How Many Flowers Can You Expect From a Single Dahlia Tuber?

Should you invest in dahlia seeds, tubers or cuttings? and where to buy ‘em

Dahlia seeds have recently become all the rage. After all, they are inexpensive and can provide a wonderful surprise. For the right person, it can even open the floodgates of a new found passion of dahlia breeding. Dahlias are quite fascinating in how dynamic they are that can lead to so many unique traits! Dahlia seeds can be easily saved from your own plants. Dahlia seeds have become quite fashionable recently, you can easily find them from Johnny Select Seeds, Floret or other small growers. And yes, plants grown from seed will produce some tubers first year. You will really want to be sure to track the ones you want to keep and cull the ones you don’t.

Starting dahlias from seed…

Following the same steps as when growing zinnias, we start dahlia seeds about 4 to 6 weeks before the last frost. Dahlia seeds can also be direct sown after the danger of frost as passed. To get a jumpstart on the season, we like to start them in the propagation house.

To accommodate the quick growth of the seedling, we prefer growing in a 50 cell tray or two-inch soil block . Dahlia seeds like warmth for germination, ideally around 70-75F. A heat mat helps to keep soil temperatures at the optimal temperature and a humidity dome will increase speed of germination by keeping the surface soil moist (but not oversaturated). When given the ideal growing conditions, germination should occur in three to five days. A key with dahlia seedlings is not letting them get too root bound. If you cannot get the seedlings out in their growing beds timely, bump up the seedlings to larger containers to keep them happy and in turn buying yourself a couple extra weeks.

To keep up with the demand for dahlias, many small growers and wholesalers have started to sell cuttings. This is especially true for the newest, most-wanted varieties that don’t produce or store tubers well.

If you need to quickly add more plants, you can also easily grow new plants from cuttings of your own tubers. From each mother tuber you can expect to get five to seven cuttings before depleting the tuber’s energy. It is great to take cuttings, especially if you want to grow more of the more expensive or “unicorn” flower types. To have your cake and eat it too, I think you should take a few cuttings and plant the tuber. Then, let it grow flowers and tubers for you.

How to propagate yourself…

Simply wake up your dahlia tubers earlier by potting them up and placing them in a warm area, an area above 55F. You can cut (with sanitized clippers) or break off a stem from the eye once they are about four inches long. Dip the cutting in a rooting hormone (our favorite is linked at the end of the post). Then place rooted cutting in a soil-less substrate (we prefer Fox Farm’s Lucky Dog or Pro-mix) in a 50-cell tray. When selecting soil-less substrate for propagating cuttings, having it with mycorrhizae is beneficial since it promotes root growth. Cover cuttings with a humidity dome lid. Keep the cutting soil moist but not soggy and mist leaves with water. With cuttings, we find ourselves misting the leaves about two or three times a day. Keep the cuttings warm, at about 65-70F but out of direct sun. A heat mat will help keep the soil temperature consistent to aide root development.

Within in about two weeks, the cuttings should begin to root. You will know they rooted when you tug on the cutting and it has resistance. Once rooted, remove the humidity dome lid.

If purchasing cuttings, be sure to get cuttings from a reputable source. It’s easy for dahlias to get diseases, and the problem gets worse when cuttings are made from plants that were not grown properly or with good hygiene. Aside from gall, tobacco mosaic virus was another one that was spreading like fire from cuttings sold. Keep plants away from your other healthy plants until you can be sure they are disease-free. Know the signs.

The good news is that you can get some great varieties for which there aren’t enough tubers, add to your stock at the last minute, and the cuttings will grow tubers for you the first year.

Tubers. Out of the three options this has been my go-to. I find quality tubers to be an easy, reliable way to get gorgeous flowers for our growing season. One bad thing about growing dahlias from seed is that I can’t be surprised by what blooms because we also do a lot of event work. A bride who wants blush isn’t typically going to go for yellow, get what I’m saying?.

When I was looking to increase stock fast, we did purchase from our wholesaler who imported from Holland. Now there is an upside: it’s a quick and inexpensive way to increase your dahlia stock. The downside is that imports can come in the incorrect variety, get cancelled or come diseased. If you do decide to buy tubers from a wholesaler, make sure to carefully check each clump before planting and again when you lift and divide them.

