August is the month to fertilize roses, dahlias, flowering containers, tomatoes, peppers, and any plant still actively making flowers or fruit. Use a diluted liquid feed or low-nitrogen, high-potassium fertilizer after watering, but stop feeding shrubs, trees, and perennials that are slowing down for fall - late, soft growth is no favor before winter.

The goal is not to turn the back yard into a botanical boot camp. It is simply to support the plants still working their little socks off during the hottest, hungriest stretch of the season.

While you decide what to feed, there is also plenty of ideas for what to plant in August for a productive fall garden. I would always recommend starting with a balanced liquid fertilizer, such as the TPS 10-10-10 available from Amazon, which is easy and quick to apply.

Start With The Plants Still Putting On A Show

The best rule for plants to fertilize in August is beautifully simple: feed what is actively flowering or fruiting, and leave anything beginning to slow down alone. A plant producing blooms, tomatoes, or peppers is using an astonishing amount of energy. An organic vegetable and tomato fertilizer from Walmart is ideal for this. It may look composed from a distance, but at root level it is the horticultural equivalent of a chef during Saturday-night service.

I always take a slow lap of the garden before mixing a feed. Look for fresh buds, new flowers, swelling fruit, and container plants that are drinking quickly. Those are your customers. Woody shrubs whose leaves are fading, tired perennials going to seed, and trees beginning their seasonal retreat should be allowed a dignified exit.

There is a useful difference between feeding and rescuing. Fertilizer cannot cure drought stress, root rot, pest damage, or a pot that has become the consistency of a brick. Water first, assess second, then feed only if the plant is genuinely still growing. This is especially important during a heatwave, when roots may struggle to take up nutrients from dry soil.

If you are tidying as you go, these plants to deadhead in August will reward you with fresh blooms to justify the effort.

Keep Container Plants Going Strong

A flourishing container is a miracle of optimism: a small amount of compost, a very large plant, and a gardener hoping nobody notices how frequently it needs a drink. By August, potting mix has been watered repeatedly and its available nutrients are often seriously depleted.

Flowering annuals such as petunias Petunia, calibrachoa, geraniums, and fuchsias benefit from a weekly or every-other-week liquid flowering fertilizer, applied at the label rate to already-moist soil. A low-nitrogen formula with more phosphorus and potassium is preferable now; you want flowers, not a spectacular new crop of leaves.

I favor a watering can rather than a hose-end dose for pots, because it makes me slow down and notice what is actually happening. This 2.6 gallon watering can from Lowe’s is a useful size for a patio collection and makes mixing liquid feed less of a circus act.

Remove exhausted flowers as you feed. It is not vanity; it redirects the plant’s energy toward new buds rather than seed production. For more inspiration on reviving an exhausted display, these summer container flowers make excellent late-season companions.

Give Roses A Final Flowering Push

Repeat-flowering roses are among the most deserving recipients of an August feed, particularly in temperate Zones 5–8 where they may still offer a generous flush into early fall. After deadheading, give established, well-watered plants a modest dose of rose fertilizer or a liquid tomato feed high in potassium.

The word modest matters. August is not the moment to heap on nitrogen and demand a forest of tender shoots that frost will later dispatch with cold efficiency. You are encouraging flowers and supporting healthy foliage, not commissioning a rose to audition for a hedge.

For gardeners who prefer a granular option, Burpee Natural Organic Rose + Bloom Plant Food offers both an initial and slower-release feed. Follow the package directions precisely; fertilizer labels are not suggestions, however much one may be feeling generous.

Container roses need particular attention, as their roots cannot roam off in search of supper. Our guide to growing roses in pots explains why a regular summer feed is so valuable for plentiful blooms.

Feed Dahlias, But Do Not Overdo It

Dahlias have no interest in moderation. Once they are blooming, they will keep producing lavish flowers with the determination of a theater star refusing to leave the stage. In August, feed them every two weeks with a liquid fertilizer lower in nitrogen and higher in potassium, especially if you are cutting flowers or deadheading regularly.

