Days to Germination
7–14 days
Alpha is a high-resin selection of Calendula officinalis, the traditional pot marigold, bred specifically for the medicinal flower trade. While ordinary calendula strains have been used in folk medicine for centuries, Alpha was selected for higher concentration of the sticky resins found in the green sepals at the back of each flower — the part herbalists actually want for salves, infused oils, and balms. Pinch a flower head and your fingers come back tacky, the way they should.
The flower itself is a single-form bright orange to gold, about 2 inches across, on a bushy plant that produces dozens of blooms across a long season. Like all calendulas it is annual, frost-tolerant on both ends of the season, and self-seeds reliably if you let a few flowers go to seed. Bees, hoverflies, and beneficial wasps work the flowers heavily — making it a useful insectary plant near vegetable gardens.
For your zone: direct seed around mid-April, or start indoors early April for earlier bloom.
Calendula is one of the easiest seeds to direct sow. The seeds are large, curved, and almost crescent-shaped — easy to handle and place individually. Sow ¼ to ½ inch deep in well-prepared soil. Light is not required for germination; cover lightly. Germination is fastest at 65–70°F soil temperature but will occur as low as 50°F, which is why calendula can be sown well before last frost in most zones.
Indoor starting is optional but gives you 2–3 weeks of earlier bloom. Start in 3–4 inch pots 4–6 weeks before your intended transplant date. Use cool-grown conditions (60–65°F) to produce stocky transplants — warm conditions produce leggy plants that flop when set out.
Calendula is frost-tolerant down to about 25°F once established, so hardening off can be brief — 4–5 days outside in graduated sun exposure is plenty. Skip hardening entirely if you're transplanting in cool, overcast weather (which is when calendula prefers to start anyway).
Set transplants out 2–3 weeks before your last frost, once the ground can be worked.
Plant 9–12 inches apart in rows 18 inches apart. Closer spacing produces taller, more upright plants that compete; wider spacing produces bushier plants with more flower stems. For cut flower or medicinal harvest, closer spacing maximizes yield per square foot. For a casual garden border, give them more room.
Calendula tolerates a wide range of soils but performs best in well-drained ground of moderate fertility. Heavy nitrogen produces lush leaves at the expense of flowers and reduces resin concentration. A light top-dressing of compost at transplant time is sufficient feeding for the entire season.
Water. Calendula is drought-tolerant once established but blooms best with consistent moderate moisture. Aim for about 1 inch per week. Avoid overhead watering during bloom — water on the open flowers reduces resin yield and can spread fungal issues.
Deadheading. Critical for sustained bloom. Pick or cut spent flowers at least once a week. Plants that are allowed to set seed will shift energy away from flower production within a couple of weeks. The flowers you remove are themselves the harvest — see below.
Heat dormancy. In zones 8 and warmer, calendula slows or stops blooming during the hottest weeks of summer. Don't pull plants — cut them back by half and they'll resume vigorous bloom when temperatures fall in early autumn.
Self-seeding. Leave 4–6 flowers to fully mature at the end of the season. The dropped seed germinates the following spring without your help. In a few years you'll have a permanent patch you never have to plant again.
Harvest fully open flowers on dry mornings, after the dew has lifted. Pinch or snip just below the green calyx. Avoid wet flowers — they mold during drying.
For fresh use in salads or garnish, harvest as needed. The petals have a mild, slightly bitter floral taste and pull off the calyx cleanly. For medicinal use, dry the entire flower head (calyx included — that's where the resin lives) on a screen or in a paper bag in a dark, warm, well-ventilated place for 5–7 days, until the calyx is brittle to the touch. Store dried flowers in glass jars away from light. Properly dried they retain potency for 12–18 months.
A single Alpha plant typically yields 30–50 harvestable flower heads across a season with consistent deadheading. For a year's supply of infused oil, plan on 8–12 plants per person.
Alpha is open-pollinated and saved seed will grow true. Let a handful of late-season flowers fully dry on the plant — the petals shrivel back and the curved seeds form in a small green crown that turns brown. Pop the seed heads off into a paper bag once they rattle, store cool and dry, and use within 3–4 years for best germination.