Calendar for Companion Sowing

Plan your entire season in one glance: this companion sowing calendar shows exactly what to sow, when to sow it, and beside which crops so your beds stay productive, pest-smart, and pollinator-rich from first frost-free day to fall cleanup. Use the simple timing windows below (based on your local frost dates) to stage early nectar, living mulches, trap crops, and flavor-boosting herbs. You’ll get steadier yields, fewer pest flare-ups, and a garden that looks intentional—not crowded.

How to Use This Calendar (In 5 Minutes)

Find your dates. Note your Last Spring Frost (LSF) and First Fall Frost (FFF). Everything is scheduled relative to these.
Map your crops. Group the bed by crop family (nightshades, cucurbits, brassicas, roots/alliums, legumes).
Pick the role. Choose companions for pollination, pest management, living mulch, soil building, or flavor.
Stage the timing. Use the windows below (e.g., “4–6 weeks before LSF”).
Succession plan. Set reminders every 3–4 weeks for quick bloomers (alyssum, dill, cilantro, buckwheat).

Tip: Put companions at edges and corners, under trellises, or in micro-islands between crop blocks. Leave air lanes so harvest stays easy.

Quick Companion Sowing Windows (Relative to Frost Dates)

Alyssum (Lobularia): Direct sow 2–4 weeks before LSF for early nectar; succession every 4 weeks. Low, non-competitive, great near lettuce, brassicas, tomatoes, and peppers.
Calendula: Direct sow 4–6 weeks before LSF; fall sow 6–8 weeks before FFF for cool-season blooms. Pairs with brassicas, onions, and carrots.
Cilantro (Coriander): Direct sow 2–4 weeks before LSF; repeat in late summer for fall. Excellent near carrots, onions, and brassicas.
Dill: Direct sow at LSF and every 3–4 weeks through midsummer. Umbels feed parasitic wasps and hoverflies; time blooms to overlap cucumber/cole crop flowering.
Borage: Direct sow at LSF. Stellar with cucumbers and squash; draws pollinators, breaks crusty soil with taproots.
Basil: Start indoors 6–8 weeks before LSF; transplant after LSF beside tomatoes and peppers. Avoid chilling.
Nasturtium: Direct sow at LSF (edges and bed lips). Useful as a soft aphid trap and to shade soil under trellises.
Tagetes (French marigold): Start 6–8 weeks before LSF; transplant after LSF. For nematode suppression, use as a prior cover crop and incorporate; interplanting helps diversity but isn’t an instant cure.
Buckwheat: Quick pollinator crop; sow from warm-up through midsummer; blooms in 30–40 days. Great between harvest waves.
Phacelia: Direct sow 4–6 weeks before LSF; repeat late summer. Exceptional nectar for beneficials.
Crimson/White Clover: Sow early spring on edges/paths or late summer for fall/winter cover. Use as living mulch after main crops establish.
Daikon/Forage radish: Sow 6–10 weeks before FFF to bio-till and mop up nutrients post-harvest.
Oats + Field Peas (cover): Sow late summer to early fall for biomass and soil health.

Bed-by-Bed Timing Recipes

1) Tomato & Pepper Bed (Nightshades)

6–8 weeks before LSF: Start basil and marigolds indoors.
At transplant (after LSF): Tuck alyssum at corners; set basil 25–35 cm from stems for airflow.
2–3 weeks later: Direct sow nasturtium along edges for gentle shading and aphid decoy.
Midseason: If pest pressure rises, interseed a narrow band of cilantro or dill for quick beneficial blooms.
After final harvest: Sow oats + peas or daikon to reset soil.

2) Cucumber & Squash Bed (Cucurbits)

At LSF: Direct sow borage at corners; it grows fast and won’t smother vines if edged.
1–2 weeks after cucurbit sowing: Direct sow dill so blooms align with early fruiting.
Early summer: Interplant buckwheat between hills; terminate before it seeds.
Note: Keep a 40–50 cm clear lane around each hill for air and harvest.

3) Cabbage, Kale, Broccoli (Brassicas)

4–6 weeks before LSF: Direct sow calendula, alyssum, and a sprinkle of cilantro to be blooming as transplants harden off.
At transplant: Add a ring of dill and phacelia 30–40 cm away to avoid shading.
Pest timing: Early nectar supports natural enemies of cabbage worms and aphids. Re-sow alyssum/cilantro every 4 weeks for continuity.

4) Carrots, Beets, Onions (Roots & Alliums)

2–4 weeks before LSF: Direct sow cilantro and calendula in thin ribbons between rows.
After emergence: Spot-sow alyssum in gaps. Carrot–onion interplanting plus aromatic flowers aids pest confusion and improves habitat.

5) Beans & Corn (Legumes & Grains)

At LSF: Sow corn first.
2–3 weeks later: Sow pole beans when corn is 15–20 cm tall; add nasturtium at the bed lip for ground cover.
Between blocks: Drill buckwheat for pollinators; mow before seed set.
Post-harvest: Plant crimson clover for winter nitrogen.

Month-by-Month Example (Temperate Northern Hemisphere)

Adjust months forward/backward using your LSF/FFF.

March: Calendula, alyssum, cilantro (direct sow); start basil and marigolds indoors.
April: Transplant brassicas; intersow more alyssum; dill first sowing near cool crops.
May: After LSF, transplant tomatoes/peppers; direct sow nasturtium, borage; second dill sowing.
June: Buckwheat between crop blocks; succession alyssum/cilantro; stake and prune for airflow.
July: Keep buckwheat going; a fresh dill sowing; edge-sow white clover where crops are well established.
August: Late cilantro and phacelia for fall nectar; start daikon.
September–October: Oats + peas or crimson clover after summer crops; final calendula sowing if frost is late.

