What is “co-planting?” We define co-planting as planting more than one microgreen variety in the same tray. Popular seed suppliers offer mixes with the seeds blended together prior to purchase. For example, True Leaf Market offers a Basic Salad Mix, which includes arugula, broccoli, cabbage, kale, and kohlrabi. We’ll discuss why we would discourage co-planting, regardless of the few benefits.
Weighing Seed: Many growers will pre-weigh their seeds into small containers before planting. We use pint-sized deli containers at Piedmont Microgreens. Each pint container holds one tray’s worth of seed. The weight of seed in each container depends on the specific variety. Before the start of each week, we’ll weigh out 300+ pint containers of seed to prepare for planting.
We have a mix of broccoli, cabbage, and kohlrabi. We could weigh out, say, 20 containers of each to plant 60 total trays. When we finish with one variety, we must put that seed away, find the next variety, and check the sowing density. If we mixed all three seed varieties, we wouldn't waste time switching crops and researching sowing densities. We could weigh out 60 containers of a single pre-mixed seed blend. The time savings here, however, are minor.
Faster Harvesting: The bigger benefit of co-planting is during harvest. With crops of a blend grown in isolation, you have to cut the product into a bin, mix the varieties, and then pack the blend. If the crops were co-planted, you could cut the tray and place the blend straight into your containers. The time savings here are significant.
Varied Grow Times: Co-planting is only possible if the crops in the blend have the same grow times. A blend of three radish varieties works well for co-planting. For example, Rambo radish, Triton radish, and Daikon radish take 6-8 days to grow. Planting three radishes together prevents one variety from growing taller and shading out the other varieties. A blend of Genovese, Purple, and Lemon basil appears to also be a good combination. However, we found at Piedmont Microgreens that Lemon basil takes two weeks to grow. Genovese and Purple basil take three weeks to grow. A poor co-planting candidate would be a mix of celery, beet, and radish. Each variety takes about 28, 17, and 7 days to grow, respectively. Celery takes 10 days just to germinate. By the time the radish is ready for harvest, the celery hasn't even emerged yet.
Yield Optimization: The goal for every aspect of your farm and business should be constant improvement. Co-planting varieties makes it much harder to run trials and learn about each crop. It complicates the process of gathering yield data, tracking changes, and making improvements. Although you mixed the seeds in equal proportions, a particular tray could be 28%, 30%, and 42% of each variety rather than the intended 33%, 33%, and 33%. If you plant each of the three varieties in isolation, you will get a clearer feedback loop between sowing density, grow time, yield, and quality. Co-planting muddies these results.
Harvest Flexibility: Most farmers offer single varieties and blends. Once you build a client roster, you'll get regular orders for both single varieties and the blends that contain them. When we harvest at Piedmont Microgreens, we always start by harvesting the orders for the single varieties. Once we fill those orders, we move on to the blends containing those varieties. Why? If you run short on a particular variety, you can’t make up for it by substituting another one. For example, if a chef orders arugula and you run out, you can’t replace it with chervil. Yes, you can get close by replacing a peppery variety like arugula with a similar variety like radish. However, if you run short on a particular variety, you can adjust its percent contribution in a blend. For example, let's say you have a blend of arugula, radish, and mustard. The ideal ratios are 25% arugula, 50% radish, and 25% mustard. If you fill your solo orders for radish but have too little left to make a blend with 50% radish, you can lower that to 40%. Increase the portions of arugula and mustard to compensate. The blend will look and taste the same so long as you stay within reasonable bounds. If you made the blend at the ideal ratios and then filled the solo orders for radish, you'd short your customers with no way to troubleshoot. This relates to co-planting because co-planting reduces your flexibility at harvest. If all or most of your arugula, radish, and mustard are co-planted, you have fewer options to fill individual crop orders.
Co-planting offers a few minor time savings compared to planting varieties in isolation. However, the drawbacks overshadow the benefits. The ability to co-plant is limited because the crops must have the same grow time. Co-planting varieties also prevents accurate testing and data collection, which is crucial to farm and yield optimization. Finally, co-planting reduces the ability to be flexible and troubleshoot during harvest. If crops die or underperform, you need the most options possible to counteract the issue. If clients place last-minute orders, you also need the most flexibility to fulfill those orders. Co-planting pigeon holes you into fulfilling orders in just one way. Planting in isolation allows you to fulfill orders of single varieties and blends.
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