Regenerative No-Dig System for Overwintering Dahlias in Zone 6b/7

Initial Planting of Dahlias

Prepare new beds for planting using no-till methods such as cardboard and deep mulch and/or cover cropping and tarping. Amend soil according to soil test recommendations. Pay particular attention to pH and mineral content. Dahlias prefer a pH around 6.5; slightly acidic. It will be difficult to change the pH once the overwintering dahlias are perennialized so be sure to take the time to make adjustments prior to planting.

In Zone 6b/7, new dahlia tubers are typically planted in early to mid-May once danger of frost has passed. Dahlias can be planted anywhere from 18” to 36” apart, depending on your goals and available space. At Love ‘n Fresh Flowers, dahlias are planted 18” apart for maximum production of cut flowers with long straight stems.

Overwintering Dahlias

For overwintering dahlias in the ground here at Love ‘n Fresh Flowers in Zone 6b/7, the following steps are taken:

1. Wait until a hard frost has turned the plants black to put the dahlias to bed. If no hard frost has happened by early November, it is safe to begin anyway.

2. Cut the dahlias down at the base, leaving only an inch or two at most of a “stump”. Lay the cut debris directly on top of the dahlias beds so it can compost in place and feed next year’s crop. Chopping up the stems into slightly smaller pieces may help them be a little more tidy on top of the beds.  *We use a mulching push mower if the plants aren\’t too massive and the mower can get through them.  You could also use a flail mower.  If you do not have a mower, just going through and cutting them down by hand.

3. After all plants are cut down in the patch, broadcast/side dress any soil amendments as determined by a soil test taken in August (i.e., sulfur or lime to adjust pH or rock dusts to address a certain mineral deficiency).

4. After soil amendments are broadcast, add a layer of aged compost to the overwintering dahlia beds, ideally 1-2 inches, to provide a rich carbon source for the soil biology over the winter and to cover the soil amendments so they are naturally incorporated more quickly.

5. OPTIONAL After the compost is added, use a broad fork to loosen the soil around the edges of each bed. While some tubers may be damaged slightly by this forking, if your overwintering dahlias are in the ground for several seasons, the soil settles and you\’ll want to get air pockets back into the soil for good oxygen exchange. Insert the broad fork deeply at the side of the bed and wiggle it back and forth to open up the “crust”. Do not invert/turn the soil in any way. Just loosen it. Do this along all outside edges of the dahlias beds.

6. Now it\’s time to put a thick blanket over the entire patch. At Love ‘n Fresh Flowers, we use a combination of leaves and straw, depending on what we can get most easily each year. Grocery stores are usually tossing straw bales from their autumn displays right after Halloween as they change over for Christmas. Perfect timing to snag them for your dahlia beds. Many people are removing leaves from their lawns in early November too so also a free resource. You may be able to partner with a lawncare service or local municipality to have them dump leaves at your farm, which is very convenient, but the quality of these sources may be questionable and include lots of trash. Pine straw is another great option if you’ve got lots of pine forests near you. Regardless of the source and material, spread 8”-12” over the entire dahlia patch (walkways included). This will insulate your tubers through the coldest days of winter.

8. OPTIONAL After spreading the leaves and/or straw, spray the surface with JMS (or what I call \”leaf mold tea\”). Create the tea by collecting a big handful of rich, decomposed leaf mold from a nearby wooded area and steeping it in a bucket of water (use cheese cloth or a fine mesh strainer to hold the leaf mold) with a boiled potato as a food source for the abundant natural biology found in the handful of leaf mold. Steep the tea for about a 4-5 days before straining it and applying it with a sprayer or watering can to the surface of your dahlia beds already tucked under their “blanket” of organic matter. This tea will enliven the entire system in your perennialized dahlias to keep the soil loose and active from season to season. I learned how to make this using the book The Regenerative Grower\’s Guide to Garden Amendments by Nigel Palmer.

9. Last step is to officially tuck in the overwintering dahlias with tarps. Use large heavy impermeable (water tight) tarps to cover the entire dahlia patch. At Love ‘n Fresh Flowers, we use old billboards, but silage tarps and/or construction tarps will also work well. Weight down the tarps with sand bags and/or rocks. Be sure to put plenty of weights on the tarps (far more than you think are necessary!) because the winter winds will blow off the tarps and expose your dahlias to cold if you don’t have them well-secured.

Maintaining Established Perennial Dahlia Beds

Once the dahlias are established, the following steps are taken to ensure their longevity and productivity:

1. Pull the tarps off of the beds in mid-April when the temperatures seem to stabilize. It helps to peek under the tarps from time to time to see if there are any shoots pushing through. If there are, it’s time to take the tarps off.   Over the course of the winter, the soil biology (earthworms, microbes, etc) will have been making good use of the organic mulch too and we find that typically there\’s only about an inch or so left of all the leaves and straw we put on at the start of the winter.  So no need to worry about pulling off the leaves/straw.  In fact, it\’s the perfect thickness to provide some weed control at the start of spring.  One thing we do right away after taking the tarps off again and repeat every three weeks or so is spread pellets of the product Sluggo Plus on the beds, which controls slugs and earwigs which sometimes build up over the winter under the tarps.  This product is organic and does a great job.  You could also use homemade beer traps or create habitat for natural slug predators like ground beetles, garden snakes, and/or toads.

