Tips From The Garden

With proper care, our dahlia tubers can be used season after season, providing you with years of lovely blooms!

How To Plant and Grow Dahlias

Planting Season & Timing 

When is the best time to plant dahlia tubers? The planting season for dahlia tubers is from early April to early June. It is best to plant your tubers when the outdoor temperature is consistently around 60 degrees (Fahrenheit).

There is no advantage to planting your tubers early if the weather is colder than 60 degrees. If you plant when it is colder you will risk the tuber rotting and will not help the dahlia tuber grow more quickly - mother nature does that for you! 

Location & Soil 

Dahlias love to be grown in a sunny location with well-drained soil. The soil should be free of rocks and tree roots. Adding a little composted steer manure, sand, and peat moss to the soil helps the dahlia tubers grow better.

  • If your soil is heavy and has lots of clay, you will need more sand and manure. 
  • If your soil is sandy, you will need more peat moss and manure.
  • If your soil is rocky or has lots of tree roots, please choose a different site.

Spacing: Depth and Distance

Each dahlia tuber should be planted 4 to 6 inches deep and approximately 14 to 20 inches apart. 

How To Plant Your Dahlia Tubers:

    1. Dig a hole for each tuber
    2. Add a handful of bone meal to each hole
    3. Lightly mix in the meal with the soil
    4. Place the dahlia tuber horizontally in the hole
    5. Cover lightly with soil
    6. DO NOT water the tubers after planting them (wait until sprouts are at least 2 inches above ground-- see further instructions below)
    7. Apply slug and snail bait around each tuber area (see details below)
    8. Optional: Mark your dahlias (see instructions below)
    9. Optional: Stake each tuber (see instructions below)

Slug and Snail Bait

It is critical that you apply slug and snail bait around each tuber area soon after planting. Many a gardener has planted the tuber perfectly, did not apply slug/snail bait and was mortified to see that these pests feasted on the early sprouts and killed their tuber.

I use the brand Sluggo with great success and it is environmentally friendly and only needs to be reapplied every two weeks. This needs to be done throughout the growing season and a little less often once you have blooms.

Marking Your Dahlias 

Planting time is also a good time to label where each tuber is planted. You can write the name of the tuber, using a sharpie marker, on a popsicle stick, plastic stick or metal marker and place it next to the tuber. 

Please note: the name on the wooden stick will fade during the growing season so you using metal or plastic garden markers costs a little more but is a better option in the long run.

 

Maintenance & Care Of Your Dahlias

Staking and Using Good Twine

Planting time is also a good time to plant sturdy garden stakes near each tuber.  Our dahlias grow 3.5 to +5 feet in height and staking is essential to keep the plant upright and sturdy to support good growth and blooms.

I grow my dahlias in long rows and stake metal fence posts every 12 feet on both sides of the row. After the dahlias are about 2 feet in height, I use a high-quality mason twine that I wrap around each stake every 1.5 to 2 feet in height totaling a minimum of 3 rows. 

If you plant your tubers in a different pattern or a smaller space you can use 3 sturdy bamboo or other garden stakes that are at least 4.5 to 5 feet in height (above ground) per plant and use the above mentioned twine method.

Watering Your Dahlias 

Please, please, DO NOT water the tubers after planting them. 

There is enough moisture in the ground to get them started. You should only begin watering them when the sprouts are at least 2 inches or more above the ground. If you water immediately after planting they will rot and you will be very sad.  Remember that dahlias are mostly water, similar to the composition of human beings and only need water when they are growing not during gestation.

Once your dahlias have grown above ground to a height of 4-6 inches you can also set up soaker hoses for regular watering. I do not recommend hand watering because dahlias are thirsty flowers and need deep watering at the soil level 2-3 times per week for 45 minutes or longer to grow their best and give you abundant blooms. Deep watering every 2-3 days is much better then watering your dahlias daily!

Weeding

Weeding should only be done by hand; so do not use any weed killers or you will also kill your dahlias. 

Spraying for Pests and Mildew

Dahlias are a beautiful plant but they do require periodic spraying for pests and mildew. For pests, I suggest that you spray the dahlia, top to bottom, every 2 weeks beginning in July and through the end of September. It is also a good idea to spray the dahlias monthly in July and August to prevent mildew from forming on the leaves. 

Thankfully there are some good inexpensive products on the market that allow you to spray with a garden hose. We use Orthene and Bayer products for bugs and a Bayer product for preventing mildew. Spraying is best done in the hour before dusk and with no chance of rain during the evening.

Cutting and Dead Heading Your Blooms

All our Dahlias are excellent cut flowers. It is always best to cut dahlia blooms early in the morning (before 8 am) and then immediately put them in fresh water.  Each cut flower bloom can last 5 to 7 days if displayed out of direct sunlight.

