12 Flowers to Deadhead in August So Your Garden Doesn’t Fade Too Early

August always plays a trick on us.

There are flowers in the garden, bees buzzing about, dahlias are finally showing their true colors and you might think, oh yes, summer still has a long way to go. You go on a walk with your morning cup of coffee and look carefully… half the zinnias are already sporting brown heads, the phlox is wilting, roses are setting their hips and the beautiful bee balm that you enjoyed in July suddenly looks quite shabby.

Let them stay a little longer!

For many of our summertime bloomers, August is actually a perfect time for deadheading. Once the flower begins forming its seed, the plant has successfully completed its mission – reproduction, and creating another dozen of beautiful blooms for us is not at all on its agenda right now.

But we do intervene a bit.

Just by making some cuts, you can make dahlias, cosmos, marigolds, salvias and repeat blooming roses continue flowering until autumn and even till frost stops them.

However, the place where the cut is done is important too.

Sometimes you need to remove only the old head of the flower, sometimes you need to follow several inches along the stem to its new side shoot and sometimes you leave a couple of faded blooms just because birds will need those seeds.

So, before your summer garden becomes autumnal, let us take a walk with the pruners and find out which 12 flowers really need to be deadheaded in August.

1. Coneflowers (Echinacea purpurea)

The color is fading from your coneflowers and you say, so what, summer is ending, there is nothing to be done about it, right? No! Deadhead the coneflowers right away and chances are good that you may get another flush of bloom from your Echinaceas in September. The blooms will be a bit smaller, but beautiful nevertheless, and quite a treat when most other things begin to fade out during the month.

Why does it work? A coneflower, as well as any other plant, has only one goal in its life – producing seeds. Once the bloom dies out and the cone becomes full of seeds, it is finished with its task and there is no need for blooming. But you cut the bloom off before seeds mature, the plant panics and tries to fulfill its reproductive mission again!

Cut the bloom off as close to the first side shoot as possible or to a pair of healthy leaves if there is no side shoot. Cutting off the bloom halfway will not help as the plant will die out anyway and the stubby stems are especially prone to rotting under wet conditions.

And remember this – don’t cut all the blooms off. Leave some cones in place. Goldfinches love them, they hang on them in October in their special upside-down pose and I find it quite amusing to watch them doing it. I deadhead probably two plants out of three and leave the rest.

For the birds. And for me, actually.

2. Lavender (Lavandula angustifolia)

Lavender is one of the plants that I would trim a little bit in August, since “deadhead it for more flowers” is certainly correct… but not to extremes.

As soon as the purple spikes fade and turn grey and papery, snip them off. This is simple – take the stem off right above the roundish cushion of leaves, normally removing the whole spike plus some ½ to 1 inch (1.2 to 2.5 cm) of soft green stem beneath.

But never trim down into the older woody portion. This is the wrong step.

English lavender (Lavandula angustifolia), as well as other types of lavender, might surprise you by producing another smaller batch of flowers in response to deadheading in August, especially if the first blooming period was relatively short and the climate remains hot. It will not be another June blooming – no way – but there will be enough new flowers to refresh your plant and interest bees a bit longer.

Personally, I use scissors for whole plants, while for young lavender I often use pruners and clip off the stems one bunch after another. It is important to retain the rounded cushion of green leaves beneath.

However, this becomes crucial in the sense that cutting back a little too much will leave many dried spikes above the plant, while cutting back too harshly, into brown and bare wood without green leaves beneath, may result in the lavender’s inability to regrow from such point.

Take a close look before making each deeper cut.

August is also a good time to prune away any broken stems and somewhat open the center if it became overcrowded, but never give your old lavender a rough trimming in August. Deadheading – yes. Light pruning – yes.

3. Phlox (Phlox Paniculata)

Oh, those glorious summer Phlox! Imagine strolling through the garden in hot August – you will smell them even without seeing them. How alluring, how intoxicating they are! Available in various intense tones, from bright magenta pink to delicate cram white. However, it should be noted that they become a real nightmare of a plant after they wilt. You could think that it is quite terrible when gigantic, magnificent bunches of flowers get dark and become soggy, especially in case of rain. You know, I agree with you, I cannot cope with this problem either!

However, there is no need to cut away the entire plant. Take a careful look at the stem, right under the dead flower head. See them? The green shoots are ready to appear, but it needs to ‘understand’ that the central flower is gone and get some extra energy to grow.

Take a sharp and sterilized blade; I find it better with phlox to use small snips. Cut the stem quarter of an inch (0.5 cm) above the tiny shoots. Do not cut too low! Cutting off the entire stem means losing a good flowering season, and your little winged visitors will not have anything to drink in September. Easy and effective! Just one cut, and in about three weeks you will be delighted with a second flush of beautiful, sweet-scented blooms of your Phlox.