2. Overwintering dahlias are pinched once or twice to improve stem quality later in the season. Plants are pinched when they are about 8 inches high and/or have four sets of healthy leaves on the stem and may also be pinched once again when they grow back to 8 inches high after the first pinch. For each pinch, half the stem is removed (the stem is cut so two sets of leaves are taken off and two sets of leaves remain). The first pinch for perennialized dahlias is usually in mid-May. You may use the cuttings from pinching to root new plants.

4. The dahlias are fed throughout the season with a foliar spray calibrated to the plants’ needs at that stage in their growing cycle. Dahlias need a lot of nutrition for good flower production and plant scaffolding. Foliar feeding is the best method for delivering nutrients to perennialized dahlias.  We use several Korean Natural Farming (KNF) applications on our dahlias here at Love \’n Fresh Flowers as well as application of fish emulsion and kelp.

5. Harvest of flowers occurs throughout the season. With perennialized overwintering dahlias in Zone 6b/7, the first substantial harvest usually begins in late June and continues through late October. Peak production is in September.

6. Take soil samples for testing in late August to determine amendments that may need to be added in the coming autumn.

7. If desired, you may dig and divide tubers to increase your number of plants. Otherwise, no digging and dividing seems to be necessary in my experience. At Love ‘n Fresh Flowers, overwintering dahlias have been in the ground for five seasons without any dividing and they continue to be highly productive and healthy.  If you\’d like to increase your number of dahlia plants but don\’t want to disturb your soil by digging up tubers, you can take cuttings instead to root and create new baby plants.

I never would have guessed at the start of this no-till flower farming journey, which I now call “regenerative land stewardship”, that I would learn so much and feel like I’m finally truly awake and observant in the flower fields.  No-till flower farming has brought a newfound awareness of just how complex the ecosystem I steward is and how powerful my presence there can be, for better or for worse.

In 2018, after eight years of tilling beds every time we flipped them over and tilling the entire field from top to bottom each fall, the soil was a homogenous, dry, lifeless substrate favored by weed seedlings far more than my flower crops.  Now, in the summer of 2020, more than two years after ceasing all tilling at the farm, it’s like I’m seeing soil for the very first time.

The soil in the fields is spongy, dark, loamy, earthy in scent, and utterly packed with life of all shapes and sizes, including rich networks of white mycelium threads weaving through it, creating gorgeous aggregates of various sizes that mean the soil is full of pores and oxygen.   It gives me so much joy to dig into this richness whenever placing new transplants, knowing the roots of the plants I’ve carefully tended from seed will now enter this thriving community and instantly be surrounded and supported by all this life.

For me, no-till flower farming has really become something different than when I first bought into this farming system.  Originally, I was just looking to solve a singular problem:  a muddy field in an excessively rainy season.  But now I realize how comprehensive and wholistic this approach is and how it changes everything about farming.

For starters: it’s way more efficient!!  No-till meant that I didn’t have to keep my tractor maintained (I’ve since given up having a tractor altogether) and didn’t have to spend aggravating time coaxing the three-point hitch and the heavy tiller to connect.   I also noticed that it was a lot easier to weed throughout the season, saving us time on hot July days (woot!).  A real surprise was that we could flip beds and plant at break-neck speed compared to the previous tilling approach.   Because I didn’t have to fuss with the tractor and tiller each time, the crew could immediately jump into a bed (a partial bed at that! No waiting for the entire bed to finish and clear!) and get to work with planting.  The soil became so loose and lovely, there was no more stabbing at dry, cracked ground with a trowel.  I’ve truly been shocked at how much faster planting is;  I’m still trying to adjust my timing for planting to keep up with this new pace.

Now that I’ve been no-till flower farming for more than two full seasons, it has evolved into a truly regenerative approach with the real focus being on SUPPORTING the LIFE in and on the soil, not just stopping the disturbance of it.  All of this is not just about tillage.  It’s also about keeping living roots in the soil at all times.  And it’s about sheltering the soil so all the life in it feels safe and cozy.  Now, rather than focusing on not disturbing the soil (the core tenant of “no till”), I’m realizing that my real role as stewardess of my farm’s land is to provide for the soil life.  And in doing such, the soil’s rich web will in turn support my flowering crops.  It’s a cycle of reciprocity, often spiritual in nature and as old as the ages, that somehow got horribly lost in modern agriculture.

