By the time August rolls around in the Midwest, my salvias have either hit their stride or started sending me very clear signals that they need attention. This is the month when heat, humidity, dry spells, and tired flower stems can either cut the show short or, with a little timely care, set the plants up for weeks of strong color right into early fall. If you love those upright spires in deep violet, red, blue, pink, or white, August is not the month to coast.
I grow several kinds every year, from tender bedding salvias to hardy perennial types like Salvia nemorosa, Salvia guaranitica, and the hummingbird magnets that seem to bloom forever if I stay on top of them. What I’ve learned is that a few practical jobs done now—watering correctly, trimming at the right moment, feeding lightly, and watching for mildew and flopping—make a dramatic difference. Here are the August tasks I consider most urgent if you want those flower spikes to keep coming strong.
1. Deadhead every faded spike before it starts setting seed
In August, the single biggest bloom-booster is deadheading. Once a salvia starts putting energy into seed, flower production slows down. I walk through my beds every 3 to 5 days with a clean pair of snips and remove spent flower spikes as soon as the lower florets have browned and the color has dulled.
Cut each spike back to just above a fresh set of leaves, a side shoot, or a lower cluster of buds. On many salvias, especially Salvia nemorosa and hybrid border salvias, that means removing 4 to 8 inches of stem. If the whole spike is finished, follow it down until you see healthy green growth and make your cut about 1/4 inch above that point. This keeps the plant tidy and redirects energy into new flowering stems instead of seed production.
2. Give leggy plants a midsummer haircut
If your salvia looks stretched, sparse, or top-heavy by August, don’t be afraid to cut it back harder. I do this all the time with perennial salvias that finished a big early flush in June or July and then began looking tired. A midsummer trim can trigger a fresh round of compact growth and another wave of spikes.
As a rule, reduce the plant by about one-third. If it is truly exhausted and floppy, you can often cut it back by as much as one-half, provided the crown is healthy and there is plenty of green foliage left below. For a 24-inch plant, that means trimming it back to roughly 12 to 16 inches. Water it well afterward, and in 2 to 3 weeks you’ll usually see strong new shoots forming. I avoid cutting into bare, woody sections with no visible leaves, because recovery is much slower there.
3. Water deeply, not constantly
August salvias suffer more from bad watering habits than from lack of attention. Many gardeners give them a quick splash every day, which encourages shallow roots and can actually make plants more vulnerable in hot weather. What works better is deep watering less often.
For established salvias in the ground, aim for about 1 inch of water per week from rain or irrigation, and in a hot spell above 90 degrees Fahrenheit, increase that to 1 1/2 inches if the soil is drying several inches down. In practical terms, I want the moisture to reach 6 to 8 inches deep. A slow soak at the base for 20 to 40 minutes is much more useful than five minutes with a hose nozzle. Container salvias are different: in August heat, they may need water every day or every other day, especially in terracotta pots or on windy patios.
4. Check the soil before you water
This sounds simple, but it saves plants. Before watering, push your finger 2 inches into the soil. If it feels dry at that depth, water. If it still feels cool and slightly moist, wait. Salvias generally prefer well-drained conditions, and keeping them overly wet invites root stress, yellow leaves, and fungal issues.
In heavier Midwestern clay, I’m extra cautious. The surface may look dusty while the root zone remains damp. In raised beds or sandy soil, the opposite is often true. I also pay attention to the leaves: slight afternoon droop that recovers by evening is not the same as true drought stress. Morning wilt, limp stems, and buds failing to open are stronger signs the plant genuinely needs a thorough drink.
5. Feed lightly, and only if the plant needs it
August is not the time for a heavy dose of fertilizer. Too much nitrogen now gives you soft, leafy growth at the expense of flowers, and that lush growth is more likely to flop or attract pests. If your salvia is pale, slow to rebound after trimming, or growing in a container where nutrients wash out quickly, a light feeding can help.
I prefer a diluted liquid fertilizer at half strength, something balanced like 10-10-10 or 5-5-5, applied once after deadheading or cutting back. For potted salvias, I may feed every 2 to 3 weeks through late August, but lightly. In garden beds with decent soil, I often skip feeding altogether and top-dress with about 1/2 inch of compost instead. That gives a gentler boost without pushing the plant too hard.
6. Mulch to stabilize soil moisture and root temperature
One of my favorite August fixes is adding or refreshing mulch around salvias that are baking in full sun. A 2-inch layer of shredded bark, pine fines, or chopped leaf mulch helps keep the root zone cooler and reduces dramatic swings between soggy and bone-dry soil. It also cuts down on weed competition, which matters more than people realize when plants are trying to rebloom.
Keep the mulch about 1 to 2 inches away from the crown and stems. Piling mulch directly against the base can trap moisture and encourage rot, especially in humid weather. I learned that lesson years ago with a beautiful violet salvia that collapsed right at the crown after a wet August. Since then, I always leave a little breathing room around the plant’s base.
7. Stake or corral tall stems before they flop
Some salvias stay neat on their own, but taller kinds—especially those reaching 30 to 48 inches—can start leaning by August after storms, heavy bloom, or rich soil. Once stems fully flop, they rarely look quite right again, so I like to intervene early.
