August is the month when begonias either settle into their stride or start looking tired, sparse, and a little sulky. I’ve grown them in window boxes, shaded patio pots, and tucked along the north side of my Chicago-area backyard, and I can tell you this much: a begonia that was gorgeous in June can fade fast in late summer if you treat August like autopilot. Heat, uneven watering, crowded growth, and exhausted soil all start to show up now, right when you want those blooms to carry the garden right through to first frost.
The good news is that begonias usually respond beautifully to a few timely corrections. In this stretch of the season, I focus on moisture, feeding, cleanup, airflow, and a bit of strategic grooming. If you do the jobs below now—not “sometime this month,” but in the next few days—you can keep wax begonias, tuberous begonias, dragon wing types, and many rex-flowering combinations looking full and colorful for another 6 to 10 weeks, depending on your local weather.
1. Reassess watering, because August heat changes everything
Begonias want evenly moist soil, not soggy soil and not bone-dry spells followed by a flood. In August, especially during Midwestern heat waves where daytime temperatures can sit at 88 to 95 degrees Fahrenheit for several days, container begonias often need water every day, while those in the ground may need a deep soak 1 to 2 times per week.
I check moisture by pushing my finger 1 inch into the soil. If that top inch feels dry, I water thoroughly until excess drains from the pot’s bottom holes. For landscape beds, I aim for roughly 1 inch of water per week, closer to 1.5 inches if we’ve had hot wind and no rain. The key is consistency. If tuberous begonias swing from dry to drenched, their buds may drop before opening, and the foliage can yellow around the edges.
Water early in the morning if you can. That gives leaves time to dry and reduces fungal issues. Avoid a light sprinkle. A shallow splash only wets the surface and encourages weak roots near the top of the soil.
2. Deadhead spent blooms before the plant wastes energy on seed
This is the August task people skip most often, and it makes a visible difference in less than a week. Begonias that are allowed to hold onto faded flowers start directing energy into seed production instead of pushing new buds. I keep a small pair of snips in my garden tote and spend 5 to 10 minutes every few days removing mushy flowers, browned petals, and limp flower stalks.
On wax and dragon wing begonias, pinch or snip just above a leaf node or side shoot. On tuberous begonias, remove the spent flower and the short stem behind it cleanly. If you grow double-flowered tuberous types, also watch for the smaller female flowers that form behind the showier male blooms; removing some of those can help the plant put more energy into larger flowers.
If the plant looks messy after a rain, don’t wait for a full grooming session. Wet, decaying blossoms invite botrytis and mildew, especially when nights start cooling into the 60s.
3. Feed lightly but regularly with a bloom-supporting fertilizer
By August, many potted begonias have used up most of the fertilizer mixed into their potting soil back in spring. If yours are blooming less or producing plenty of leaves but fewer flowers, they may simply be hungry. I prefer a diluted liquid fertilizer every 10 to 14 days rather than one heavy feeding.
A balanced formula such as 10-10-10 or a bloom-leaning option like 5-10-5 works well at half strength. If the label says 1 tablespoon per gallon, I use 1 1/2 teaspoons per gallon instead. For small 10- to 12-inch patio pots, 2 to 3 cups of diluted feed is usually enough per application. Always water the soil lightly first if it is dry, because feeding thirsty roots can cause burn.
Don’t overdo nitrogen in late summer. Too much pushes soft, leafy growth that is more prone to disease and less impressive in bloom. With begonias, steady and modest feeding wins.
4. Remove yellow leaves and thin crowded stems for better airflow
Dense, overgrown begonias can trap humidity in their own canopy. In August, that’s a recipe for powdery mildew, stem rot, and a generally tired look. I go through each plant and remove any yellowing leaves, damaged stems, and foliage pressed tightly against the soil surface.
If a container planting has become a thicket, thin out a few interior stems to let air move through. You do not need to butcher the plant. Even removing 10 to 15 percent of the most congested growth can help. On dragon wing begonias, I often trim back a few leggy stems by 2 to 4 inches, cutting just above a node. That small haircut usually encourages branching and fresh bloom growth.
Sanitize pruners with rubbing alcohol between plants if you see signs of disease. It’s a small step, but it prevents you from carrying trouble from one pot to the next.
5. Refresh the root zone with mulch or a top-dressing of new potting mix
In-ground begonias benefit from a thin mulch layer in August, especially when the sun is stronger than the tag at the nursery may have led you to expect. I use 1 to 1 1/2 inches of shredded leaf mulch or fine bark, keeping it about 1 inch away from the stems. That helps stabilize soil moisture and reduces the hot-cold swings roots experience after a scorching day and a cool night.
For container begonias, the trick is a top-dressing. If the soil level has dropped 1 to 2 inches since planting, add fresh potting mix around the root zone without burying the crown. This gives the plant a little new organic matter, improves water retention, and covers exposed roots that may dry out quickly.
I’ve revived many late-summer patio pots simply by scraping off the top 1 inch of crusted mix and replacing it with fresh potting soil plus a light feeding. It sounds minor, but begonias notice.
6. Watch for scorch and move containers before leaves burn
Many begonias appreciate bright shade or morning sun with afternoon protection. In August, sun angles and reflected heat from brick, concrete, and siding can become surprisingly harsh. If you notice bleached patches, crisp brown margins, or flowers that collapse by midafternoon, your pot may be getting too much direct sun or heat reflection.
