How To Grow Dahlias

Growing dahlias is equal parts science, patience, and a little bit of magic. They’re not difficult flowers—but they do reward growers who understand their rhythm. This guide is designed to help you grow strong, healthy plants and enjoy a season full of blooms.

🌱 What Are Dahlias?

Dahlias are tender perennials grown from tubers (not bulbs). They thrive in warm weather, love sunlight, and bloom continuously from mid-summer until frost when properly cared for. They especially enjoy early fall, when night time temperatures begin to cool down a bit.

At Red Clay Dahlias, we grow with the belief that dahlias don’t need perfection—just consistency, good soil, and attention at the right times.

📍 When to Plant Dahlias

Plant after your last frost date. Dahlias are cold-sensitive and should never be planted into cold or soggy soil.

Ideal soil temperature: 60°F or warmer
In most zones, planting occurs between late April and early June
Here in the WNC mountains, wait until Mother’s Day (think blackberry winter!)

If you’re unsure, wait. Dahlias planted a week late will almost always outperform dahlias planted a week early.

🌞 Where to Plant

Dahlias need full sun to thrive.

Minimum: 6 hours of direct sunlight
Ideal: 8+ hours per day

Choose a location with good airflow and well-draining soil. Avoid low spots where water collects. (On a slope? No problem—in fact, all of our dahlias are grown on a fairly steep slope!)

🌱 Soil Preparation

Dahlias prefer loose, fertile, well-draining soil.

Before planting:

Amend heavy clay soil with compost and amendments such as Michigan peat and soil conditioner. (If you’re local, you can find these at Troy’s Greenhouse in Burnsville, NC.)
It is widely suggested to avoid high-nitrogen fertilizers with dahlias, but we disagree—at least early on. In the beginning, the plant is focused on growing foliage, and nitrogen is essential for this stage. Once buds begin to appear, switching to a low-nitrogen fertilizer allows the plant to focus on blooms instead of foliage.
Soil pH should be slightly acidic to neutral. Dahlias thrive in the range of 6.5–6.8.
If planting in containers or grow bags, one excellent option is the following method (working from the bottom up):

1. Fill about 1/3 with soil conditioner

2. Add an 1 inch mushroom compost

3. Top off with a good potting soil

(This is a “Wade Certified” recommendation. All of the items mentioned above are available at Troy’s Greenhouse, 30 Cherry Lane, Burnsville, NC.)

Healthy soil equals stronger plants and better blooms.

If you want to grow the absolute best dahlias possible, soil testing is highly recommended. Testing is easy and is the only way to know exactly which amendments and fertilizers your soil needs. While soil testing is absolutely not required to grow beautiful dahlias, it makes it much easier to prevent—and treat—soil-related problems before they occur. Contact your state’s Cooperative Extension for more information. (If you’re local to Burnsville, visit the NC Cooperative Extension Office next to Rio’s Mexican Restaurant for assistance.)

🌸 How to Plant Dahlia Tubers

Once you have a good spot to plant:

Dig a hole 4–6 inches deep (If planting in red clay soil, we recommend planting 3–4 inches deep.)
Lay the tuber horizontally, with the eye (growth point) facing up
Cover lightly with soil
Do not water immediately unless the soil is very dry—then only lightly moisten it. (The tuber has no roots at this stage; all of the energy it needs to begin growing is stored inside the tuber.)

Overwatering before sprouts appear is the #1 cause of tuber rot.

(If slugs are an issue in your area, we recommend using Sluggo Plus—not regular Sluggo—or alternatives such as beer traps before shoots appear.)

💧 Watering

Once plants are established (about 4 inches tall):

Start watering lightly and allow the soil to dry out between waterings
Water deeply 2–3 times per week (In red clay soil, this is often less, as clay naturally holds moisture and dries slowly. Avoid sticking to a strict schedule—always check your soil first.)
Increase watering during extreme heat if needed; early morning watering is best
Always water at soil level

Avoid overhead watering when possible to prevent foliage issues such as powdery mildew. Overhead watering can also weigh down blooms, increasing the risk of stem breakage.

