Introduction
Imagine walking into your garden on a sunny July morning with a pair of clean shears and a harvest bucket. You see a dozen perfectly formed dahlia blooms swaying in the breeze, and instead of feeling like you are "losing" those flowers by picking them, you know that cutting them will actually result in even more blooms next week. This is the magic of gardening with dahlias. These plants are the ultimate workhorses of the summer garden, offering an abundance of color that keeps giving until the first frost.
At Longfield Gardens, we believe that every yard deserves the vibrant, diverse beauty that only dahlias can provide. Whether you are a beginner looking for your first success story or an experienced gardener wanting to fill every vase in your home, dahlias are a perfect choice. This guide will help you understand the "cut and come again" nature of these stunning plants and show you how to maximize your harvest throughout the season.
We will cover the science of why dahlias keep blooming, the essential technique of "pinching" your plants, and the best ways to harvest and deadhead for a continuous display. By the end of this article, you will feel confident and excited to start your own dahlia-cutting garden. Dahlias are remarkably generous plants, and the more you interact with them, the more they will reward your efforts.
Why Dahlias Are the Ultimate Cut and Come Again Flower
The term "cut and come again" refers to plants that have the biological ability to regenerate new flowers after the existing ones are harvested. While some flowers, like peonies or many types of lilies, bloom once per season and then focus their energy on leaf growth or bulb storage, dahlias are different. They are programmed to produce as many flowers as possible to ensure their survival through seed production.
When you grow dahlias, you are working with a plant that responds to your touch. In the wild, if a flower is eaten by an animal or broken by the wind, the plant recognizes the loss and immediately redirects its energy to the dormant buds located further down the stem. As home gardeners, we take advantage of this natural survival mechanism. Every time we snip a stem for a bouquet, we are essentially telling the plant, "Keep going! We need more."
This process is driven by a concept called apical dominance. In most plants, the main central stem produces a hormone that prevents side branches from growing too quickly. This helps the plant grow tall to reach the sun. However, when we remove that central bloom, the supply of that hormone is interrupted. This sends a signal to the "lateral" or side buds to start growing. Instead of one single tall stem with one flower at the top, you suddenly have two, four, or even six new stems pushing outward, each ready to produce its own set of blooms.
Key Takeaway: Dahlias are naturally designed to produce more flowers when they are picked. Cutting the blooms prevents the plant from going to seed, which keeps it in its reproductive "bloom phase" for several months.
The Importance of Early Season Pinching
To get the most out of your "cut and come again" experience, the work starts before the first flower even appears. One of the most rewarding steps you can take is a technique called pinching. While it might feel a bit strange to cut off the top of a healthy, growing plant, this is the single best way to ensure a bushy, productive dahlia.
When your dahlia plant is about 8 to 12 inches tall and has developed four or five sets of "true" leaves, it is time to pinch. True leaves are the mature-looking leaves that appear after the very first small sprouts. At this stage, the plant usually has one strong central stalk reaching upward. Using your fingers or a sharp pair of clean snips, simply remove the very top 2 to 3 inches of that center stem, cutting just above the highest set of leaves.
This simple action changes the entire architecture of the plant. Within a few days, you will notice new growth emerging from the junctions where the leaves meet the stem (called the leaf axils). These will become your new primary branches. Pinching early in the season results in a plant that is structurally stronger and much more prolific. Instead of a single "top-heavy" plant that might fall over in a summer storm, you create a sturdy, multi-stemmed shrub that can support dozens of flowers at once.
How to Pinch Your Dahlias Correctly
- Wait for the right height: Ensure the plant is at least 8 inches tall so it has enough established roots and leaves to recover quickly.
- Locate the center stem: Find the main upward-growing stalk that is leading the growth.
- Count the leaf sets: Look for at least four sets of leaves along that main stem.
- Make the cut: Snip off the top of the stem just above the top set of leaves, taking about 2 to 3 inches of growth.
- Observe the growth: Over the next week, watch as the side buds begin to take over and form a bushier shape.
