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    37 Garden Plants That Can Harm Each Other

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    37 Garden Plants That Can Harm Each Other

    You’ve probably heard about companion gardening – the concept of planting certain plants near each other for natural benefits such as better growth, higher yields, and pest control. However, you may not realize that just as some plants grow better together, others do not. In fact, some plants can be hampered by close proximity to certain other plants.

    First, let’s look at some general rules to follow to avoid companion planting problems . Then, we will examine certain garden vegetables that don't grow well next to certain other plants.

    Keeping in mind the main things plants need in order to thrive – light, nutrients, and water – will help you in determining which plants should be grouped together in the garden.

    In terms of light, some plants are incompatible because of their size differences and their light requirements. For example, avoid planting tomato plants, which can grow tall and leafy, beside bush beans. The tomato plants likely will overshadow the smaller bush bean plants.

    Many gardeners successfully avoid this shadow problem with careful spacing and by placing smaller plants in their own row as an edge to a garden bed that also contains taller plants.

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    All plants don’t have the same needs for water and soil nutrients. Be sure to give thirsty plants plenty of space so they don’t hog all the moisture and fertilizer away from other plants. Be diligent with your weeding, as weeds are notorious for leeching soil, water, and sunlight from other plants as they grow.

    Another reason to avoid planting certain plants near each other is that one plant may attract a type of insect that harms the other.

    Additionally, some plants can compete in other ways with your garden plants. Scientists use the term allelopathic for plants that can chemically hinder the vital systems of nearby plants. Although these plants typically are weeds, certain landscape and vegetable plants also leave behind allelopathic chemicals.

    Here are all the plants that you should avoid planting near certain other plants in your garden.

    Asparagus

    Avoid planting asparagus neat fennel, garlic or onion.

    However, asparagus plants will do well when planted near marigolds, nasturtiums, parsley, and basil.

    Beans

    Beans make a good companion plant for many other plants because they enrich the soil with nitrogen, but avoid planting them near broccoli, cauliflower, chives, garlic, kale, leeks, onions, and sweet or spicy peppers.

    Pole beans and beets are incompatible, and sunflowers that are too close by will stunt bean growth.

    Broccoli

    Another gardener’s favorite because it is easy to grow, broccoli has few enemies in the garden. However, broccoli and cauliflower prefer to be away from peppers, all types of squash (including pumpkins), tomatoes, and strawberries.

    Cabbage

    Cabbage plants (including kale) do not do well if planted close to basil, tomatoes, garlic, or strawberries.

    Cabbage does do well when planted near the herbs rosemary, sage, thyme, and mint because they help keep away insects. Other good companion plants for cabbage include beets, onion, celery, potatoes, lettuce, peas, and marigolds.

    Carrots

    Carrots do not like to be planted near dill and celery.

    For optimal carrot yields, plant them near peas and beans that add nitrogen to the soil. Carrots also do well when planted near leeks, onions, radishes, parsley, and lettuce.

    Cucumber

    Cucumber plants can be easy to grow, but they do not like to be near potato or cauliflower plants or aromatic herbs such as basil, rosemary, sage, or marjoram.

    Cucumbers do well with beans, asparagus, celery, lettuce, radish, tomatoes, peas, dill, chives, and nasturtiums as companion plants.

    Tomatoes

    Although they are a staple of most home gardeners, tomatoes attract many pests, which can, in turn, affect many of their neighboring plants.

    Avoid planting tomato plants near broccoli, cauliflower, cilantro, cucumbers, dill, eggplants, peppers, or potatoes. Additionally, corn attracts insects that are harmful to tomatoes.

    Good companions for tomatoes include asparagus, carrots, basil, chives, celery, nasturtium, parsnip, onion, parsley, mint, and marigolds.

    Here are a few other plant combinations to avoid making in your garden.

    • Beets do best when not in close proximity with beans or mustard plants.
    • Brussels sprout growth can be impeded by strawberries and tomatoes.
    • Celery plants prefer to be away from parsnips and potatoes.
    • Peas thrive best when not near garlic, leeks, chives, or onions.
    • Potato plant growth can be negatively affected by nearby cucumbers, squash, melons, tomatoes, sunflowers, and turnips.
    • Radishes are easy to grow, but they are incompatible with broccoli, Brussels sprouts, cabbage, cauliflower, potatoes, and turnips.
    • Sunflowers should be planted at least one foot away from any other plant.

    To make this information easier to process, I created a table where you can cross-reference the plants to see if they’re okay to plant near each other. In many cases, one plant would be harmed while the other would be okay, but obviously, you'll want to avoid planting them near each other anyway.

