Zinnia elegans Seeds | Purple Prince Zinnia
LATIN NAME: Zinnia elegans
COMMON NAME: Purple Prince Zinnia
Plant Profile
Purple Prince is a dahlia-flowered zinnia, with fully double blooms 8-10 cm across in a deep violet-purple that is unusual in the genus. Plants reach 75-90 cm, with stiff stems and opposite, rough-textured leaves, and they flower from July until the first frost.
The colour is the reason to grow it: most zinnias sit in the red, orange and pink range, and a true purple is rare enough to be worth a row of its own. The flowers hold their colour as they age rather than fading to pink, which is not true of every purple strain.
Zinnia elegans comes from Mexico, where it grows in scrub and on hillsides, and it was taken to Europe in the eighteenth century. The dahlia-flowered class was developed in the twentieth century for cut flowers, with tight centres and multiple rows of petals.
Science & Biotechnology
Zinnia is a model for the study of flower form: the difference between a single daisy and a fully double dahlia-flowered bloom is a change in the identity of the disc florets, which develop as petals instead of tiny fertile flowers. That change is controlled by a small number of genes now used in ornamental breeding.
Purple in zinnias comes from delphinidin-based anthocyanins, and the pathway that produces them is the same one that gives delphiniums and pansies their blue. True blue is rare in the genus because the final chemical step is absent, which is why breeders chase purple as the closest available colour.
Zinnias are also among the most susceptible garden plants to powdery mildew, particularly in humid weather and in crowded plantings. Breeding has concentrated on resistance, and the narrow-leaved Zinnia angustifolia has been used as a source of it.
Uses & Benefits
Purple Prince is a cut flower: long stems, a tight centre and a colour that holds in water for a week or more. It also works in a border, where its height and its stiff habit suit the middle of a sunny bed and its purple reads well against lime-green foliage.
The flowers are a steady nectar and pollen source for butterflies late in the season, and they are one of the best annuals for a cutting garden. Commercially the dahlia-flowered zinnias are grown for floristry, particularly in the US, where they are a standard wedding flower.
Growing from Seed
Sow at 21-24°C, 5 mm deep, six to eight weeks before planting out. Germination is fast, five to seven days, and the seedlings are vigorous. Do not overwater, since damping off is the main risk in the first fortnight.
Plant out at 30-40 cm apart in full sun after the last frost. Zinnias resent root disturbance, so handle the root ball carefully. Pinch out the growing tip at the fourth leaf for a bushier plant with more stems. Water at the base rather than overhead, and space plants for airflow to reduce mildew. Harvest stems when the flower is fully open and the stem is firm.
Our Take
A purple that reads as purple, on a plant that produces more cut flowers per square metre than almost anything else.
Related Reading
Gardeners who grow Purple Prince Zinnia often pair it with these related subjects: