Dahlia Seeds

At Marshalls Garden, we offer a wide range of Dahlia seeds to choose from including your favourites from Unwins. Our selection of Dahlia seeds can produce beautiful open flowers in a range of bright colours to delight us and attract pollinating insects. All our Dahlia seeds are of the highest quality and selected for good germination. Each seed packet has detailed instructions on how to sow. Perfect for eye-catching summer beds and borders.

  • Wide variety of high-quality Dahlia seeds.
  • Excellent as cut flowers.
  • 24-hour despatch on all in-stock seed orders 7 days a week.
  • Express delivery is provided as a standard.
  • Contact customer services six days a week, including bank holidays.

    Dahlia Seeds
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    Dahlia Seeds FAQs

    Take a look at some of the frequently asked questions we receive from those looking to buy Dahlia Seeds in the UK. You can contact our Customer Service Team or browse our general FAQs for further advice.

    When to plant Dahlia seeds

    You can sow Dahlia seeds in late winter or early spring in a greenhouse or propagator, dahlia seeds will produce young plants ready to plant outdoors in late May to flower this year.

    How to Sow Dahlia seeds

    The ideal time to sow the seeds is in spring, with a recommended germination temperature of around 18°C. Given the substantial size of the seeds, they should be sown individually to prevent overcrowding. Three options for raising them as half-hardy annuals include:

    • Sow in a seed pot or tray and then transplant into a flat seed box. If the seedlings become crowded in the box, potting up may be necessary.
    • Sow in a seed pot or tray and later transplant into individual pots.
    • Sow directly in cell packs or small containers, then potting into individual pots.

    The choice of compost is not critical, as long as it provides some drainage, such as perlite or sharp sand. John Innes Seed Compost is also suitable. After sowing and spacing out the seeds, cover them with sifted compost to a depth of approximately 3mm. The compost must be moist but not saturated before filling the pot, and the sifted compost over the seed should also be moist. A light watering with a fine rose from a watering can is sufficient.

    Place the seed pot in a propagator at a temperature of 18°C. No additional covering is necessary, except for the propagator lid and any shading material needed to prevent overheating.

    Germination typically occurs within 10-14 days, with a quicker process at higher temperatures. Once the seedling leaves touch, it's time to pot them up. Since most seeds germinate simultaneously, carefully remove the compost from the pot, breaking it up to free the seedlings. Handle the seedlings with care, as the root system may be well-developed by potting time.

    How long do Dahlia seeds take to grow

    When growing dahlias from seeds, the process typically involves starting the seeds indoors before transplanting them outdoors. Here is a general timeline:

    Start dahlia seeds indoors about 6 to 8 weeks before your area's last expected frost date. Dahlias are tender perennials, and they are sensitive to frost.

    Fill seed trays or pots with a seed-starting mix and plant the dahlia seeds about 1/4 inch deep.

    Keep the soil consistently moist, and provide warmth and light for germination. The ideal temperature for germination is around 21-24°C.

    Dahlias typically take 1 to 2 weeks to germinate, although it can vary.

    Once the seedlings have emerged and have developed a couple of sets of true leaves, they can be transplanted into larger pots.

    Wait until the danger of frost has passed before transplanting the seedlings outdoors. This is usually after the last expected frost date in your area.

    Dahlias prefer well-drained soil and a sunny location.

    Space the plants according to the specific variety's recommended spacing.

    Dahlias grown from seeds typically bloom in late summer to fall, but the exact timing can vary based on the variety.

    The overall time from sowing the seeds to seeing blooms can range from a few months to half a year or more, depending on various factors like the specific variety of dahlias, growing conditions, and your location. Keep in mind that growing dahlias from tubers or dividing existing plants is a more common and faster method for obtaining blooming plants in a shorter time frame.

    Why Grow Dahlia from Seed?

    Growing dahlias from seed offers several advantages, and while it may take longer compared to other propagation methods like tubers or cuttings, it can be a rewarding and cost-effective way to expand your dahlia collection. Here are some reasons why people choose to grow dahlias from seed:

    Growing dahlias from seed allows you to explore a wide range of dahlia varieties that may not be readily available as tubers. This opens up the opportunity to discover unique colours, shapes, and sizes that might not be found in commercial tuber offerings.

    Seeds provide a source of genetic diversity. Each seedling is unique, and you may uncover new and interesting traits as the plants mature. This can be particularly appealing to gardeners who enjoy experimentation and the surprise of seeing what characteristics emerge in the offspring.

    Seeds are generally more affordable than purchasing dahlia tubers or established plants. If you have the time and patience to wait for them to grow, starting from seeds can be a budget-friendly way to acquire a large number of plants.

    Growing dahlias from seed can be a valuable learning experience, especially for gardening enthusiasts who enjoy the entire lifecycle of plants. It provides an opportunity to understand the germination process, observe plant development, and gain hands-on experience in nurturing plants from the early stages.

