Natural State Gardening is a weekly blog about organic gardening techniques.
As we approach a season change, we need to think about our next batch of crops. Besides considering our next crops based on their ideal growing temperatures (as covered in the Seasonal Planting post), we need to think about crop rotation.
WHAT IS CROP ROTATION?
Crop rotation is a process of planting different crop families in the same space from season to season, year to year. So, for example, instead of planting tomatoes (nightshade family) in the same corner of the garden every year, it is better to plant other crops (not nightshade family) in that corner and wait a few years before planting tomatoes or other nightshades again.
WHY CROP ROTATION MATTERS
Crop rotation helps prevent buildup of soil diseases and avoid soil nutrient depletion.
DISEASE: Diseases can linger in the soil, but they need a host similar to the original plant host to persist. That is, the disease usually needs a plant from the same family to remain active. If no such host is available (because the gardener rotated their crops properly!), the disease subsides.
NUTRIENT DEPLETION: Crops from the same plant family use up soil nutrients similarly, so they can deplete the soil of particular nutrients if repeatedly grown in one location. It is much easier to keep the soil nutritionally balanced by growing a variety of crop families in one location over time.
HOW DOES CROP ROTATION WORK?
The main principal of crop rotation is to not plant the same family in same spot year after year. Give at least two years between planting the same family in the same location; 3-4 years is better. This is especially important for the nightshade, cucurbit, and brassica families as they are most prone to disease. Here’s a breakdown of the plant families (with Latin names in parentheses):
- NIGHTSHADE (Solanaceae): tomatoes, potatoes (NOT sweet potatoes), peppers, eggplant
- CUCURBIT (Cucurbitaceae): cucumbers, squash, melon, watermelon, gourd, zucchini, pumpkin
- BRASSICA (Brassicaceae): broccoli, cabbage, cauliflower, kohlrabi, kale, collards, radish, rutabaga, turnip, mustard, Brussels sprouts, Asian greens (bok choy, tatsoi, pak choi, etc.)
- LEGUME (Leguminosae): beans, peas, fava beans, runner beans, cowpeas, lentils, garbanzos, peanuts, clover
- GOOSEFOOT (Chenopodiaceae): beets, mangels, spinach, chard, orach, quinoa
- MORNING GLORY (Convulvaceae): sweet potatoes
- SUNFLOWER (Asteraceae, Compositae): lettuce, endive, sunflowers, salsify, artichoke, cardoon, Jerusalem artichoke, tarragon, chamomile, marigolds
- ALLIUM (Alliaceae): garlic, onions, leeks, chives, shallots
- GRASS (Graminae, Poaceae): corn, rice, barley, wheat, oats, rye, millet, sorghum
- PARSLEY (Umbelliferae, Apiaceae): carrots, parsnips, parsley, cilantro/coriander, fennel, celery
- MALO (Malvaceae): okra
- BUCKWHEAT (Polygonaceae): buckwheat, rhubarb
- LILY (Liliaceae): asparagus
- VALERIANACEAE: mache/corn salad
- AIZOACEAE: New Zealand/Malabar spinach
- PORTULACEAE: purslane, portulaca, miner’s lettuce/claytonia
In addition to rotating the nightshades, cucurbits, and brassicas, it is beneficial to incorporate the legume family in your crop rotation. Why? Legumes add nitrogen to the soil via nodules in their roots!
CROP ROTATION SYSTEM
So, what’s a good system for crop rotation? One method is to have a separate portion or quadrant of the garden for each of the most disease-prone plants, but also include the beneficial plants (legumes): nightshades, cucurbits, brassicas, and legumes. In each quadrant, you can fill in gaps with crops from other crop families (not the four just mentioned). In year 2, Quadrant A’s crops then move to B, B’s move to C, C’s move to D, and D’s move to A. Example:
- quadrant A (nightshades): peppers, tomatoes; gaps filled with leeks
- quadrant B (cucurbits): melons, squash; gaps filled with lettuce
- quadrant C (brassicas): kale, cabbage, radishes; gaps filled with beets and onions
- quadrant D (legumes): peas, runner beans; gaps filled with herbs
- quadrant A (legumes): peas, runner beans; gaps filled with herbs
- quadrant B (nightshades): peppers, tomatoes; gaps filled with leeks
- quadrant C (cucurbits): melons, squash; gaps filled with lettuce
- quadrant D (brassicas): kale, cabbage, radishes; gaps filled with beets and onions
- I strongly recommend keeping written records of planting locations year after year, as it can be hard to remember plantings from years ago. For the Heights Neighborhood Garden, I am keeping these records, so don’t worry!
- Crops with foliage that blocks sunlight (such as potatoes, sweet potatoes, summer squash, or densely planted lettuce) or mulched areas will help clear weeds for weed-sensitive root crops to follow. So, you might follow a summer squash with fall carrots or beets.
- Crop rotation can get complicated over time, as you will likely not want to grow the same amounts or same families of crops each year. Just be flexible and do your best to rotate.
- If you are feeling extra adventurous, try planting your next crop with a companion plant. Companion plants have traits that benefit one another, such as the weed blocking squash benefiting the carrots or beets that follow. There are also antagonists, which are harmful to one another. Here is a table of companion plants and antagonists to consider: Companion Planting Chart
If you take only one thing away from this post, I hope it’s that you shouldn’t plant the same crop family in the same location in successive years. Remember not to view these gardening tactics as burdens. Instead, view them as fun and challenging puzzles that result in healthy crops with abundant harvests.