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Garden Planning, Succession & Crop RotationCompanion Planting Calendar
Companion planting is popular and full of folklore. This guide separates practical timing and spacing from claims that research has not confirmed.
Key points
- Companion planting mixes sound ideas with tradition, and evidence varies by pairing.
- Fit the timing of each plant, using frost dates, not just the neighbors.
- Companions do not replace scouting or good spacing.
- Test pairings in your own garden and keep notes.
What is companion planting?
Companion planting means growing different plants near each other for a benefit: shading, support, pest confusion, attracting beneficial insects, or making better use of space. Some pairings have good evidence. Many others rest on tradition, and research on them is limited or mixed.
Treat companion advice as a set of ideas to test in your own garden, and keep honest notes about what happens.
Many gardeners enjoy the practice because it makes the garden more varied and more interesting to observe, even where the measurable benefit is small.
What do we know and not know?
Several mechanisms are well understood. Tall plants can shade cool-season crops in hot weather. Trellised crops can use vertical space. Flowering plants can feed beneficial insects such as hover flies and small wasps, which may help with pests. Interplanting can sometimes make it harder for pests to find their host.
Other claims, such as one herb repelling another plant's pests or one crop improving another's flavor, have weaker or inconsistent support. The honest answer for many popular pairings is that evidence is thin. Ask your extension office what has been tested in your region.
One practical use of the calendar is to plan flowering strips. Plants that bloom early, midseason and late keep nectar available for beneficial insects across the whole season, so mark bloom times beside your crop times and fill any gaps.
How does timing fit into a companion calendar?
A pairing only works if both plants are in the ground at the right time. Draw the growth periods of each crop as bars on your calendar: when each is sown, when it reaches full size, and when it is harvested. A fast crop such as radish or lettuce can be harvested before a slow neighbor needs the space, which makes the pairing fit in time as well as in space.
Set the timing from your frost dates. Cool-season crops can start before the last frost, and a warm-season companion can be set between them later, as the early crop is harvested or when frost danger has passed.
Remember that some plants spread aggressively. A companion that seeds itself everywhere can become a weed problem, so check with your extension office before adding something new, and contain it where needed.
- Fast crop between slow crop rows, harvested before the slow crop fills in
- Tall warm-season crop shading a cool-season crop as summer heat arrives
- Trellised crop above a low crop
- Flowering strip planted early so beneficial insects arrive before pests
What pairings have practical value?
Beans or peas on a trellis with a low-growing salad crop underneath use space well, as long as the shade suits the lower crop. Flowers or herbs left to bloom near vegetables provide nectar for beneficial insects. A quick radish or lettuce crop sown between slow brassica seedlings uses space that would otherwise grow weeds.
Keep spacing in mind. Crowding reduces airflow and can encourage disease, and plants compete for water and nutrients. Companions that share a bed still need adequate room, so follow extension spacing guidance.
How should you handle pests when using companions?
Companions are not a substitute for scouting. Check plants weekly, learn to identify pests and beneficial insects, and ask your extension office before treating. Any pesticide used must follow its label, observe the pre-harvest interval, and protect pollinators, and licensing rules vary by state.
Avoid planting a companion that shares pests with the main crop. Placing two members of the same family together, for instance, may give pests an easy path.
Pollinator protection matters here too: flowering companions attract bees and other beneficial insects, so any spray used nearby carries extra risk and must follow label directions.
How do you test a pairing yourself?
Plant two rows of the main crop, one with the companion and one without, under the same conditions. Note the dates, the pest counts you observe, and the harvest. Repeat across seasons because one year proves little.
Share your results with a local gardening group. Over time, local results are worth more than a generic chart, since soil, weather and pests differ from place to place.
A few seasons of side-by-side tests will tell you far more than a generic chart ever could, and the notes make good material to share with other gardeners.
Sources and further reading
Last reviewed: November 2026. Educational information, ranges only. Confirm timing with your county extension office.