging the roots later. Water sparingly at the start, then adjust the supply as the foliage grows.

Growth and flowering

Size, flowering & harvest

Mature height

Jusqu’à environ 150 cm

Width / spread

Environ 50 cm

Flower color

Coral rose to pale mauve

Foliage color

Green

Foliage type

Null and void

Growth rate

Quick

Growth habit

Touffe dressée

Fragrance

Parfum non marqué

Bloom period

Spectacular blooms of very large decorative watermelon pink flowers from July until the first frosts. Giant Dahlia 'Penhill Watermelon' (Dahlia 'Penhill Watermelon') The giant dahlia 'Penhill Watermelon' unfurls large double flowers with petals that range from coral pink to pale mauve. From mid-summer until the first frost, the flowers continuously bloom on stems that are useful for beds, cutting gardens, and large containers. Install a sturdy support at the time of planting, as the clump can reach 150 cm (59 in) and the large flowers retain rain.

Harvest

July to October. Harvest the flowers early in the morning when fully open to ensure excellent vase life. Continue to deadhead spent blooms to encourage the production of new buds.

Garden companions

Garden associations

Companion plants & uses

Companion plants

Salvias, cosmos, Verbena bonariensis, echinaceas, and ornamental grasses beautifully highlight its large, softly colored flowers. The dark green, bronze-tinged foliage creates a rich contrast. Their nuanced palette changes with the light, creating a romantic focal point without appearing uniform. Pair 'Penhill Watermelon' with purplish-blue salvias, white gaura, chocolate cosmos, and coppery grasses. These companions emphasize the coral-pink and pale mauve tones while allowing the wavy petals to breathe.

Other recommended plants

Associez-le à des cosmos blancs ou à des graminées légères dans un massif ensoleillé.

Garden use

Giant Dahlia 'Penhill Watermelon' (Dahlia). Giant Dahlia 'Penhill Watermelon' (Dahlia) The giant dahlia 'Penhill Watermelon' displays large double flowers with petals that transition from coral pink to pale mauve. Broad, wavy, and twisted, the florets curve in multiple directions, giving the flower head a supple, almost aquatic movement. The dark green foliage, tinged with bronze, creates a rich contrast. Van Noort's No. 1 tuber produces an upright clump that can reach approximately 150 cm (59 in) in height and 50 cm (20 in) in spread. From mid-summer until the first frost, flowers continuously bloom on stems useful for beds, cut flower gardens, and large containers. Before planting, observe the bed from the path you use most often. Position the plants to keep the flowers visible, without obscuring smaller ones behind overly dense foliage. Repeating groups connects different parts of the flowerbed, while an isolated planting draws more attention to a detail. Also, maintain access to water, weed, and remove spent flowers without trampling young shoots. When adding neighboring plants, compare their light and moisture requirements. A pleasant display should remain easy to maintain once all vegetation has reached its full size, and not just on planting day.

Frequently asked questions

'Penhill Watermelon' giant dahlia: when to plant the Penhill Watermelon dahlia?

For the 'Penhill Watermelon' giant dahlia, plant the tuber after the last frost, once the soil has warmed up and is no longer saturated. Lay it 10 cm (4 in) deep, bud facing up, in fertile, humus-rich, well-drained soil. Leave 50 cm (20 in) around the crown and install a support immediately. In a cold region, start it in a pot four to six weeks earlier, then gradually acclimate the shoot before moving it outdoors. Water very sparingly before emergence to prevent rot, then increase the amount once the roots and stems are active. Full sun develops strong stems and intensifies the contrast from coral pink to pale mauve.

'Penhill Watermelon' giant dahlia: what colors are the 'Penhill Watermelon' flowers?

For the giant dahlia 'Penhill Watermelon', Penhill Watermelon produces pale mauve florets, broadly colored with coral pink towards the tips and edged with a fine red border. The proportion of red varies from one petal and flower head to another, creating a lively pattern rather than a perfectly regular stripe. The international register mentions flowers reaching approximately 18 cm (7 in), while Van Noort classifies the variety as a Dinnerplate. Abundant light helps the stems remain firm and makes the contrast sharper. However, avoid wetting the flowers when watering: water retained between the petals can mark the colors and promote gray mold in cool weather.

'Penhill Watermelon' giant dahlia: how to support and encourage blooms on Penhill Watermelon?

For the giant dahlia 'Penhill Watermelon', install a sturdy stake at the time of planting to avoid damaging the roots later. Secure the stems with soft ties as they grow. Pinch the young shoot back to 20 to 30 cm (8 to 12 in.) to encourage branching. Water deeply at the base when the surface is dry, then allow the excess water to drain. Incorporate mature compost at the start, then use a moderate fertilizer, richer in potassium once the buds have formed. Avoid excess nitrogen, which produces soft stems and too much foliage. Regularly remove faded flowers so that the energy is directed to the next buds until the first frost.

'Penhill Watermelon' giant dahlia: can Penhill Watermelon grow in a large pot?

For the 'Penhill Watermelon' giant dahlia, yes, choose a stable 40–50 L container that is deep, well-draining, and filled with rich but airy potting soil. Plant a single tuber 10 cm (4 in) deep and insert the support before the roots develop. Place the pot in full sun, protected from gusts. Water sparingly before sprouting, then abundantly when the top layer dries, without leaving water in the saucer. Apply moderate liquid fertilizer, richer in potassium once buds appear. Rotate the container weekly, pinch the young shoot, and remove faded flowers to maintain a balanced silhouette and generous blooms.

'Penhill Watermelon' giant dahlia: how to overwinter 'Penhill Watermelon' in Quebec?

For the 'Penhill Watermelon' giant dahlia, after the first frost blackens the foliage, cut back the stems, leaving a short section. Lift the tuber with a garden fork, working far enough away to avoid damaging it. Gently remove excess soil, let the surface dry in a ventilated area, and clearly label it 'Penhill Watermelon'. Store it in a dark, cool, dry, and frost-free place, in a slightly insulating material that limits dehydration without retaining water. Inspect it monthly. Remove only the parts showing active rot and increase ventilation if condensation appears. Wait for the last spring frost and warmed soil before replanting it.

Wildlife and pets

Wildlife & precautions

Reported toxicity

Yes

Supporting wildlife

The very double florets limit access to pollen and nectar. Penhill Watermelon contributes primarily to ornamental value. To feed bees and butterflies, plant salvias, verbenas, echinaceas, or other simple flowers rich in resources nearby. The coral pink to pale mauve contrast remains sharper when the plant receives at least six hours of direct sunlight and regular feeding without excess nitrogen.