When Is It Too Late To Cut Back Mums?

Chrysanthemums, or mums, are arguably one of the most famous and beautiful flowers. Originating from East Asia, these flowers have numerous symbolic meanings. However, you have to be careful to cut them back at the right time to ensure they can bloom beautifully.

The middle of July is too late to cut back chrysanthemums. Ideally, you should cut back your plant in late spring. It is still safe to do so until the end of June or early in July, depending on the climate in your area. Cutting them back beyond that will result in poor blooms in the fall.

Mums do not require heavy pruning, but they can benefit from adequately timed cutting so that you can enjoy their best blooms. This article will discuss when to cut back mums and how to do so properly. I will also share what will happen if you cut back mums at the wrong time.

Proper Timing to Prune Chrysanthemums

The best time to cut back mums is in the spring when the shoots have grown at least 6 inches (15 cm) tall. Trimming the shoots will result in branching for a bushier plant with more bloom in the fall. After the blooming period, when the leaves fade in winter, you can cut back your mums.

Although spring is the best time to cut back mums, some gardeners also pinch some spent flowers during the blooming period and do light pruning during winter. Proper timing and technique are key to keeping your mums healthy for the following years.

The Pruning Process: An Overview

There are a few phases in which we should take care to cut, trim, or pinch chrysanthemums:

  • Growing season
  • During the blooming period
  • After the blooming period

I’ll discuss each of these key periods below:

During the Growing Season

As the weather becomes steadily warmer in spring, your dormant mums will bounce back to life and start growing new shoots. 

You might notice some branches failing to grow. This could be because of winter injury that either slowed the growth or killed off the branch. Spring cutting can help remove these otherwise dead or unhealthy branches

On the other hand, other healthy branches will grow normally. When they reach at least 6 inches (15 cm) in height, you can trim them back by an inch (2.5 cm). Doing so will encourage the branches to spread out.

You can also cut the new growths after they reach another 6 inches (15 cm). Some experienced gardeners use this opportunity to encourage the plant to grow into the shape they want. The right skills can help you direct the branches into the right position.

Randomly trimming the tips of the plant may result in an oddly shaped shrub, and doing it beyond the middle of July will result in new growths that don’t have blooms. This is where timing and technique play a crucial part.

During the Blooming Period

If you trim the tips of your chrysanthemums the right way and at the right time, you can expect a bush full of blooms in the fall. Seeing green spots on top of the bush early in the blooming period means you timed the cutting of those parts wrong.

Mums typically bloom for up to 8 weeks, starting from the time the first buds open. Those green spots will eventually be filled with blooms. To ensure this happens, you will need to remove spent flowers.

The long blooming period will inevitably result in several spent flowers. When you notice some of your flowers curling back or their tips turning brown, you can just pinch them off. Doing so will help the plant focus its energy on developing buds and opening them instead of maintaining old blooms.

This process will ensure you can maximize the blooming season with abundant and healthy blooms.

After the Blooming Period

After the blooming period late in the fall, give your mums some time before cutting them back. Typically, the leaves will be killed off by the frost. A week after all the blooms are spent and pinched off, you can cut back your mums close to the ground.

Leaving dying leaves on the plant will result in winter injury as the snow sits and melts on them. If your chrysanthemums are planted into the ground, you must protect them from fluctuating temperatures. 

Applying mulch around the crown of the plant late in the fall will help maintain a steady temperature for the roots to avoid or reduce the damage caused by cold winter temperatures.

Pruning Techniques for Optimal Growth

There are several ways to cut back mums, depending on the purpose. Cutting them properly can help them avoid diseases and ensure optimal growth every year.

Here are some ways to cut back mums:

Trimming New Growths

When trimming the new growths, you can use your fingers to pinch the tips off or use small pruning shears. When using your hands, you must wash them with soap and water and be sure not to handle soil or other plants before dealing with your chrysanthemums.

If you plan to use tools, you can keep them clean or sterile by soaking them in hot water before using them on your chrysanthemum. This will ensure that no fungi, viruses, or bacteria can infect your plant’s new growths soon after they emerge from a cold winter.

Trimming the top inch (2.5 cm) of the new growth should be enough to allow the branch to regrow into multiple lateral branches. You can do the same to new branches when they grow long enough (6 inches / 15 cm).

Stop trimming your chrysanthemums 90-100 days before the expected bloom time to allow the plant to develop enough buds. 

The start of the blooming period depends on several factors, including:

  • The cultivar
  • The climate in your area
  • The annual weather pattern
  • The soil type
  • The overall health of your plant

You can ask your local supplier or fellow chrysanthemum growers in your area for the estimated bloom time. It can help you determine when to stop trimming the branches.

If you don’t have access to anyone who can give you such advice, a good rule of thumb is to stop trimming by the end of June.

Another helpful tip is to understand the cultivar’s growth pattern. Early bloomers typically bloom in late summer. Regular types open their buds early in the fall, while late bloomers start blooming in the middle of fall.

Pinching Your Spent Blooms

Some new gardeners may be worried about how to remove spent blooms properly. The truth is, it’s pretty simple.

Here’s how:

  1. You must wash your hands properly with soap and water to ensure you don’t have harmful microorganisms on your fingers or nails that can infect your plant.
  2. Hold the flower between your thumb and index finger.
  3. Pinch immediately at the base of the flower with your nails.

Cutting Back in Winter

When all the flowers are spent and pinched off, your chrysanthemum’s leaves will eventually dry up and die. Remove all the dead or dying foliage from the branches to prevent snow from resting and melting on them.

You must apply 2-3 inches (5.1-7.6 cm) of mulch around the plant’s crown to keep the roots warm in winter. Therefore, you must cut the branches back 3-4 inches (7.6-10.2 cm) above the ground, leaving roughly an inch (2.5 cm) poking out above the layer of mulch.

Doing so can help you locate your mums easily in spring and allow them to grow beyond the layer of mulch.

Dividing Overgrown Mums

When chrysanthemums have lived through two or more winters, they most likely have already spread widely. You need to cut or divide them to avoid overcrowding, which will otherwise compromise the quality and appearance of their blooms.

Most mums grow suckers, allowing them to spread. As these suckers sprout from the ground, you might mistake them for old branches and trim their tips, resulting in overly bushy growths. 

While it may seem like a good idea to have more blooms later on, overcrowding can actually be counterproductive for your chrysanthemums. That’s why it is best to cut these new growths from the roots every year.

In early or the middle of spring, when you notice new shoots emerging from the ground, you can dig around your chrysanthemums and use sterile garden shears or a sharp spade to cut the lateral roots with new suckers. 

You can plant the cuttings into the ground, ideally 2 feet (60 cm) away from the mother plant.

Cutting Too Late Will Result in Some Spots Void of Flowers

If you cut back mums at the wrong time, you risk missing the chance to enjoy their best blooms in the fall. Cutting early bloomers too late in July will result in some spots void of flowers for most of the blooming season.

You can trim late-blooming cultivars until late in July. Regardless of what cultivars you have, remember to cut the plants no later than 90-100 days before their expected blooming season.

Pruning Encourages Flowering and Prevents Winter Damage

If you don’t cut back mums during the growing season in spring, the growth and later blooms will appear sparse. On the other hand, failure to cut them back in winter will allow snow to melt on the leaves and expose the plants to excessive moisture, eventually damaging them.

Final Thoughts

Correct timing and proper cutting techniques are necessary to ensure that your chrysanthemums can grow and bloom their best. These plants are often grown as perennials, making pruning an essential part of their growth and development.

Pay attention to the weather patterns in your area and understand your plants’ growth patterns to determine how and when to cut them back. 

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