How to plant dahlia tubers
Open the tuber package as soon as possible. Check that the tuber looks dry but not shriveled up. If there are any broken “necks” where pieces of the tuber are dangling, clip those off. They will not grow when broken from the main tuber and they will become a rot liability in the ground.
Look for an eye. These were very difficult for me to spot at first, but over time it becomes easier. If your tubers have been stored in a moderate temperature and spring is here, they may even be sending up shoots already! (It is totally fine to plant your tuber and bury this shoot, even if there is green on it. The shoot will work itself up above the ground). If you see a shoot and it breaks off, don’t worry. The eye will grow a new shoot - just plant and watch.
Here are some examples of eyes and shoots starting to grow.
Dahlias are rather tolerant of soil conditions. They do not like a ton of nitrogen in the soil. Well-drained soil is key - they will not do well planted in heavy clay or where ground stays wet.
When planting tubers in our climate 8b in western Washington, wet soil and rain can be an issue. My usual safe rule of thumb is to plant on Mother’s Day or beginning of May if the weather forecast looks fair. Definitely wait until after last frost, but also be mindful of how much rain is forecast. The most vulnerable period of time is when the tuber is first planted until green growth/leaves show above ground. If the ground is too wet or the weather consistently rains, the tuber could rot as it sits in wet soggy ground and does not yet have the root system/leaves to begin photosynthesizing.
Do not water your tubers until green growth shows. Damp earth is perfect for them to start developing. If your soil is very dry, one light watering at planting time is good.
Identify the eyes and lay tuber horizontally in a hole several inches deep. You can see my fingers as a reference to show how deep the hole is - about 4-6 inches is ideal.
Cover the tuber with soil, press down, and depending on outside temperatures and if you had shoots visible when planting, you should see growth in 2 weeks, give or take a bit.
Now is the time to label next to your dahlia tuber, and also to stake it. Some method of support is needed for dahlias (especially for bigger bloom size dahlias!) because rain weight or wind can damage blooms and branches later in the season if the plant is not supported.
If you are only planting several plants - the easiest method is to get a thick stake and drive into the ground right now at planting time. Then there is no risk to spearing the underground tuber. Drive the stake deeply into the ground - the bigger your dahlia variety, the more weight and bulk will be hanging onto your stake, so stake accordingly! If you plant dinnerplate size dahlias and/or are in a windy area, you could benefit from two stakes on either side of the tuber to give additional support late in the season. As the plant grows, simply tie twine around the plant and around the stake.
If you are planting a large number of tubers in a row, there are “shoelace” methods of staking around the edges of the row and then zig-zagging heavy twine criss-cross through the plants. Hortanova netting and metal hoops are the method I use. T-posts can also be used for support.
Now is also the time to ensure you have slug control ready to go for when baby green dahlia leaves show above ground. As excited as you’ll be for dahlias, slugs are even more excited! You need to take steps to defend your babies until they become big enough to withstand slug pressure. I recommend and use Sluggo Plus - an OMRI-certified organic pest deterrent aimed at slugs and earwigs (which are the main pests I battle in the Pacific Northwest when it comes to dahlias).
Please comment or contact me if you have any questions - I’m excited for your dahlia venture and ready to help however I can! Better yet, send me photos of your dahlias growing or when they bloom - I love to celebrate your growth!