Purchasing from other small scale growers is my true preference. I like to support small scale farms when I can. There have been a handful of times where I did get either blind tubers, rot or even disease. These problems don’t go away when you buy dahlia tubers from small-scale growers, but they happen less often, and small-scale growers do put more care into their products.

With a handful of tubers, I know I can usually quickly multiply my stock. Dahliaaddict.com is one of my favorite resources but honestly, I tend to find growers I’ve come to love and stick with them since I appreciate their commitment to quality.

Big Box/ Retail Nurseries

I decided to throw Big Box/Retail nurseries in their own group. You can easily find tubers at big box stores, usually beginning in about March. You may or may not get what is actually pictured on the label. You can also find dahlia plants available at places such as Costco. Here are some great options for people who aren’t counting on the dahlias to sell as cut flowers. If you are growing plants to sell, I suggest that you only buy them from reputable stores that sell varieties that look good as cut flowers. There are tons of beautiful dahlia varieties but some are better for the landscape.

Because tubers are the most common way to grow dahlias, let’s talk about what a dahlia tuber is, how to fix it, and what it looks like.

Dahlias are tougher than we give them credit for, so are their tubers. That being said, it’s important to be able to tell the difference between a healthy tuber and a diseased one. Let’s talk about the body’s parts. If you need more visuals, there are some videos at the end of this post.

First, knowing the anatomy of a dahlia tuber helps tremendously.

There are three main parts to a dahlia tuber:

The crown is the root’s top part; this is where the plant’s eye comes from. Without an eye, there will be no plant and thus no flowers.

The neck is the part of the dahlia in the middle that connects the eye to the body. The body is where the dahlia plant gets its energy. Ideally, the neck should be intact to produce a viable plant. A broken neck may result in the the plant not having enough energy to mature and dying off.

The tuber should be firm to the touch and look plump. Slight shriveling doesn’t mean that the tuber isn’t viable but too much shriveling and it won’t be.

An eye that sends out a sprout that looks like cauliflower or something from a horror movie where a million eyes are trying to push out of one eye socket is a sign of the tuber. Commonly this is leafy, crown gall or what is commonly called “dahlia gall. Gall will have many stems of leaves (if the plant doesn’t die first), but no flowers, and the plant usually dies. This is because of Rhodococcus fascians, a bacteria that can be easily spread from plant wounds like cuttings. This is easily transmittable which is the bane of the dahlia world. Sanitizing tools in-between plants with a diluted bleach solution or hydrogen peroxide is recommended. If gall is suspected it is best to follow the practice “when in doubt throw it out. ” This particular bacteria does naturally occur in the soil and can transmit even through water. Rotating your dahlia crop along with sanitation practices can help prevent the spread.

Having gall is different than a tuber having multiple sets of eyes on the crown. In fact, having more than one set of eyes means that many more stalks will grow, which is a good thing! A quick Google search should give you more information. a great visual to decipher between a diseased tuber versus one with happy eyes.

Dahlias are from Mexico and like it hot. They don’t do well in cold weather, but I’ve found that the hybrid varieties we have now are much tougher than zinnias. Dahlias are best grown once the soil temperatures reach minimally 60-65F.

We plant potatoes in the field in late April or early May, depending on how our spring is going. There have been times when a late frost hit and killed the new plants, but new growth quickly came up. This did delay flowering and stress the plants more than we would have liked. In places where temperatures change quickly or there is late frost, planting plants and putting them under micro frost cloth tunnels may help them do better.

Soil Prep, spacing and planting

We use good compost and slow release fertilizer to improve our dahlia patch in the same way we do our other garden beds. Dahlias aren’t extremely hungry plants. When planting tubers, the majority of the storage is in the tuber itself. We have soil that is lower in nitrogen, luxury amounts of phosphorous and are in an arid climate. Dahlia tubers are prone to rot, having well draining soil greatly helps combat this. Over the years, we’ve added organic matter to our soil and made it a good place for soil-beneficial worms to live, which has naturally made the soil better. Dahlias should have a soil test done, and from what we’ve seen, over-fertilizing can hurt their health and productivity, leaving them open to aphids and with more leaves than flowers. Sometimes less is more, dahlias is one of those crops where this applies.