Best Practices for Harvesting Your Blooms
Once your dahlias start blooming, the "cut and come again" cycle is in full swing. To keep the plant healthy and ensure your flowers last as long as possible in a vase, the way you harvest matters. Unlike some flowers that continue to open after they are picked, dahlias do almost all of their opening while still attached to the plant. If you pick a dahlia when it is a tight bud, it will likely stay a tight bud.
The ideal time to harvest a dahlia is when it is about three-quarters of the way open. You can check the maturity by looking at the back of the flower head. The petals on the back should be firm and fresh. If they are starting to look limp, papery, or brown, the flower is slightly past its prime for a vase, though it still looks beautiful in the garden.
When you go to make your cut, do not be afraid to take a long stem. Beginner gardeners often make the mistake of only cutting a few inches of stem because they don't want to "waste" the smaller buds they see lower down. However, taking a long, deep cut—about 12 to 18 inches—actually encourages the plant to produce longer, stronger stems for the next round of flowers. We recommend cutting all the way back to a point where the stem meets a main branch. This keeps the plant tidy and prevents "stubble" from forming in the middle of your foliage.
Key Takeaway: Harvest dahlias when they are nearly fully open. Cut stems deep into the plant to encourage longer replacements and a more organized growth habit.
Deadheading: Keeping the Bloom Cycle Moving
Even if you aren't planning to fill your house with bouquets, you still need to "cut" to make them "come again." This process is called deadheading—the removal of spent or faded flowers. If you leave a dahlia bloom on the plant until it withers and dries, the plant begins to shift its energy into creating seeds. Once the plant thinks it has successfully produced seeds, it may stop producing new flower buds entirely.
Deadheading is one of the most relaxing and satisfying garden chores. A quick walk through your dahlia patch once or twice a week is usually enough to keep things on track. The most important skill to learn here is distinguishing a new, unopened flower bud from a spent flower head that has already bloomed. They can look remarkably similar at first glance!
A new dahlia bud is typically round and firm, like a marble. A spent flower head (one that has finished blooming) is usually more pointed or cone-shaped. The petals will have fallen off or turned into a mushy, brown clump inside the green casing. If you see a pointed tip, it is a seed pod, and it needs to be removed. Like harvesting, you should cut the spent flower stem deep into the plant rather than just nipping the head off. This keeps the plant's energy focused on the new, round buds waiting to pop.
Deadheading Success Steps
- Check frequently: A quick five-minute walk every few days is better than a long session once every two weeks.
- Identify the shape: Look for the pointed "cone" shape of a spent bloom and avoid the round "marble" shape of a new bud.
- Cut deep: Remove the entire stem of the faded flower back to a leaf junction.
- Clear the debris: Removing old petals from the foliage helps prevent mold and keeps the plant looking its best.
Choosing Varieties for Maximum Bloom Production
While all dahlias are technically cut and come again flowers, some varieties are more prolific than others. At Longfield Gardens, we have observed that certain shapes and sizes are natural "production' varieties. If your primary goal is to have an endless supply of flowers for cutting, it helps to choose varieties known for their high bud count and long stems.
These are the undisputed champions of the cutting garden. Varieties like 'Jowey Winnie' or 'Cornel' produce perfectly symmetrical, round blooms that are incredibly sturdy. Because the flowers are smaller (usually 2 to 4 inches), the plant can produce many more of them at once compared to giant varieties. They also have the longest vase life, often staying fresh for seven to ten days.
Waterlily Dahlias
These dahlias have a flattened shape and petals that curve upward, looking much like a lotus or waterlily. They are generally very productive and have a graceful, airy look in arrangements. They tend to have strong, slender stems that make them easy to work with in bouquets.
Cactus and Semi-Cactus Dahlias
With their spiky, narrow petals, these dahlias add a unique texture to the garden. They are often very vigorous growers and will pump out blooms quickly. Because their petals are thin, they are less likely to hold heavy rainwater, which can sometimes be a challenge for the larger, heavier types.