4. Zinnias (Zinnia Elegans)

And now, Zinnias! If you have some in your border, you are very fortunate since these flowers are great bloomers. Ample, vigorous and colorful flower always does its best, except when you make it upset. But here’s the catch: being so generous, zinnias become neglected by many gardeners. They notice a brown and dry flower, shrug their shoulders and say “There’s lots of them anyway!” Oh, how you waste their potential!

If the zinnia flower dies, remove it, being really harsh. I see people just cutting the dead head in the top. That leaves ugly stick in the middle of the leaves. How useless!

But what you should do is to trace the stem downward to the place where two new side stems begin to grow. Usually, it’s somewhere in 8 to 12 inches (20 to 30 cm) from the top. Make the cut.

Yep, remove the whole long stem! Though you might consider this to be an act of destruction, your garden’s queen “will get the message” for sure.

And she will reward you with a really long, firm stems for the following flowering. So you’ll have beautiful flowers that you will cut and put in the vase.

5. Black-Eyed Susans (Rudbeckia fulgida)

Late summer hits, and suddenly your bright golden borders look like a pin cushion full of black spikes! Rudbeckia is incredibly tough. It handles the sun like a champion. But those faded blooms? They just drain the life out of the plant.

Don’t leave them sitting there! And whatever you do, please don’t just pinch the black cone off the top. I walked past a neighbor’s house yesterday and saw a whole row of naked, headless stems sticking up from the foliage.

This looks awful.

What you have to do is trace the rigid stem downwards until you spot a vibrant green leaf, preferably a little new side shoot growing at a joint. Then get a nice pair of bypass pruners and snip that flower right off, normally trimming 4 to 6 inches (10 to 15 cm) of the plant.

It diverts all that seed production energy into flowering. However, I will admit one thing. Do not deadhead by September. Just leave the latest cones on the stems because migrating goldfinches will certainly visit your garden to feed on them!

6. Snapdragons (Antirrhinum majus)

But wait, what about Snapdragons? Or Antirrhinum majus, for those who know their botanical names. And oh, how rare is this particular situation! Right now, you could look at them and see absolutely nothing but lifeless stems with crispy brown pods on them, instead of those soft and velvety jaws they are famous for.

It seems like they do not like the hot and humid weather in August! It makes them tired and exhausted, and they just give up and fall into eternal sleep…

I feel you, I am literally dying in these hot days! But please, don’t dig them out of the ground!

These plants like cool weather, and if you take care of them properly, then they will come to life again in September and bloom again! But you have to be brutal here! Don’t just pinch the upper flower. Take your sharp knife and cut the whole main stem almost in half, or even two thirds of it! Indeed, cut it to the lower, green and fresh leaves, leaving only about 5 to 7 inches (12 to 18 cm) of the stem above the ground.

7. Roses

Repeat-flowering roses are still busy working their magic in August, so don’t allow every dead flower to form a hip.

Instead of doing that little pointless snip just below the flower as soon as the petals start falling, follow the stem down and find a strong leaf – preferably a leaf with five leaflets pointing outward – at the bottom of the stem, and cut about ¼ inch (6 mm) above the bud in the axil.

It may mean cutting off 4 inches (10 cm) of stem. Or even 8 inches (20 cm). But don’t be a stickler for numbers: find the bud.

If the rose is a spray type, let most of the flowers on the spray fade, take off the dead ones along the way, then take out the whole spent spray all the way down to a strong leaf.

But always remember to use sharp bypass secateurs. The rose stems cut with blunt blades take a long time to heal, and August is definitely not the month when I want to have ugly wounds surrounded by leaves.

The only exception – and an extremely important one – is that once-flowering old roses will not magically bloom again because you deadhead them. And if you value hips, do not deadhead the later flowers on those roses at all.

However, for repeat-flowering roses continue to August. In colder climates I might start tapering off from mid-August to early September instead of constantly producing soft new growth before the first frost.

8. Salvia (Salvia nemorosa)

Salvia can keep flowering for a surprisingly long time, but by August those first flower spikes are often half brown, half blue, and no longer doing much for the plant.

Once most of a spike has faded, cut it back.

Follow the flower stem down to the first strong pair of leaves or a fresh side shoot and make the cut about ¼ inch (6 mm) above that point. On compact salvias this may only remove 2 to 4 inches (5 to 10 cm), while taller varieties can easily take 6 inches (15 cm) or more if that brings you back to good leafy growth.

I would not just nip off the dry tip.

