Introduction
Dahlias are the undisputed stars of the late-summer garden. These spectacular plants offer an incredible range of colors and shapes, from petite pompons to dinner-plate-sized blooms that can reach ten inches across. At Longfield Gardens, we believe that every gardener should experience the joy of watching these tubers transform into lush, flowering machines. Whether you are looking for a pop of color in a container or a dedicated cutting garden for fresh bouquets, dahlias are a rewarding and accessible choice.
This guide will walk you through the simple steps of how to take care of dahlia plants throughout the entire growing season. We will cover everything from selecting the right spot and planting at the perfect time to the simple maintenance tricks that keep the blooms coming. You do not need to be an expert to grow professional-quality dahlias; you just need to follow a few basic principles.
By understanding what these plants need to thrive, you can enjoy a garden filled with vibrant, healthy blossoms from midsummer until the first frost of autumn.
Finding the Best Location
Success with dahlias begins with picking the right spot in your yard. These plants are sun-seekers that need plenty of energy to produce their elaborate flowers. We recommend choosing a location that receives at least six to eight hours of direct sunlight every day. Morning sun is especially beneficial, as it helps dry the dew off the leaves and prevents moisture-related issues.
Dahlias also appreciate a bit of protection from the wind. Because some varieties can grow quite tall, a stiff breeze can occasionally tip them over if they are in a completely open area. Planting them near a fence, a building, or behind a row of sturdy perennials can provide a natural windbreak.
Soil quality is the next important factor. Dahlias prefer "well-draining" soil, which simply means the water should move through the soil rather than sitting in puddles. If your soil is heavy clay, it may hold too much water, which can lead to problems for the tubers. You can easily improve your soil by mixing in a bit of compost or aged manure before you plant. This adds nutrients and creates a lighter texture that helps the roots expand.
Key Takeaway: Choose a sunny, sheltered spot with soil that doesn't stay soggy after a rain. Good drainage and six or more hours of light are the foundations of dahlia success.
Timing and Planting Basics
One of the most important rules for how to take care of dahlia plants is to wait for the right weather. Dahlias are native to Mexico and Central America, so they love warmth and cannot tolerate frost. We suggest waiting to plant your tubers until the soil temperature reaches about 60°F and all danger of spring frost has passed. A good rule of thumb is to plant your dahlias at the same time you would plant tomatoes in the ground.
When you are ready to plant, follow these easy steps:
- Dig a hole: Create a space about 6 to 8 inches deep.
- Position the tuber: Lay the tuber horizontally in the hole. If you can see the "eye"—the small bump where the sprout will emerge—point it upward.
- Spacing: Large varieties need about 18 to 24 inches between plants, while smaller border dahlias can be spaced about 12 inches apart.
- Cover and wait: Fill the hole with soil so the tuber is covered by 3 or 4 inches of earth.
The most important tip for this stage is to skip the watering. It may feel natural to water a new plant, but dahlia tubers contain all the moisture they need to get started. Watering them before they have sprouts can cause the tuber to rot in the ground. Wait until you see the first green shoots peeking through the soil before you start your regular watering routine.
Watering for Healthy Growth
Once your dahlias have emerged from the soil, they will start growing rapidly. This is when they begin to need consistent moisture. The goal is to keep the soil evenly moist but not saturated. In most climates, a deep watering two or three times a week is sufficient. If the weather is exceptionally hot and dry, you may need to water more frequently.
When you water, try to aim the stream at the base of the plant. Keeping the foliage dry helps prevent common garden issues like powdery mildew. If you have a large garden, using a soaker hose or drip irrigation can be a great way to deliver water directly to the roots.
For gardeners using containers, remember that pots dry out faster than the ground. Check the top inch of soil with your finger; if it feels dry, it is time to water. High-quality potting soil usually drains well, so you don't have to worry as much about rot once the plant is established and growing.
Nutritional Needs and Fertilizing
Dahlias are often called "heavy feeders," but this doesn't mean they need complicated chemicals. They just appreciate a steady supply of nutrients to fuel their big blooms. We recommend using a fertilizer that is lower in nitrogen and higher in phosphorus and potassium. In gardening terms, look for a label with numbers like 5-10-10 or 10-20-20.
High nitrogen (the first number on the package) encourages lots of green leaves but fewer flowers. By choosing a "bloom-booster" style fertilizer, you encourage the plant to focus its energy on making those beautiful buds.