While everyone loves the massive, 8- to 10-inch blooms of varieties like 'Café au Lait' or 'Emory Paul,' it is important to remember that these take more energy for the plant to produce. You will still get a "cut and come again" effect, but the "coming again" part might take a bit longer between harvests. We suggest planting a mix: a few dinnerplates for the "wow" factor, and several ball or decorative types for a steady stream of flowers.
Site Selection: The Foundation for Continuous Blooms
For a dahlia to successfully "come again" all summer, it needs the right environment. These plants are sun-worshippers and heavy eaters. If your dahlias aren't producing as many flowers as you expected, the first thing to check is their access to light.
Dahlias need at least six to eight hours of direct sunlight every day. Sunlight is the fuel that allows the plant to create the energy needed for constant blooming. In areas with very hot afternoon sun, a little bit of dappled shade in the late afternoon can help prevent the blooms from bleaching or wilting, but generally, the more sun, the better.
The second critical factor is drainage. Drainage is simply a measure of how fast water moves through the soil. Dahlias grow from tubers—fleshy, potato-like roots—that are sensitive to sitting in soggy ground. If the soil stays too wet for too long, the tubers can rot before the plant has a chance to thrive. We recommend planting in well-draining soil enriched with compost. If you have heavy clay soil, planting in raised beds is an excellent way to ensure the drainage your dahlias need.
Watering and Feeding for High Performance
Because dahlias are so productive, they require a consistent supply of moisture and nutrients. Think of them like high-performance athletes; they are doing a lot of work, so they need plenty of fuel.
Watering should be deep and intentional. Instead of a light sprinkle every day, it is better to water deeply two or three times a week. This encourages the roots to grow deep into the soil, making the plant more resilient during hot spells. When you water, try to aim the hose at the base of the plant rather than over the leaves. Keeping the foliage dry helps prevent common issues like powdery mildew.
When it comes to feeding, dahlias appreciate a balanced approach. When you first plant your tubers, mixing some compost or a slow-release fertilizer into the soil provides a great head start. Once the plant begins its heavy blooming phase in mid-summer, a monthly application of a fertilizer low in nitrogen can be helpful. High-nitrogen fertilizers encourage lots of green leaves but can sometimes result in fewer flowers. Look for a fertilizer where the middle number (phosphorus) is equal to or higher than the first number (nitrogen) to support those beautiful blooms.
Supporting Your Heaviest Bloomers
As your dahlias continue to "come again," they will become quite large and heavy. A healthy dahlia plant can easily reach four or five feet in height, and when it is covered in dozens of water-heavy blooms, a summer breeze or rain shower can cause the stems to snap or the whole plant to topple.
Providing support is essential for a successful cutting garden. There are several ways to do this:
- Individual Staking: Place a sturdy bamboo or wood stake next to each plant at the time of planting. As the plant grows, loosely tie the main stem to the stake using soft twine or garden ties.
- The Tomato Cage Method: For smaller or medium-sized dahlias, a heavy-duty tomato cage can work well. Place the cage over the plant while it is still young, and it will grow into the support.
- The Corral Method: If you have a row of dahlias, place t-posts at the corners and run several levels of strong twine around the perimeter of the bed. This creates a "corral" that keeps the plants upright and allows them to lean against the twine for support.
Supporting the plants doesn't just prevent breakage; it also keeps the blooms off the ground, which protects them from pests and keeps them clean for your indoor arrangements.
Realistic Expectations: Weather and Timing
While dahlias are incredibly reliable, their performance can vary based on your local climate. Most dahlias begin their peak blooming season in late July or August and continue until the first hard frost. If you experience a period of extreme heat (over 90°F) for several days, you might notice that the plants slow down their production or the flowers become smaller. This is normal; the plant is simply conserving energy. Once the temperatures cool down in the evening or a rain shower passes through, they will quickly resume their "come again" behavior.
