Dahlia Growing Guide

Dahlias are a beautiful addition to any garden and a great way to multiply the flowers you grow year after year. 

Dahlia tubers purchased from our farm have been grown, split and inspected by us for viability. Your tuber will have at least one visible eye upon packaging.

All our of dahlias come from a long line of local farms and are not imported.

In the PNW, you will be safe to plant your tuber by Mother’s Day. We will start planting our tubers in late April through Mother’s Day, being mindful of heavy rains and frost. 

Planting:

Plant your tuber horizontally in a well-draining and sunny location. We have planted ours in clay soil, however they do have some trouble with rot. Wool pellets (coming soon!) and adding organic matter such as compost and leaves in the fall can help with aeration if you have clay soil. You can also amend your soil before planting with some compost and a good balanced fertilizer. We use blood meal at time of planting for a nitrogen boost, but we have also used bone meal. 

Plant your tubers about 6-8” deep to give your plant a stable start. We’ve found that if we plant them too shallow, the plants will topple in strong wind. Once you have your hole dug, place your tuber horizontally in the hole. Your tuber eye (sprout) should be facing up, but it is not absolutely critical as plants just want to grow and they will find their way. For the home gardener, space your tubers 16”-18” apart.

Watering & Feeding:

Since it is quite rainy in the PNW, we do not bother to water in during planting as tubers can easily rot before they send out shoots and roots. Once you see green shoots above the soil, you can begin a watering schedule (dependent on rainfall). Dahlias do require quite a bit of water. Water plants deeply 2-3 times per week. We try to make sure the soil is damp about 1-2” below the soil surface.

Slugs love dahlias, so to keep them away from the tender shoots we scatter wool pellets around our growing plants to keep the slugs at bay (they don’t like wool!). We have also used the product Sluggo. 

Once our dahlias have several sets of true leaves and are about 12-18” tall, we start giving them some more nutrition through foliar feeding (using a spray fertilizer) about every two weeks. We mix Alaska fish fertilizer, molasses (1 Tbsp/gallon), and a water-soluble calcium (WCA) we make at home with our farm eggs for an extra calcium boost. Molasses helps increase the dahlias sugar content (BRIX) which keeps pests like aphids and earwigs at bay, while also helping provide nutrition through the fertilizer and WCA. 

Another great add for pest control is to plant sweet alyssum between your dahlias. Beneficial insects love sweet alyssum as a food source and will help you combat your typical dahlia pests.

Staking:

Last year, we did not stake our dahlias (a perk of clay soil!) and almost all did really great. We really focus on planting and pinching deeply to give the dahlias the most support. However, you can stake dahlias with t-posts, rebar or bamboo. If we were to stake our dahlias, we would surround our rows with T-Posts about every 8 feet and corral with twine. There are plenty of methods online regarding dahlia staking. 

Want blooms all season long?

Keep cutting your dahlia blooms. This will keep telling the plant their job is not yet done. Once a bloom starts dying and going to seed, that tells the plant its job is done. 

To dig or not to dig….

Historically, we have dug up most of our dahlias. We’re currently testing out leaving them in the ground with a wool & leaf mulch, we will keep you posted. In our growing zone on Orcas Island (9a), you can leave your dahlias in the ground with a thick layer of mulch. You just need to be weary of rot as it’s usually excess rain (plus freeze and thaw) that causes loss here. Ask us how we know! 

You can carefully dig up dahlias with a potato fork and store in a cool, dark place over winter (our space was about 40 degrees most of the winter). As the season draws to an end, we will share more details on dahlia digging and storing – be sure to sign up for our email list and follow us on Instagram.

Happy growing!