Gadenin日本語Get the appThe seed is smaller than you expect
Open a packet of ice plant seed over a white plate before you do anything else. What comes out looks like brown dust, and a single packet may hold several hundred seeds in a heap the size of a match head. People who have grown tomatoes or beans routinely tip the whole packet into one pot without realizing what they have done, then find two hundred seedlings in a three inch (8 cm) container.
Two consequences follow from the size. First, the seed carries almost no food reserve, so it cannot push a shoot up through soil. It must germinate on the surface. Second, it needs light to germinate at all. Cover it, even with a light dusting of compost, and germination drops sharply or stops. Nearly every complaint that ice plant seed did not come up traces back to burying it.
The third thing to know is that the seed germinates on warmth, not on daylength. It comes from dry, warm, bright places, and at 65 to 75F (18 to 24C) it will show in seven to fourteen days. Below 60F (16C) it is slow and erratic. There is no benefit to sowing early into cold compost; you simply lose the seed.
| Condition | Target | What happens if you get it wrong |
|---|---|---|
| Sowing depth | On the surface, uncovered | Buried seed rarely germinates at all |
| Light | Bright light on the seed | Dark cupboards and covered trays give nothing |
| Temperature | 65 to 75F (18 to 24C) | Below 60F (16C) germination is slow and patchy |
| Surface moisture | Damp, never wet, never dried out | One dry afternoon kills seedlings at the thread stage |
| Days to emerge | Seven to fourteen | Longer means it was too cold, not that seed was dead |
Mix the seed with a pinch of dry fine sand in the palm of your hand before sowing. You can see where the sand lands, so you can see where the seed has gone, and it spreads far more evenly than seed alone.
The mix to sow into
Sow into something lean and gritty rather than rich seed-starting mix. A standard mix cut half and half with coarse sand or fine perlite is right. This plant grows a low, sprawling succulent frame, and it grows it soft and floppy in rich compost. Starting it lean sets the habit early and, more to the point, gives you the firm, well-lit, quick-draining surface the tiny seed needs.
Firm the surface properly before sowing. Press it flat with the base of another pot until it is level and smooth. Dust-fine seed that lands in a crevice ends up half an inch (1 cm) down in shade and is lost. A flat firm surface keeps every seed where light reaches it.
Water the mix from below before you sow, not after. Fill a tray with an inch (2.5 cm) of water, stand the pot in it until the surface darkens, then take it out and let it drain. Watering a sown surface from above washes the seed into corners or straight over the rim.
- Fill and firm Fill the pot or tray with a half-and-half mix of ordinary compost and coarse sand or fine perlite, to a quarter inch (5 mm) below the rim. Press the surface level and firm with a flat base. The surface should be smooth enough that a seed cannot fall into a hole.
- Wet from below first Stand the container in shallow water until the surface goes dark, then lift it out and let it drain for ten minutes. Sowing onto an already damp surface means you never have to water over the top of the seed.
- Scatter the seed thinly Mix the seed with dry sand and sprinkle it over the surface from a few inches up. Aim for seeds roughly half an inch (1 cm) apart. That looks impossibly sparse for a packet this size, and it is still probably too thick.
- Do not cover it Leave the seed sitting on the surface. Press it down very gently with a flat palm so each seed is in contact with damp mix, but put nothing on top of it. Contact matters, covering does not.
- Keep the surface damp with a fine mist Mist the surface once or twice a day, or cover with a clear lid until germination. The surface must never dry out completely at this stage, but it must not be sodden either, or the seedlings damp off within days.
Where and when to sow
Direct sowing works in warm, dry, mild conditions, but it is a gamble. Bare soil dries out in an hour of sun and one dry spell at the thread stage takes out the whole sowing, so most gardeners start in trays or pots and plant out. Sow indoors under bright light or in a greenhouse four to six weeks before you intend to plant out.
Plant out once the last frost is well past and nights hold above 45F (7C). This plant is not frost hardy and cold wet nights rot the crown, but it takes heat, wind and dryness far better than almost any other salad crop. Space plants twelve to sixteen inches (30 to 40 cm) apart, because a single plant sprawls into a mound a foot and a half (45 cm) across by midsummer.
If you want a supply over a long season, sow twice rather than once. The plant is an annual and eventually runs to flower, so a second sowing six to eight weeks after the first keeps young, glittering, tender shoots coming when the first plants have coarsened.
| Stage | Timing | What to do |
|---|---|---|
| First sowing indoors | Four to six weeks before last frost | Surface sow under bright light at 65 to 75F (18 to 24C) |
| Transplanting seedlings | At two true leaves | Move to individual small pots in a lean gritty mix |
| Hardening off | One week before planting out | Increase sun and wind gradually, keep the mix on the dry side |
| Planting out | Nights above 45F (7C) | Twelve to sixteen inches (30 to 40 cm) apart in full sun |
| Second sowing | Six to eight weeks after the first | Keeps young tender shoots coming later in the season |
Transplant with a plant label or a cocktail stick rather than fingers. Seedlings at that size are a millimeter of stem holding two tiny leaves, and finger pressure crushes them.
Thinning, and what to write down
Thinning is not optional with this crop. Sown thick, the seedlings stretch towards the light, grow pale and thin, flop over one another and never develop the bladder cells that make the plant worth growing. Thin to one seedling every inch (2.5 cm) in the tray as soon as you can handle them, then transplant into individual pots at two true leaves.
Thinnings at that size are too small to eat, so simply snip them off at surface level with scissors rather than pulling. The root systems of neighboring seedlings are already interlaced and pulling one lifts three.
Two numbers make next year's sowing much easier, and both are easy to record while you are doing the work. Write down the date you sowed and the date the first seedlings appeared, and note the temperature you germinated at. This is a crop where germination speed is a direct readout of warmth, so the gap between those two dates tells you whether your propagation spot is warm enough or whether you should move it.
- Thin at the first true leaves Snip out the crowded seedlings with fine scissors, leaving one every inch (2.5 cm). Do it as soon as you can see individual plants. Waiting until they are tangled means damaging the ones you keep.
- Give them the brightest place you have Seedlings that stretch are ruined for this crop. As soon as they germinate they need the strongest light available, and they will take direct sun on a windowsill. Leggy pale seedlings do not recover into good plants.
- Record the sowing and emergence dates Note both dates and the rough temperature. Seven to ten days means your conditions are right. Three weeks means the spot was too cold, and next year the tray belongs somewhere warmer and brighter.
- Note how many plants you actually needed One plant covers a lot of ground and picks over many weeks. Record how many you planted and whether you had too many, because the packet size tempts everyone into growing five times what a household eats.