You can start fertilizing about a month after planting and continue every three to four weeks through mid-September. If you have already improved your soil with plenty of compost, your plants may need very little extra help. Always follow the instructions on the product label to ensure you are giving the plants the right amount.
What to Do Next:
- Wait for the first green sprouts to appear before watering for the first time.
- Set a schedule to water deeply 2-3 times per week at the base of the stems.
- Apply a low-nitrogen fertilizer once a month starting in early summer.
The Secret of Pinching
If you want the most flowers possible, there is one simple trick you should use: pinching. Many new gardeners are hesitant to cut their plants, but pinching actually helps the dahlia become stronger and more productive.
When your dahlia plant is about 12 to 16 inches tall and has several sets of leaves, snip off the very top of the center stem. You only need to remove about an inch or two. This tells the plant to stop growing straight up and start growing outward.
By removing that top bud, you encourage the plant to send out side branches. More branches mean more stems, and more stems mean more flowers for you to enjoy. This simple "haircut" results in a bushier, sturdier plant that can better support the weight of its blooms later in the season.
Staking Your Dahlias
Because dahlia flowers can be heavy and the stems can be hollow, tall varieties often need a little extra support. This is especially true for big-blooming dinnerplate dahlias, where a single flower can weigh quite a bit. Staking prevents the plants from flopping over during a heavy rain or a windy day.
It is best to put your stakes in the ground at the time of planting. This prevents you from accidentally poking a hole through the tuber later in the season. You can use bamboo poles, wooden garden stakes, or even sturdy tomato cages.
As the plant grows, use soft garden twine or strips of fabric to gently tie the main stem to the stake. Check the ties every few weeks to make sure they aren't too tight as the stem thickens. For a large row of dahlias, some gardeners use the "corralling" method, where they place stakes at the corners of the bed and run twine around the entire perimeter to hold the group together.
Harvesting and Deadheading
The best part of learning how to take care of dahlia plants is the harvest. One of the most rewarding facts about dahlias is that the more you cut them, the more they bloom. When you take flowers for a vase, the plant views it as a signal to produce even more buds.
For the best results, cut your dahlias in the cool of the morning. Unlike roses or lilies, dahlias will not open much further once they are cut, so wait until the flower is nearly fully open before snipping the stem. Place the stems immediately into a bucket of room-temperature water.
If you choose to leave the flowers in the garden, you will need to deadhead them. This simply means removing the flowers once they begin to fade. If you leave the old flowers on the plant, it will start to produce seeds, which tells the plant its job is done for the year. By removing faded blooms, you trick the plant into thinking it needs to keep blooming to try and make those seeds. This keeps the color going until the first frost.
Key Takeaway: Regular cutting and deadheading are the keys to a long blooming season. Don't be afraid to fill your house with fresh bouquets; the plant will thank you with more flowers.
Managing Common Garden Visitors
Dahlias are generally very healthy, but they do have a few common visitors you should watch for. Slugs and snails are the most frequent guests, especially when the plants are young and the weather is damp. They love to nibble on the tender new leaves. We find that a simple barrier of crushed eggshells or a pet-safe slug bait can keep them at bay.
You might also notice "powdery mildew," which looks like a dusting of white flour on the leaves. This usually happens in late summer when the air is humid. You can minimize this by ensuring there is plenty of space between your plants for air to circulate. If it becomes a problem, removing the lower leaves of the plant can help improve airflow.
If you see tiny insects like aphids or mites, a strong blast of water from the garden hose is often enough to knock them off. Most dahlia problems can be solved by simply keeping the plants healthy with the right amount of sun and water. Healthy plants are naturally more resistant to pests.
End of Season Care and Overwintering
When the first frost arrives, your dahlia plants will turn black and die back. This is perfectly normal. How you take care of dahlia plants at this stage depends on where you live.
In warmer climates (USDA Hardiness Zones 8 and higher), the ground doesn't freeze deep enough to harm the tubers. You can simply cut the stems down to about 2 inches above the ground and cover the area with a few inches of mulch to protect them for the winter.
In colder climates (Zone 7 and lower), the tubers need to be protected from the freezing ground. Here is the simple process for "lifting" them:
- Cut back: After the first frost, cut the stems down to about 4 inches.
- Dig gently: Use a garden fork to lift the tubers out of the soil. Be careful not to nick or break them.
- Clean and dry: Shake off the excess dirt and let the tubers dry in a protected, shady area for a day or two.
- Store: Place the tubers in a box filled with slightly damp peat moss, sawdust, or vermiculite. Store them in a cool, dark place (like a basement or crawl space) where the temperature stays between 40°F and 50°F.