    There's a unique satisfaction in successfully growing a plant from seed to maturity. Watching your dahlia seedlings develop into blooming plants can be particularly rewarding, and you may feel a greater sense of accomplishment compared to planting more established materials.

    Seeds produced by dahlias that have successfully grown in your specific growing conditions may be better adapted to your local environment. This can potentially result in hardier plants that thrive in your garden.

    While growing dahlias from seed requires more time and patience, the process can be enjoyable for those who appreciate the journey of plant cultivation. If you are looking for quick and reliable results, using tubers or cuttings might be a more suitable option.

    Where can you grow Dahlias?

    Dahlias are versatile plants that can be grown in various climates, but their specific requirements need to be met for optimal growth. Here are some general guidelines on where you can grow dahlias:

    Dahlias thrive in full sun. They require at least 6-8 hours of direct sunlight each day for optimal growth and flowering. In regions with intense summer heat, some afternoon shade may be beneficial to protect the plants from extreme temperatures.

    Dahlias prefer well-drained, fertile soil. They grow best in a slightly acidic to neutral pH range (6.5 to 7.0). Heavy or clayey soils should be amended with organic matter to improve drainage.

    Dahlias prefer moderate temperatures. They do well in climates with warm summers but can tolerate a range of temperatures. Extreme heat may cause stress to the plants, so providing adequate moisture is essential during hot periods.

    Dahlias require regular watering, especially during dry spells. Consistent moisture is important for healthy growth and flower production. However, it's crucial not to overwater, as soggy soil can lead to root rot.

    Dahlias can be grown in garden beds, borders, or containers. When grown in containers, use a well-draining potting mix, and make sure the containers have drainage holes. Container gardening allows for greater flexibility in terms of placement and can be suitable for those with limited garden space.

    In colder climates where dahlias are not reliably hardy, the tubers need to be lifted and stored indoors during the winter. This is typically done after the first frost when the foliage has died back. In warmer climates, dahlias may be left in the ground year-round.

    Before planting dahlias, it's advisable to check the specific recommendations for the particular variety you have, as some may have specific requirements or preferences. Additionally, local climate conditions, such as average temperatures and frost dates, should be taken into account for successful dahlia cultivation.

    Can you harvest Dahlia seeds?

    Yes, it is possible to harvest dahlia seeds. Dahlias produce seeds in their flowers, and if you're interested in growing new dahlias from seed, you can follow these general steps:

    Leave some flowers on the plant to mature and form seed pods. The petals will wither and fall off, leaving behind the seed pod.

    Once the seed pods have formed and started to dry, you can harvest them. The seed pods are usually located in the centre of the flower where the petals are attached.

    Use scissors or pruners to carefully cut the seed pods from the plant.

    Place the harvested seed pods in a dry and well-ventilated area to allow them to further dry. This is important for preventing mould and ensuring the seeds inside are fully mature.

    Once the seed pods are completely dry, you can open them to extract the seeds. Be careful when handling the pods, as they can be brittle.

    Separate the seeds from the pod and any chaff. You can do this by gently breaking open the pods and shaking out the seeds.

    To clean the seeds further, you can use a fine mesh sieve to remove small particles and separate the seeds.

    Store the cleaned seeds in a cool, dry place. It's a good idea to label and date the storage container.

    Some gardeners choose to stratify dahlia seeds before planting. Stratification involves exposing the seeds to a period of cold to simulate winter conditions. You can place the seeds in a moist medium (such as damp peat moss) and refrigerate them for a few weeks before planting.

    When you're ready to plant the seeds, start them indoors about 6-8 weeks before the last expected frost in your area. Plant them in a well-draining seed-starting mix, and keep the soil consistently moist.

    It's important to note that dahlias grown from seed may not necessarily resemble the parent plant, as they can exhibit genetic variations. If you have a particular dahlia variety that you want to propagate true to type, it's better to use tubers or division methods.

    Growing dahlias from seed can be a rewarding process, allowing you to explore new variations and potentially discover unique traits in the resulting plants.

    Why Buy Dahlia Seeds from Marshalls?

    • Our customers are supported by a team of experts dedicated to providing valuable advice. You can also use our growing guides, backed by 70 years of experience, to get the best results from your dahlia seeds and other plants.
    • You can contact us six days a week – including bank holidays – to discuss our products and services or to chat about all things gardening.
    • We pride ourselves on offering fast delivery on all orders, with any 'in stock' plants and seeds sent out within three working days. We're green-fingered in more ways than one, too, thanks to our fully recyclable packaging.
    • We won second place at the 2022 Great British Growing Awards for Best Online Retailer.
    • Thousands of five-star reviews on Feefo and a 100% satisfaction guarantee on all our products show that we're a company you can trust.