Paeonia 'Yellow Dream' offers cheerful lemon yellow semi double flowers with red markings at the centre.

Paeonia 'Yellow Waterlily' has heavily doubled butter yellow flowers stuffed with petals around an orange centre.

Pandanus amaryllifolus, known as pandan or screw pine, is an evergreen tropical with fragrant leaves used in culinary dishes.

Panicum virgatum 'Totem Pole' forms a strongly upright column of steel blue leaves and powder blue stems to 6 feet.

Penstemon pinifolius 'Mersea Yellow' has lemon yellow flowers that will draw every hummingbird from miles around.

This evergreen orchid sports 12" spikes of waxy, fragrant yellow flowers with red markings on the lip in early summer.

Phlomis fruticosa is a bold, architectural perennial or subshrub with felted, grey-green, sage-like leaves and clusters of bright yellow flowers in summer.

Phlomis russeliana is a tall and stately Jerusalem sage with mounds of fuzzy foliage and stems with clusters of buttery yellow flowers.

Phygelius 'Moonraker' is a South African fuchsia-like sub-shrub with soft creamy yellow, tubular flowers all summer long.

Piper nigrum is a beautiful fast-growing woody vine prized as the source of black, white, green, and red peppercorns.

Portulaca molokiniensis has unusual, stacked, emerald green, succulent foliage on stems topped with yellow flowers.

Primula auricula Bavarian Gaudi 'Anna' is an auricula primrose with double yellow flowers and thick, evergreen leaves.

Primula auricula Bavarian Gaudi 'Hanni' is an auricula primrose with single flowers in rings of yellows and red with light evergreen leaves.

Primula auricula Bavarian Gaudi 'Stanzerl' is an auricula primrose in shades of cream, lemon yellow, and burgundy.

Primula Belarina 'Buttercup Yellow' has enormous heads of fragrant spring double flowers in buttery yellow.

Primula 'Yellow Ruffles' has enormous heads of fragrant spring double flowers in yellow.

Primula vulgaris 'Oakleaf Yellow Picotee' is a primrose that has unusually lobed leaves and umbels of bright yellow, orange, and red flowers.

Primula Prima Belarina 'Goldie' offers fully double, ruffled, golden yellow flowers with strong fragrance.