Seasonal articles on dahlia care — Mid Island Dahlia Society

Days grow shorter … Nights grow longer….

it’s time to close your dahlia garden

Before the first frost, consider reviewing how your dahlias performed. You can use this dahlia template to guide your garden choices next spring. All the information you should record is given ***here*, NEDS October 2024 Newsletter.**

1: Cutting down and digging up your tubers.

As show season is over and our beautiful dahlias begin to wind down and slowly wither, our thoughts and efforts will now turn to digging them up and storing them for the winter.

I will describe what we do for our two (2) display gardens (Eisenhower and Cornell / East Meadow Farm) of about 250 plants/garden. . Continue reading here.

2: Curing and storing your tubers.

When the tubers slow down or stop putting out moisture on our plastic covers (about 3-4 weeks) it is time to box them up for storage. Here’s how we box and store the tubers.

A personal note from Robert on storing dahlias.

The New England Dahlia Society (NEDS) has a several informative articles on how to divide and store dahlias.

Overview; 2. Tuber dividing; 3. Tuber storing

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Early Summer Dahlia Care

June is a pivotal month for dahlia care. By this time, your dahlia plants should be on their way to becoming well rooted, robust plants. A little extra attention now will ensure an abundance of vibrant blooms in your late summer garden.

Pruning

June is the time to prune young dahlia plants to achieve specific growing goals. Whether you want a brilliant display of color for your fall garden, an abundant harvest of cut flowers for bouquets, or quality blooms worthy of competition, different pruning techniques can be used to manage plant growth and encourage a desired plant shape or form.

Here’s a brief overview:

· Topping: This is a training technique where you cut off the top part of the main stem of a plant to encourage the growth of multiple stems from the sides, rather than one main stem. When you top a plant, it redistributes the plant’s hormones, which are responsible for vertical growth, to the lateral branches. This results in a bushier plant that leads to a higher yield of flowers or fruit.

· Pinching: Is a gentler technique that involves removing just the tips of the plant’s new shoots using your fingers. This method also encourages the plant to produce more side shoots and branches, leading to a fuller plant. It’s commonly used on herbaceous plants and flowers to significantly increase the production of flowers and create longer and stronger stems.

· Stopping: Similar to topping, stopping involves the removal of the growing point of a plant to encourage the development of side shoots. This is an uncommon term that is mostly used in the context of growing dahlias.

· In summary, topping is a more drastic form of pruning that involves cutting off the top of the main stem, while pinching is a less invasive method that simply removes the new growth tips to encourage branching. Both methods are used to create a desired plant shape and to maximize the plant’s potential for growth and productivity.

· Disbudding: Disbudding is the recommended practice of removing excess buds to allow the remaining buds to produce full size, attractive blooms on long sturdy stems suitable for home display or exhibition. If being grown only for landscape color, rather than for cut flowers or exhibition, disbudding is less necessary. Without disbudding, you’ll have more flowers, but they won’t be as large, and the stems won’t be as long.

· Buds usually appear in clusters of three. Disbudding simply entails removing the outer two side buds when they are pea size and allowing the middle or center bud to have sufficient energy to grow on to maximum size on a strong stem.

· This process results in a larger, more robust bloom suitable for showing. For more info: https://www.youtube.com/watch?v=l-KAIl7o7Ik

· Dead Heading: Is simply removing spent blooms to promote new ones.

Watering Wisely

June brings hotter temperatures and increased evaporation. Water your dahlias deeply at least once a week, aiming for the soil around the base of the plant rather than the foliage. Don’t over-water to prevent the tubers from rotting. If you're unsure whether your plants need water, feel the top inch of soil – if it's dry to the touch, it's time to water. Once the plants are a little larger, apply a light mulch around the base to retain moisture and control weeds.

Feeding for Flowers

As your dahlias transition from foliage growth to bud production, they'll benefit from a fertilizer rich in phosphorus and potassium. Look for a formula with an NPK ratio like 5-10-10 or 10-20-20, where the middle and last numbers are higher than the first. Avoid fertilizers overly high in nitrogen, which can promote leafy growth at the expense of blooms. Apply fertilizer every 3-4 weeks until early September, following the product's instructions for application rates. Stop fertilizing by early September to allow the tubers to mature.

Supporting Stately Stems

Dahlias, particularly taller varieties, will become top-heavy as flower buds develop. To prevent them from flopping over or breaking off, frequently tie the growing stems to a support stake using soft twine or other garden ties. Tie loosely to allow room for the stems to expand and to allow the plant to sway slightly with the wind.

With these suggestions, you are hopefully well on your way to a dazzling dahlia display for late summer.

Additional information on dahlia grooming can be found on the ADS’s Dahlia University website

Waking up and planting tubers for a new season.

