Gadenin日本語Get the appThe shape of the year
Garden balsam is a frost tender annual that goes from seed to flower in eight to ten weeks and dies in a single night at the first frost. Both ends of the season are hard limits, and everything in between is fast. That speed is the reason it can be sown straight into the ground rather than started under cover, and it is why there is no advantage in sowing very early.
The season starts when the soil is reliably above 60F (16C), which is usually two to three weeks after the last frost rather than on it. Germination takes eight to fifteen days in warm ground. Flowering begins about eight to ten weeks after sowing and continues without a break until the frost, with a pause in the hottest weeks of high summer and a strong return as the nights cool.
The two jobs that are particular to this plant both fall in the flowering period: stripping the lower leaves so the flowers can be seen, and dealing with the seed pods. Neither can be done in a single visit. Both are weekly habits from midsummer to the end.
| Stage | Timing | Main jobs |
|---|---|---|
| Soil warming | Two to three weeks after the last frost | Fork in compost, rake fine, wait for 60F (16C) soil |
| Direct sowing | Once the soil is above 60F (16C) | Sow a quarter inch (5 mm) deep, water gently, protect from slugs |
| Germination | Eight to fifteen days after sowing | Keep the surface damp; never let it crust dry |
| Thinning | At the second true leaf | Thin to 10 to 14 inches (25 to 35 cm); transplant the spares |
| Early growth | Three to six weeks after sowing | Steady water; pinch the tip now if you want a branched plant |
| Staking | At 18 inches (45 cm) | One cane per plant, tied in two places |
| First flowers | Eight to ten weeks after sowing | Start stripping the leaves that hide the blooms |
| High summer | Above 90F (32C) | Daily water, midday shade; expect flowering to pause |
| Late summer | Nights cooling | Best flush of the year; remove pods weekly or let seed fall |
| First frost | Overnight | Plants blacken; clear the debris and note where seed fell |
Spring: waiting for warm soil
The main spring job is not sowing but waiting. Balsam seed sitting in cold ground rots rather than germinating, and seedlings that come up into cold nights sit still for weeks. Push a finger into the bed in the morning: if it feels cold rather than merely cool, it is too early. A soil thermometer reading 60F (16C) at two inches (5 cm) deep is the reliable version of the same test.
Prepare the ground while you wait. Garden balsam wants moisture retentive soil in shade or half shade, so fork in a good quantity of well rotted compost and rake the surface fine, because the seed is small and needs contact with crumbly soil rather than clods. Do not add fresh manure or a heavy general fertilizer; rich ground gives you a large leafy plant with the flowers even more thoroughly hidden than usual.
If you want a head start of a few weeks, sow in pots indoors four to six weeks before you would sow outside and plant out after the soil warms. It is worth doing only in a short season, because direct sown plants generally overtake pot raised ones within a month and never suffer a transplant check.
Summer: growing on and showing the flowers
Once the seedlings are through, thin at the second true leaf to 10 to 14 inches (25 to 35 cm) apart, transplanting the spares rather than throwing them away. Decide about pinching now: a tip taken out at six inches (15 cm) gives a branched plant of moderate height, while leaving it alone gives one tall spire with a long flowering column. Stake the tall ones at 18 inches (45 cm), before they need it.
The first flowers open in the lower leaf axils eight to ten weeks after sowing, and you will not see them unless you look. From that day, stripping the leaves that cover the blooms becomes the weekly job, working up the stem as flowering climbs it and leaving the top crown of foliage in place. This is the difference between a green column and a flowering one.
Water is the other constant. Balsam collapses flat when the soil dries and recovers within hours, but each collapse costs the buds it was carrying, leaving permanent gaps in the flowering column. A good soak every second day in the ground, daily in containers, and two inches (5 cm) of mulch keeps it steady. Feed at half strength every two to three weeks at most, and not at all in rich ground.
Write down the date you sowed and the date the first flower opened. Eight to ten weeks is the usual gap, and knowing your own figure lets you time a second sowing precisely, or work backwards from when you want the display at its best.
Late summer to frost: pods, seed and the end
As the nights cool, flowering picks up again after the high summer pause and this is usually the best display of the year. It is also when the pods arrive in quantity, roughly a fortnight behind each flower. Decide what you want: pick pods off weekly and the plant flowers harder and for longer, or leave them and accept both a shorter flowering season and a stand of seedlings next spring.
If you want to save seed, work on pods that are firm but have begun to pale, cupping a hand around each one before you pinch, because a fully ripe pod fires at a touch and throws its seed six to ten feet. Slipping a paper bag over a whole flowering stem and leaving it a week collects a large quantity with no effort at all.
The first frost ends everything overnight. The plants go from full flower to collapsed black stems with no warning and nothing to salvage, so anything you wanted, whether seed or a photograph, has to be taken beforehand. Clear the dead material promptly rather than leaving it over winter, bagging anything that showed downy mildew instead of composting it, and note on a sketch of the bed where you let seed fall so you recognize the seedlings in spring.
The date of your first frost, and the date the last flower opened before it, are the two most useful figures to carry into next season. They tell you how much of the autumn flush you are actually getting, and whether a sowing a fortnight earlier would buy you more of it.