Please remember that any spent blooms on your plants need to be dead headed.  Dead headed means that dying and/or fully opened blooms that are losing their petals need to be cut regularly. Regular cutting of these blooms at the base of the bloom will actually help more blooms to grow in the future. Dahlias are an amazingly prolific blooming plant. So you cut more and they in turn bloom more.

Fertilizers Or Not?

We personally do not apply any fertilizers to our dahlias during the growing season. If you properly ameliorate the soil prior to planting, fertilizers really are not necessary.

If you feel compelled to fertilize them; use fertilizers sparingly (monthly) and use a fertilizer that is low in nitrogen and high in phosphorus.

Dahlias also do best with open soil so do not put any mulch around the plants as this will result in withered and or rotted tubers and of course, more sadness.

 

How To Grow Dahlias in Containers, Planters, and Large Pots

Dahlias can also be grown in large pots and containers. It is best to not use potting soil. Instead, use planting soil mixed with some composted steer manure. Dahlias grown in pots still need to be staked and will need to be watered more often.

Follow the same procedure for spraying and growing care described above.

 

Summary of Tips For Maintaining Healthy Dahlia Blooms:

  • Stake your plants
  • Deep water 2-3/week for 45 minutes or longer
  • Weeding by hand
  • Spray for pests (every 2 weeks) and mildew (every month)
  • Dead head your blooms

 

Winter Storage Of Dahlia Tubers

Digging & Dividing Dahlia Tubers

We recommend that you dig up your dahlia tubers annually and divide and store the tubers during the winter months. After the first strong frost in the fall (usually around Halloween in the Northwest) and earlier in Northern climates. If you do not experience an early killing frost, then expect to dig them up in mid to late November.

After the frost, cut your dahlia stocks 6 inches above the bottom of the stocks and allow the tubers to cure for about two weeks before digging them up. 

How To Dig Up Your Tubers For Storage:

  1. Gently dig up each plant using a pitch fork
  2. Wash off all the dirt around the tubers
  3. Allow the tubers to semi-dry for 24 hrs in a dry and protected environment 

How To Divide Your Tubers:

Note: Not all tubers will should be kept. Make sure that the tubers you keep have a small round bump or eye attached to the main stock. With a little practice you will be able to spot the eyes more readily.

  1. Cut the center stock in to smaller clumps, and then separate each tuber using a sharp clipper and/or pairing knife; making sure that a small part of the center stock is included with each tuber.
  2. After dividing the tubers you can write the name of the tuber on each dahlia using an indelible ink pencil. (This is best done while the tuber is still moist and preserves the dahlia name on the tuber).
  3. Allow the cut tuber to dry for a minimum of 12-18 hrs
  4. Once dried, layer a cardboard box with many sheets of newspaper and put 2 inches of moist peat moss on top of the newspaper.
  5. Gently place each tuber horizontally on the peat moss ensuring than none of the tubers are touching each other. Usually peat moss that you purchase is the perfect moistness for storing the tubers. The peat moss helps ensure that the tubers maintain moisture and warmth from cool weather. 
  6. Continue to layer each layer of tubers with adequate amounts of peat moss and store your tubers in a dry and cool location - with a constant temperature of 40-45 degrees Fahrenheit. Make sure your storage location doesn't freeze as the dahlia tubers, if frozen, will rot.  If you store your tubers in a location that is too warm they may dry out and shrivel. 
  7. Please check your tubers monthly during the storage months to ensure that they are happily wintering in their cardboard box peat moss protected nest. If the peat moss appears to be getting too dry you can also lightly moisten the moss with a spray bottle.

With a little effort and proper storage your tubers will winter well and be ready to plant in the spring!

 

Summary of Suggested Additional Supplies 

  • For Planting: 
    • Garden Trowel or shovel
    • Bone meal 
    • Optional: Composted steer manure, sand, peat moss
    • Slug and snail bait (we use Sluggo)
  • For Marking:
    • Marker: Metal or plastic or popsicle stick
    • Sharpie
  • For Staking:
    • Garden stakes or bamboo (4.5 - 5 feet in height above ground)
    • Good twine (mason twine)
  • For Watering:
    • Soaker hose for deep water
  • For Maintenance: 
    • Optional Fertilizer that is low in nitrogen and high in phosphorus
    • Your hands for weeding :)
    • Pest spray (we use Orthene and Bayer products)
    • Mildew spray (we use a Bayer product)
    • Pruning shears or scissors for dead heading
  • For Dividing & Storage:
    • Sharp clipper and/or pairing knife
    • Indelible ink pencil
    • Cardboard box
    • Many sheets of newspaper
    • Moist peat moss
    • A cool, dry location (40-45 degrees Fahrenheit)