As you look around your garden throughout August, you’ll see plenty of plants that can still benefit from a nutritional boost. Not all need it, but for those that do, the key is using the right feed for their late-season needs, and there is one specific fertilizing mistake you must steer clear of.
That crucial fertilizing mistake to avoid in August is using high-nitrogen feeds. These encourage the wrong type of growth in late summer. Not only this, but it creates a real risk of burning plants and damaging their long-term health.
It is a high price to pay for using the wrong fertilizer. You never want to over-fertilize plants, and certainly not with high-nitrogen feeds at this time of year. If you want to fertilize plants in August, it is better to use a balanced feed or a bloom booster, such as this Miracle-Gro Bloom Booster at Amazon. This can benefit any flowering or fruiting plants this month, whereas other feeds won’t.
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The Dangers of Excess Nitrogen in August
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Fertilizing is important, but it doesn’t come without risks. Different fertilizers promote different responses in plants. Feeding plants correctly ensures you encourage the right response at the right time of year. This is why giving plants lots of nitrogen is such a key fertilizing mistake to avoid in August.
Late summer is a time of abundant growth across the garden. Summer annuals and perennials are blooming, and fall flowers aren’t far behind. Elsewhere, your late-season vegetables are developing while your summer crops are primed for picking.
At this time of year, two of the three essential plant nutrients are more important than the other. Phosphorus and potassium are crucial – they help with flowering and fruiting, which is what you want in August. On the other hand, nitrogen primarily promotes lush, green growth of stems and foliage, not ideal for late summer.
If you do give shrubs, perennials, or crops high-nitrogen fertilizers in August, you’ll see the plants respond by putting out young green growth, not flowers and fruit. This unseasonal late flush causes issues over the rest of the year, as the plant is not prepared for fall or winter.
‘It pushes soft growth this late that won’t harden before frost. You’re growing leaves for winter to kill,’ warns Mirela Bajic, Senior Garden Designer at House Designer. As well as being susceptible to the first frosts, tender new growth encouraged by lots of nitrogen is more vulnerable to pests and disease.
Encouraging the wrong growth doesn’t just apply to feeding flowers or vegetables. It is also a mistake to fertilize a lawn this month with excess nitrogen, as this would encourage weak, leggy growth rather than strengthen the lawn as it prepares for dormancy.
Some gardeners may reach for fertilizers in an attempt to rescue heat-stressed plants in late summer. This is not the best course of action, especially if you mistakenly use nitrogen-rich feeds.
‘When it is extremely hot outside, plants are going to slow down with growing and flowering, and more fertilizer is not going to fix that,’ warns Lindsey Chastain, an experienced gardener, homesteader, and editor at The Waddle and Cluck.
‘Instead, what can happen is that you can overfertilize and burn your plants, especially with a high-nitrogen fertilizer.’
Over-fertilizing or fertilizer burn shows itself as discolored foliage, stunted growth, wilting, or shedding of leaves, flowers, or fruits. If you see these signs this month, flush the soil with lots of water to wash away the build-up and refrain from using any feed for the rest of the season.
What to Use Instead
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Certain plants around the yard don’t need any feeding in late summer. It is not an ideal time for fertilizing shrubs, trees, or early-flowering perennial plants, for example. These want to be slowing down and preparing for fall and winter, so ease off and let nature do its job.
Any plants that are still actively blooming and developing fruits do benefit from extra nutrients this month. This includes popular plants such as roses, dahlias, tomatoes, and peppers, and especially any flowering or fruiting plants growing in containers.
The best summer fertilizers for flowering and fruiting plants are higher in phosphorus and potassium. These products will have the latter two numbers of the NPK ratio on the packaging higher than the first. This indicates more phosphorus and potassium than nitrogen – which is what you want to see in August.
You can extend the flowering season and ripen the remaining crops by using this kind of liquid fertilizer every week or two until around six weeks before your first frost. If you have flowering and fruiting plants in container gardens, they definitely need a weekly feed.
Look for products described as bloom boosters or tomato feeds, as they are reliably higher in phosphorus and potassium than nitrogen. A good summer fertilizer encourages what you’ve got to end the season on a high note, rather than promote late, soft growth that does more harm than good.
Shop Late Summer Fertilizers
This super-concentrated feed has an NPK of 2-15-15 and is diluted to one teaspoon per two gallons of water. It provides the right nutrients to plants late in the season.
This bloom booster has an NPK ratio of 10-30-20 and comes as a powdered concentrate to mix with water. It comes with a measuring spoon to avoid over-fertilizing plants.
This bloom booster has an NPK of 1-34-32. Add 1/4 teaspoon per gallon of water and apply it to plants to promote bigger blooms.
Another way to guarantee late-season flowers on your annuals and perennials is deadheading. Removing spent blooms stops energy from going into seed production and focuses it on opening new flowers.
Sweet peas, roses, dahlias, phlox, bee balm, and snapdragons are all among the top flowers to deadhead in August to keep those blooms coming and extend the display.
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