Getting it to bloom

Why won't my Dahlia 'Penhill Watermelon' bloom? (and how to make it flower)

Also called Penhill Watermelon dahlia, giant decorative dahlia (Dahlia 'Penhill Watermelon').

More about dahlia 'penhill watermelon'

About Dahlia 'Penhill Watermelon'

Dahlia 'Penhill Watermelon' · also called Penhill Watermelon dahlia, giant decorative dahlia · flowering

'Penhill Watermelon' is a giant decorative dahlia with enormous, twisted, recurved petals in soft watermelon-pink fading to cream. Tuberous and frost-tender, it produces colossal blooms from late summer to frost on tall stems that demand firm staking. Grow in full sun and rich, moisture-retentive, free-draining soil; lift the tubers where winters freeze.

Plant type: flowering

Watch for — Stems snapping under bloom weight: The giant heads break unsupported stems in wind. Stake heavily at planting with a robust cane or grid and tie in stems frequently as they elongate.

The reasons dahlia 'penhill watermelon' isn't blooming

Almost every non-blooming dahlia 'penhill watermelon' traces back to one of these, roughly in order of how common they are:

Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.
Too much nitrogen feed, driving lush foliage at the expense of flowers (very common with general or lawn feeds).
The plant has not been deadheaded, so it stops flowering once it sets seed.
Irregular watering — drought or waterlogging at the budding stage makes buds abort.
It is still too young or was checked by a transplant and is rebuilding before flowering.

Feeding dahlia 'penhill watermelon' a high-nitrogen general feed and growing it in too little sun — you get a big leafy plant and almost no flowers.

The fix — how to get dahlia 'penhill watermelon' to flower

Maximise sun. Give dahlia 'penhill watermelon' the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers.
Switch the feed. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.
Deadhead regularly. Remove spent flowers often to keep it producing more rather than stopping to set seed.
Water consistently. Keep moisture even through budding and flowering — drought-then-flood swings make buds drop.

Light and feeding do most of the heavy lifting here. Dial in the spot with the light guide for dahlia 'penhill watermelon' and get the feeding right with the dahlia 'penhill watermelon' fertilising schedule — the wrong feed (too much nitrogen) is one of the most common silent reasons a healthy plant makes leaves instead of flowers.

Bloom season and what to expect

Dahlia 'Penhill Watermelon' flowers across its growing season (mostly summer) and, kept fed and deadheaded, can bloom for many weeks or right up to frost.

Post-bloom care so it flowers again

Deadhead, keep feeding lightly, and many will rebloom; collect seed from the best plants at the end of the season if you want to grow them again.

For everything else this plant needs day to day, see the full dahlia 'penhill watermelon' care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Dahlia 'Penhill Watermelon' blooming — frequently asked questions

Why won't my dahlia 'penhill watermelon' flower?

Dahlia 'Penhill Watermelon' blooms on the season's growth given enough sun, warmth and the right feed — there is no cold or photoperiod trick, just good growing conditions and a bloom-leaning feed. The most common reason it is not happening: Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.

How do I make dahlia 'penhill watermelon' bloom?

Give dahlia 'penhill watermelon' the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.

When does dahlia 'penhill watermelon' normally bloom?