Dahlias are stunning summer-blooming tubers that come in a dazzling range of colors, shapes, and sizes With proper timing for planting and care, they will reward you with eye-catching flowers from midsummer until fall frost But getting the timing right is essential, especially in cooler climates like zone 5. Plant too early, and a late frost can wipe out your dahlias before they even have a chance to break ground. Plant too late, and your plants won’t have time to reach maturity and produce many blooms.
So when exactly should you be planting dahlias in zone 5? Let’s take a look at how to optimize your planting schedule for a beautiful dahlia display.
Understanding Zone 5 Conditions
Knowing your specific growing conditions helps narrow down the ideal planting time. Zone 5 covers a large section of the continental U.S. but conditions vary across the region. Here are some key zone 5 factors to consider
- Last spring frost date: Mid to late May
- First fall frost date: Late September to mid October
- Growing season: 130-180 days
- Summer high temperatures: 80-90°F
- Winter low temperatures: -10 to -20°F
These relatively short, cool seasons mean dahlias have a smaller window of opportunity compared to hotter zones. Timing is everything for success!
When to Start Dahlia Tubers Indoors
Getting a head start indoors is recommended for zone 5. This gives tubers time to sprout before transplanting outside after all danger of frost is past.
Aim to start tubers indoors 4-6 weeks before your expected last spring frost date. For most of zone 5, tubers can be started in pots inside in early to mid April. Here is a more detailed zone-by-zone guide:
- Zone 5a: Start tubers indoors in early April
- Zone 5b: Start tubers indoors in mid April
- Zone 6a: Start tubers indoors in late April
Pot up tubers in a fast-draining potting mix, keeping the soil evenly moist and in a warm spot (65-75°F). A sunny windowsill is ideal. You should see sprouts emerging within 1-2 weeks.
When to Transplant Dahlias Outdoors
Once sprouted indoors, dahlia tubers can be moved outside after all danger of frost has passed. Again, planting times vary across the large zone 5 region:
- Zone 5a: Transplant sprouted tubers in mid to late May
- Zone 5b: Transplant sprouted tubers in late May to early June
- Zone 6a: Transplant sprouted tubers in early to mid June
Work in compost or organic material when preparing planting beds. Plant tubers at the recommended depth for each variety, water well, and add mulch to retain moisture. Stake tall varieties at planting time to avoid later root damage.
Direct Planting Dahlias Outdoors
If you forgot to start tubers early or want to skip the indoor process, you can direct plant them outside once the soil has warmed sufficiently:
- Zone 5a: Plant tubers directly in early June
- Zone 5b: Plant tubers directly in mid June
- Zone 6a: Plant tubers directly in late June
Just keep in mind growth will be delayed compared to tubers started indoors, so you may get less overall bloom time before frost. Choose early flowering varieties to help maximize blooms.
Tips for Planting Dahlias in Zone 5
Follow these tips to ensure dahlia success in your zone 5 garden:
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Test soil pH and amend if needed. Dahlias prefer a slightly acidic pH between 6.5-7.0.
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Prepare beds with compost or aged manure. Dahlias are heavy feeders.
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Choose a sunny location sheltered from strong winds.
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Stake tall dahlia varieties at planting to avoid later root damage.
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Use black or red plastic mulch to warm the soil and deter weeds.
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Water tubers well after planting and keep evenly moist, especially when blooming.
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Apply a balanced liquid fertilizer monthly once plants are established.
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Pinch off the first set of leaves after planting to encourage branching.
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Deadhead spent blooms to prolong flowering into fall.
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In very hot weather, give plants a deep watering in morning and lighter one in evening.
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Watch for slugs, earwigs, and other pests and treat organically as needed.
Extending the Growing Season
Since dahlias need a long season to reach their full potential, here are some methods to stretch out spring and fall in zone 5:
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Use cloches, cold frames, or row covers early and late in season.
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Opt for dark-leaved varieties that absorb more heat.
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Position containers against south-facing walls or structures.
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Paint concrete or wood structures near plants black to absorb and radiate warmth.
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Site dahlias in microclimates protected from chill, such as against foundations.
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Choose early-blooming and smaller dahlia varieties over large late bloomers.
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Mulch heavily around tubers in fall until hard freeze is forecast.
