Gadenin日本語Get the appWhat the flowers do, and why they seem to come and go
The flowers are small, five-petalled and funnel-shaped, white through pink to lilac or yellow depending on the species, carried in loose clusters on thin stalks that stand a couple of inches above the leaf mound. Individually they are unremarkable. In quantity, held clear above a dark purple or bright shamrock-green cushion of foliage, they are the reason people grow the plant.
They come in flushes rather than continuously. A pot builds up over a week or two, holds a good display for two to four weeks, and then goes quiet for a similar period before the next round. A healthy plant in good light will run three or four flushes through a growing cycle. Judging a plant on any single week is therefore misleading, and so is repotting or moving one because it has stopped flowering for a fortnight.
The flowers also close, like the leaves, at dusk and in dull weather, folding the petals back into a tight spiral so that a pot that was covered in bloom at noon looks bare at six in the evening and on a heavily overcast day. This catches people out constantly. If your oxalis appears to have lost its flowers overnight, look again on the next bright morning before concluding anything.
Individual flowers last around three to five days. Once a stalk has finished, it yellows and can be pulled out at the base with a light tug.
The four things that decide whether you get flowers
Almost every case of oxalis that grows well but refuses to flower comes down to one of four causes, and three of them are things the grower is doing. Work through them in order, because light is by a distance the most common and the easiest to fix.
Light comes first. Flower stalks are expensive for a small bulb to build, and a plant in marginal light spends what it has on leaves instead. A plant that has stretched, whose purple has gone dull, or which sits more than a few feet from a bright window, is a plant that will not flower no matter what else you do. Second is nitrogen. General-purpose houseplant feed given at full strength produces a superb mound of foliage and very few flowers. Third is dormancy: a plant that has been kept ticking over for two or three years without a proper rest gradually stops flowering, and the rest is what resets it. Fourth is age and density of the bulbs, since a pot that has multiplied into a solid mass of small crowded bulbs produces leaves from all of them and flowers from none.
| Cause | How to recognize it | Correction |
|---|---|---|
| Insufficient light | Stretched stalks, faded color, leaves half shut by day | Move to an east window or several hours of gentle direct sun |
| Too much nitrogen | Lush oversized leaves, soft floppy stalks, no buds | Halve the strength and switch to a balanced or high-potash feed |
| No dormancy for several cycles | Progressively smaller leaves, flowering fell off gradually | Force a dry rest of six weeks, refresh compost, restart |
| Overcrowded bulbs | Dense pot, many thin shoots, root mass fills the pot | Tip out at the end of a cycle and replant fewer, larger bulbs |
| Temperature too high | Flowering stopped in a hot spell, leaves shut in the day | Move somewhere below 80F (27C) with air movement |
| Simply between flushes | Healthy compact plant, good color, flowered recently | Wait two to four weeks, change nothing |
| Buds forming then dropping | Small buds yellow and fall before opening | Check for erratic watering and for aphids on the stalks |
Keeping a flush going and bringing the next one on
There is a small amount of active work that measurably increases the number of flowers a pot produces over a cycle, and it takes about two minutes a week.
- Pull spent flower stalks out at the base Once every flower on a stalk has gone over, take the stalk between finger and thumb at compost level and pull with a steady light force. It comes away cleanly. Leaving spent stalks in place costs the plant reserves and leaves damp tissue sitting in the leaf mound.
- Switch the feed toward potash while it is in bud A high-potash liquid feed, the kind sold for tomatoes or for flowering houseplants, at half strength every three weeks during a flush encourages the next one. Keep off the balanced or high-nitrogen feeds while you want flowers.
- Keep the watering even Water when the top inch (2.5 cm) is dry, consistently. Buds are the first thing a plant sheds when it swings between saturated and bone dry, so an erratic watering pattern shows up as buds that yellow and drop before opening.
- Turn the pot a quarter turn each week Flower stalks lean toward the light much harder than leaves do. Turning the pot regularly gives you a display that stands upright over the whole mound rather than one that has thrown itself at the window.
- Give it more light between flushes, not more food The gap between flushes is the moment people reach for fertilizer. Moving the pot to the brightest position it will tolerate without scorching does more, and does not cost you a batch of soft leaves.
Flowering, dormancy and the end of the cycle
Flowering and dormancy are linked, in both directions. A rest is what makes the next round of flowering strong, and a heavy flowering period is often what precedes a collapse. It is normal for a pot to finish its best flush and then start to yellow within a few weeks, and that dieback is not a sign that flowering exhausted the plant fatally. It is the cycle closing.
This means that letting the foliage die back properly, rather than cutting it off, is a flowering decision as much as a dormancy one. The reserves that build the next season's flower stalks are moved out of those dying leaves and into the bulbs during the collapse. A plant that is stripped green, or that is thrown out and replaced, never accumulates the reserve that produces a really full display.
It also means that the way to fix a plant that has quietly stopped flowering over two or three years is to rest it deliberately rather than to keep coaxing it. Withhold water, let it go over, clear the dead foliage, keep it dry and cool for six to eight weeks, refresh the compost and thin the bulbs, then restart. Flowering typically returns in the cycle immediately after.
What to record about flowering
Three dates per cycle tell you almost everything about how your plant behaves and let you plan the next one instead of waiting to see. Note the date the first flower opened, the date the first flush finished, and the date the second flush started. The interval between those last two is your plant's rhythm, and it is remarkably consistent from cycle to cycle in one set of conditions.
Alongside them, note how many weeks elapsed between the restart of the pot and that first flower. In most ornamental oxalis that is somewhere between eight and fourteen weeks, and knowing your own number lets you time a restart so the plant is in full bloom when you want it, for instance on a table indoors during the darkest part of the year.
Finally, write down the feed you used and where the pot stood. When one cycle produces four flushes and the next produces one, the difference is nearly always a change of position or a change of fertilizer, and neither of those is something anyone reliably remembers three months later.
Count flower stalks rather than trying to count individual flowers, and count on the same day of the week each time. A stalk count taken weekly through a flush gives you a shape you can compare between cycles; an impression of how good it looked does not.