To me, one of the most exciting things about growing dahlias is the mystery of sowing the seeds and waiting to see what grows. Breeding dahlias from your own seed you collected during the last season saves you money and is incredibly fulfilling.
It’s an exciting process because you never really know what you will get, and there’s even the potential to breed a new cultivar that you could put on the market.
So, if you’re a dahlia lover and want to try growing them from seed, let’s explore how to breed dahlias.
Why Breed Dahlias from Seed and Not Tubers?
Dahlia seeds are not true replicas of the parent plant due to being open-pollinated and cross-pollinated with other dahlias in the area. The seed contains the genetic material from two plants: the pollinating parent and the plant that contains the pollinated disc florets.
The tubers of that plant, on the other hand, will be true to that one parent. The tubers only contain the genetic material of the parent that they’re growing from, so that’s an important distinction. Cuttings are the same way.
To potentially breed a new variety of dahlia, it needs to start with the seed.
With all things nature-orientated, you must plan ahead, assuming that not everything will turn out perfectly. I find that for every 30 dahlia plants I grow from seed, only one has the potential to be a new cultivar worth pursuing.
That’s because often, although beautiful, they don’t have all the desired dahlia properties or may not be consistent quality flower producers.
There really are an incredible number of variables with dahlias and what you could end up with, mainly due to the DNA structure of the species of plant.
Dahlias have eight sets of chromosomes (octoploids), and their genetic structures shift in sequence, giving us the incredible numbers of types and cultivars that we see today.
The shifts in genetics do not always produce a winning formula, so it is best to go into breeding dahlias from seed with a “let’s just see” perspective.
There is something magical about this process, and I recommend having a go. If you decide to breed dahlias by seed, you’re also making a budget-wise move as tubers can be expensive depending upon the type and its popularity.
When to Sow Dahlia Seeds
Dahlia seed needs to be kick-started well ahead of when you want blooms. Depending upon the climate at that time and the speed at which the subsequent seedling grows determines when a bloom will appear.
This process is slower than when planting a tuber because you are starting from scratch, and the seed not only needs to germinate, but also grow roots, start developing a tuber, and sprout greenery. The good news is that as the seedling develops, it will grow quickly.
A good rule is to sow your seed after the danger of the last frost has passed. You can get ahead by planting seeds in pots indoors in a seed starting mix, and keeping them inside until big enough to transplant when the weather permits.
What Types of Dahlia Seeds are Best for Breeding
There are many sources for obtaining seeds if you don’t have any of your own collected from your plants in previous years. Many seed companies offer a choice of ranges, such as spiral dahlias, giant dahlias, rare mixed, dwarf, and dinnerplate.
It really is up to you which selection you want to try. Contacting a local flower farmer to purchase some of their seed is also a good way of exploring the world of breeding dahlias.
It depends upon what you want the dahlias for and your preferred type. Here are a few categories:
Any dahlias that are open-faced from the moment they bloom are best if you’re trying to attract pollinators. But most blossoms will fully open in time as they mature anyway, so pretty much any dahlia will do.
Size and Visual Impact
Dinnerplate dahlias definitely provide visual impact, although sizes may vary depending on how the seed was produced, whether they were open-pollinated by insects or cross-pollinated in a targeted way by the grower of the parent plant.
Keep in mind that some cultivars like ‘Cafe au Lait’ are hybrids, so the seeds won’t grow true to the parent.
Small dwarf dahlias are best if you want a carpet of flowers. Look for cultivars like ‘Small World,’ ‘Unwin,’ and ‘Milena Fleur.’
Dahlias with more petals than the open-faced singular types provide longer vase life. Choose seeds of the more decorative types such as giant, cactus, pompon, decorative, or dinnerplate.
Sowing Dahlia Seeds
Once you have your hands on some seeds, you need to get them in the ground (or pots) and nurture the plants so you can start to breed dahlias.
Consider direct sowing the seeds outside in USDA Growing Zones 8 to 11. The optimum soil temperature is about 65-70℉, but make sure all danger of frosts has passed.
Here’s how to start dahlias in pots:
- Utilizing seed trays, sow one seed per pot or cell. You want plenty of room for the dahlia to grow before planting out.
- Use a good quality seed starting mix that holds moisture but drains well, as you don’t want the seed or growing seedling sitting in water.
- Sow the seed point end down, about a quarter inch deep, and lightly cover with the seed starting mix.
- A dahlia seed takes 14-28 days to germinate in the right conditions.
- Make sure the seed is close to the edge of each pot or cell to encourage tuber formation. The faster the roots hit something hard, the quicker a tuber will form.
