Gadenin日本語Get the appTwo ways of flowering
The name comes from the kinds that open in the evening. Their buds unfurl in minutes around dusk, often fast enough to watch, release a sweet scent for night-flying moths, and wither by the following midday. O. tetraptera opens white and fades to pink by morning, so a plant carries both colors at once.
Other members of the genus flower by day. Showy evening primrose (O. speciosa) opens pale pink cups in the morning, sundrops (O. perennis) carry small yellow flowers in daylight, and O. rosea has little rose-pink blooms. Whatever the kind, look into the center of a flower and you will see the family mark of the genus: a stigma split into four lobes in the shape of a cross.
| Kind | Opens | Color | Height | Habit |
|---|---|---|---|---|
| O. tetraptera | Evening | White fading to pink | 6-12 in (15-30 cm) | Low, loose |
| O. stricta | Evening | Yellow, aging reddish | 1-3 ft (30-90 cm) | Upright, may need staking |
| O. glazioviana | Evening | Large pale yellow | 3-5 ft (90-150 cm) | Tall; dies after seeding |
| O. acaulis | Evening | White aging pink, or yellow | About 4 in (10 cm) | Stemless rosette |
| O. caespitosa | Evening | White aging pink | About 4 in (10 cm) | Tufted, alpine |
| O. speciosa (showy) | Day | Pale pink to white | 12-16 in (30-40 cm) | Spreading, divisible |
| O. rosea | Day | Rose pink, small | 4-16 in (10-40 cm) | Bushy |
| O. perennis (sundrops) | Day | Yellow, small | About 6 in (15 cm) | Compact clump |
| O. macrocarpa (Missouri) | Evening, lasting into the day | Large lemon yellow | About 8 in (20 cm) | Trailing |
When they bloom
Most evening primroses flower from late spring through summer, with a steady supply of new flowers rather than one big flush. Each bloom lasts a single night or day, but a healthy plant opens new ones for weeks. Missouri evening primrose and showy evening primrose are especially long-flowering in a hot, sunny spot.
Seed-raised plants of most kinds flower in their second year. The large-flowered O. glazioviana behaves as a biennial or short-lived perennial: it makes a rosette, flowers heavily on tall spikes, sets seed and dies, leaving seedlings to carry on.
Why an evening primrose does not flower
Too little sun is the most common reason. A plant in partial shade makes leaves and lanky stems but very few buds. The second is rich soil or too much fertilizer, which produces lush foliage at the expense of flowers. The third is simply age: a first-year seedling of a biennial kind is still building its rosette and taproot.
If a plant is in full sun, in lean soil, and in its second year or later but still sparse, check for flea beetles stripping the young shoots, and make sure the crown is not sitting wet.
- Give it more sun Move pots to the brightest spot you have. For plants in the ground, sow or divide into a sunnier bed rather than lifting an established taprooted plant.
- Stop feeding Stop fertilizing plants in the ground entirely and cut container feeding back to one light spring dose.
- Deadhead the day bloomers Pinch off faded flowers and developing seed pods on showy evening primrose and sundrops to keep new buds coming, but leave some pods on the kinds you want to save seed from.