Growing Dahlias from Seed vs. Tubers: 7 Pros and Cons
Dahlias are some of the most spectacular flowers in the garden. You can grow them from seeds or tubers. But which one is best? Gardening expert Melissa Strauss looks at the pros and cons of growing these beauties both ways.
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Dahlias have seen a significant resurgence in popularity in recent years. Once considered an old-fashioned flower, they are quickly becoming a favorite among cut flower gardeners. You can grow dahlias from seeds or from tubers, which are the roots that form after a year of growth.
There are benefits and disadvantages to growing these plants by both methods. Some of these may be easy to guess, and others might surprise you. Ultimately, the decision comes down to a handful of factors.
Whether you decide to grow by one method or the other, you’re sure to enjoy the results. It’s always good to make an informed decision based on your personal objectives, which should determine which direction you should take. Let’s discuss the pros and cons of planting seeds vs. growing your dahlias from tubers.
Pro 1: Cost Savings
Dahlia tubers can be costly. Some rarer varieties can run up to $100 each. Granted, that’s unusually pricey, but it’s not unheard of. I’ve found that most of the more common varieties run about ten dollars each, and the rarer types come in around $25-30.
Seeds, on the other hand, are quite reasonably priced in most cases. If you’re not picky about the varieties you are looking for, a packet will run between two and five dollars. That’s as affordable as a packet of zinnia seeds! Being able to grow about 50 dahlia plants for five dollars is a significant savings. It’s also significantly less expensive to ship them, so you’re not spending more on simply shipping tubers than you would spend on several packets.
When it comes to cost, there is no doubt that seeds are far more reasonable than tubers. If you’re just getting started and want to see how dahlias grow in your climate, this is the way to go. They are great for experimenting with and won’t break the bank.
Pro 2: Wider Variety to Choose From
This one has some caveats, to be certain, but it’s a bonus all the same in my eyes. Not all seeds breed true, so there is a bit of risk involved when you order them with one specific variety in mind.
There tends to be a wider variety available when you’re purchasing this way because they are more plentiful and easy to harvest. I’m often disappointed when I wait too long into the season and then look for a particular dahlia. Often, the highly desirable ones sell out early.
Because a single flower can produce up to 100 seeds, they sell out more slowly. Compare this to only a handful of tubers produced by an entire plant, and it’s not hard to see why tubers can be harder to find.
Pro 3: Pleasant Surprises
Another fun part of growing dahlias from seeds vs. tubers is that you’ll often get surprises in your packet. They can be unpredictable because of the extensive hybridization of these plants. We will explore this as both an advantage and a drawback, because it really does depend on your objective.
Again, if you’re just getting started with dahlias and want to see how they perform, this method is great. You can get an idea of how difficult the plants are to care for and whether you want to give them the attention they need in your environment. You can also experiment with cross-pollination to develop your own new cultivars.
Pro 4: Pollinator-Friendly
As a general rule, flowers with an open center are more pollinator-friendly than those with more densely petaled forms. A double flower makes it more difficult for pollinators to access the center. Some long-tongued bees and hummingbirds will still be able to harvest nectar from more elaborate flowers. However, smaller native bees will struggle and are unlikely to waste time on the fancier blooms.
How does this apply to the all-important question? Seeds are more likely to produce open-centered flowers. This is particularly true of mixes. With tubers, you know exactly what you’re getting. The fancier types tend to be more popular, but they aren’t necessarily as beneficial for pollinators.
Con 1: May Take Longer to Bloom
The list of drawbacks is short, but if these reasons are important to you, they will make all the difference. First of all, there is the most obvious disadvantage: bloom time.
When you plant tubers, they require about three months to reach blooming maturity. If you keep them hydrated and happy, they will continue to bloom throughout the summer and into the fall months. Typically, they will stop with the first frost, and then the plants will die back for the winter.
Seeds take a bit longer. Depending on the climate and conditions, when you plant them, you’re looking at up to four months to see flowers. This isn’t a hugely significant time-lapse, but a month is still a month, so it’s worth mentioning.
Con 2: Unpredictability
This goes both ways, as it can be nice to end up with some surprises. But, if you’re hoping for one particular variety, seeds won’t always give you what you’re looking for. Those produced by hybrids often revert to traits from one or both of the parent plants.
With them being so inexpensive, this isn’t usually tragic. But, if you had your heart set on that one flower, it can be a disappointment. In this case, it’s a good idea to go ahead and get a tuber for the flower you’re longing for. There’s no harm in picking up some seeds as well to see how they work out.
Con 3: Typically Smaller Blooms
Finally, when you grow dahlias from seeds, you’re unlikely to end up with those spectacular dinnerplate-sized flowers. It’s not an impossibility, but more often than not, the majority of your plants will be on the shorter side of the spectrum. They’re also more likely to have smaller, single-petaled flowers.
Seeds are a great way to experiment with dahlias in your garden or find small, attractive cultivars to fill in spaces. However, if you want to guarantee large, flashy blooms and specific cultivars, you’ll need to grab a few tubers.
Growing Dahlias From Seeds
You can sow directly in the garden or indoors ahead of time. Stratifying them will give you a better germination rate and doesn’t require much additional effort. Follow these steps for a good germination rate and strong plants. Start about eight to ten weeks ahead of time, with the intention of moving them outside about a week or two after the last frost date.
1. To stratify your seeds, place them in a container of moist potting mix or sand. Place them in the refrigerator for about a month.
2. After stratification is complete, you can sow indoors or out. I recommend indoors, as they take a long time to germinate and grow slowly.
3. Sow in trays in moist potting or seed starting mix. Place them 1/4 to 1/2 inch deep, lightly covering them with soil.
4. Dahlias like warm temperatures, so a heating mat will help to speed germination. The ideal temperature is between 65-80°F (18-27°C). It takes anywhere from 10-28 days for these to sprout.
5. As soon as the last frost date passes, harden off your seedlings. Place them in a spot that gets indirect sun during the day, and bring them indoors at night. They are susceptible to cold, and an unexpected frost will kill them. Gradually increase the amount of time they spend outdoors, as well as the amount of exposure.
6. After about a week, your plants should harden off and be ready for their final location.
7. Plant your dahlias about two to three feet apart to give them room to grow.
8. When your plants are about ten inches tall and have at least three sets of leaves, pinch them. Use your fingers or a small pair of shears to snip off the top set of leaves. This will encourage branching.