- Keep the pot or tray somewhere warm with direct light for at least six hours per day.
- Keep the medium moist; the seed needs moisture to germinate and grow, but don’t overwater.
- Once at least four fully shaped leaves are on the main stem, pinch off the top shoot. This encourages better growth and triggers the plant to grow more stems. This will eventually give you a fuller, more productive dahlia display.
- Prepare to plant out once strong greenery grows above the seed starting mix and after the last frost.
How to Care for Dahlias
Dahlias are tender perennials, which means they are affected by over-watering, heavy rainfall, consistently wet soil, strong wind, and humid conditions. The potential for disease and pest issues starts from the moment the seed is planted.
There are steps that can be taken to support and reduce the risk of damage.
- Plant the seedlings in mounds of well-rotted compost or well-draining potting mix if using large containers. The main factor is it must be free-draining soil.
- Dahlias should be planted in areas of plenty of sunshine or partial shade.
- Ensure the plants aren’t too close together to reduce the risk of powdery mildew and other diseases. Leave about 12-18 inches between them for air circulation.
- Use garden stakes or floral netting to support the growth against wind and heavy rain. This is particularly important for large types like dinnerplates.
- Keep the soil moist. Water at the soil level and avoid overhead watering on the foliage to reduce the risk of powdery mildew, wilt, blight, and other diseases caused by fungi.
- Protect from pests such as snails, earwigs, and slugs by setting up traps using old plastic pots and newspaper or using clean, crushed egg shells around the base of the plant. Empty the traps regularly.
- When the dahlias bloom, take photos and label them so you know what type you have grown. You can highlight the ones you particularly like and want to keep breeding.
- If you aren’t seed-saving for breeding trials, cut off spent blooms to encourage more growth.
- In the fall, let the greenery die back and lift the tubers to store until the next growing season. Dahlias can be left in the ground but tend to rot quickly in the colder months. They can become diseased or become lunch for pests looking for winter snacks. Lifting lets you check the tubers’ condition and divide them to increase your preferred breeding dahlias the following year or trade with other growers.
- Dahlias can be cold hardy in USDA Growing Zones 8-11, depending on ground temperatures and weather conditions. Excessively wet ground conditions or freezing are unsuitable, so keep an eye on the long-range forecast. Cold and wet affect the tubers, and rot can set in, destroying any chance of blooms during the next growing season.
As the flowers develop, you can leave them to the whims of nature but if you intend to breed dahlias to create a specific look that you envision, you’ll need to take some control.
Each seed on a dahlia flower can have a different pollen parent if you leave nature to run its course. To have more control over the breeding process, you should hand-pollinate the flowers.
To do this, take a small artist’s paintbrush and pick up pollen from the dahlia you want to use in your breeding program. Wipe that pollen onto the disc floret of the other dahlia you’re using in your breeding program.
If you want to be certain that the flower isn’t pollinated by anything but the flower you’ve chosen, you’ll need to isolate the parent flower before you pollinate it by wrapping the head in gauze.
Next Seasons Breeding and Seed Saving
After you have pollinated them, leave the blooms to mature on the plant to develop seeds. Blooms need to die back for the full development of the seed, so let them dry out on the stem.
Harvest too early, and there’s a risk the seed won’t be able to germinate properly when planted. To check the stage of development, carefully look at the outer seeds. They should be plump and almost tear-drop in shape.
A dahlia bloom that develops seeds will not be covered in seeds at the center like, say, a sunflower. Rather, the first two or three outer layers will be seeds.
Closer to the center of the dahlia head will be less developed, more straight like tiny sticks rather than plump seeds.
If you find crown or leaf gall on a dahlia, discard that plant’s seed, as the disease can travel on and infect the seed.
To make sure the seed you are saving lasts till you are ready to plant, separate it from the paper-thin petal material on the exterior. Keep them away from sunlight and heat, and store them in an air-tight container.
Use something that won’t allow moisture or potential pests in.
Next year, start the process all over again, planting the seeds and watching to see what develops. Breed those flowers that show characteristics you like and deadhead the ones that don’t.
How to Get Your Breeding Dahlias Recognized
You did it! You succeeded at breeding a dahlia that you love and want to share with the world. Congrats!
There are avenues to trade your bred dahlia tubers and seek advice on registering a new variety. There is The American Dahlia Society, which has a large amount of advice and information.
There are also Facebook groups that are set up for trading homegrown dahlias and providing networking opportunities.
Look for national shows in your country. These are places for people to submit their finest breeding examples. It’s also well worth seeing if your local community has a flower show or gardening competition where dahlia entries are allowed.
Go forth and breed dahlias. Good luck!