Rule #1: Keep the Soil Covered

Rarely in the diverse world of agriculture is there one golden rule or one silver bullet for every single farm. But when it comes to soil health and long-term farm sustainability, there is:  never leave the ground bare and exposed. Without something covering it, soil is at risk of erosion and the vast cosmos of life that inhabit the soil experience high mortality from exposure and lack of food. Fertility takes a huge hit when ground is left bare, particularly with continuous mechanical tillage. American and Canadian farmers learned this lesson the hard way back in the 1930s when the Dust Bowl devastated the Midwestern plains and brought North American agriculture to its knees.  

In 2014, scientists working with the United Nations estimated that if the world population continued to increase at the same rate while soil degradation also continued unchecked (the biggest culprits being large-scale conventional agriculture and deforestation), we only had 60 harvests left on this planet. While the exact science behind that calculation has been frequently debated since, the statement was nonetheless a stark wake-up call that has spurred a greater awareness that soil conservation—particularly in farming—is critical. Even small farms have a big role to play in making sure our top soils don’t blow away and as much carbon as possible is being sunk back into the earth instead of going into our atmosphere.

Quick Vocabulary Breakdown

Cash crop—a crop the farm is growing with the intention of selling the harvest.

Cover crop—a crop the farm is growing to cover and protect the soil in the off-season.

Green manure—a crop the farm is choosing to grow instead of a cash crop, typically to increase fertility or address a situational challenge.

The best way to put armor on your soil and boost a farm’s long-term fertility through carbon sequestering is to keep living roots in the soil at all times. The roots of plants help hold the soil in place when harsh wind and rain come knocking, while also feeding myriad life-forms in the soil with their exudates. In turn, the living community in the soil—consisting of microbes and macro beings like earthworms and beetles—eat and poop and decay, all of which feeds the plants in return. When there are no living roots in the soil, this generous cycle of give-and-take is broken. In surprisingly short order, soil degrades, aggregates break down, compaction builds up, runoff increases, and ultimately fertility plummets. Oh, and a lot of carbon goes “poof!” up into the atmosphere.

As farmers, we cannot always manage to keep a productive cash crop going in every bit of the earth we steward. The colder months are particularly challenging. This is where cover crops come into the equation of soil health and fertility.

Cold-hardy species like rye, triticale, and barley will provide a living blanket for the soil through the winter. In the warmer months, a farmer may choose to let a piece of the field rest for a little while. In this instance, buckwheat, cow peas, and sorghum can be excellent green manures that feed soil life with root exudates during growth and then biomass for a longer-term deposit in the organic matter bank when they get mowed down.

There are several considerations a farmer typically takes into account when choosing what exactly to grow in terms of cover crops or green manures. It can be daunting to sort this all out on your own. Much has been written on cover cropping for large farms with big equipment and forage needs. But few, if any, guides on cover crops for small-scale flower farming exist. So here is my take on it.

When I am choosing cover crops for flower farming here at my five-acre flower farm in Philadelphia, I focus on the following three considerations:

1) Window for Sowing/Growing
2) Termination Method
3) What Does the Soil Need

Window of Sowing/Growing

Cover crops and green manures are always direct seeded. As such, the soil’s temperature at the time you plan on sowing the seed is critical to successful germination. Some cover crops do well germinating in cooler soils. Some seeds would simply rot away in the same conditions.

Additionally, how long do you have before you want something else to grow in that same spot? Cover crops growing over the winter are relatively easy to schedule. But if you’re plugging in green manures to your summer planting rotation, you will need to carefully consider how long a given crop needs to do its thing. For this reason, buckwheat is a big favorite around Love ‘n Fresh Flowers; it loves our hot, humid summers and it reaches its peak biomass in just 30-40 days!

Termination Method

Coupled with when to sow and how long it takes to grow is determining how the cover crop or green manure will be “terminated”. Essentially, how are you going to kill this stuff so you can go back to growing a cash crop? If you’ve got a tractor and a flail mower, you can handle just about any cover crop. But many flower farms are smaller, with a bed layout that is not conducive to bringing a tractor into the middle of the field at the height of summer. In this case, you’ll want to use tarps and/or a smaller piece of equipment like a push mower or string trimmer.
The following steps are used at Love ‘n Fresh Flowers to terminate a cover crop or green manure:

1) Tall, dense crops like winter rye are first knocked down with a string trimmer. If the crop is not tall and dense, we skip this step.

2) Tender crops like buckwheat and the tougher crops that were already trimmed down get mowed super low with a mulching push mower.

3) Depending on the size of the space/bed, landscape fabric or tarps are placed over the area that was cover cropped, and left in place for about 10-15 days, depending on the weather and our planting schedule. This excludes light and weakens the cover crop. You could leave the tarps in place longer if desired. I choose to take them off as soon as feasible so we can get the bed replanted with new living roots to keep feeding the soil community and to keep the farm as profitable as possible.

4) Prep the bed for planting per usual.

Regardless of your termination method of choice, be sure to stay on top of terminating the crop prior to it going to seed. If you do not, then you’ll have a whole new weed problem on your hands!

What Does Your Soil Need?

The third major consideration when choosing cover crops for flower farming is what exactly are you trying to accomplish. What does your soil need? If you have sandy soil and struggle with getting your organic matter (OM) percentage up, you’ll want to choose a crop that is known for its biomass. If you have compacted clay soil and struggle with drainage, you’ll want to choose a crop that is known for having a large and fibrous root system. If you want to capture nitrogen naturally, you’ll choose a legume crop that can form nitrogen-gathering nodules on its roots. If you want to combat a fungal disease or pest buildup, you’ll want to choose a crop known for disease suppression or beneficial insect habitat. Each farm’s needs will be unique so this part will require a little research on your behalf. SARE and many agriculture seed retailers like Johnny’s provide excellent reference materials for which cover crop solves which problem.

My Top Five Favorite Cover Crops at My Farm

1) Winter rye: excellent for loosening clay soils, really good at feeding soil community over the winter, great biomass for organic matter, and you can cut seed heads for spring bouquets.
2) Vetch: fixes nitrogen, good biomass, nice mixed with rye for diversity (but don’t let it go to seed!)
3) Mustard: fight soil-borne diseases and you can let it flower in the spring to cut it for bouquet filler.
4) Buckwheat: so fast to grow, great for beneficial insects, and breaks down quickly for more rapid bed flip.
5) Dwarf sorghum: big time biomass, excellent weed suppression, and you can cut immature plumes for fall bouquets.

Did you notice there are three in the list above that can do double duty as a cut as well? Now there’s no excuse not to add cover crops to your micro farm!

Hopefully this article leaves you feeling empowered to tackle building soil health and fertility. Nothing is quite so rewarding as to look out over a swath of lush cover crop, knowing it is doing so much good for your farm!

For more discussion on soils and sustainability in flower farming, be sure to follow @notillflowers on Instagram and read more articles on my website

Jennie Love

Love ‘n Fresh Flowers

Jennie Love is owner of Love ‘n Fresh Flowers. Contact her at [email protected]