Evaluating Weed Suppression for Saffron Production: Manual, Flame Weeding, Tarping, and Cover Crops

Final report for FNE22-032

Project Type: Farmer
Funds awarded in 2022: $12,011.00
Projected End Date: 04/01/2024
Grant Recipient: Hobby Hill Farm
Region: Northeast
State: Vermont
Project Leader:
Erica Walch
Hobby Hill Farm
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Project Information



I wanted to figure out how to manage weeds in my saffron beds. The field beds I planted in 2020 (5,000 corms) were overwhelmed by weeds. I proposed studying the existing beds plus four new beds using the same weed management strategies in both. My plan went somewhat awry, as I wasn't able to plant more field beds (due to extremely rocky soil) so I planted raised beds. What I learned was that raised beds of densely planted saffron maintained by hand weeding with weed blocking around the beds is the most effective weed management strategy (at least out of the strategies I studied).

Project Objectives:

This project seeks to compare weed mitigation techniques in new and established saffron fields, in order to quantify the amount of time (manpower hours per week) various techniques require as well as their impact on yield of crop. 

I will compare a high-growing cover crop (buckwheat), a low-growing cover crop (red clover), putting silage tarps down at dormancy (in June or July) and doing manual weeding on saffron beds. Some beds were originally planted in 2020 and some will be planted at the start of this study. Comparisons will be made between the impacts of the weed mitigation strategies on new and on established beds. 

This will help other farmers know how to mitigate weeds in their beds and make an accurate estimate of time needed for weeding their crop.


Saffron is a high-value crop. It is often stated that saffron costs more than gold; the going rate for Vermont saffron is $60/gram. It takes approximately 150 saffron flowers to produce one gram of sellable product. Saffron is produced from the fall-flowering crocus sativus, a flower that is about three inches tall. It is a perennial crop and the corms reproduce underground with each "mother corm" producing approximately three "baby or secondary corms" per year. Saffron sends up green shoots in September, which die back in June or July, then the flowers emerge in October through early December. 

The beds where saffron is planted are essentially not doing anything above ground for most of the weed-growing season. This makes them a tremendous weed magnet. Saffron growers have a few options - spend hours each week weeding these empty-looking beds (and risk pulling up the saffron corms underground), cover the beds with plastic to block weeds (this can encourage voles, who love to eat saffron corms), ignore the weeds over the summer and just weed in the fall (this is a bad plan, but frequently happens and can impede the nutrients the corms get underground and if you leave it too late, you may not be able to tell the saffron from the grassy weeds), plant a complimentary crop or plant a cover crop. 

Researchers at URI have mentioned planting basil as a complementary crop, but have not published results (that I could find). A commercial grower in Italy planted clover as a cover crop, but has not shared the results of that Saffron cover crop - Zafferano Emiliano - Growing Saffron. A study carried out in Iran in 2013-2014 and published in 2017 tried various cover crops with various results (all positive on weed reduction and flower production) Effects of cover crops on weeds density, agronomic characteristics, flower and corm yield of saffron (Crocus sativus L.) (fao.org) 

I heard about the use of plastic sileage tarps as weed blockers at the 2021 Saffron Conference (held at UVM), but I don't believe there is published research about it. I tried putting sileage tarps down on some of my saffron beds this year after dormancy. It worked to block some weeds, but in some beds, as soon as I removed them, weeds began to grow. 

So, in this experiment, I plan to start a fresh saffron research field and plant four beds of 200 corms each. On one bed, I will plant a low cover crop (red clover), on one I will plant a tall cover crop (buckwheat), on one, I will cover with sileage tarps at dormancy, and on one I will do nothing but will weed manually (with flame weeder and by hand). I will compare the results in terms of hours of work required, crop yield, predator loss, and soil and saffron quality. I will do the same on my existing saffron bed (of 5,000 - 8,000 corms) and will see if there are any differences in the established bed vs the new bed (established bed also has established weeds).

This research will help existing and prospective saffron farmers gain an understanding of the amount of time needed year-round to maintain their beds and options that can reduce that time by reducing weeds. Less weeds also means more saffron, more profit.

