Gadenin日本語Get the appWhat a flowering salvia needs
Salvias flower in response to light and warmth, not to feeding. Given six to eight hours of direct sun, ground that drains freely and a summer that reaches the seventies Fahrenheit (low twenties Celsius), the hardy border kinds open their first spikes in early summer and the tender shrubby kinds start a little later and then simply keep going until the first frost stops them.
The flowers themselves are hooded and two-lipped, carried in whorls up a spike, and the colored part that lasts longest is often the calyx rather than the petals. This is why a spike can look good for weeks after the individual flowers have dropped, and why a plant can appear to be in full flower when it has actually finished. Look at the tips of the spikes: if new buds are still opening upwards, the flush is running; if the top is bare and the whorls below are empty husks, the flush is over and it is time to act.
The four reasons a salvia will not flower
Work through these in order, because they account for nearly every case. The commonest by a wide margin is too much nitrogen, and the second is too little sun.
Fixing the light problem means moving the plant, which is done in spring rather than in the middle of the season. Fixing the feeding problem means stopping, which takes one season to show its effect but is entirely reliable.
| What you see | Cause | What to do |
|---|---|---|
| Tall, soft, dark green, almost no spikes | Too much nitrogen from rich mulch or lawn feed drifting into the bed | Stop feeding entirely for a season; mulch with grit rather than compost |
| Stems stretched and leaning, thin short spikes | Fewer than six hours of direct sun | Move the plant in spring to the sunniest position you have |
| Plenty of growth but flowering stops abruptly in midsummer | Seed set after the first flush | Cut back by a third as the flush finishes |
| Nothing at all from a plant cut in autumn | A tender shrubby kind hard-pruned late, then damaged over winter | Cut only in spring; take cuttings in autumn as insurance |
| A young plant that only makes leaves | First season, root system still establishing | Wait. Most salvias flower properly from their second year in the ground |
The cutback that buys you a second flush
On the hardy border kinds the first flush is heavy and finite. Once about two thirds of the spikes have gone over, shear the entire plant back by roughly a third of its height, cutting just above a pair of healthy leaves. New shoots break from the joints below the cut within two to three weeks and carry a second flush that runs well into late summer.
The timing matters more than the exact height. Cut too early and you throw away flowers you could still have enjoyed. Cut too late, after seed has formed and the lower stems have hardened, and the plant regrows slowly and thinly because it has already committed its reserves to seed. The window is roughly a fortnight wide, and it opens when the plant starts to look scruffy in the middle.
For a longer display, cut half the clump when the first flush starts fading and the other half a fortnight later. You lose the single spectacular peak but you gain flowers continuously from early summer to autumn, which in a small garden is usually the better trade.
The tender shrubby kinds do not need this treatment because they never stop. What they need instead is the occasional shortening of a single stem that has run away from the plant's shape, taken back to a leaf pair, which is a job you do whenever you notice rather than on a schedule.
- Watch for the middle of the plant going bare The signal is not the calendar. It is the moment when the flush has thinned enough that you can see through the center of the clump and the lowest whorls on the spikes are empty.
- Shear across the plant, not stem by stem Take a third of the height off in one pass with shears. Finish each cut above a leaf pair. Clear the trimmings out of the crown rather than letting them sit and rot there.
- Soak once, feed nothing One thorough watering if the ground is dry. Feeding at this point pushes soft leafy regrowth and delays the second flush rather than hurrying it.
Bees and hummingbirds are part of the point
Salvias are among the most reliably worked flowers you can grow. Bumblebees hang on the lower lip of each flower and push into the tube all day, and in regions that have them, hummingbirds work the tubular red and pink kinds constantly, often returning to the same plant on a circuit every fifteen or twenty minutes. Long-tongued bees reach the nectar properly; short-tongued ones sometimes bite through the base of the tube instead, which leaves a small slit near the calyx and does the plant no harm.
This is a good reason to be careful about any spray on a salvia in flower. There is almost never a pest problem on these plants serious enough to justify treating a flowering spike, and doing so takes out the insects that make the plant worth having.
It is also an argument for the staggered cutback described above. A clump cut in two halves a fortnight apart is in flower for far longer, and the value to bees late in the season, when little else is open, is much greater than the value of a single peak in early summer.
Note the date the first spike opened and the date the second flush opened after cutting. Two seasons of that pair of dates lets you time the cut so the second flush covers the gap in your own garden rather than someone else's.
After the flowers
Deadhead spent spikes through the season on the bedding kinds and on the tender shrubby ones by cutting the whole spent spike back to the first pair of good leaves below it. Snapping off just the dead top leaves a bare stub that neither flowers again nor looks like anything.
On hardy border kinds, stop deadheading as autumn approaches and let the last spikes stand. The seed heads feed birds, the standing stems shelter the crown through winter, and there is a reasonable chance of seedlings appearing around the parent in spring. Those seedlings will not be identical to the parent, but many of them are perfectly good garden plants.
Do not cut hardy salvias down in autumn. The dead top growth is genuine winter protection for the crown, and clearing it in autumn is one of the commonest reasons a hardy plant fails to reappear. Cut it away in early spring instead, when the old stems snap off cleanly at the base and you can see the new shoots you are working around.