    Note: This table does not indicate which plants harm which. For example, sage harms cucumber but cucumber doesn't harm sage, and the table doesn't say which does which–it just says that they should not be near each other.

    For each plant listed in the left column, you'll find a list of plants in the right column that should not be near it. This is just a quick and easy way to make sure the wrong plants aren't near each other. If you're wondering about a plant in your garden, just find it in the left column and next to it you'll see all the plants that shouldn't be near it.

    Primary PlantPlants That Shouldn't Be By The Primary Plant
    AsparagusFennel, Garlic, Onion
    BasilCabbage, Cucumber, Kale, Rue
    Beans (Bush)Beets, Broccoli, Cauliflower, Chives, Garlic, Kale, Leeks, Onion, Peppers
    Beans (Pole)Beets, Broccoli, Cauliflower, Chives, Garlic, Kale, Leeks, Onion, Peppers
    BeetsBeans (Bush), Beans (Pole), Mustard Greens
    BroccoliBeans (Bush), Beans (Pole), Peppers, Pumpkin, Radishes, Squash, Strawberries, Tomatoes
    Brussels SproutsRadishes, Strawberries, tomatoes
    CabbageBasil, Garlic, Radishes, Strawberries, Tomatoes
    CarawayDill
    CarrotsCelery, Dill
    CauliflowerBeans (Bush), Beans (Pole), Cucumbers, Peppers, Pumpkins, Radishes, Squash, Strawberries, Tomatoes
    CeleryCarrots, Parsnips, Potatoes
    ChivesBeans (Bush), Beans (Pole), Peas
    CilantroTomatoes
    CornTomatoes
    CucumberBasil, Cauliflower, Marjoram, Potatoes, Rosemary, Sage, Tomatoes
    DillCaraway, Carrots, Tomatoes
    EggplantTomatoes
    FennelAsparagus, Tomatoes
    GarlicAsparagus, Beans (Bush), Beans (Pole), Cabbage, Kale, Peas
    HyssopRadishes
    KaleBasil, Beans (Bush), Beans (Pole), Garlic, Strawberries, Tomatoes
    KohlrabiPeppers
    LeeksBeans (Bush), Beans (Pole), Peas
    MarjoramCucumbers
    MelonsPotatoes
    Mustard GreensBeets
    OnionsAsparagus, Beans (Bush), Beans (Pole), Peas
    ParsnipsCelery
    PeasChives, Garlic, Leeks, Onion
    PeppersChives, Garlic, Kohlrabi, Leeks, Onion
    PotatoesChives, Garlic, Leeks, Onion, Pumpkins, Squash, Tomatoes, Turnips
    PumpkinsBroccoli, Cauliflower, Potatoes
    RadishesBroccoli, Brussels Sprouts, Cabbage, Cauliflower, Hyssop, Potatoes, Turnips
    RosemaryCucumbers
    RueSweet Basil
    SageCucumbers
    SquashBroccoli, Cauliflower, Potatoes
    StrawberriesBroccoli, Brussels Sprouts, Cabbage, Cauliflower, Kale
    SunflowersBeans (Pole)
    TomatoesBroccoli, Brussels Sprouts, Cabbage, Cauliflower, Cilantro, Corn, Cucumbers, Dill, Eggplant, Fennel, Kale, Peppers, Potatoes
    TurnipsPotatoes, Radishes

    Most allelopathic plants store their protective – and potentially damaging – chemicals within their leaves. As leaves drop to the ground in the fall and then decompose, the toxins can affect nearby plants. Some allelopathic plants also release chemicals through their roots, which then can reach and affect neighboring plants and trees.

    Common plants with allelopathic properties include English laurel, Bearberry, Rhododendron, Sumac, Elderberry, Forsythia, Goldenrod, Some Fern, Garlic, Perennial Rye, Tall Fescue, Kentucky Bluegrass, and Mustard Weed.

    Some common trees use allelopathy as a way of protecting themselves from encroaching plants that might take away their nutrients and water supply. Most allelopathic trees release their toxic chemicals through their leaves.

    Black walnut trees, for example, store chemicals within their buds, nut hulls and roots. Since the roots can spread out quite a distance, avoid planting certain plants in proximity to a black walnut tree. The plants most susceptible to growth problems from a black walnut tree include tomatoes, potatoes, peppers, eggplants, and azaleas.

    Other trees with allelopathic tendencies are maple, pine and eucalyptus trees.

    As you learn more about what grows and thrives in your soil and your region, you may find exceptions to some of these combinations. Most experienced gardeners find out which plants do well together – and which ones don’t – through a process of trial and error. Learn to observe your plants closely, noticing changes and recording what you learn in a journal that you can refer to from season to season.

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