🌿 Fertilizing

Dahlias are heavy bloomers—but don’t rush the fertilizer.

Wait until plants are 12–18 inches tall
Use an all-purpose fertilizer (such as 10-10-10) until buds begin to form. Then switch to a low-nitrogen fertilizer(such as 5-10-10).
Stop fertilizing about 3 weeks before your expected first frost to encourage tuber development
Apply fertilizer every 3–4 weeks during bloom season

Too much nitrogen can result in tall plants with fewer flowers, so be sure to make the switch once buds appear.

✂️ Pinching & Pruning

Pinching encourages bushier plants and more blooms.

When plants reach 12–16 inches, pinch just above a leaf set (typically when the plant has 2–3 leaf sets formed)
Remove spent blooms regularly (deadheading)

Yes—it feels wrong. Yes—it works.

🪵 Staking & Support

Most dahlias need support—and staking doesn’t have to be complicated.

Stake at planting time (and be careful not to accidentally stab your tuber!)
Use T-posts and twine, tomato cages, corrals, or horizontal Hortanova netting
Taller varieties must be supported early

Waiting until plants flop makes support harder and increases the risk of stem breakage.

If you’re growing a large number of dahlias on a slope, we highly recommend using 2–3 layers of horizontal Hortanova netting. Another excellent option is the Florida Weave—a quick online search will bring up many helpful how-to videos.

🐞 Pests & Problems

Common issues include:

Slugs
Thrips
Earwigs
Powdery mildew

Prevention tips:

Good airflow
Morning watering
Regular inspections

Healthy plants resist pests better than stressed ones. If you’re struggling with pest pressure or have prevention questions, feel free to email us—we’re always happy to help.

🌼 Bloom Time

Dahlias typically bloom:

8–10 weeks after planting
From mid-summer until first frost

The more you cut, the more they bloom—this is key!

❄️ End of Season Care

After frost blackens the foliage:

Cut plants back, leaving approximately 6 inches of stalk above the soil
Leave tubers in the ground for 2–3 weeks to allow them to form protective “winter skin,” which is vital for successful storage
Carefully dig tubers
Allow them to dry
Store in a cool, dry, frost-free location

Proper winter storage ensures strong tubers for the next season. Please refer to our upcoming “To Dig… or Not to Dig” FAQ for more details on successfully overwintering dahlias.

❤️ A Final Note

Dahlias don’t ask for perfection—but they are famously dramatic divas. They ask for attention, yet they’re surprisingly resilient. For example, your dahlias may look happy, healthy, and gorgeous at 9 a.m., then appear completely wilted by 4 p.m. on a blazing hot July afternoon. Dramatic? Absolutely. Dangerous? Usually not. This natural drooping helps the plant conserve water—so don’t panic.

If you’re learning as you go, you’re doing it right.

If you ever have questions, I’m always happy to help—because growing flowers should feel empowering, not intimidating.

— Red Clay Dahlias

How To Grow Dahlias

Growing dahlias is equal parts science, patience, and a little bit of magic. They’re not difficult flowers—but they do reward growers who understand their rhythm. This guide is designed to help you grow strong, healthy plants and enjoy a season full of blooms.

🌱 What Are Dahlias?

Dahlias are tender perennials grown from tubers (not bulbs). They thrive in warm weather, love sunlight, and bloom continuously from mid-summer until frost when properly cared for. They especially enjoy early fall, when night time temperatures begin to cool down a bit.

At Red Clay Dahlias, we grow with the belief that dahlias don’t need perfection—just consistency, good soil, and attention at the right times.

📍 When to Plant Dahlias

Plant after your last frost date. Dahlias are cold-sensitive and should never be planted into cold or soggy soil.

Ideal soil temperature: 60°F or warmer

In most zones, planting occurs between late April and early June

Here in the WNC mountains, wait until Mother’s Day (think blackberry winter!)

If you’re unsure, wait. Dahlias planted a week late will almost always outperform dahlias planted a week early.

🌞 Where to Plant

Dahlias need full sun to thrive.