Move containers 2 to 6 feet into deeper shade, or shift them to a spot with sun before 11 a.m. and filtered light afterward. On my own patio, the difference between “too much” and “just right” has sometimes been one step away from a pale concrete wall. Tuberous begonias are especially prone to scorch, while wax and dragon wing types often tolerate a bit more light.
If moving a large planter is difficult, use temporary afternoon shade from a patio umbrella or place the pot behind taller companion plants. The goal is not darkness. Begonias still need bright conditions to bloom well; they just don’t want to bake.
7. Inspect for mites, mealybugs, slugs, and mildew now—not after damage spreads
August pests can sneak up on you. Spider mites thrive in hot, dry conditions and often show up as stippled leaves or faint webbing under foliage. Mealybugs hide in leaf joints. Slugs chew ragged holes, especially after rainy stretches. Powdery mildew can appear as a dusty white film when days are warm and nights are cooler.
I inspect begonias twice a week, especially the undersides of leaves and where stems meet the main crown. If I find spider mites, I rinse the plant thoroughly with water, paying close attention to leaf undersides, then follow up with insecticidal soap every 5 to 7 days for 2 to 3 treatments. For mealybugs, a cotton swab dipped in 70 percent isopropyl alcohol works well on small infestations. Slugs can be hand-picked at dusk or trapped; iron phosphate bait is another garden-friendly option when used according to label directions.
For mildew, improve spacing, remove affected leaves, and avoid wetting foliage late in the day. The earlier you intervene, the more likely your begonias will keep blooming instead of spending the rest of the season recovering.
8. Rotate potted begonias so growth stays even and floriferous
This sounds fussy, but it helps more than most people expect. Pots sitting on porches, balconies, and apartment terraces almost always lean toward their best light source. When one side gets all the energy, the other side becomes thin and bloom-poor.
I rotate containers a quarter turn every 3 to 4 days in August. That small habit keeps plants symmetrical and encourages more balanced bud formation. It also helps me notice issues sooner, because I’m seeing every side of the plant regularly instead of admiring only the “good side.”
Do this gently with tuberous begonias that carry heavy blooms, since brittle stems can snap if you grab them carelessly. Lift from the pot, not from the plant itself.
9. Pinch back legginess before it ruins the plant’s shape
If your begonias have grown long, floppy stems with bloom clusters only at the tips, don’t be afraid to pinch. August is late, but not too late, for a small corrective trim. I usually shorten the most awkward stems by 2 to 3 inches, making the cut just above a leaf node. Within 10 to 14 days, many begonias respond with side shoots that fill in the plant.
This is especially useful for dragon wing and cane-like begonias in containers. For compact wax begonias, you may only need to pinch a few stems. Avoid removing more than about one-quarter of the plant at once this late in the season, because a hard cutback can temporarily reduce bloom while the plant regrows.
Think of it as editing, not starting over. A little shaping now keeps the display handsome through September and into October in many regions.
10. Check drainage holes and saucers after summer storms
August thunderstorms can dump 1 to 2 inches of rain in an hour, and begonias hate sitting with their roots submerged. After heavy rain, inspect every container. Empty saucers within a few hours, and make sure drainage holes are not blocked by roots, soil, or fallen leaves.
If a pot feels heavy for more than a day or the soil smells sour, tip it slightly and let excess water run out. In severe cases, use a chopstick or plant label to gently clear the drainage opening from the bottom. Persistent waterlogging can lead to root rot, dropped buds, and yellow leaves that many gardeners mistakenly blame on drought.
When I plant begonias in decorative containers, I’m strict about drainage. If a pot has no hole, I use it only as a cachepot and keep the begonia in a plain nursery pot inside. August is when that decision really pays off.
11. Stop big disruptions and focus on maintenance, not major repotting
Late summer is not the ideal time for major transplant shock. Unless a plant is clearly failing because it is root-bound beyond reason, avoid moving begonias into dramatically larger pots in August. They would rather settle into a stable routine than recover from root disturbance in heat.
If roots are circling heavily and water runs straight through the pot, you can slip the plant into a container just 1 to 2 inches wider in diameter, using fresh potting mix around the edges. But for most begonias, a top-dressing, better watering, and light feeding will do more good than a full repot.
This is a lesson I learned the hard way years ago with a handsome salmon-colored tuberous begonia. I repotted it during an August hot spell, and instead of rewarding me, it spent two weeks dropping buds in protest.
12. Start planning for cool nights and the run to first frost
If you want blooms until frost, August is when you prepare for September and October. Keep an eye on overnight temperatures. Once nights begin regularly dipping below 55 degrees Fahrenheit, growth may slow, especially for heat-loving varieties, but flowering can still continue nicely if plants stay healthy and dry at the crown.
For potted begonias, decide now where you’ll move them during early cold snaps—a covered porch, garage overnight, or near the house where radiant warmth buys a few extra degrees. If you grow tuberous begonias and plan to save the tubers, begin reducing fertilizer by early September and let the plants gradually ease toward dormancy after the first light chill. For fibrous-rooted wax begonias, I often take a few 3- to 4-inch tip cuttings in late August as insurance, rooting them in water or moist potting mix indoors.
That little bit of planning can extend the display by a couple of weeks outdoors and preserve favorite plants for next year. And if you’ve ever had a begonia hit its stride in late September, you know those extra weeks are worth every bit of effort.