Gadenin日本語Get the appHow a gerbera makes flowers
Every flower stem comes singly out of the crown, from a growing point at the base of a leaf. That means the plant flowers in proportion to how many healthy leaves it is producing, and anything that slows leaf production slows flowering a few weeks later. There is no branching stem to prune into shape and no truss to thin; the plant either has the energy to push another stem or it does not.
A well grown plant in strong light produces a stem every few days through the warm part of the year, and holds several open blooms at once. A plant in a dim room produces one, rests for a month, and produces another. The difference is not the plant and rarely the feeding. It is the light.
Buds also abort, which confuses people. A bud that appears deep in the crown, reaches a quarter to half an inch (0.5 to 1 cm), goes brown and dries up is telling you the plant started a flower and then could not fund it. That is the classic low light signal, and it is also what a plant does immediately after a spell of cold or of drying out badly.
Light is the main lever
Six hours of direct sun is the working minimum for free flowering, and more is better up to the point where afternoon heat scorches the leaves in a hot climate. Indoors, put the plant within a foot (30 cm) of the brightest window you have, on the sunniest aspect of the house. A gerbera two yards back from a window is in deep shade as far as it is concerned, regardless of how bright the room looks to you.
The tell for insufficient light is the shape of the plant rather than its color. Leaf stalks lengthen and lie down, the rosette opens out flat and hollow in the middle, and the leaves are large, thin and soft. In good light the same plant is compact, the leaf stalks stand up, and the leaves are smaller, thicker and darker.
Turn a pot a quarter turn every few days if it sits against a wall. A gerbera leans hard towards its light source, and the flower stems follow, so an unturned plant ends up with every bloom facing the glass and a bare side towards the room.
| What you see | Most likely cause | What to do |
|---|---|---|
| Long floppy leaf stalks, hollow center | Not enough light | Move to full sun over two weeks; expect buds in three to four |
| Big dark leaves, thick growth, no buds | Too much nitrogen | Switch to a high potassium feed for six weeks |
| Buds form then dry off at half an inch | Light shortage, or a recent cold or drought check | Correct the cause; do not increase feeding |
| Very short stems, flowers sitting in the leaves | Cool temperatures or a young plant | Normal in cool weather; stems lengthen as it warms |
| Growth and flowering both stopped, crown dark | Crown buried or wet | Clear mix off the crown; stop overhead watering |
| Flowers open small and fade in two days | Heat above 85F (29C) | Shade through the hottest hours; it recovers as it cools |
A buried crown stops flowering before it kills the plant
When potting mix creeps up over the crown, the growing points at the leaf bases sit in permanently damp material. The plant does not die at once. It stops producing new flower stems first, then stops making new leaves, then goes soft in the middle weeks later. A gerbera that has quietly stopped flowering while looking otherwise reasonable is worth checking at soil level before anything else is changed.
Scrape the mix back from the center with a finger until the crown stands half an inch (1 cm) clear and you can see the bases of the leaf stalks. If the plant has sunk in the pot rather than the mix rising, lift it and reset it higher, adding mix underneath rather than around the top. This is worth doing at any time of year; the disturbance costs less than another month of a buried crown.
Then change how you water. Water at the rim of the pot so it soaks in from the outside. As long as the crown is being wetted every few days, resetting the plant only buys time.
Feeding for buds rather than leaves
A gerbera in fresh potting mix has enough nutrition for six to eight weeks. After that it needs feeding, but the type matters more than the amount. A general feed high in nitrogen produces exactly what it promises, which is leaf, and a plant pushed with it makes a magnificent rosette and almost no flowers. Once the plant is established, use a feed with more potassium than nitrogen, on the pattern of a tomato feed, at half strength every two weeks.
Do not try to force flowers with a heavy dose. Gerbera roots are fine and shallow and burn easily, and the first sign of over-feeding is brown crisp leaf margins on the newest leaves rather than any improvement in flowering. If you suspect salt build-up, flush the pot with twice its volume of plain water and resume at a weaker rate.
Feeding stops earning its keep when the plant is cold or dark. Through winter, or through a dull cool spell, drop to a feed once a month or stop entirely and start again when new leaves appear.
Remove finished flowers the right way
Leaving spent blooms on the plant slows the next flush, and cutting them off badly rots the crown. Follow the finished stem down to where it meets the crown, grip it low, and pull it sideways with one firm tug. It releases with a small snap and leaves a clean point. Do it while the plant is dry rather than just after watering.
Never cut a gerbera flower stem partway with scissors and leave the stub. The stem is hollow, the stub fills with water, and the rot travels down into the crown. This applies equally to stems you cut for a vase: take the whole stem out of the plant, then trim it to length in your hand.
Once you are clearing spent stems promptly and the plant has light, the flush pattern becomes obvious. Most gerberas produce in waves, with a heavy period, a fortnight of little, then another wave. Note the dates of the first bloom of each wave for a season and you will know your own plant's rhythm well enough to tell a normal lull from a real problem.
- Check the crown height first Before changing feed or position, look at soil level. If the crown is buried, nothing else you do will bring flowers back.
- Move the plant into real sun Increase exposure over two weeks to avoid scorching soft leaves, then leave it in the brightest place available.
- Switch to a high potassium feed Half strength every two weeks while the plant is in growth. Give it six weeks before judging the result.
- Clear every spent stem weekly Pull them out sideways from the base. Two minutes a week, and it keeps the crown clean at the same time.
- Write down when each wave starts The date of the first open flower in each flush, and where the pot was standing. Two seasons of that tells you which positions actually work.