Cutting a little deeper encourages the plant to branch from those lower nodes, and that is where your next flower spikes come from.

If the whole plant has gone rather floppy after its first flush, you can shorten several stems by roughly one-third, but keep plenty of green foliage underneath. Do not cut hard into old woody growth on shrubby salvias in August.

9. Marigolds (Tagetes spp.)

The marigolds have no problem blooming again, so I’d keep deadheading them well into August.

Once the flower starts to brown out, turn papery, or curl inward, track down the stem until you get to the first sturdy leaves or side shoot and cut it ¼ inch (6mm) above it. In the case of the compact French marigolds (Tagetes patula), you may find yourself cutting only 1 to 2 inches (2.5 to 5 cm) of stem. The taller African marigolds (Tagetes erecta), however, are capable of taking even 3 to 5 inches (7.5 to 12 cm) if you need to.

And do not just strip the dead petals from the flower.

The swelling of the stem where the petals emerge is where the seeds grow. If you still want flowers, make sure you strip out the entire old head.

I would do that every 3 or 4 days in August. They bloom quickly, wilt quickly, then repeat the process, and a neat-looking plant on Monday morning may look quite different come Friday afternoon.

If some stalk gets too long, too bare, and generally silly-looking, trim it back into the vegetative part of the plant rather than leaving the stem sticking above the mound of foliage. Marigolds readily branch out at the lower nodes.

An exception would be if you are planning on saving seeds for next year.

10. Cosmos (Cosmos bipinnatus)

Cosmos are the ballet dancers of the August garden – those silky pink and white cups floating on feathery stems, swaying with every breeze! And here’s the thing about them: they are annuals in a hurry. An annual lives to seed, fast, and every fading cosmos flower that stays on the plant is another step toward “job done, season over.” Deadhead, and you interrupt that plan beautifully!

The flowers don’t fade all at once – each plant carries buds, open blooms and spent heads together, like a family of different ages. Go through every two or three days, and of a flower’s petals have dropped and the center is drying into a little star, follow its stem down to the first set of leaves – or better, to a side shoot with a fat bud on it – and snip just above. On cosmos that can mean a cut of 6 to 12 inches (15 to 30 cm), and don’t be timid about it, because a long clean cut keeps the plant branching instead of going lanky!

11. Dahlias

Dahlias can flower astonishingly late if you keep after them in August, sometimes right until frost, but you really cannot leave those spent heads sitting there.

And there is one little trap.

A finished dahlia flower can look surprisingly similar to a new bud. Before you cut, look closely: a fresh bud is round, firm and quite plump, while a spent head becomes softer, pointed and slightly cone-shaped, usually with a few dry petals clinging around it.

Once you find an old one, don’t snip immediately underneath the flower.

Follow that flowering stem down until you reach the next strong pair of leaves or a proper branching point, then cut about ¼ inch (6 mm) above it. Depending on the variety, you may remove 4 to 8 inches (10 to 20 cm) of stem, and on tall dinnerplate dahlias sometimes a little more.

I prefer that deeper cut. It leaves the plant cleaner and, more importantly, those leaf joints below can push fresh side shoots carrying the next buds. Leave a long naked stalk above them and it will simply turn brown.

In August I would check dahlias every 2 or 3 days. They flower quickly now, and so they fade quickly too.

And keep cutting flowers for the house! Dahlias do not know whether you call it deadheading or picking a bouquet; either way, you have removed the flower before it can spend energy making seed, and the plant gets on with producing another one.

Just don’t cut below all the healthy leafy growth.

12. Daylilies (Hemerocallis)

The name speaks for itself, “hemeros” meaning “day” in Greek and “-callis” – beautiful. However, poetic though this might be, the day is too much. Beautiful the first day, this gorgeous saffron or ruby-red flower quickly changes into a gooey, sticky and transparent mess right next to the brand new buds!

And if you let those dead flowers hang around, they develop seed pods that deprive the roots of strength.

Deadheading a daylily is unbelievably enjoyable experience that doesn’t require any special equipment; you don’t even need your secateurs. Just go out in the morning when the air is cool. Take one of the gooey flowers and, holding it by its stem near the point of connection with the main plant body, give it a quick downward pull with a flick of your wrist. The flower comes off easily, leaving the tight buds completely unharmed. Your fingers become sticky from the sweet sap of the flower, but the sap washes easily away.

But now comes the important part! After each bud has bloomed and has been pulled off, you are left with an ugly naked green stalk pointing to the sky. Do not leave it there! Go all the way down the thick stem of the daylily to its crown in the ground, and yank it out. Or cut the stem off level with the soil. It tidies the border immediately!