At a glance
- Some summer flowers root deep and resent every move. They belong sown straight into the bed, not raised in pots.
- The best window for direct sowing is late April to mid-May, that is CW 17 to 20, once the soil has dried out and warmed up.
- Nasturtium, calendula, cornflower and corn poppy germinate reliably in place and need no seed tray.
- Leave a few spent heads standing and next year hands you a free second sowing.
- Fine or coarse: seed size decides the sowing depth. Rule of thumb, twice as deep as the seed is thick.
There are summer flowers that reward you with blooms precisely when you leave them in peace. No starting on the windowsill, no pricking out, no weeks of hardening off. You draw a shallow furrow, scatter the seed and wait. These are exactly the species that answer a raising regime with sulking or delayed bloom, because their taproot never forgives being moved out of the little pot. This piece shows you which summer flowers are born for direct sowing, when the window is open, and how to turn a handful of seed into a bed that refills itself year after year.
Why some summer flowers resent being moved
The reason lies underground. Species like corn poppy, cornflower or nasturtium form a fine, deep-reaching root early on. If it tears during pricking out or planting, the plant does branch anew, but it loses time and vigour. The result is a stunted specimen that blooms later and never reaches the fullness of a directly sown plant. With poppy it is especially dramatic: a raised little pot almost always collapses when you plant it out.
There is a purely practical point on top of that. Many tough summer flowers germinate so willingly and quickly that the whole raising ceremony is simply superfluous. Why nurse a seed tray for three weeks when the seed comes up within ten days in warm May soil? Nature makes it easy for you here, you only have to catch the right moment.
A simple test for soil readiness: take a handful of soil and squeeze it together. If the clod crumbles again when you tap it, the soil is ready to sow. If it clings together in a tough lump, wait a few more days.
The right window: CW 17 to 20
Direct sowing lives by the soil weather, not by the calendar date. Still, a guide helps: in most parts of Germany the good window opens in late April and stays open until mid-May, so roughly CW 17 to 20. By then the soil has warmed to ten degrees and more, and the nights turn mild enough that seedlings do not stall in a late cold spell.
Frost-tender species like nasturtium are better sown only after the Ice Saints, so from mid-May. Cold-hardy classics like calendula, cornflower and poppy, on the other hand, tolerate a cool start and may go into the ground as early as late April. If you like, sow in two stages two to three weeks apart. That way you stretch the bloom well into late summer.
A late cold night in May is no drama for cold-hardy seedlings. Calendula and cornflower shrug off light frost. Only the frost-tender nasturtium and cosmos react sensitively, which is why these two wait for the mild nights after mid-May.
The nasturtium is the perfect beginner's direct sowing. Its seeds are the size of a pea, you place them one by one with your finger into a two-centimetre hole and firm the soil. It climbs or trails along the ground, blooms from June until the frost and gives you edible flowers and leaves with a peppery taste on the side. It blooms most lavishly on poor soil, too much fertiliser only pushes leaves.
How to sow directly: the sequence
Prepare the bed
Loosen the top five centimetres, rake the surface fine and pull out coarse stones and root remnants. A fine, crumbly seedbed gives the small seeds good soil contact.
Draw furrows or broadcast
For a tidy bed, draw shallow furrows with the handle of a rake. For a natural flowering carpet, mix fine seed with a little dry sand and broadcast it. The sand spreads the seed more evenly.
Sowing depth by seed size
The rule of thumb is: twice as deep as the seed is thick. Fine seeds like poppy stay almost on top and are only firmed in, thick seeds like nasturtium go two centimetres deep. Never cover light-germinators like poppy with soil.
Firm in and water
Firm the seed gently with the back of your hand or a board so the seed makes contact with the moist soil. Water with a fine rose, never a hard jet, or you will wash the seed away.
Keep moist until germination
Until the seedlings stand, the surface must not dry out. On warm days that means going over it once daily with the rose. After emergence you water less often but more deeply.
Tough species that love direct sowing
Not every summer flower suits sowing outdoors, but the following classics succeed almost by themselves. They germinate reliably, tolerate the moods of April weather and reward you with months of bloom.
- Nasturtium
Thick seeds, effortless germination, edible flowers. Likes poor soil and full sun. Frost-tender, so sow only from mid-May.
