One of the more confusing experiences for new vegetable growers is the bombardment of crop rotation expectations from various sources. A lot of the crop rotation logic seems to be based in the fear that one crop will take something from the soil and leave the following crops more susceptible to nutrient deficiency and disease. I admit that in my earlier years of growing, I was caught up in this same fear, but the more I learned about soil health, the less it seemed like crop rotation should be necessary. I therefore began devoting more energy to maintaining fertile soil and happily abandoned worries of crop rotation for the sake of crop rotation. Since then, I have seen many crops perform fine planted in the same location as a similar crop the year before. I have grown corn in the same bed as corn the year before, beans in the same bed as beans the year before, tomatoes in the same bed as tomatoes the year before. The list could go on, and I have yet to see a consequence for any of our non-rotated crops in terms of their plant health. Below are two photos of the same bed in our home plot planted with corn in two consecutive years, 2021 and 2022. Can you tell which crop came first? Guess what I'm growing in this bed in 2023?
So provided you are looking after your soil health, it seems to be quite possible to grow the same crop in the same location in consecutive years. Therefore, I encourage you to grow on the wild side with me and give it a try sometime. It’s quite freeing.
That said, there is one circumstance when I still do practice crop rotation and that is the point of this whole article. The one case when I will still make an effort to rotate our crops is to avoid some pest problems. Unfortunately, we can't avoid ALL pests by moving our crops around. Some so-called pests can travel throughout your garden easily and find whatever they are after. For example, it doesn’t make sense to rotate a crop to stop birds from snacking on your pea shoots or to try to prevent a cabbage moth from finding your brassicas. Other pests are more territorial though and they may even overwinter in our garden soil, emerging in spring ready to start munching on more of their favourite vegetable delicacies. These are the pests that we can escape from more effectively with the help of a little crop rotation. A few common examples of pests that would fall into this category would be potato beetles, flea beetles, and slugs, and we've had to deal with them all at some point, so in the next few paragraphs, I'll share a bit about how we've been using crop rotation to do our best to keep these pests at bay.
Potato beetles are infamous in some neighbourhoods of our city and mysteriously absent in others. Since I was growing on up to 7 different plots for our urban farm at one point, I witnessed the difference in potato beetle pressure firsthand. In some plots, I could grow potatoes freely with no sign of these little monsters, while in other plots, any potato planting would invite an immediate infestation thanks to the network of backyard gardens that had continued to provide food for these potato beetles and keep their population alive for decades. Today, we grow on three separate garden plots that were all free of potato beetles until this spring when we discovered a new population at one plot. How can this be? Well, believe it or not, potato beetles have wings and they can apparently achieve flight, although I have yet to witness one of them in the air. A couple of adult potato beetles must have migrated a short distance to this one plot of ours this spring, quickly settling in among our potatoes. This was a surprise attack for me this season so I sadly did not catch them until hundreds of eggs had already hatched. We’ve been squishing the larvae regularly ever since and will remain committed to winning the battle for this potato territory so that we can still harvest a nice crop of potatoes this season. Despite our best efforts, I know our bug squishing won’t be perfect though. Some of the beetles will slip through all of our attacks, overwinter in this garden plot, and emerge next spring in search of more potatoes to munch. Knowing this, I could choose to plant potatoes here again next season and fight the same battle, or avoid the problem by moving our potato beds to a different area. If it's not obvious, I'll be choosing the later option, and as some added insurance, I will likely start next season’s potato crop under insect netting to make sure no new adults can discover our crop and start laying eggs.
Flea beetles are another vegetable garden pest that I avoid with the help of some crop rotation. Insect netting is an effective method of preventing flea beetle populations from exploding around our brassica crops, but occasionally there are gaps in our netting and a few flea beetles get word about our tasty snacks. If we are not attentive and careful a flea beetle population can quickly explode and since these beetles overwinter in the soil, we are very likely to experience the same problem in the following season if we plant desirable crops in the same area. So if there is ever a breach of our insect netting, it’s time to move. I even start to get jittery if I see flea beetles hanging out on our insect netting as shown in the photo above. One recent example of this is the cautionary relocation of our walk-in netted tunnel this spring. We had been using this tunnel on our home plot for the last 3 years in a row, but last season I noticed a few flea beetles in and around this tunnel. The population never got out of hand, but I knew now that there was a chance that some flea beetles could have overwintered in the beds protected by our tunnel. If they were to emerge in spring and find a tunnel full of fresh new brassica plants, I could have a real problem on my hands. It was a safer option to move the tunnel to another location where brassicas had not been grown recently. This way, I would be more likely have a pest free start to the season in my walk-in netted tunnel.
One pest that is unaffected by our insect netting barriers is the slug. Thankfully, they are not nearly as adept at moving their bodies around the garden so any slug problems that develop are typically quite localized. That’s why this is one more example when crop rotation can play an important role. If I discover a slug problem amidst an easily damaged crop like cabbage, lettuce, or celery, something significant has to change. If I were to just ignore the problem or attempt to seek and destroy the secretive slugs by hand, it would cost be quite a bit of time and I would still end up with severely damaged cabbage as shown in the stock photo below.
Since slugs are so territorial, planting a favoured crop in a sluggy area repeatedly is just encouraging the problem to persist by providing the slugs with food and habitat. Instead, I will make sure to find another location for desirable crops the following season, and the slug problem will be remedied with the removal of their preferred habitat and the use of a few iron phosphate pellets if necessary. Once the slug population is small enough to go unnoticed, I will be able to plant any crop freely in that location once again.
So there are three examples of when we have used crop rotation to discourage the increase of pest populations in our gardens. This is when crop rotation matters most. A pest filled garden can take time to recover from so a bit of extra energy spent rotating crops to avoid pests is well spent in my mind. We’ll continue to use this practice to recover from any pest problems when they do arise and keep our gardens relatively pest free, but otherwise, don’t be the least bit surprised if you see the same crop growing in the same location of our garden two years in a row.