Description of farm operation:

I have a small diversified farm of about 12 acres. I started farming in 2017 and raise laying hens (about 50) and pigs for pork (6-10 per year) as well as growing saffron. I planted a small orchard in 2021 (and will be expanding it in 2024), which should start producing apples in 2028. My farm hosts the Windham County Beekeepers' Club apiary. I have two farmstays (short-term rentals) on the farm. My gross revenues are about $20,000 - $30,000 per year, the largest part of this is from agritourism. I am mostly a one-person operation, but I had help on this project from a helper for 6 hours per week. I also work off-farm.


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Materials and methods:

PLANNED ACTIVITIES: In the spring of 2022, I will prepare a new saffron planting area (clear, till, and fence it). I will plant buckwheat in all the beds to prepare the soil and suppress weeds and grasses. In August 2022, I will pull up the buckwheat in all but one of the beds and will plant red clover in one bed and use a sileage tarp to cover one bed. In September 2022, I will plant four beds of 200 saffron corms each in this planting area. One bed will get saffron interplanted with the buckwheat, one bed will be planted with the red clover, and two beds will not have other crops (one will have had a month of sileage tarp coverage). 

The same interventions (clover, buckwheat, tarp, and nothing) will be done to four beds of established saffron, with +/- 200 corms per bed.

Once the saffron is planted, I and an employee will spend up to three hours each week (total of up to six hours weekly) weeding the beds by hand through harvest time (October/November) and we will weigh the weekly weed harvest and record manpower hours bed by bed. We will also measure the harvest of crop per bed (number of flowers) and weigh the saffron per bed. We will send a sample of the soil from each bed to UVM for soil analysis.


YEAR ONE (2022): I had the area for the new beds cleared (tree and brush removal), but when I went to till it and install the fence, it was too rocky to work with, so I instead got 12" high raised bed planters and filled each with 9 cubic yards of professional planting mix (bagged, which contained perlite). The buckwheat I planted failed to take in any of the beds (old or new), but the clover did. Weeding took far longer than six hours per week in the established bed - the weeds were relentless (mostly grass and raspberries but also an invasive - Carolina Horse Nettle - that is a horror and rightly nicknamed "Satan's Tomato"). We wound up not weighing the weeds, but there were a lot. At least two wheelbarrows worth per week from the four beds. The raised beds with pro soil had zero weeds. 

I sent soil samples to UVM right in the midst of saffron flowering. The results were interesting (this was my first time ever doing soil testing). In the bagged professional soil, the bed with the clover was super low on potassium, and all of the plots (except for the established one where buckwheat was planted but didn't take) needed a lot more limestone. 

The saffron harvest in the new plantings (raised beds with professional planting mix) was decent -- four and a half grams of dehydrated saffron from 1,000 corms planted (avg 200 plants per gram). The plants were obviously healthy and robust with lots of green shoots post-harvest (noticeably less robust in the bed with the clover cover crop). The saffron harvest in the established beds was meager - about a half a gram. Shoots came up in most of the established plots, but there wasn't a lot of flowering. The plot that I had tarped during weeding season had no flowers or greens, and when I dug through the earth I found no corms -- indicative of voles getting in under the tarp, where they're invisible to owls and hawks, and eating the corms.  The green shoots of the established plants are also less dark green, less tall, and generally less robust than those in the raised beds. The soil was very compacted in the established beds too. 

YEAR TWO (2023): Starting in May 2023, we started weeding the eight beds (established and new, with same four interventions), but by the end of July, the field beds were just unmanageable. The area where the saffron was planted is so rocky and steep that it's impossible to get a mower in there, and even though I went at it with a weed whacker, it was just out of control. Bears were also living in the plot. So with my TA's support, we just abandoned this area and learned the following lesson: forget about planting saffron in field rows in weedy/grassy areas. 

