Gadenin日本語Get the appSow a quarter inch deep and no more
Marigold seed is a long black sliver with a pale feathery tuft at one end, big enough to place individually with your fingers. Push each one a quarter inch (6 mm) into the compost and firm the surface. Deeper than half an inch (12 mm) and a fair share of the seedlings exhaust themselves before they reach the light, which is the usual reason a tray comes up patchy when the seed itself was fine.
Lay the seed flat rather than standing it on end. It does not matter which way the tuft points, because the root turns down on its own, but a seed left half proud of the surface dries out on the first warm afternoon and dies without you ever knowing it germinated.
The seed carries no dormancy and stays viable for two to three years in a cool dry drawer, so a packet from last season is worth sowing thickly rather than throwing away. Germination drops off gradually rather than falling off a cliff.
- Fill and firm before sowing Level the compost and press it down with a flat board until it sits about half an inch below the rim. Sowing into loose fluffy compost lets the seed sink further than you intended when you water.
- Space the seed as you sow Two inches (5 cm) apart in a tray, or two or three seeds to a three inch (7.5 cm) pot. The seed is large enough to place one at a time, so there is no excuse for a crowded tray that has to be untangled later.
- Water from below the first time Stand the tray in an inch of water until the surface darkens, then take it out. A hard watering from above buries the seed deeper and washes it into the corners.
Wait for 65F soil rather than a calendar date
Marigolds are frost tender annuals from Mexico and Central America and will not tolerate a touch of frost at any stage. Seed sits and sulks below 60F (15C) and often rots in cold wet compost. At 70 to 75F (21 to 24C) you see the loops of the seedlings within four to seven days.
Indoors, sow about six weeks before your last expected frost. That is early enough to have plants in bud when the weather turns and late enough that they do not become drawn and leggy on a windowsill. Direct sowing outside works well once the soil holds above 65F (18C), and a direct sown plant catches up with a transplant within a month because it never checks.
| Stage | Soil or air temperature | What to do |
|---|---|---|
| Six weeks before last frost | Indoors at 70F (21C) | Sow in trays or pots on a warm sill |
| Two weeks before last frost | Nights still near freezing | Pot up and start hardening off in a sheltered spot |
| After the last frost | Soil above 65F (18C) | Plant out, or direct sow where they are to flower |
| Early summer | Soil above 70F (21C) | Sow a second batch for late flowers |
| Late summer | Warm but shortening days | Too late to sow, take cuttings instead |
In a warm summer climate you can direct sow straight into the bed and skip trays entirely. Marigolds are one of the few bedding plants where that costs you almost nothing in flowering time.
The two types need different spacing
The seed you sow falls into two broad groups and they want very different room. The French type stays small and bushy, six to twelve inches (15 to 30 cm) high, with many small single or double flowers and finely cut foliage. The African type, sometimes sold as American, runs to two or three feet (60 to 90 cm) with big heavy pompon heads on thick hollow stems.
There is also a fine leaved signet group with small single flowers and lemon scented foliage that makes low mounds around eight inches (20 cm) high. Read the height on the packet before you space the tray out, because an African type crammed in at French type spacing ends up as a thicket of leaf with the flowers buried inside it.
| Type | Height | Habit and flower | Spacing |
|---|---|---|---|
| French | 6 to 12 in (15 to 30 cm) | Bushy, many small heads, fine foliage | 8 in (20 cm) |
| African | 24 to 36 in (60 to 90 cm) | Upright, few very large pompon heads | 12 to 18 in (30 to 45 cm) |
| Signet | 8 to 12 in (20 to 30 cm) | Low mound, small single flowers, citrus scented leaves | 8 to 10 in (20 to 25 cm) |
Thin early, and thin properly
Marigold seedlings put on bulk fast, and a tray left unthinned goes from healthy to drawn and pale in about ten days. Thin to one plant per station as soon as the first pair of true leaves opens, which is usually two weeks after germination. Waiting until they touch means every plant has already stretched, and a stretched marigold stem never thickens up properly.
Snip the surplus off at soil level with scissors instead of pulling. Marigold roots knit together quickly and pulling one seedling lifts the neighbor with it. If you want to keep the thinnings, prick them out at the seed leaf stage instead, when the root is still a single unbranched thread.
- Thin at the first true leaves Keep the shortest, stockiest seedling rather than the tallest. Height at this stage means it was reaching for light, not that it is vigorous, and it will flop first.
- Pot up before roots circle Move a tray sown seedling into a three inch (7.5 cm) pot when it has three or four true leaves. Left in a plug it goes hard and blue green, and a checked marigold flowers late and small.
- Bury the stem when you pot on Marigolds root readily from the buried stem, so a leggy seedling can be sunk up to its lowest leaves. This is the only clean fix for a batch that stretched on a dark windowsill.
Write down the sowing date and the date you first see seedlings. Two seasons of that record tells you exactly how early you can start on your own sill without producing drawn plants, which no packet can tell you.