I’ve still got so much to learn about using farming to heal the earth, starting with the six acres under my care at the moment.  I’m reading books, watching documentaries, listening to podcasts, experimenting with making natural fertilizers with ingredients like raw milk, egg shells, and molasses (it really works!), propagating mycelium on rye seeds, observing how cover crops have so much more potential than being simply “green manure”, and spending time in my fields standing still, letting Nature teach me through observation.   I will definitely be writing a lot more on the topic of no-till flower farming and other regenerative farming practices.  Observing, appreciating and supporting the earth’s community, of which we humans are a minuscule part, has really become a deep passion of mine!

So, here’s what I’m thinking after implementing this no-till tulip planting technique:

No-till flower farming is a system of farming that (nearly, if not entirely) eliminates the turning over of the soil, be it with machinery or by hand. There are many reasons that may spur a farmer to decide to go with no-till farming practices.  Mine specifically were a notable decrease in yields due to soil compaction, continual loss of organic matter that I could just never seem to add enough to replace, and a very wet growing season in 2018.  That last bit is what really catapulted me into going wholly into no-till flower farming in 2019.  The tractor and tiller have not come out once yet this season!

I’m by no means an expert in no-till farming at this point.  Honestly, I’m barely a beginner.  I leaned heavily on my winter reading and research to get going.  Andrew Mefferd’s book The Organic No-Till Farming Revolution: High Production Methods for Small-Scale Farmers has been the foundation for what I\’ve decided to implement this first season of no-till flower farming.  I highly recommend giving it a read for the numerous case studies that it contains from diversified farms all over the country/world!  I\’ve also gleaned a lot of information from my inspiring friends, Tony and Denise, at Bare Mountain Flower Farm out in Oregon.  

The system for no-till flower farming that I’ve currently settled on for the 2019 growing season is as follows:

1. Cover crop (a mix of rye, vetch, and clover) that was sown last fall and growing vigorously this spring was maintained with bi-weekly mowing until a given bed was ready to bring into production, at which point, the cover crop was “scalped” with a push mower.
2. A single layer of large cardboard pieces was placed on top of the bed. Cardboard was 4’ wide and beds are 200’ to 250’ long.*
3. A deep layer (3”-4”) of well-aged compost was spread on top of the cardboard the full length and width of the bed. I was very careful to source a high-quality, aged compost for this.
4. Guide strings were used to keep straight lines as we transplanted four rows per bed, spacing between plants has been 4” to 6”, depending on the crop. A soil knife has been the best tool for planting, as we have been able to puncture the cardboard with it to ensure the transplant root systems can reach the soil below as they spread out.  The transplants do not initially reach the soil though; their root balls are surrounded by the compost only.  We have not attempted any direct seeding into this system.
5. Three lines of drip tape are placed on top of the bed after planting is finished. We had originally put the tape on first but we were hitting it too much under the compost and had a bevvy of leaks so putting it on top seems to be prudent with this system.

*A quick note about cardboard, as I’ve fielded a lot of questions about this already whenever the topic of no-till flower farming comes up in conversation:  I\’m using mostly cardboard that a local appliance store puts out for recycling.  I’ve also been using some shipping boxes that a retail florist occasionally brings over.  The key is to use big pieces of corrugated, brown (not colored) cardboard so that it’s easier lay out a long row quickly and efficiently.  Little pieces of cardboard would blow around in the breeze.  Basic corrugated cardboard is made from all-organic materials (soy based ink, animal hide glue, paper) so it is completely safe to use in your growing operations.  The cardboard in the beds here at my farm has been noticeably breaking down about 3 weeks after planting so it doesn’t stick around too long, but long enough to suppress the cover crop and any weeds that would want to pop up among the young transplants.

So far, I give this system a big thumbs up!  It’s not perfect by any means, but it’s working well.  The downside has been the extra labor of hauling all that cardboard and compost around.  The compost is also fairly pricey, but I figure it\’s a worthy long-term investment into future seasons of higher yields.  In terms of labor, our weeding time has gone WAY down so far this season on all our no-till flower farming beds (in comparison to our old system of using plastic mulch over a tilled bed. 

Another potential downside has been that plants initially are sluggish to get growing until the cardboard starts breaking down.   I was worried at first.  But the plants start growing vigorously as soon as they get really settled in after a few weeks and now seem to be outpacing where they would normally be at this point in the season.  I believe I’ll forego using cardboard in another season or two.  First, I need to master the art of stale-bedding with tarps in a more timely fashion so that the cover crop is truly dead before we start planting in a bed.  For now, the cardboard has been essential.

Ultimately, what I had hoped for with this pivot to a no-till flower farming system has indeed happened:  we’ve been able to plant right on schedule even throughout a stormy, wet spring.  If I was still relying on my tractor and tiller, we’d be weeks behind.  So even if the plants are a little sluggish after planting, I’ll still take it.  Because, HEY, they got planted!!

Read more flower farming related blog posts here and expect an update on no-till flower farming at the end of this growing season.  

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