Gadenin日本語Get the appSow direct, and sow late
This is an annual that goes from seed to first flower in eight to ten weeks, which is fast enough that there is no real advantage in starting it indoors. Sown straight into the ground once the soil is warm, it germinates in eight to fifteen days, grows away without any transplant check, and generally overtakes pot raised plants of the same age within a month. Direct sowing also suits its shallow, brittle root system, which resents disturbance once the plant is past the seedling stage.
The condition to wait for is soil temperature rather than a date on a calendar. Balsam seed wants 65F to 70F (18C to 21C) to germinate quickly and will do it, more slowly, down to about 60F (16C). Below that it sits in cold damp ground and rots. In practice that means sowing two to three weeks after the last frost rather than on it, when the surface of the bed feels warm to a hand laid flat on it in the morning rather than cold.
Where the season is genuinely short, sow indoors four to six weeks before you would sow outdoors, in individual pots rather than a tray so the roots are not torn apart at planting time, and set the plants out only once the ground has warmed. Even then, sow a few seeds direct at the same time as a comparison. Most gardeners who try both stop bothering with the pots.
| Item | Detail |
|---|---|
| Soil temperature | 60F (16C) minimum, 65F to 70F (18C to 21C) ideal |
| Timing | Two to three weeks after the last frost |
| Depth | A quarter inch (5 mm), barely covered |
| Spacing at sowing | Stations of two or three seeds, 10 inches (25 cm) apart |
| Final spacing | 10 to 14 inches (25 to 35 cm) for tall types |
| Germination | Eight to fifteen days in warm soil |
| Thin at | The second true leaf |
| First flower | Eight to ten weeks after sowing |
Preparing the bed and getting the depth right
Choose a spot in shade or half shade with soil that holds moisture, ideally where the plants get gentle morning light and shade through the afternoon. Fork in a generous quantity of well rotted compost, which is about moisture retention rather than feeding, and rake the surface to a fine crumb. Do not add fresh manure or a heavy general fertilizer; rich ground produces a huge leafy plant that flowers poorly and hides what flowers it has.
Sow a quarter inch (5 mm) deep, which in practice means scattering the seed on a raked surface and sifting the barest covering of fine soil over it. The seed benefits from some light, so burying it half an inch or more is a common way to get patchy germination. Firm the surface gently with the back of a rake to bring the soil into contact with the seed, then water with a fine rose so as not to wash it out of position.
Sow in stations of two or three seeds about 10 inches (25 cm) apart rather than in a continuous drill. It uses less seed, makes thinning simpler, and leaves the eventual plants where you actually want them. Mark the row, because balsam seedlings look much like a number of common weeds when they first come up and are easy to hoe off by mistake.
- Test the soil before you open the packet Lay a hand flat on the bed in the morning. If it feels cold rather than cool, wait another week. Two inches (5 cm) down should read 60F (16C) or better on a soil thermometer.
- Prepare a fine, damp surface Fork compost through the top six inches (15 cm), rake to a fine crumb, and water the bed the day before sowing so the seed goes into moist ground rather than onto dust.
- Sow shallow and firm gently Two or three seeds per station, barely covered with sifted soil, firmed with the back of a rake and watered in with a fine rose. Label the row.
- Keep the surface damp until emergence A light watering every day or two in dry weather. A seedbed that dries and crusts over will kill the germinating seed underneath it, and this is the commonest reason for a failed sowing.
Emergence, slugs and thinning
Expect the first seedlings in eight to fifteen days in warm soil, longer and more raggedly if the ground is cooler. They come up with two rounded seed leaves and grow quickly from there. The critical period is the fortnight either side of emergence: the surface of the seedbed must not be allowed to dry and crust. That does not mean soaking it, but a light watering every day or two in dry weather, ideally in the morning.
Slugs and snails will take out an entire row of balsam seedlings in a single damp night, and they favor exactly the shaded, moist positions the plant wants. Put protection down from the day you sow rather than waiting for the first damage; by the time you have seen it there may be nothing left to protect. Young plants become far less vulnerable once they are past about four inches (10 cm).
Thin at the second true leaf to one plant per station, and go further than feels comfortable, to 10 to 14 inches (25 to 35 cm) between the tall single stemmed types. Crowded plants stretch, flower less, and hold damp still air among themselves, which is how mildew gets going in a bed. Lift the spares with a spoon and as much soil as you can rather than pulling them, and they transplant successfully at that size; water them daily for a week afterwards.
If you want to pinch the tip out for a branched, shorter plant, do it at about six inches (15 cm) tall. Left alone, the plant makes a single upright spire with a long flowering column on the main stem, which is the classic effect and needs a cane. Decide for the whole batch at the same time so the planting looks deliberate.
Saved seed, self sown seedlings and keeping notes
Seed collected from your own plants germinates well and stays viable for several years, though the first two are the most reliable. Store it dry, cool and in paper rather than plastic. Sow it exactly as you would bought seed, and expect variability if it came from double flowered parents, which throw a mixture of doubles and singles in a spread of colors.
You may not need to sow at all after the first year. Ripe pods fire their seed several yards, and a patch left to itself produces a mass of seedlings in late spring once the soil warms, at almost exactly the moment you would have sown. Thin those to spacing and transplant the spares and you have a full stand for no work. If you would rather not have them, remove the pods weekly from midsummer, well before any of them ripen.
Record the sowing date, the soil temperature on that day, and the date the seedlings emerged. After two seasons those figures tell you the earliest date that actually works in your own garden, which is invariably later than the general advice and always earlier than the date you eventually settled on out of caution.