The raised beds, however were manageable. We hand weeded until dormancy. We also took some leaves from the field beds and the raised beds and found the average length of the field bed leaves just prior to dormancy (June) was 8 inches, while the average length of the leaves in the raised beds was 14 inches. Longer leaves means healthier plants.

From May - July, the beds with the cover crops: buckwheat and clover, had very few weeds. This was a very rainy year. In 2021, I lost most of my crop due to what I know believe was corm rot because it was such a wet year. 2023 was also a very wet year, but the raised beds did fine. It was very manageable to weed them and took maybe half an hour per week. The clover again was very dominant and the buckwheat was very sickly and leggy. The areas around the raised beds, though, had a lot of weeds, even though it was rocky soil that we had put a two-inch thick layer of wood chips down on. So that is where my helper and I concentrated on weeding. When the beds went dormant, around July 10th, we dug up sample corms from each raised bed and measured them and looked for corm rot. No corm rot found, but we did find that the corms in the clover bed were smallest. The corms in the hand-weed bed were the largest. So once everything was measured, we put the sileage tarp on one bed (half white-side-up, half black-side-up) and planted new buckwheat. After the big storm in July, I dug up more corms to check for corm rot and they all looked fine. The buckwheat continued very leggy and poor-looking and clover got extremely vigorous. I did soil samples in September and got advice from UVM that the results suggested soil amendments, which I did. In September, I pulled up the buckwheat and clover and removed the tarp. I continued to do light hand-weeding (there were very few weeds) and in mid-October, leaves appeared, followed by the first flower on October 18. 

I harvested and counted the flowers from each bed a few times in October. Then dried and packaged the saffron for sale.

Research results and discussion:

My original plan was to study two field crops for weed suppression techniques, with four established beds and four new beds. When I went to plant the new beds, the soil was so rocky that I couldn't get in it, so I got permission to do raised beds instead. I got wooden (untreated cedar) boxes and filled them with store-bought "organic professional growing soil". The field bed continued to get totally overrun with weeds, and I eventually just abandoned it due in part to the weeds, but also because some bears were sleeping in it (they'd broken through the fence). 

The cover crops I used (buckwheat and red clover) competed with the saffron for nutrients and space. Silage tarps to cover dormant beds allowed for rodents to eat corms undetected. The best yield and least weeds were in the hand-weeded bed. 

The table below shows the 2023 harvest 

  Buckwheat Clover Tarp Hand Weed  
10/19/23 75 75 7 90  
10/22/23 50 70 100 125  
10/27/23 25 40 90 80  
10/28/23 8 8 15 20  
11/5/23 4 5 5 3  
          TOTAL TOTAL
BED TOTALS 162 198 217 318 895


The highest yield of flowers was in the hand-weed bed, followed by the tarped bed. The yield of saffron by number of flowers this year also approximated what the "industry standard" is of 160 flowers to make one gram of saffron. This is much better than previous years, as shown in the comparison chart below:

  Corms Planted Expected total plants from reproduction and 20% loss of corms Sellable Saffron Grams Flowers per gram of sellable saffron Notable events
2020 5,000 n/a 9 gathered, but I burned one Not measured burned one gram
2021 n/a 8,000-15,000 0.75 gram Not measured massive flooding, corm rot, resulted in near total loss of crop
2022 1,000 no reproduction, but got a few flowers from the original field beds 5.5 grams 170 a little from old field beds, maybe half a gram
2023 n/a 2,000 - 3,200 5.5 grams 162 lots of rain, but raised beds were fine, then deep freeze in early November froze some flowers and production stopped

I had expected to get more than 6 grams this year, but the deep freeze and snow in early November killed/ruined several flowers and basically stopped the harvest season. 

Research conclusions:

I wanted to learn about how to fight/suppress/avoid the weeds that were taking over my small-scale saffron operation. I thought that cover crops or silage tarps were the answer. What I really learned is that planting corms densely in raised beds, using store-bought growing mix to start, employing hand weeding and ensuring good weed suppression all around the outside of the beds is really the way to go. 