Minimum: 6 hours of direct sunlight

Ideal: 8+ hours per day

Choose a location with good airflow and well-draining soil. Avoid low spots where water collects. (On a slope? No problem—in fact, all of our dahlias are grown on a fairly steep slope!)

🌱 Soil Preparation

Dahlias prefer loose, fertile, well-draining soil.

Before planting:

Amend heavy clay soil with compost and amendments such as Michigan peat and soil conditioner. (If you’re local, you can find these at Troy’s Greenhouse in Burnsville, NC.)

Soil pH should be slightly acidic to neutral. Dahlias thrive in the range of 6.5–6.8.

If planting in containers or grow bags, one excellent option is the following method (working from the bottom up):

1. Fill about 1/3 with soil conditioner

2. Add an 1 inch mushroom compost

3. Top off with a good potting soil

(This is a “Wade Certified” recommendation. All of the items mentioned above are available at Troy’s Greenhouse, 30 Cherry Lane, Burnsville, NC.)

Healthy soil equals stronger plants and better blooms.

🌸 How to Plant Dahlia Tubers

Once you have a good spot to plant:

Dig a hole 4–6 inches deep (If planting in red clay soil, we recommend planting 3–4 inches deep.)

Lay the tuber horizontally, with the eye (growth point) facing up

Cover lightly with soil

Do not water immediately unless the soil is very dry—then only lightly moisten it. (The tuber has no roots at this stage; all of the energy it needs to begin growing is stored inside the tuber.)

Overwatering before sprouts appear is the #1 cause of tuber rot.

(If slugs are an issue in your area, we recommend using Sluggo Plus—not regular Sluggo—or alternatives such as beer traps before shoots appear.)

💧 Watering

Once plants are established (about 4 inches tall):

Start watering lightly and allow the soil to dry out between waterings

Water deeply 2–3 times per week (In red clay soil, this is often less, as clay naturally holds moisture and dries slowly. Avoid sticking to a strict schedule—always check your soil first.)

Increase watering during extreme heat if needed; early morning watering is best

Always water at soil level

Avoid overhead watering when possible to prevent foliage issues such as powdery mildew. Overhead watering can also weigh down blooms, increasing the risk of stem breakage.

🌿 Fertilizing

Dahlias are heavy bloomers—but don’t rush the fertilizer.

Wait until plants are 12–18 inches tall

Use an all-purpose fertilizer (such as 10-10-10) until buds begin to form. Then switch to a low-nitrogen fertilizer(such as 5-10-10).

Stop fertilizing about 3 weeks before your expected first frost to encourage tuber development

Apply fertilizer every 3–4 weeks during bloom season

Too much nitrogen can result in tall plants with fewer flowers, so be sure to make the switch once buds appear.

✂️ Pinching & Pruning

Pinching encourages bushier plants and more blooms.

When plants reach 12–16 inches, pinch just above a leaf set (typically when the plant has 2–3 leaf sets formed)

Remove spent blooms regularly (deadheading)

Yes—it feels wrong. Yes—it works.

🪵 Staking & Support

Most dahlias need support—and staking doesn’t have to be complicated.

Stake at planting time (and be careful not to accidentally stab your tuber!)

Use T-posts and twine, tomato cages, corrals, or horizontal Hortanova netting

Taller varieties must be supported early

Waiting until plants flop makes support harder and increases the risk of stem breakage.

If you’re growing a large number of dahlias on a slope, we highly recommend using 2–3 layers of horizontal Hortanova netting. Another excellent option is the Florida Weave—a quick online search will bring up many helpful how-to videos.

🐞 Pests & Problems

Common issues include:

Slugs

Thrips

Earwigs

Powdery mildew

Prevention tips:

Good airflow

Morning watering

Regular inspections

Healthy plants resist pests better than stressed ones. If you’re struggling with pest pressure or have prevention questions, feel free to email us—we’re always happy to help.

🌼 Bloom Time

Dahlias typically bloom:

8–10 weeks after planting

From mid-summer until first frost

The more you cut, the more they bloom—this is key!

❄️ End of Season Care

After frost blackens the foliage:

Cut plants back, leaving approximately 6 inches of stalk above the soil