Saving Calendula Seed and Managing the Self-Sown Plants

Let the heads ripen on the plant, then take the whole ring

Saving calendula seed is about as easy as seed saving gets. Choose two or three good plants at the height of flowering and simply stop deadheading them, leaving the rest of the row to be picked as usual. On the chosen plants the petals drop, the central disc swells, and within two to three weeks it has become a ring of curved gray hooks sitting in a papery cup. The whole ring comes away in one piece when you pinch the head off.

Wait for the seeds to go hard and gray to brown before you take them. A ring that is still green and soft will shrivel indoors instead of ripening. Unlike many annuals the head does not shatter and scatter the instant it is ripe, so there is a comfortable window of a week or two to collect, though after that the ring falls apart and the seeds drop straight down.

1. Mark the plants you are saving from Tie a length of string round two or three good plants at full flower and stop deadheading only those. Keep picking from the rest of the row.
2. Wait for hard gray seed The ring should be dry and brittle and the individual hooks hard between finger and thumb. Green soft seed shrivels and never germinates.
3. Pinch off the whole head Take the entire ripe head into a paper bag rather than picking individual seeds out. Rub it apart later when it is dry.
4. Dry a week before storing Spread the heads one layer deep on paper somewhere dry and airy for a week, then rub and store in a labeled envelope. Bagged straight from the garden it goes moldy.

Calendula seed stores far better than most annual seed. Kept cool, dark and dry it germinates well for three to four years, so one good collection covers several seasons.

What comes true, and what does not

Calendula is insect pollinated and crosses freely with any other calendula flowering nearby, so saved seed comes true only as far as your garden is uniform. Plain single orange and single yellow types breed close to true and reproduce reliably from saved seed. Doubles, and the unusual colors with dark centers or pale apricot tones, split in the next generation and drift back towards plain orange singles over a few years.

That drift is not a failure, and single flowers are better for bees and just as good for drying, but it is worth knowing before you assume a saved packet will look like the parent. If you want a particular form to hold, save from a block of only that form with no other calendula flowering within a hundred feet (30 m), and rogue out anything off type before it opens. What is always worth selecting is not color: save from the plants that stayed compact, mildewed last and flowered longest, and mark them while they are flowering because at seed time every plant looks equally tired.

Volunteers are welcome, and they beat your sowings

Calendula self seeds generously, and this is a feature rather than a nuisance. Seed shed in autumn overwinters in the soil and germinates as soon as the ground warms, often weeks before you could get out to sow, and those volunteers grow into bigger and better branched plants than the ones you sow deliberately in spring. In many gardens the self sown plants become the main crop and the packet is only used to start a patch in a new bed.

The seedlings are easy to recognize, with long narrow pale seed leaves and slightly sticky, faintly aromatic true leaves, and they are easy to move at three or four leaves. That combination is what makes calendula volunteers manageable in a way that most self seeders are not. Go through in spring, keep the strongest at twelve inch (30 cm) spacing, move a few to fill gaps elsewhere, and hoe off the rest.

1. Decide the boundary before it seeds In late summer choose where volunteers are allowed. Keep deadheading everything outside that area so it never sheds.
2. Do one thinning pass in spring When the volunteers have three or four leaves, thin to twelve inches (30 cm) and pull the rest. A dense self sown mat stretches and mildews by midsummer.
3. Move the surplus rather than binning it Lift with a trowel and a lump of soil at three or four leaves and water in at once. They take readily and fill gaps in other beds.
4. Hoe rather than dig to reduce them Digging buries fresh seed and lifts older seed into germinating conditions. Surface hoeing exhausts the seed bank faster.

In a mild climate autumn shed seed germinates the same autumn and overwinters as flat rosettes. Those plants flower earliest of all in spring, so leave them where they are rather than tidying them off in autumn.

Raising plants in modules, and why cuttings are pointless

Where slugs make direct sowing hopeless, calendula raises perfectly well in modules, which sets it apart from taprooted annuals. Sow one seed per cell half an inch (1.5 cm) deep, keep it at around 60F (15C), and plant out at four to six true leaves before the roots circle the cell. Plants held too long in a small cell flower prematurely on a stunted frame and never build a proper branched plant.

Cuttings are not worth attempting. Calendula stems are soft, hollow at the base and rot before rooting, and there is no crown to divide on an annual. Since the seed germinates in under a week in warm soil, keeps for three or four years and drops itself around the garden for free, seed is the only method anyone needs.

Label the seed and map where it fell

Put the year on every envelope. Calendula seed keeps three or four years, which is long enough for undated batches to accumulate and for you to lose track of which is which. Add the parent plant's position and one word for why you chose it, such as compact or late mildew, so the selection you made in summer actually reaches next spring's sowing rather than being forgotten over winter.

Keep a sketch of the bed with each plant marked and the area you allowed to self seed shaded in. Next spring that sketch tells you at a glance which seedlings are volunteers to thin and keep, which are strays to hoe off, and where there is bare ground waiting for a fresh sowing. Note the germination of any batch more than three years old before you rely on it, so you know whether to sow thicker or start again.