A liquid tomato fertilizer is a sound, practical choice. Espoma Organic Tomato-Tone from Amazon is formulated for flowering and fruiting plants, and it is easy to dilute in a watering can. Apply it to damp soil around the root zone, never to a bone-dry plant that is wilting theatrically in full sun.

Do not feed newly stressed or diseased dahlias until the underlying problem is corrected. And resist the urge to increase the dose in the hope of producing flowers the size of dinner plates. That way lies lush foliage, soft growth, and regret.

Alongside feeding, regular cutting is essential. Our guide on how to fertilize dahlias has more detail on choosing the right ratio, while these August dahlia jobs will keep the display running until frost.

Tomatoes and peppers are still producing in earnest in August, and they are not shy about their needs. Once plants are flowering and fruiting, a weekly liquid tomato feed can help support a steady harvest, particularly in containers, grow bags, and raised beds where nutrients are more quickly washed away.

Feed in the cool of morning after watering, aiming at the soil rather than splashing foliage. This is also the time to maintain even moisture. A tomato that alternates between drought and deluge may respond with split fruit, blossom-end rot, or the sort of general sulkiness with which gardeners become sadly familiar.

Eggplant, cucumbers, squash, and container-grown strawberries can benefit from the same approach if they are actively flowering or setting fruit. A potassium-rich feed supports the task at hand without pushing unnecessary leafy growth.

Tomato fertilizer has a surprisingly broad social life; our guide to plants that benefit from tomato feed explains where else it can earn its keep.

Refresh Tired Soil Rather Than Reaching For More Feed

Sometimes a plant does not need more fertilizer. It needs better soil, a larger pot, or a layer of compost to help retain moisture and improve root health. This is especially true with containers whose potting mix has shrunk away from the sides, creating a root ball that water runs around rather than through.

A thin mulch of homemade compost around flowering borders and vegetable beds is useful in August, provided you keep it away from stems. It helps hold moisture, supports soil life, and gives roots a steadier environment through hot spells. For raised beds or a tired border, organic compost from Walmart is a practical soil improver to have on hand.

In my own garden, the biggest improvement often comes from watering deeply, mulching well, and then using half the fertilizer I first imagined. Gardening has a habit of rewarding the person willing to do slightly less, but do it consistently.

If you are adding fresh crops among the fading summer abundance, these vegetables to plant in August will make good use of a newly refreshed bed.

Know Which Plants To Stop Feeding Now

Late summer feeding is not a universal kindness. Stop fertilizing deciduous trees, shrubs, hedges, and most established perennials as they begin slowing down, especially in colder temperate zones. You do not want to stimulate lush new growth that will be too soft to withstand approaching cold.

Avoid feeding spring-flowering shrubs such as lilac (Syringa vulgaris), forsythia, and flowering quince () now. Likewise, established hydrangeas and peonies () do not need a late-summer fertilizer salvo. Their next important task is to settle down, not embark upon an ill-advised second adolescence.

Hold off on feeding lawns, too, unless a local lawn-care schedule specifically recommends it for your region. In many parts of the US, an early-fall lawn feed is more appropriate than a high-summer application, when heat and drought can make the grass resentful.

The same principle applies to houseplants moved outdoors for summer: reduce feeding as growth slows and light levels begin to decline. Plants understand the calendar even when we are still wearing sandals.

What to Shop

The cleverest August gardener is not the one with the largest collection of products. It is the one who sees what is still growing, waters properly, feeds lightly, and knows when to stop.

Focus on flowering containers, repeat-blooming roses, dahlias, and fruiting crops. Use a liquid fertilizer in small, regular doses, pair it with consistent watering, and give the rest of the garden permission to start its gradual journey toward fall. It is less dramatic than throwing handfuls of fertilizer around at sunset, admittedly, but your plants will be healthier for it, and so will your conscience.

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