Our main growing beds for the dahlias is our 3 1/2 feet wide by 100 feet long rows. In each bed, we plant three rows of dahlias at 15” apart. This spacing allows us to fit 240 dahlias per bed. If your soil has more nitrogen or you live in a more humid area, you may need to give your dahlia plants more room to let more air flow through and keep them from getting diseases.

When planting dahlias, we have used the trench method, a post hole digger and a hori knife. Our current favorite method is using a drill auger, allowing us to plant quicker and more efficiently.

A majority of what we plant, especially that last few seasons, are single tubers. We finally found the best way to bury the dahlia tuber: we dug a hole 1.5 to 2 times as deep as the tuber and laid it on its side instead of up and down. We saw that our plants were stronger and that the dahlia necks were less likely to break during the growing season. The roots will grow from the drips, so I turn the dahlia tuber so that the body is closer to them.

Because our area is dry, we’ve found that dahlias need a lot of water as soon as they are planted. In fact, we severely under-watered our dahlias for more seasons than I’d like to admit out of fear that it would kill them. So that we can give plants a deep watering, we use low-flow drip irrigation with emitters eight inches apart. Based on the weather and wind, we water our dahlias for an hour every other day or every day. Make sure to check how wet the soil is and keep an eye on your plants to figure out how much to water them. Lack of growth or shriveling may indicate too little water. Yellowing and blackening of plants may indicate too much.

Some types of dahlias, like dinner-plate varieties, can become so top heavy that a gust of wind or a good rain can knock the plant over. Sometimes the falling of the plant can even lift the tuber from the ground. The “corral” method is our favorite way to train dahlias so that they don’t break and we can still easily harvest and lift the tubers in the fall. This is where we take baling twine and rebars and wrap the twine around the growing bed. You can see that the dahlias are standing straight thanks to the plants and the trellis.

Using Dahlias in Designs

Dahlias steal the show! They are our most requested flower, even surpassing peonies. Dahlias are a luxury flower and we use them as such: the star focal flower. Especially as a wedding farmer-florist each form of dahlia has its purpose in design. Dinnerplates are gorgeous for larger designs such as arbors but can be equally beautiful in a bridal bouquet. Many of the other types of buttons are bigger than the pom ones, but the pom ones are cute and last a long time when used for boutonnieres or corsages. For “kitchen table” items, the ball varieties are the best because they last longer in vases. Dahlias can look like they were picked from the garden, or they can be very classy for a wedding.

In our area, the winter is too cold to safely overwinter the tubers in the ground. Dahlias are hardy down to hardiness zone 8 (we are 6b, even with the new hardiness map being released… we still feel we are zone 6b). Though, there are many tricks to be able to overwinter them in colder zones and we have even done so successfully, we find it too risky.

In the fall, the tubers are dug up and stored for planting the next spring. If that seems like too much effort, mulching the dahlias heavily may protect them enough to overwinter. Either way has risks. When we dig up and store potatoes, some of them can rot if they are not stored correctly, or they can just rot for no reason at all. Storing properly will help. We will soon be writing a blog post about the best way to store potatoes in our dry climate.

To learn more about lifting, watch the video below!

How to Plant Dahlia Tubers From Start to Finish

FAQ

How many dahlia tubers should you plant together?

How many shoots per dahlia tuber?

Do dahlias flower multiple times?

Will a single dahlia tuber grow?

What size Dahlia tuber do I Need?

After that, the root system growing from the tuber is responsible for health of the plant. According to Michael Genovese of Summer Dreams Dahlia Farm, a tuber the size of a AA battery or larger is considered usable. All three of the tubers pictured below are acceptable, but the two tubers on the right are considered ideal sized.

Why do dahlia plants have tubers?

And that starts with the tubers. During the growing season, each dahlia plant produces a clump of tubers, just below the soil surface. These tubers are a way for the plant to store energy to help fuel its growth the following spring. Other types of plants that develop tubers include potatoes, cannas, caladiums, tuberous begonias and anemones.

Can you plant dahlia tubers?

Dahlia tubers are widely available for purchase and it’s surprisingly easy to plant them yourself. Use this reference guide to grow your own dahlias starting with when and how to plant tubers to dividing and storing them through the off-season.

How many dahlia plants will one clump turn into?

AA Battery for size reference. That one clump will turn into eight new plants! Whew! This took me a lot longer to put together than I realized it would! I hope you found this guide helpful. If you did, make sure you share it with all your fellow dahlia addicts!