In most parts of the United States, dahlias are treated as annuals or tender perennials. This means they cannot survive the freezing ground temperatures of winter in zones 7 and colder. If you want to enjoy your dahlias again next year, you can dig up the tubers in the fall after the foliage has been blackened by the first frost, store them in a cool, dry place over winter, and replant them in the spring. If you live in a warmer climate (zones 8–11), you can often leave them in the ground, provided the soil doesn't stay too wet during the winter months.
Troubleshooting Common Bloom Issues
If your dahlias aren't producing the "come again" results you hoped for, don't worry! Most issues have a very simple fix. Here are the most common reasons a dahlia might stop blooming and how to get it back on track:
1. Lack of Sunlight If the plant is mostly leaves and very few buds, it might be in too much shade. If it’s in a container, try moving it to a sunnier spot. For garden plants, make a note to choose a brighter location next year.
2. Too Much Nitrogen If the plant is massive and green but has zero flowers, your fertilizer might be too high in nitrogen. Stop fertilizing for a few weeks and give the plant a chance to balance its nutrient levels.
3. Pests Slugs and earwigs love tender dahlia buds. If you see chewed petals or buds that never seem to open, check the plant at night with a flashlight. Using a pet-safe slug bait around the base of the plant early in the season can prevent a lot of heartache later on.
4. Not Enough Cutting It sounds counterintuitive, but if you stop picking the flowers, the plant will stop making them. If your dahlia is covered in old, dying blooms, it thinks its job is done. Give the plant a "hard deadheading"—cut back all the old flowers and even some of the leggy growth—and it will usually reward you with a fresh flush of buds within two weeks.
Conclusion
Dahlias are truly one of the most rewarding flowers you can grow. Their unique "cut and come again" nature makes them a perfect partner for anyone who loves to have fresh flowers in their home. By following the simple steps of pinching your young plants, harvesting at the right maturity, and deadheading spent blooms, you can enjoy a spectacular display of color for months on end.
- Pinch your plants when they are 8–12 inches tall for a bushier habit.
- Harvest deep into the plant to encourage longer, stronger stems.
- Deadhead frequently to keep the plant from producing seeds.
- Provide plenty of sun, water, and support for the best results.
The beauty of dahlias is that they are always ready to try again. If you miss a week of deadheading or forget to harvest a few blooms, the plant will wait for you to return and start the cycle over. We invite you to explore the wide variety of colors and shapes we offer at Longfield Gardens and start your own journey with these incredible flowers. There is nothing quite like the feeling of a garden that gives back more than you take.
"To grow a dahlia is to enter into a partnership with nature where the more you enjoy the blooms, the more the plant flourishes. It is the ultimate rewarding experience for any home gardener."
FAQ
How many flowers can I expect from one dahlia plant?
The number of flowers depends on the variety, but a well-cared-for dahlia can produce anywhere from 20 to over 100 blooms in a single season. Smaller varieties like ball and pompon dahlias usually produce the highest quantity of flowers, while giant dinnerplate varieties produce fewer but much larger blooms. Regular cutting and deadheading are the best ways to ensure your plant reaches its maximum potential.
Will dahlias bloom the first year they are planted?
Yes! Dahlias are very fast growers. When you plant a dahlia tuber in late spring once the soil has warmed, it will typically begin blooming within 80 to 100 days. You will get a full season of "cut and come again" flowers in the very first year. They will continue to produce new blooms until the first frost of autumn kills the top growth.
Why are my dahlia stems so short?
Short stems usually happen for two reasons: a lack of pinching or shallow harvesting. If you don't pinch the plant when it is young, it may produce many short, congested branches. Additionally, if you only cut the very top of the flower stem when harvesting, the plant will produce its next set of buds from that same high point. By cutting deep into the plant (12–18 inches), you force the plant to grow longer, stronger replacement stems.
How do I tell the difference between a bud and a spent flower?
This is a common question for beginners! Look at the shape of the green casing. A new flower bud is almost perfectly round, like a small green ball or marble, and feels very firm. A spent flower head (which has already bloomed) will have a more pointed, triangular, or cone-like shape. If the tip is pointed, the petals have likely already fallen off or are dying inside, and it should be removed to encourage new growth.
