Germination temperature
Optimum soil temperature 18-29 °C (65-85 °F); minimum about 4 °C (40 °F), maximum about 35 °C (95 °F).
Herb growing guide
Parsley is famously slow: seed can take two to six weeks to come up, and most failures come from giving up or letting the soil dry out in that time. This guide covers what actually speeds germination, and how to keep flat-leaf plants cropping.
Optimum soil temperature 18-29 °C (65-85 °F); minimum about 4 °C (40 °F), maximum about 35 °C (95 °F).
About 0.5-1 cm (1/4-1/2 in) of fine soil or compost.
About 12-14 days at 20-30 °C (68-86 °F), 17 days at 15 °C (59 °F), 29 days at 10 °C (50 °F); outdoors often a month or more.
Seed is covered; it does not need light to germinate.
Optional overnight soak; the evidence that it helps is mixed. Fresh seed and steady moisture matter more.
Direct sowing is preferred; transplant young module-raised seedlings with the root ball intact.
Use fresh seed where possible. Parsley seed lots vary a lot in vigour, and slow, uneven emergence is normal even in good field conditions. Mark the row, because seedlings appear long after weeds do.
Not recommended. In an Oregon State University trial, rubbing seed on fine sandpaper before priming reduced both the speed and the percentage of germination in soil compared with untreated seed.
Not needed. Parsley has no cold requirement; seed simply germinates faster in warm soil than in cold soil.
Optional. Many growers soak seed in water for up to 24 hours, and Purdue notes that controlled osmotic priming can improve emergence in poor, cold spring soils. But the popular idea that a germination inhibitor in the seed coat must be washed out is not well supported: in the Oregon trial, water priming did not beat untreated seed (88% germination in field soil), and an earlier study found water or gibberellin soaking reduced germination. If you soak, sow the seed the same day and do not let it dry out.
Parsley germinates over a wide range: the optimum soil temperature is 18-29 °C (65-85 °F), with a minimum around 4 °C (40 °F) and a maximum around 35 °C (95 °F). Cold, wet soil is the main cause of slow and patchy stands.
RHS advises a drill about 1 cm (1/2 in) deep; Purdue advises no deeper than 6 mm (1/4 in). On heavy soil that crusts, cover the seed with sand, sieved leaf mould or seed compost instead of garden soil.
A fine seed compost or a crumbly, well-drained seedbed. In trials, seed came up faster in potting mix than in field soil, probably because seedlings struggled to push through the soil crust.
Keep the surface constantly moist for the whole germination period. A single drying-out during the 2-6 week wait is enough to lose a sowing.
No light is needed for germination, so cover the seed. Seedlings need a bright position as soon as they emerge.
In the UC Davis soil-temperature data, emergence took about 29 days at 10 °C (50 °F), 17 days at 15 °C (59 °F), 14 days at 20 °C (68 °F) and 12-13 days at 25-30 °C (77-86 °F). RHS warns that outdoor sowings can take a month or more, and up to six weeks.
Sow in place where you can, to avoid root disturbance. If you raise plants in modules, move them when they are 10-15 cm (4-6 in) tall, harden them off for a few days, and plant at the same depth with the root ball intact.
Seedlings look grass-like at first, with two narrow seed leaves. Thin to 15-30 cm (6-12 in) apart; flat-leaf types are taller and need the wider spacing. Eat the thinnings.
Cause: usually normal parsley slowness, made worse by cold soil, old seed, or a dry surface. Fix: keep the bed moist and wait up to six weeks before resowing; sow when soil is above about 15 °C (59 °F) for faster emergence.
Cause: damping-off, mainly Pythium fungi in cold, wet soil. Fix: use clean seed compost, avoid overwatering trays, and sow into warmer, well-drained soil.
Cause: Septoria leaf spot, the most important foliage disease of parsley; it can be seed-borne and spreads by water splash. Fix: use good-quality seed, water the soil rather than the leaves, and remove spotted leaves.
Cause: parsley is a biennial and flowers in its second season, after which leaf quality drops. Fix: sow fresh plants every year rather than keeping old ones.
Cause: aphids, leaf miners, slugs and snails, and caterpillars; parsley shares many pests with carrot and celery. Fix: check leaf undersides, pinch out mined leaves, and grow in pots if slugs are severe.
Parsley germinates well in warm soil, but the plants crop best in mild weather. In most of the Indian plains sow after the monsoon for a winter harvest; in hill areas sow from spring to late summer. Give afternoon shade in hot spells.
Italian flat-leaf parsley grows taller and looser than curly parsley and has a stronger flavour that most cooks prefer; space it at the wider end of the range. Curly parsley forms compact, dense clumps suited to edging and pots.
Cut whole outer stalks close to the base, one or two at a time, instead of trimming the tops. This keeps new leaves coming from the centre. Leave at least 2.5 cm (1 in) above the crown when cutting a whole bunch.
Sow a short row every few weeks so you always have young plants coming on while older ones slow down.
Start a patch of Italian flat-leaf parsley for a steady supply of fresh leaves.
Parsley is naturally slow and uneven. At 20 °C (68 °F) it takes about two weeks to emerge, and in cold soil a month or more. Keep the soil moist the whole time and do not give up before six weeks.
You can, for up to 24 hours, but trials show mixed results: soaking did not improve germination over untreated seed in an Oregon State trial. Warm soil, fresh seed and constant moisture make a bigger difference.
Seed germinates up to about 30 °C (86 °F), but the plants grow best in mild weather. In the plains, the post-monsoon and winter months give the best crop; summer plants need shade and regular watering.