My original approach to saffron (5,000 corms in a field) was unmanageable due to weeds and corm loss from excessive rain that rotted the corms. This new approach with raised beds is more profitable and takes less time, although it costs more to establish. I plan to add 5,000 more corms in 20 additional raised beds next year (2024). Unlike the first 5,000 corms I planted in the field that yielded 9 grams (8 sellable grams due to farmer-error in burning a gram) at $60/gram or $480 in revenues, this new 5,000 grams in raised beds, along with the existing 1,000 corms planted in 2022 (and their babies) should produce at least 25 grams, which, at the same price of $60/gram, will yield $1,500 in revenues, and will turn a profit in 2025. 

So my conclusions from this research are that for small-scale saffron operations that are part of a diversified farm (like mine), the ideal set up is to:

  • Tarp ground to kill weeds for 3-6 months to prepare planting area
  • Optional: use hardware cloth in the bottom of raised beds if underground rodents are likely to come up to eat your corms (less applicable in rocky soil)
  • Use permanent raised beds made of wood (untreated cedar is a good choice) 12 inches deep 
  • Use store-bought soil/growing mix and fill the beds 12 inches deep
  • Plant your corms as close to the bottom of those 12 inches and plant them 24 plants per square foot (six rows of four corms per SF)
  • Put a weed barrier around the pathways (cardboard and wood chips is a low-cost and non-plastic method)
  • Hand weed
  • Test the soil and amend as necessary
  • Check corms for rot when they go dormant
  • Separate and replant every 3-4 years (probably on the 3 year side if planted so close together)
Participation Summary
1 Farmers participating in research

Education & Outreach Activities and Participation Summary

1 Curricula, factsheets or educational tools
2 On-farm demonstrations
4 Tours

Participation Summary:

12 Farmers participated
Education/outreach description:

I hosted tours and talks during Open Farm Week in September. 

I would like to present at the Saffron Conference in March of 2024.

A power point that describes research done on a small farm to find ways to fight weeds when growing saffron: Weed-Suppression-Techniques-For-Growing-Saffron-in-Southern-Vermont

Learning Outcomes

1 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key areas in which farmers reported changes in knowledge, attitude, skills and/or awareness:

Weed suppression

best practices

measuring/record keeping

Project Outcomes

1 Farmers changed or adopted a practice
1 Grant applied for that built upon this project
1 Grant received that built upon this project
$12,011.00 Dollar amount of grant received that built upon this project
Project outcomes:

Well, like I said, I'll be getting rid of the field and planting in raised beds with the growing mix and putting down weed barriers around the beds from now on. The labor is minimal - very little weeding. It was so frustrating to go out in that field and face the weeds day after day. Having healthy, non-weedy beds was deeply satisfying, and having an easy and productive harvest after a difficult 2020 and a horrible 2021 was certainly good for my quality of life. 

I'm trying to make a living on my small diversified farm, so having a succesful crop with a proven growing method that I can scale up next year is great.

Assessment of Project Approach and Areas of Further Study:

I am so glad that I chose rocky soil to try to plant more beds and was allowed to try raised beds instead! I learned that the way I was approaching saffron growing was basically all the least productive and most time-consuming and frustrating way possible. I will be doing it totally differently from now on, abandoning field planting and using raised-beds and bagged soil (to start the beds) from now on. And I'll test and amend the soil in the beds. This method requires just a bit of regular hand weeding (provided that paths around the saffron are kept weed-free) and requires far less time than the original field plantings. 

I did answer the question I set out to study, but in a surprising way. 

I guess additional research might look into the optimal corm density for planting and then how frequently corms would need to be dug up and separated if planted more or less densely. Also, optimal soil composition would be a good thing to research. Maybe someone could create a saffron-specific planting medium. 

I think anyone who is interested in starting small-scale saffron would benefit from learning what I found. Large operations with acres of crops and employees can spend the time and money to grow in the field, and the raised beds and bagged soil is probably prohibitively expensive for a large operation, but for a small scale, diversified farm looking to add a fall crop, I think my method is a good one. You'll invest a couple thousand dollars at start up, but should make it back in two or three years without needing much additional input.

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Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.