Knowing When It’s Too Late to Pinch Your Dahlias

Pinching dahlia plants is an important technique for encouraging bushier growth and more flowers But there is a point when it becomes too late in the season to pinch them. I want to provide some guidance on when pinching is and isn’t recommended so you can get the best results from your dahlias

Why We Pinch Dahlias

Pinching is the process of using your fingers to remove the top few inches of the dahlia plant’s new growth. This damages the tip of the stem and triggers the plant to produce lateral shoots near the pinched area.

The advantages of pinching dahlias include

• More stems and branching. Pinching promotes bushier, fuller plants.

• Stronger stems. The stems that grow after pinching tend to be sturdier than the original stems.

• More flowers. Instead of one large flower on the end of each stem, pinching results in multiple stems with multiple blooms.

• Shorter plants. Pinching controls the plant’s height, keeping it more compact.

So in general, pinching is a great way to maximize the number of flowers and create shorter, sturdier dahlia plants. But it needs to be done at the right time.

When to Pinch Dahlias

The optimal window for pinching dahlia plants is when they are 8-18 inches tall with 3-4 sets of true leaves formed.

Pinching should never be done before 3 sets of true leaves have developed, as the plant will be too young and unable to recover quickly. Ideally, target pinching around the 12 inch/4 sets of leaves stage.

This pinching window generally occurs 4-6 weeks after transplanting young plants outdoors in the spring. If starting with tubers, it’s about 4-6 weeks after they’ve sprouted.

Pinching during this height range allows time for the dahlia to form multiple new shoots before the summer heat causes rapid vertical growth. It maximizes branching while minimizing delay in bloom time.

Signs It’s Too Late to Pinch

As a rule of thumb, avoid pinching dahlia plants once they exceed 18 inches in height. Pinching tall, mature plants causes too much stress and delays flowering significantly.

Here are signs that indicate it’s too late for pinching:

• The plant is over 18 inches tall
• Thick, woody stems have formed
• Flower buds are visible
• Mid summer heat has arrived

At this point, pinching will shock the plant. The new growth triggered won’t have time to mature and bloom before frost. You run the risk of losing out on flowers for the year.

Resist the urge to do a late pinch on a stretched out plant in hopes of keeping it compact. It’s better to stake/cage tall plants to support flopping stems instead.

Consequences of Pinching Too Late

What happens if you pinch dahlia plants too late in the growing season? Here are some potential consequences:

• Delayed flowering: Pinching removes the hormonal growing tip of the plant. When done late, the dahlia won’t recover and generate new flower buds quickly enough before summer ends.

• Lack of blooms: The new shoots created after late pinching may not mature enough to produce flowers before the first fall frost. You essentially halt the bloom cycle too late for it to restart in time.

• Weak growth: Young shoots produced in late summer heat tend to be weaker and less resilient. The plant has less time to harden them off properly.

• Increased pest/disease pressure: High summer temperatures combined with soft new growth makes the dahlia more vulnerable to mites, aphids, powdery mildew and other issues.

• No seeds: Late pinching won’t allow enough time for the flowers to be pollinated and form viable seeds before frost.

• Reduced tuber size: likewise, the plant won’t be able to send sufficient energy to enlarge the tuber roots for next year.

• Topple risk: Pinching off heavy, top-heavy stems late in the season can cause the remaining plant to flop over without that central leader.

To summarize, pinching too late negatively affects the bloom, foliage, resilience and overwintering ability of dahlia plants.

Tips for Avoiding Late Pinching

Here are some tips to ensure you pinch your dahlias during the optimal window:

• Mark your calendar 4 weeks after transplanting or sprouting as a reminder.

• Check height weekly once plants are 6 inches tall so you can pinch at the right moment.

• Pinch plants at 12 inches even if not 4 sets of leaves yet to avoid missing the window.

• Feel stems – pinch when still pliable & green, not thickening to wood.

• Don’t wait for visible flower buds which means it’s too late!

• Err on the side of pinching early (8″) rather than too late.

• Stake tall plants instead of pinching if you missed the window.

Alternatives to Pinching Late in the Season

If your dahlias are already too tall and mature to pinch, consider these alternatives to pinch them:

• Use stakes, cages, trellises or hoops to support flopping stems and prevent breakage.

• Prune back any secondary shoots to outward facing buds to encourage bushiness.

• Remove the first set of lower leaves & cover 2-4″ of stem with soil or mulch to stimulate new roots and shoots.

• Cut back any diseased, damaged or spent blooms to direct energy to new growth.

• Reduce water & fertilizer which encourages rapid growth you want to avoid late in the season.

• Plan to pinch newly sprouted tubers next spring at the right stage.

• Accept the single-stemmed, taller than desired but still gorgeous dahlias this year!

When in Doubt, Don’t Pinch

I know it can be tempting to panic upon seeing your leggy, stretched out dahlias and pinch them in hopes of keeping plants compact. But remember, it’s always safer to avoid pinching altogether rather than do it too late.

Tall, unpinched dahlias will still flower beautifully at the end of their long stems. But late pinched dahlias may produce little to no blooms before frost arrives.

So when in doubt about whether it’s too late to pinch – don’t chance it! Let those plants continue growing au naturel this year and start fresh with proper pinching next season.

The key is learning the ideal window for your climate and conditions. With experience, you’ll get a feel for exactly when your dahlias have reached that perfect pinching stage. Then you can pinch with confidence for the fullest, bushiest plants around.