Saving Zinnia Seed and Rooting Cuttings for Free Plants

Let the heads dry on the plant

Zinnia seed is only viable if the flower has been left to mature fully, which means going against everything you do the rest of the season. Pick out two or three plants you like early on, mark them, and stop cutting from them. Let the flowers open, fade, and then brown and dry on the stem, which takes four to six weeks from the flower first opening.

The head is ready when the whole thing is brown and papery and the petals pull away with a dry rustle rather than a soft tear. A head that still feels cool and slightly damp in the center is not ready, and seed taken from it will mold in storage. If autumn weather turns wet, cut the whole stem with a foot of stem attached and hang it upside down somewhere dry and airy for a fortnight to finish.

Because you are sacrificing the flowers on those plants, choose ones at the edge of the bed where you will not miss them. One good head yields fifty to a hundred seeds, so two or three heads is more than enough for the following year.

1. Mark your seed plants early Tie a length of colored string on two or three healthy plants when they start flowering, so nobody cuts from them by habit later in the season.
2. Leave the flowers to brown fully Wait until the head is dry, brown and papery all the way through, which is 4 to 6 weeks after opening. Rushing this is the main cause of dud saved seed.
3. Pick the whole head on a dry day Snap or cut the head off in the afternoon when there is no dew on it, and drop it into a paper bag. Never use plastic, which traps moisture and causes mold.
4. Dry indoors for another week Spread the heads on a tray somewhere warm and airy out of direct sun for seven to ten days before you break them apart, even if they feel dry already.

Cleaning the seed takes two minutes a head

Break the dried head apart over a bowl with your fingers and it falls into a heap of chaff and seed. The seed itself is a flat arrowhead, roughly a quarter inch (6 mm) long, pale tan to dark brown with a pointed tip and a broader base. It looks nothing like the round black specks people expect, and beginners often throw the good seed away with the chaff.

Sort by eye rather than by sieving, because the chaff is a similar size. Spread the debris on a pale plate and pick out the arrowheads. The wide flat ones with a visible thickened base are the viable seed. Thin papery slivers with no substance to them are empty and will not germinate.

Store the cleaned seed in a paper envelope, labeled with the year, somewhere cool, dark and dry. Zinnia seed stays reliably viable for three to five years, so a good year gives you several seasons of sowing. A sealed jar with a sachet of silica gel in a cool cupboard extends that further.

Saved seed from a mixture will not come true

Zinnias are insect pollinated and cross freely with anything flowering nearby, and most garden plantings are mixtures to begin with. Seed saved from a bed of mixed colors and forms gives you a jumble the following year, typically with more single flowers and fewer fully double ones than the parents had, because doubling is the trait most readily lost.

This is not a reason to avoid saving seed. A tray of unpredictable zinnias is still a tray of good zinnias, and many gardeners prefer the mongrel result to the packet. But if you are relying on a particular color or flower form for a scheme, buy fresh seed for that and save your own for general filling.

If you want seed that does come closer to true, grow a single form on its own with no other zinnias within a hundred feet (30 m), and save only from plants that show the characteristics you want. Two or three seasons of selecting like that produces a strain that is recognizably yours.

Save from the healthiest plants rather than the prettiest. Selecting each year from whichever plants stayed cleanest of mildew longest genuinely shifts your saved line towards more resistance over a few seasons.

Cuttings root in about two weeks

If you want an exact copy of a particular plant, take cuttings rather than seed. Zinnias root readily from soft growth in warm weather, and a cutting taken in midsummer will be flowering within six weeks. This is also how you rescue a good plant when frost is approaching, though a rooted cutting needs a bright frost free windowsill to get through winter.

Take non flowering side shoots four to six inches (10 to 15 cm) long in the morning while the plant is turgid. Cut just below a leaf joint, strip the lower leaves, and remove any bud. Push them into a pot of damp gritty potting mix, cover loosely with a clear bag or a propagator lid, and keep them out of direct sun.

Roots appear in ten to fourteen days at 70F (21C), signaled by the tips starting to grow again. Pot them individually as soon as they resist a gentle tug, because zinnias hate root disturbance and a delayed cutting tangles with its neighbors. Take twice as many as you need, since some will rot in the humid conditions.

1. Choose a shoot with no bud on it A side shoot 4 to 6 in (10 to 15 cm) long with no flower or bud. A shoot carrying a bud puts its energy there instead of into roots and usually fails.
2. Cut below a leaf joint and strip the base Cut cleanly a fraction below a leaf joint and remove the leaves from the bottom half. Leave two or three leaves at the top, halving them if they are large.
3. Insert into gritty potting mix and cover Push into damp compost mixed roughly half and half with grit or perlite, several to a pot. Cover with a clear bag held clear of the leaves and keep at 70F (21C) out of direct sun.
4. Pot on the moment they root Check for resistance to a light tug at 10 days. As soon as they hold, pot each one separately. Waiting means untangling roots, which a zinnia will not forgive.

Note the date you took each batch of cuttings and how many rooted. Cuttings taken in the warmth of high summer strike far better than ones taken as the nights cool, and your own dates tell you where that cutoff falls in your garden.