Zantedeschia 'Millenium Gold' is a spotted calla lily with bright yellow trumpet-shaped flowers with green bases.
Zantedeschia 'Summer Fun' has bright yellow trumpet-shaped flowers with green bases and bright green leaves with white spots.
Zanthoxylum piperitum, the Japanese pepper, is an aromatic, spiny shrub with small, yellowish green flowers and scarlet fruits used in Japanese and Korean cooking.
Zanthoxylum simulans, the Sichuan pepper, produces brownish red fruits that are used in Sichuan cuisine having a spicy, numbing effect.
Zephyranthes citrina or citron zephyr or rain lily is an amaryllis relative with beautiful deep yellow flowers.
Zingiber mioga is the culinary myoga shade ginger from Japan with edible young shoots and yellow flowers.
Zingiber mioga 'Dancing Crane' is a variegated form of this culinary ginger from Japan.
Zingiber mioga 'Silver Arrow' is a rare variegated selection of the hardy, edible Japanese ginger.
Zingiber mioga 'White Arrow' is a hardy edible ginger with tropical foliage margined and feathered with white.
Zinnia grandiflora 'Gold on Blue' is hardy to zone 4 with fine, textured, bluish-green foliage topped with golden yellow flowers all summer.