Gadenin日本語Get the appThe shape of the year
Portulaca is a warm-season plant with a narrow window. It germinates and grows only when it is genuinely warm, flowers hardest through the hottest weeks of the year, and is killed outright by the first frost rather than fading gradually. Everything in the calendar below is therefore anchored to soil temperature and to the last and first frosts rather than to any calendar date, so it reads the same in either hemisphere.
The two moments that decide the season are the sowing and the planting out. Sow too early indoors and you get stretched seedlings that resent transplanting; plant out too early and the young plants sit in cold ground doing nothing for weeks while later ones overtake them. Waiting is almost always the right call with this plant.
The season closes as abruptly as it opens. Once nights drop towards 50F (10C) the flowering slows noticeably, and the first frost ends it. If you want the same plants again, the work happens in late summer while it is still warm, not in autumn once things have cooled.
| Season | What the plant is doing | What you do |
|---|---|---|
| Late winter | Dormant or absent; overwintered stock plants are stretched | Sow indoors six to eight weeks before the last frost; cut overwintered plants back and take cuttings |
| Early spring | Seedlings growing slowly under cover | Thin or transplant, keep bright and barely damp, no feed |
| Late spring | Ready to move, but the ground is often still cold | Harden off; plant out only after the last frost and once soil is above 70F (21C) |
| Early summer | Rooting in and branching | Pinch the tips once; water in and then leave alone |
| Midsummer | Full flowering | Water only when leaves wrinkle; no feeding; watch for aphids |
| Late summer | Growth going leggy, flowering thinning | Shear back by a third on a dry morning; take cuttings for next year; collect seed |
| Autumn | Slowing as nights cool | Bring cuttings and stock plants indoors before frost; let self-sown capsules drop where you want plants |
| Winter | Dead outdoors; indoor cuttings ticking over | Water indoor plants roughly once a fortnight, only when leaves soften |
Late winter and early spring: getting a head start
Sow indoors six to eight weeks before your last expected frost. The seed is dust-fine and needs light to germinate, so it goes on the surface of a gritty mix and is not covered. Keep the tray at 70 to 75F (21 to 24C) and in the brightest position you have, and expect germination in seven to fourteen days. Water from below so you do not wash the seed about.
The mistake at this stage is warmth without light. Seedlings raised on a warm windowsill with weak late-winter light stretch into thin pale stems that never make good plants. If you cannot give them strong light, sow later; a plant sown two weeks later in better light will overtake a stretched early one.
This is also the time to deal with any plants you overwintered indoors. Cut the stretched growth back hard, let the cuttings dry for a day, and root them in gritty mix. The young plants you get will be far better than the tired parents, which can then be discarded.
Late spring and early summer: planting out
Do not plant out on the basis of the calendar. Wait until the last frost has passed and the soil in the intended spot has reached about 70F (21C) at a depth of two inches (5 cm). Portulaca planted into cold ground stops, sulks and is vulnerable to rot; the same plant set out a fortnight later grows away immediately.
Harden off over a week to ten days, increasing the time outdoors gradually, because seedlings raised under cover have soft leaves that scorch in full sun. Choose the hottest, driest, brightest position you have: gravel, a bank, a wall top, the front edge of a bed that bakes. Space plants six to eight inches (15 to 20 cm) apart, or one to a shallow pan of at least eight inches (20 cm) across.
Water once at planting to settle the roots, then pinch each plant's tips out about two weeks later once it is visibly growing. That single pinch produces a branched, dense plant rather than a few long stems, and the pieces you remove will root if you want more plants.
Midsummer and late summer: the flowering weeks
Through the hottest weeks there is very little to do, and doing very little is the point. Water only when the leaves soften and wrinkle, which is roughly every five to seven days for a container and rarely at all in open ground. Do not feed, do not mulch with compost, and do not deadhead individual flowers, since each bloom lasts a single day and the plant carries on regardless.
By high summer many plants run to long trailing stems with flowers only at the tips. Shear the whole plant back by about a third on a hot dry morning and it will branch and reflower within two to three weeks. Choosing a dry morning matters: cuts made in damp weather let rot into the soft stems.
Late summer is when the work for next year happens. Take cuttings while it is still warm so they root in days, and collect seed capsules as they turn papery but before the lids lift. If you want volunteers in a particular place, let the capsules ripen and shed there rather than shearing that plant.
Autumn, winter and what to record
Bring rooted cuttings and any stock plants under cover well before the first frost, and keep them bright, cool and almost dry through winter. There is no dormancy to manage in the sense of a bulb or a tuber; the plant simply ticks over slowly in poor light and needs water perhaps once a fortnight, and only then if the leaves have gone soft. Outdoors, pull the frosted plants and clear them, leaving the self-sown seed where you want next year's volunteers.
The dates worth writing down are the sowing date, the date you planted out, the date the soil actually reached 70F (21C), the first flower, the mid-season shear, and the frost that ended it. That short list, kept for two or three years, converts all the vague seasonal language above into your own garden's real timetable.
Add a note of which positions performed and which did not, with the hours of direct sun each receives. With this plant that single variable explains most of the difference between a bed that flowers all day and one that never seems to open, and it is the note you will reach for first when planning the next season.