Gadenin日本語Get the appWait for warm soil, then sow shallow
Four o'clock seed will not do anything useful in cold ground. It wants soil above 65F (18C) and germinates best between 70 and 80F (21 to 27C), at which point it comes up in seven to fourteen days. Sown into cold spring soil it sits, absorbs water, and rots. Wait until after the last frost and until the soil has actually warmed, which is usually a week or two later than the frost date suggests.
Sow half an inch to one inch (1 to 2.5 cm) deep. The seed is large enough to handle individually, so place it rather than scattering it, and firm the soil over it. Keep the bed evenly damp until the seedlings appear; after that, an established seedling needs far less water than most people give it.
To gain a few weeks, start indoors four to six weeks before the last frost in individual pots at least three inches (8 cm) across. Four o'clocks make a taproot and a young tuber very early and resent being disturbed once they do, so avoid trays and avoid transplanting twice. Harden off over a week and plant out only once night temperatures are reliably above 50F (10C).
| Factor | Target | Notes |
|---|---|---|
| Soil temperature | 65F (18C) minimum, 70 to 80F (21 to 27C) ideal | The single biggest cause of failure is sowing too early |
| Sowing depth | Half an inch to one inch (1 to 2.5 cm) | Place seeds individually; they are large enough to handle |
| Pre-treatment | Soak 12 to 24 hours, or nick the coat | Cuts germination time by several days and evens it out |
| Days to emerge | 7 to 14 in warm soil | Three weeks or more means the soil is too cold |
| Final spacing | 24 to 36 inches (60 to 90 cm) | Thin early; the plant reaches its full width by mid summer |
| First flowers | About 8 to 10 weeks after germination | Later in a cool summer or in part shade |
Soaking or nicking the hard coat
The seed has a thick, hard black coat, and untreated seed germinates unevenly over two or three weeks. Soaking in water at room temperature for 12 to 24 hours before sowing softens it and typically brings the whole batch up together in a week. Sow immediately after soaking; soaked seed left on a saucer for a day is spoiled seed.
Nicking works even better and is easy on a seed this size. Rub one side against a nail file or fine sandpaper, or take the tiniest chip off the coat with a knife, on the side away from the pale scar where it was attached. You want to break the coat, not cut into the white tissue inside. Nicked seed can be sown dry or soaked for a few hours first.
Do not treat the whole packet if you are unsure of your technique. Nick half and sow the rest untreated alongside it; the comparison after ten days tells you exactly what your handling is worth and costs nothing, since you have far more seed than you need.
Thinning, and what to do with volunteers
Sow two or three seeds per station, 24 to 36 inches (60 to 90 cm) apart, and thin to the strongest one as soon as the seedlings have their first pair of true leaves. Thinning feels absurd at that stage because the seedlings are three inches (8 cm) tall and the gaps look enormous. Do it anyway. That gap is filled by mid summer, and a plant left crowded flowers less and sprawls into everything around it.
Thin by snipping the unwanted seedlings off at soil level rather than pulling them, so you do not disturb the taproot of the one you are keeping. Seedlings more than a few inches tall do not transplant well for the same reason, so if you want plants elsewhere, sow there rather than moving them.
Where the plant has grown before, you will get self-sown seedlings in spring without doing anything, sometimes in dozens. They are easy to recognize: two fat oval seed leaves on a thick stem, coming up in a dense patch directly under where the parent stood. Keep one or two, hoe the rest off while they are small, and remember that every seed you failed to strip last summer is in that patch. If you want a colony, this is free planting; if you do not, this is the year to start stripping seed weekly.
- Test the soil before sowing Push a soil thermometer two inches (5 cm) down in the middle of the afternoon for three days running. If it is not reading 65F (18C) or above, wait. Nothing is gained by sowing into cold soil and seed is often lost to rot.
- Soak or nick the seed Soak for 12 to 24 hours in room temperature water, or rub one side on fine sandpaper until the black coat is just broken. Sow straight afterward. Wear gloves and keep the seed away from children; it is poisonous if eaten.
- Sow at stations, not in rows Place two or three seeds together every 24 to 36 inches (60 to 90 cm), half an inch to one inch (1 to 2.5 cm) deep, and firm the soil. Keep evenly damp until emergence, then water deeply and less often.
- Thin at the first true leaves Snip all but the strongest seedling at each station off at soil level. Do this within a week or two of emergence, while the roots have not yet tangled and while the plant still looks far too small to need the space.
What to write down
Record the soil temperature on the day you sowed and how many days the seed took to emerge. After two seasons that pair of numbers will tell you the earliest date your own garden can carry a sowing, which is worth much more than a general frost-date rule.
Note whether each batch was soaked, nicked or sown dry, and what proportion came up. Note where each station was and how wide the resulting plant got, and mark the spots where self-sown seedlings appeared the following spring, since those positions are where the colony will keep coming back whether you sow there again or not.