Warm-Winter / Hot-Summer Adjustments

Mild winters (little frost): Treat autumn as your cool-season sowing window for calendula, cilantro, alyssum, and phacelia. Many “spring” companions can be fall-sown for late-winter/early-spring blooms.
Intense heat: Shift dill, cilantro, and alyssum to shoulder seasons (late winter/early spring and late summer/early fall) to prevent bolt or stall.
Monsoon/humid periods: Prioritize airflow. Keep aromatic herbs and flowers off main drip lines and use wider spacing.

Spacing & Placement That Actually Works

Edges over centers: Most companions deliver value without competing if kept on bed edges or corners.
Heights: Low (alyssum, clover) under taller crops; medium (basil, calendula) mid-row but staggered; tall (borage, dill) on the north side to avoid shade.
Distances:
- Alyssum every 30–45 cm along edges.
- Basil every 35–45 cm among tomatoes/peppers.
- Calendula clumps 40–50 cm apart near brassicas and roots.
- Dill in pockets 30–45 cm from main stems.
- Nasturtium 20–30 cm inside the bed lip.
Living mulch: Interseed micro-strips (5–10 cm wide) after main crops are knee-high. Mow or shear if competition rises.

Proven Companion Roles (Match to Your Goal)

Pollination boost: Borage, phacelia, buckwheat, calendula.
Beneficial insects: Alyssum, dill, cilantro, yarrow (edge), phacelia.
Soft trap crops: Nasturtium for aphids; radish as flea beetle distractor in spring.
Soil services: Clover (N-fix), daikon (bio-till), oats + peas (biomass, weed suppression).
Flavor/herbal lift: Basil with tomatoes and peppers; cilantro near peppers and roots.

Common Timing Mistakes (And Quick Fixes)

Too-early living mulch: Let main crops establish first; then interseed thinly.
All bloom at once: Stagger sowings every 3–4 weeks so nectar never runs out.
Shade creep: Keep tall companions on north edges; prune dill and borage if they cast too much shade.
Expecting marigolds to “cure” nematodes instantly: For root-knot suppression, grow dense Tagetes as a preceding cover crop and incorporate before planting the susceptible crop.
Fennel in the mix: Fennel can inhibit neighbors. Plant it separately.

A Simple Four-Bed Rotation With Companion Calendar

Bed A (Nightshades this year): Spring alyssum/cilantro; summer basil/marigolds; fall daikon.
Bed B (Cucurbits): Spring calendula at edges; sow borage at LSF; dill in early summer; fall oats + peas.
Bed C (Brassicas/Greens): Early alyssum/cilantro; repeated dill/alyssum; fall phacelia.
Bed D (Roots/Alliums/Legumes): Spring cilantro/calendula; interplant beans after early carrots; late summer crimson clover for winter.

Rotate the bed roles each year, and carry the same companion timing with the family as it moves.

Micro-Calendars for Containers & Small Spaces

Window boxes & grow bags: Alyssum + basil are compact and forgiving; sow alyssum early, add basil after nights stay warm.
Balcony trellises: Nasturtium at the rim, borage at one corner, dill in a dedicated pot to control height.
Patio tomatoes: One basil per pot and a ring of alyssum is usually enough.

Weekly Maintenance Rhythm (Simple & Repeatable)

Week 1–2 of each month: Succession sow one quick nectar plant (alyssum or cilantro).
Week 3: Thin or shear living mulch; refresh a corner with buckwheat if a gap opens.
Week 4: Spot-sow dill or phacelia where you just harvested.

This “little-and-often” approach keeps diversity high without clutter.

Frequently Asked Questions

How do I translate this to my hardiness zone?
Use your LSF/FFF to shift the windows. If LSF is a month later than the example, slide every spring action one month later. For mild-winter climates, fall becomes your main cool-season window.

Should I start companions indoors or direct sow?
Start basil and marigolds indoors for reliable transplants. Most others—alyssum, dill, cilantro, borage, calendula, buckwheat, phacelia—are easy and faster by direct sowing.

How close should companions be to the crop?
Keep low growers (alyssum, clover) within 10–20 cm of the row. Place medium/tall companions 30–50 cm away to avoid shading. Corners and bed lips are prime real estate.

Do marigolds really control nematodes?
They can help when used as a solid, preceding cover crop and incorporated before planting. Scattered interplants offer biodiversity benefits but won’t replace a true rotation or soil testing.

What if my garden is tiny or I only have two beds?
Run a two-year rotation: Year 1 nightshades + cucurbits, Year 2 brassicas/roots/legumes. Keep companions mostly on edges and use mini successions (alyssum/cilantro every 4 weeks).

Which companions should I avoid mixing?
Avoid fennel within vegetable beds due to allelopathy. Keep sunflowers a short distance away to prevent shading and potential competition.

How do I keep companions from stealing water?
Sow thinly, mulch well, and irrigate deeply but less often. If competition appears, shear living mulches and top-dress with compost.

Can I use clover as a full living mulch under tomatoes?
Yes—but after tomatoes are established and with careful mowing. Otherwise, use clover on paths/edges, which is simpler and safer for yield.

Your Season, Simplified

Build your calendar around clear roles (pollination, pest support, soil, flavor), clean edges, and staggered sowings. With a handful of reliable companions—alyssum, dill, cilantro, basil, calendula, borage, nasturtium, buckwheat, and clovers—you can keep beneficial insects fed from cool spring through warm summer and back into fall, all while protecting crops and improving soil. Mark the windows on your planner once, set a monthly reminder for quick successions, and enjoy a garden that works as hard as it looks.