Checking on your stored tubers once or twice during the winter is a great idea. If they look shriveled, you can lightly mist the packing material with water. If any spots look soft or rotten, simply trim those parts away.
Dahlias in Containers
If you have limited space, you can still enjoy these beautiful plants. Many smaller varieties, often called "Border Dahlias" or Gallery Dahlias, are perfect for pots and window boxes. When growing in containers, follow these simple guidelines:
- Size matters: Use a pot that holds at least 2 to 5 gallons of soil, depending on the variety's size.
- Drainage: Ensure the pot has holes in the bottom. Dahlias do not like "wet feet."
- Potting Mix: Use a high-quality, well-draining potting soil rather than garden soil, which can be too heavy for containers.
- Feeding: Container plants need a bit more frequent fertilizing, as nutrients wash out with every watering. A liquid fertilizer every two weeks works well.
Growing in containers also makes it easy to move your plants to the sunniest spot on your patio as the seasons change. It is a fantastic way to bring the beauty of Longfield Gardens' varieties closer to your living space.
Troubleshooting Common Issues
Sometimes, despite our best efforts, a plant might not perform exactly as expected. Here is how to handle the most common situations:
The plant is tall but has no flowers. This is usually caused by too much nitrogen in the soil or not enough sunlight. If the plant is in a shady spot, it will stretch toward the light and forget to bloom. If you suspect your fertilizer is the culprit, switch to a bloom-focused formula with more phosphorus.
The leaves are turning yellow. Yellow leaves can be a sign of overwatering. Check the soil moisture; if it feels soggy, let it dry out for a few days. Ensure your soil or container has good drainage so the roots can breathe.
The flowers look small. If you want fewer but much larger flowers, you can try "disbudding." This involves removing the two smaller side buds that grow next to the main central bud on a stem. The plant will then send all its energy into that one single bloom, making it much larger.
The plant is wilting even though the soil is wet. This can unfortunately be a sign of tuber rot. If the soil has been saturated for a long time, the tuber may have struggled. The best fix is to ensure your planting site has better drainage for next year or to use raised beds, which offer excellent control over moisture levels.
Conclusion
Taking care of dahlia plants is a journey that pays off in a spectacular display of garden color. By getting the basics right—sunlight, drainage, and timing—you set the stage for a successful season. Remember that gardening is meant to be an enjoyable experience. Whether you are harvesting a single bloom for a bedside table or a whole bucket for friends, the effort you put into your dahlias will be returned many times over in beauty.
We are proud to help you create a more beautiful yard with our high-quality tubers. At Longfield Gardens, we 100% Quality Guarantee our plants and are here to support your gardening success every step of the way.
- Wait for warm soil (60°F) before planting tubers.
- Don't water until you see green sprouts above the ground.
- Pinch the center stem when the plant is 12-16 inches tall for more blooms.
- Cut flowers often to encourage the plant to keep producing new ones.
Growing dahlias is one of the most rewarding projects a home gardener can undertake. With just a little bit of patience and the right simple steps, your garden will be the talk of the neighborhood all summer long.
The next step is to choose your favorite colors and shapes and get ready for a season of growth. We invite you to explore our selection and find the perfect varieties to match your style.
FAQ
How deep should I plant my dahlia tubers?
Dahlia tubers should be planted about 6 to 8 inches deep in a hole. Once you place the tuber in the hole, cover it with 3 to 4 inches of soil. As the plant grows, you can gradually fill in the rest of the hole until it is level with the ground, which provides extra stability for the developing stems.
When will my dahlias start to bloom?
Dahlias typically begin blooming about 8 to 12 weeks after they are planted. This usually means you will see your first flowers in mid-to-late July, with the peak blooming period occurring in August and September. They will continue to produce new flowers right up until the first hard frost kills the foliage.
Why do I need to pinch my dahlia plants?
Pinching involves removing the top of the main stem when the plant is about a foot tall. This encourages the plant to grow multiple side branches rather than one single tall stalk. More branches result in a sturdier, bushier plant and a significantly higher number of flowers throughout the season.
Do dahlias need to be dug up every year?
Whether you need to dig up your dahlias depends on your USDA Hardiness Zone. If you live in Zone 8 or warmer, you can usually leave them in the ground with a layer of mulch for protection. In Zones 7 and colder, the ground freezes deep enough to kill the tubers, so they must be lifted and stored in a frost-free area over the winter.