- Calendula
The indestructible long-bloomer. A cold-hardy self-seeder, it blooms from June to November and draws hoverflies and bees.
- Cornflower
Brilliant blue, cold-hardy, ideal for naturalistic beds and meadows. Self-seeds reliably and fits into any flowering mix.
- Corn poppy
The classic move-refuser. Fine light-germinator seeds only firmed in, never covered. Blooms silky red and self-seeds freely.
- Love-in-a-mist
Delicate blue flowers in feathery green, followed by decorative seed pods for the vase. A charming self-seeder for romantic beds.
- Cosmos
This airy beauty grows tall and light, blooms until the frost and is one of the best cut flowers for your own bed. Frost-tender, sow from mid-May.
The finest side effect of direct sowing only arrives in the second year. Leave a few spent heads of cornflower, calendula or love-in-a-mist standing in late summer, and the ripe seeds fall to the ground of their own accord and germinate in place next spring. Over the years this creates a bed that sustains itself and looks a little different every year. If you want to steer the self-seeding, shake the ripe pods out deliberately where colour will be missing next year.
Steer self-seeding instead of fighting it
Self-seeders have a reputation as little anarchists. That only holds if you leave them entirely to themselves. Two gestures keep the bed in shape anyway: first, in spring you weed out the seedlings where you do not want them, while they are still small. Second, you deliberately cut off the heads you do not want to let seed, and let only the finest plants set seed. That way, over the years, you decide which colours and forms prevail.
A self-seeder in the bed is not a weed but a gift you only have to nudge into the right spot.
Old gardener's wisdom
A bed of direct sowing and self-seeding is never sterile and ordered, and that is exactly its charm. The cornflower turns up beside the poppy, the calendula jostles in between the nasturtium, and over the years a loose, living picture emerges that no garden-centre bedding display can imitate.
Tropaeolum majus
- Familie
- Tropaeolaceae
- Standort
- Sunny to part shade, poor soil
- Saison
- Direct sow from mid-May · CW 20
- Wasserbedarf
- Moderate, avoid waterlogging
- Frosthärte
- Frost-tender, annual
What matters after emergence
Once the seedlings are up, the hardest part is done. Two things help them along now. Thinning: if the seedlings stand too close, pull out the weakest until the strong ones have enough room. As a rough guide, nasturtium wants twenty centimetres of spacing, cornflower and calendula ten to fifteen. And restraint with fertiliser: most tough summer flowers bloom most beautifully on poor soil. Too much nitrogen gives you tall green plants with few flowers.
Cut a few flowers regularly for the vase and you spur the plant into ever-new buds. Cornflower, cosmos and calendula reward the cut with fresh supply into October.
Common questions about direct sowing summer flowers
Common questions about direct sowing
Which summer flowers can I sow straight into the bed?
Especially well suited are nasturtium, calendula, cornflower, corn poppy, cosmos and love-in-a-mist. All germinate reliably outdoors and do not take to being raised; on the contrary, many bloom even more lavishly after direct sowing because their taproot grows undisturbed.
When is the best time for direct sowing?
The main window falls between late April and mid-May, that is CW 17 to 20, once the soil has warmed to around ten degrees and dried out. Cold-hardy species like calendula and cornflower may go into the ground as early as late April, frost-tender ones like nasturtium and cosmos wait until after the Ice Saints in mid-May.
How deep should I sow the seeds?
The rule of thumb is: twice as deep as the seed is thick. Thick seeds like nasturtium go about two centimetres deep, fine seeds are only firmed in. Light-germinators like poppy must not be covered with soil at all, or they will not germinate.
Why won't my directly sown poppy germinate?
Usually it is down to sowing too deep. Poppy is a light-germinator; its fine seeds are only scattered on the surface and firmed in, never buried. On top of that, the surface must not dry out before germination. A fine rose instead of a hard jet protects the tiny seeds from being washed away.
Will the flowers come back on their own next year?
Many tough summer flowers are diligent self-seeders. Leave a few spent heads of cornflower, calendula, poppy or love-in-a-mist standing in late summer, and the ripe seeds fall to the ground and germinate in spring by themselves. That way the bed refills itself for free, year after year.
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