Gadenin日本語Get the appFirst work out which kind you are growing
Salvia is a huge genus and the plants sold under the name behave in completely different ways. The single most useful thing you can do for your plants is to sort them into three groups, because the group decides when you cut, whether you feed, and whether the plant is expected to survive the winter outdoors at all.
The hardy border kinds die back to a low woody crown or disappear entirely each autumn, throw up upright spikes in early summer, and are cut back in spring rather than in autumn. The tender shrubby kinds keep a permanent framework of thin woody stems, carry small paired leaves and open a long succession of small hooded flowers from early summer until frost; they are the ones that need cuttings taken as insurance. The bedding kinds with dense scarlet or purple spikes are grown as annuals and simply die at the first frost, which is not a failure on your part.
If you are unsure which you have, look at the plant in late autumn. A hardy border salvia will have collapsed into a heap of dying foliage over a tight crown at ground level. A tender shrubby one will still be standing, still be woody, and still be opening a few flowers well after everything around it has stopped.
| Group | How it looks | When you cut it | Winter |
|---|---|---|---|
| Hardy border kinds | Dies to a crown; upright spikes in early summer | Leave the stems on over winter, cut to the crown in early spring | Survives outdoors in the ground |
| Tender shrubby kinds | Permanent thin woody stems, small paired leaves, flowers until frost | Light tidy in spring only; never hard-cut in autumn | Marginal outdoors; take cuttings as insurance |
| Bedding kinds | Dense short spikes, soft stems, one long flush | Deadhead spent spikes only | Killed by the first frost |
Write down which group each plant in your garden belongs to, along with the position it is in. That one line of record removes the annual guesswork about what to cut in spring and what to leave alone.
Full sun and drainage that is faster than you think
Salvias want at least six hours of direct sun, and eight is better. In less than that they still grow, but the stems stretch, the gaps between the leaf pairs lengthen, the spikes come thin and short, and the whole plant leans and then falls over. A salvia that flops every year in the same spot has a light problem far more often than a staking problem, and moving it in spring solves what no amount of tying up will.
Drainage matters more than fertility. These plants come from open sunny ground and they cope with heat, wind and a dry summer far better than they cope with sitting wet. On heavy clay the answer is not to dig a hole and fill it with compost, because that makes a sump that holds water around the crown. Improve the whole bed with grit, or raise the planting position by three or four inches (8 to 10 cm) so that water moves away from the crown rather than towards it.
In containers use a free-draining mix with about a third by volume of coarse grit or perlite, and never stand the pot in a full saucer. A salvia in a saucer of water through a cool wet spell is a salvia that will be dead by spring.
Water established plants sparingly
For the first six to eight weeks after planting, water thoroughly every three or four days in dry weather so the roots move out into the surrounding soil. Aim the water at the base of the plant and give it enough to wet the ground to a spade's depth, rather than a daily sprinkle that only wets the surface and keeps the roots shallow.
After that first season, established plants in the ground need almost nothing. A deep soak every ten days in a long dry spell is plenty, and many gardeners in temperate climates never water border salvias at all after the first year. A plant that wilts at midday in high summer and stands up again by evening is not short of water; it is regulating itself in heat, and watering it in response is how plants get rotted.
Containers are the exception, because the root ball dries out completely. Judge them by weight rather than by the surface. Lift or tip the pot: a watered pot is unmistakably heavy, and a dry one swings. Water until it runs from the base, then let the top two inches (5 cm) dry before doing it again.
| Situation | How often | What to look for |
|---|---|---|
| Newly planted, first two months | Every three or four days in dry weather | Keep the original root ball damp, not just the soil around it |
| Established in the ground | A deep soak every ten days in drought only | Midday wilt that recovers by evening needs no action |
| In a container, high summer | Every one to two days | Lift the pot to judge the weight |
| Cool wet spell, any plant | Stop entirely | Empty saucers, and check the crown is not sitting in mud |
Feed lightly, and never with a high nitrogen feed
Salvias flower best in ground that is only moderately fertile. A generous mulch of rich compost around the crown, or a scattering of high nitrogen lawn feed that drifts into the border, produces exactly the wrong plant: tall soft dark green growth, wide gaps between the leaves, weak stems that fall apart in the first storm, and very few spikes. If your salvias are enormous and leafy but barely flowering, you are feeding them too well.
One application of a balanced general fertilizer as growth starts in spring is enough for plants in the ground, and in reasonable soil you can skip even that. Container plants are different because the compost is exhausted after about eight weeks; give them a liquid feed higher in potassium than nitrogen, on the pattern of a tomato feed, once a fortnight through the flowering season.
Mulch is still worth applying, but keep it as a ring that stops two inches (5 cm) short of the crown. Mulch piled against the woody base of a salvia holds moisture exactly where the plant least wants it and is a common cause of losing plants that were otherwise perfectly hardy.
Cut back by a third after the first flush
This is the piece of care that makes the biggest visible difference, and most gardeners never do it. When the first flush of spikes on a hardy border salvia is about two thirds spent and the plant is starting to look untidy in the middle, shear the whole plant back by roughly a third of its height. Take it down to just above a pair of healthy leaves and do not be timid about it; you are removing flowers that were finishing anyway.
Within two to three weeks the plant pushes new shoots from the leaf joints below the cut, and those carry a second flush that opens well into late summer. Left uncut, the same plant puts its energy into seed, goes bare and woody at the base and gives you nothing more that year. On a plant that has flopped open in the middle, the cutback also rebuilds it into a dense mound rather than a ring of leaning stems around a hole.
The tender shrubby kinds are handled differently. They flower continuously rather than in flushes, so they need shortening of individual straggly stems through the season rather than one shear across the whole plant, and they must never be cut hard in autumn. Late hard pruning on a tender salvia strips it of the top growth that protects the crown, and it will not come through a cold wet winter.
Do not deadhead the very last spikes of the season if you want seedlings, and leave the dead stems of hardy kinds standing over winter. They shelter the crown and hold snow, and they are far easier to remove in spring when they snap off cleanly.
- Wait until the first flush is two thirds over Cutting while the plant is at full flower throws away the display. Cutting too late, once seed has set and the stems have gone woody, gives a much weaker regrowth.
- Shear the whole plant by a third Work across the plant with shears rather than snipping individual stems. Finish each cut just above a pair of leaves so the new shoots break from a strong joint.
- Water once and leave it alone Give one thorough soak after cutting if the ground is dry, then do not feed heavily. The regrowth comes from stored reserves and appears within two to three weeks.
Record the week you cut back and the week the second flush opened. After two seasons you will know your own garden's interval precisely, and you can time the cut so the second flush lands where you want it in the season.