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

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.

ACTUAL ACTIVITIES:

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.