Use discreet ring supports, short bamboo stakes, or a simple peony hoop placed low in the foliage so the support disappears as the plant fills in. Soft garden twine works too; just tie loosely in a figure-eight so stems are not pinched. If a clump is badly splayed, combine staking with a one-third trim. That reduces top weight and encourages sturdier new stems.
8. Improve airflow to prevent powdery mildew and leaf problems
August humidity can be rough on salvias, especially when plants are crowded or overhead watering keeps foliage wet into the evening. Powdery mildew often starts as a faint gray-white film on leaves, then spreads fast if conditions stay muggy.
Thin out neighboring annuals, remove damaged lower leaves, and give each salvia enough room so air can move through it. For medium perennial varieties, that usually means spacing them 18 to 24 inches apart; larger forms may need 30 inches or more. Water the soil, not the foliage, and do it early in the day. If mildew has already started, remove the worst leaves promptly and dispose of them rather than composting heavily infected material.
9. Watch for spider mites, whiteflies, and aphids in hot weather
Salvias are generally sturdy, but August heat can bring out a few persistent pests. Spider mites are the ones I check for first during dry stretches. You may notice fine stippling on leaves, a dull gray cast, or delicate webbing on the undersides. Whiteflies flutter up when disturbed, and aphids cluster on tender stems and buds.
I inspect plants every week, especially containers and specimens against hot walls or pavement. A strong spray of water aimed at the undersides of leaves can knock back light infestations. For heavier pressure, insecticidal soap works well, but apply it early in the morning or late in the day when temperatures are below about 85 degrees Fahrenheit to reduce leaf stress. Always spray thoroughly, because missing the leaf undersides is the most common reason treatments fail.
10. Pull weeds that compete for water and nutrients
It is not glamorous, but August weeding directly affects bloom performance. Fast summer weeds can rob salvias of moisture just when they need steady access to it for repeat flowering. Crabgrass, spurge, and volunteer vines are especially aggravating because they creep right into the crown area and make air circulation worse.
I hand-pull weeds after watering or after a rain, when the roots come out more cleanly. Around established salvias, I work gently so I don’t disturb the crown or surface roots. Even 10 minutes spent weeding a salvia bed can noticeably improve the look of the planting and reduce stress on plants trying to push new spikes.
11. Remove spent or broken stems after storms
Late-summer thunderstorms can leave salvias looking battered. Bent stems, snapped flower spikes, and mud-splashed foliage all drag down the plant’s appearance and can create entry points for disease. I like to clean plants up within 24 to 48 hours after a storm if possible.
Cut broken stems back to healthy tissue with sharp pruners, and remove any flower spikes lying on the soil. If a stem is split but still attached, don’t try to tape or splint it unless it’s a particularly valuable specimen; salvias usually recover more cleanly from a proper cut. Then check whether runoff exposed roots or compacted the soil around the base. A little fluffing at the surface and a mulch refresh can help reset the plant.
12. Keep container salvias on a stricter August schedule
Potted salvias are wonderful, but by August they are living a much harder life than those in the ground. The root zone heats up faster, dries out faster, and runs through nutrients faster. If your container salvia has slowed down, the problem is often not mysterious at all—it simply needs more consistent maintenance.
Check pots daily. In hot sun, a 12- to 14-inch container may need water every day, and during a heat wave, even morning and evening checks are wise. Deadhead more often, feed lightly every couple of weeks, and rotate the pot a quarter turn every 5 to 7 days if one side is stretching toward the light. If roots are circling tightly at the drainage holes and the plant dries out within hours, move it to a container 2 inches wider or plan to pot it up next season.
13. Know which salvia you have, because August care is not identical for all of them
This is a point I bring up often when friends ask why one salvia rebounds beautifully after cutting while another sulks. Bedding salvias, annual salvias, and tender perennial types are not managed exactly the same way as hardy border salvias. Salvia splendens, for example, benefits from steady deadheading and regular moisture, while Salvia nemorosa often responds very well to a more decisive shear after the first big flush.
Taller, later-blooming kinds like Salvia guaranitica may still be building toward their best display in August, so I deadhead selectively and avoid overly harsh cuts that remove promising buds. If you saved the plant tag, this is the month to use that information. If not, spend 5 minutes identifying the variety before you prune aggressively. It can save you from cutting off the very show you were hoping to encourage.
14. Plan for September blooms now
Everything you do in August shows up in September. That is the month when many salvias can look surprisingly fresh again, especially if nights start cooling into the 60s. I think of August not as salvage season, but as reset season. A tidy deadheading session, a strategic haircut, proper watering, and a bit of mulch can transform a worn-out clump into a plant that looks intentional and abundant again.
If I want a border to carry color into fall, I make one final late-August pass: remove every spent spike, trim any tired stems, check supports, water deeply, and clear away weeds. It is one of those small garden rituals that pays back generously. When the next flush rises cleanly above the foliage, the whole bed looks revived—and the salvias once again become the stars they were meant to be.