Taking care of dahlias: the trick with deadheading

taking care of dahlias purple dahlia

To my mind, one of the greatest strengths of dahlias, is that they can go on flowering from mid-summer right until the first frosts.

Depending on where you live, that could mean that you can have dahlias in bloom for three, four or even five months.

However, the most important word in that first sentence was can.

Once you know how to grow dahlias, they can flower for extended periods but only if you, the gardener, help them do so.

Taking care of dahlias involves the usual necessities of feeding, watering and mulching. But to get prolonged flowing, you need to dead head.

And it can be a little bit harder to dead head dahlias than it is for most flowers, unless you are aware of one important fact – how to identify the spent flower head.

(I have to say, I can never think of dead heading, without thinking of the Grateful Dead. But maybe that’s just me.)





The two step tip for dead heading dahlias

In case you don’t know, dead heading is simply a matter of removing spent flower heads.

This prompts the plant to produce more flowers, because removing the spent flowers deprives the plant of the potential seeds that evolution is driving it to produce.

Step 1 – Identify the spent flower

This is what makes dead heading dahlias a little bit tricky.

The problem is that once all the petals have fallen from a spent dahlia, the hard green part at the base of the flower (the calyx) closes over and what is left looks very much like like a bud.

So unless you know how to tell the difference between the buds and the remains of the spent flowers, you can end up removing the very buds that you are trying to induce into flower.

Fortunately, it is pretty easy to tell which is which when you know how. So here’s the trick:

The buds are rounded and the dead heads are cone shaped.

Take a look at the picture below.

This is a bud.

It is rounded, a kind of flattened sphere of compressed petals, with the calyx (the hard green outer ring of sepals) fanned out below the bud.

taking care of dahlias bud

Rounded dahlia bud - do not remove

In contrast, what you see below is the spent flower.

Notice how the overall shape is pointed rather than flattened, a cone instead of a sphere. In addition the sepals of the calyx have folded up to enclose and protect the reproductive parts of the plant.

These are what you need to remove.

taking care of dahlias dead head

Cone shaped spent dahlia flower: remove these

Step 2 – Cut right back

This is the easy part.

When you remove the dahlia’s dead head, don’t just cut it off below the flower. If you do, you’ll leave a flowerless stem that will just look ugly.

Instead, cut back, with sharp secateurs, to just above the point where the flower stem joins a main stem.

As you do so, you’ll probably notice a couple of tiny buds nestling there. With the removal of the spent flowers, those will sparked into life and they will bloom in a week or two.

If you are attentive in taking care of your dahlias and keep up your dead heading regime all summer, you’ll have blooms until the plant is knocked over by the first frost.





What you might need

If you’re just deadheading your dahlias, you can just as easily use kitchen scissors. But if you’re anything like me, then you’ll be scanning the garden for anything that needs a prune or a bit of cutting back while you’re there.

I pretty much never step into the garden without my classic Felco Classic number 2 secateurs. These are the best secateurs or pruners I’ve ever found – and, believe me, I’ve tried plenty.

413Mf63yiNL. SL160  .

Buy dahlias

For a great selection of dahlias, check out what is on offer at DirectGardening.com – you’ll find quality plants at great prices.


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These unique dahlias are shipped as large, number one size clumps. This Powder Puff Dahlia is almost the size of dinner plate dahlias. Produces rose petals with a creamy white center and a deep rose heart. Grows 40-44" tall.






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More on taking care of dahlias

Read more on how to grow dahlias, with full cultivation notes here.

taking care of dahlias






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Comments

  1. Sheila Fox says:

    Thanks. Glad to get that info on dead heading dahlias. Looking forward to more blooms.

  2. Do they come up every year? Can’t remember the term names.

  3. Oh! Are they annuals or perrenials?

  4. Lesley Miller says:

    Question; do Dahlia’s grow & bloom best in clay pots? Plastic? I have gophers and don’t trust them in the ground,….
    Thanks for getting back to me /us :)

    Lesley
    Santa Cruz, CA

    • Hi Lesley
      On the whole they do better in the ground and are easier to look after (not so much watering). But there’s no reason why they can’t grown in pots. I’ve always grown dahlias in the ground but I’m actually growing a dahlia in a pot for the first time at the moment, so I’ll keep you posted on how it goes.

      You can use clay or plastic pots, although I’d usually choose a clay pot because sometimes plastic pots can get really hot and damage the roots of the plants. This is less of an issue if it’s a large plastic pot.

      When growing dahlias in pots, you need to make sure they don’t dry out and keep them well fed – see this post on growing dahlias.

      Hope this helps.

  5. Chuck Lasher says:

    I have had great luck storing my dahlias in Pro-Mix. It is light, fluffy and dry. After lifting, cleaning and drying, I divide each clump, which is the hard part, then put each division in a ziploc bag , covered with Pro-Mix then zipped shut. These are then placed in the coolest corner of the basement. Nearly 100% success every year.

    • Sounds like you’ve got it very well under control Chuck.

      I agree dividing dahlia tubers is a bit hard. I always end up with a few loose ones with mo growing point. That’s why I always wait till there’s a sizable clump.

      Thanks for your tip.

    • Your dahlias are abutoslely amazing. Are they perennials where you live? We have to lift the bulbs in the fall, which is why I’ve never tried to grow any.

  6. How do you prepare the plants for winter? They are brown and look dead. Do you cut the plant off at the ground?

    Thanks,

  7. I liver in central Florida, will the blooms continue all year or will plant die back in the cooler weather?

    • Hi Lynn
      I think they’ll still go through the perennial plant cycle of growth and die back, but you’ll probably get a longer flower season. You could try some heat tolerant varieties, e.g. Bloodstone,Thomas Edison, Juanita, Prince Noir, Jersey’s Beauty, Bishop of Llandaff, Deuil du Roi Albert, Surprise, Lavengro, Princess de Suede or Winsome. Also make sure they are well watered but that the soil is free draining. They won’t cope with being waterlogged.

  8. if I leave the tubers in the ground over winter do I need to cut them to ground level first

    • Hi Harry
      Yes, once they’ve been hit by the first frosts or bad autumn weather, you should cut them down to ground level and then apply a good layer of mulch. They should be fine if your temperatures don’t get much below -5 on a regular basis, although the tubers could rot if you get lots of rain and the soil is sodden for extended periods.

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