As our dahlias orders arrive and we wake up last year’s tubers let's think forward to our 2024 dahlia growing season.

Place your stored tubers in a warm room for about two (2) weeks and you will see them begin to " eye up ". After they "eye up" you can plant them in a mixture such as Pro - Mix to start them growing. Don't over water them and don't let them be exposed to cold temperatures. A small inexpensive greenhouse works really well and protects them from colder night temperatures during the spring. A light cover of plastic or sheet will also work, anything to give them some protection.

When soil temperatures begin to warm up about the third (3rd) week in May you can think about planting them in your dahlia garden. They like soil temperatures to be about 60 degrees. I like to start my plants in pots before planting because I can regulate the amount of water they receive as they start to grow. If we get to much rain sometimes the developing tubers can rot out before they get a chance to start growing.

Plant your tubers about 4" - 6" deep and about 18” apart. You can mix in a small amount of 10 -10 -10 fertilizer if you like. Don't forget to put your stake at the head of the dahlia. By staking while planting, you will not risk piercing the tuber when it is covered up with soil. I like to cover up the tuber or plant as it grows until the filled hole is level with the rest of the garden soil.

And just like that our thoughts turn to spring …. March 2024

Reminder, Long Island hardiness zone is now 7B with last frost predicted for the last week of April.

Starting Dahlias from Seeds

Growing dahlias from seeds isn’t any harder than growing most other annuals from seeds. However, there are a few things to keep in mind.
The flowers of dahlia seedlings rarely look like their seed parents. Due to the octoploid genome (8 sets of chromosomes), countless combinations of different genetic traits can occur in seedlings.
Some of the dominant traits that tend to prevail in seedlings are open disc centers, low petal count, small blooms, tall plants, poor form, weak stems, downward facing blooms, or a single set of petals. Thus, most seed dahlias don’t look like the flashy big show dahlias most of us admire. But seed plants are usually much more vigorous and healthier than plants grown from tubers. They will do great in a garden border and are a fall favorite of many pollinators. Most seed dahlias will also make tubers that can be overwintered.
Desirable traits such as high petal counts, strong stems, good tubers, large blooms, and closed centers are far less common. It’s estimated that only 1 out of 1,000 seedlings has the right combination of desirable traits to become a show flower variety.
Seed germination typically takes between 3 days to 1 week and up to 2 weeks. However, due to the complicated genetics, even fat looking seeds might not sprout. Germination rates can sometimes be very low. Seeds can be pre-sprouted between wet paper towels in plastic bags to save space. Paper towels need to be checked daily and sprouted seeds have to be transplanted immediately and very carefully into pots with soilless growing medium.
Alternatively, sow seeds densely into soilless or seed starter mix and prick them out into larger pots as they germinate.
Dahlia seeds are very cold sensitive and should be started indoors 4 to 8 weeks before planting outside. Keep seedling trays or wet paper towels at a temperature of 70°F or higher.
Plant seedlings outside in late May. They should be well rooted and have at least 3 sets of true leaves.
Space plants 12 inches apart. If you want to increase the number of seedlings to evaluate, plant them 4 inches apart and then cull seedlings with undesirable traits as they bloom.
You can save your own seeds or buy seeds. However, many fully double show dahlia varieties make no or only few seeds. Therefore, high quality seeds from experienced dahlia hybridizers may cost $.50 to $2 for each seed.
Seeing a completely novel dahlia bloom, one you cultivated from seed, is a joy beyond measure.

https://www.newenglanddahliasociety.org

Waking up Tubers for Cuttings ONLY

February is generally too early to plant tubers indoors in pots

—> wait to pot up tubers until March/April - unless you have a heated greenhouse available

Timing for dahlia cuttings (approximate – differs by variety)

Waking up tubers: 2 to 5 weeks (some varieties need longer)

Root cuttings: 3 to 6 weeks (visible roots)

Grow on cuttings to planting size: 3 - 4 weeks

Read the full article. (with photos) here.

Winter 2024 notes (January)

We have recently checked on the condition of the stored Eisenhower Park and Cornell/EMF tubers in the root cellar at Planting Fields. Most were in excellent condition but as seen by the photos some were not. The rotten tubers were removed and dusted with sulfur and diatomaceous earth to prevent further rotting. One box had wet (not damp) paper which was a result of a very damp location and rotting tubers. This box was discarded and the tubers cleaned up. The cleaned- up tubers were then put in a new lined (newspaper and wax paper) dry apple box.

If the newspaper is bone dry, check the tubers for any shriveling. If there is some shriveling, you should add some moisture to the box by spraying some water between the newspaper and the box. Do not spray water directly on the tubers, as this will promote rot.

It is very important for you to check on the condition of your winter stored tubers. Failure to do so can result in complete tuber loss and even worse, the loss of the surrounding tubers as the rot spreads.