Overwintering Dahlias in Zone 5
To save tubers for replanting next year:
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Leave plants intact until frost blackens the foliage.
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Cut stems to about 6 inches above the ground after frost.
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Once soil cools below 55°F, carefully dig up tubers and remove excess soil.
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Allow to dry in garage or basement for 1-2 weeks.
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Store tubers in boxes of vermiculite, sawdust, or dry peat at 35-40°F over winter.
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Check monthly and remove any rotting tubers to prevent spreading.
With the right indoor start timing and protection from late frosts, zone 5 gardens can burst into color with dahlias. Follow these zone 5 planting guidelines for happy, healthy plants andmasses of bright blooms to enjoy all season long.
Where to Plant Dahlias
Dahlias look their best in late summer and fall, when many other plants are starting to drop their leaves. Be sure you know the ultimate height of each dahlia variety you are planting. While some are suitable for growing in containers, others can reach 4 to 5 feet tall.
Entryways, Patios. and Decks: Border dahlias are ideal for growing in containers or for edging a walkway. These bushy, compact plants grow just 18-24″ tall and cover themselves with flowers from midsummer to frost.
Along Fences or for Screening: Dahlias can be functional as well as decorative. Full-size varieties can be planted along a property line to add privacy. You can also put them in pots to close off an area or put them in the garden to block a view you don’t want to see.
Vegetable Gardens: Dahlias and tomato plants both do best in rich, well-drained soil that stays moist and gets lots of sun. Try planting a few dahlias with your tomatoes and peppers. When harvesting your dinner, you can bring in an armload of fresh flowers for your table.
Cutting Gardens: Dahlias are fabulous cut flowers and just a few plants will give you months of blooms. Growing several different flower styles (such as double, ball and decorative) will give your bouquets a professional look.
How to Support Your Dahlias
Dahlias have hollow stems that are susceptible to breaking in rain and wind. If you want your dahlias to be taller than 3 feet, you’ll need to give them support so the stems don’t break. You can use stakes, cages or a corral method.
If you are using stakes, you will need at least one sturdy, 5- or 6-foot stake per plant. Insert the stakes at planting time to avoid damaging the plant or tubers later in the season. Drive the stake into the ground 8 to 10″ deep. As the stems grow, tie them to the stake every foot or two.
You could also put a tomato cage or a custom-made cage made of reinforcing wire around each plant. These cages can be used year after year. Be sure to put them in place shortly after planting.
Flower farmers often use a corral method to support rows of dahlias. Insert stakes every 3 to 4 feet down both sides of the row. Starting at a height of about 12″, wrap twine from one stake to the next to keep the plants inside the corral. As the plants grow, you may need to add a second or even third row of twine. For beds that contain a double rows of plants, adding a center stake will provide even more support. (See above).
Planting Dahlia Tubers for my Cut Flower Garden – Sunshine and Flora – Zone 5a Flower Farmer
FAQ
Do dahlias come back every year in Zone 5?
What month do you plant dahlias?
Can dahlias overwinter in Zone 5?
What happens if you plant dahlias too early?
Should you plant dahlias in Zone 5?
In this article, gardening expert Liz Jaros examines the optimal timing to plant your dahlias in zone 5. Patience and grit, commitment and optimism. These are the must-have qualities of a zone 5 gardener. Winter does not pass quickly in these parts. It takes its sweet, snowy time.
When should I plant dahlias?
When planting dahlias in colder zones, it is a good idea to start them off in pots. In zone 5, dahlia growth can be started in pots sometime in late April. Hopefully, you’ve saved your gallon-sized nursery pots from the previous season and can use these to get things going. If not, any gallon pot with good drainage will do the trick.
Do dahlias get into the ground early?
Winter does not pass quickly in these parts. It takes its sweet, snowy time. For dahlia lovers, anxious to bring their favorite dahlia tubers up from the basement and get some whimsy back in the yard, spring can feel like an eternity. There are some plants that zone 5 gardeners can get into the ground earlier.
How do you grow dahlias?
The secret to growing dahlias is to master their ideal environment, and know when to plant them. Wait until the ground is 60°F (15.5°C) or above, then plant them in full sun and well-draining fertile soil.