Turnips and rutabaga are the two easiest crops to get wrong for the same reason: people treat them as one plant. They are different species, they want different spacing, and one takes nearly twice as long to mature. Get that right and the companion planting question becomes much simpler. what to plant with asparagus
The other thing worth knowing up front is that the most important neighbour decision for these crops is not what you plant beside them. It is what grew there last year, because both are brassicas and brassicas carry a soil disease that outlasts almost anything else in your garden.
Here is what this covers:
Key Takeaway
The evidence-backed companion for turnips and rutabaga is a low clover living mulch between the rows, sown after the crop is established. Trials in related brassicas found reduced pest pressure with no measurable yield loss. Almost everything else in the folklore is untested.
This is where the two crops diverge, and it matters for what else fits in the bed. University of Illinois Extension recommends sowing turnip seed half an inch (1.3 cm) deep with rows 12 to 24 inches (30 to 61 cm) apart, thinning to 2 to 4 inches (5 to 10 cm) in the row once seedlings reach about 4 inches tall.
Rutabaga needs more room. University of Georgia Extension recommends the same half-inch seed depth with rows 14 to 18 inches (36 to 46 cm) apart and thinning to about 4 inches (10 cm) between plants.
| Factor | Turnip | Rutabaga |
| Seed depth | 1/2 in. (1.3 cm) | 1/2 in. (1.3 cm) |
| Row spacing | 12-24 in. (30-61 cm) | 14-18 in. (36-46 cm) |
| Thin to | 2-4 in. (5-10 cm) | ~4 in. (10 cm) |
| Days to maturity | Roughly 60-100 | 90-100 |
| Sow before first frost | ~70-75 days | ~100 days |
| Storage life | ~3 months | Up to 6 months |
Sources: University of Illinois Extension, University of Georgia Extension, Washington State University Extension
Illinois gives the cleanest timing rule anywhere in the extension literature: sow rutabaga about 100 days before your first expected hard frost, then sow turnips 3 to 4 weeks later. Two sowing dates, one harvest window.
Washington State adds a soil temperature floor. Do not seed rutabaga until soil reaches at least 50°F (10°C), because germination drops off badly below that. They also put water demand at up to 1.5 inches (3.8 cm) per week for good root quality.
Clover undersown between the rows, and the trial data comes from broccoli rather than turnips. That is a real caveat, but the pest complex is shared, so the mechanism should carry over.
University of Hawaii research on clover living mulches found that lepidopteran eggs and caterpillar densities were significantly higher on bare-ground broccoli than on broccoli undersown with clover, and that insect contaminants per harvested crown dropped. Critically, the trial recorded no yield reduction.
The National Center for Appropriate Technology's brassica production guide reaches the same conclusion for aphids, summarising trials where broccoli and cabbage in clover living mulch carried fewer cabbage aphids than clean-cultivated plantings.
Why This Works: Inappropriate Landings
Pests find your crop from a distance by smell, then decide whether to stay based on what they land on. Fill the ground between the rows with a non-host plant and a large share of those landings are on clover instead of turnip, so the insect leaves or gets eaten while it is still searching. This is why ground cover beats scattering "repellent" flowers around, and it is the same logic behind living mulch generally.
Sow the crop first, alone
Get turnips or rutabaga up and thinned before anything else goes in. Clover sown at the same time competes with seedlings for light and moisture, which is where most undersowing attempts fail.
Widen your rows to the top of the range
Use 20 to 24 inches (51 to 61 cm) between rows rather than 12 to 14. Undersowing only works without a yield penalty when the primary crop still has its full spacing.
Broadcast clover between rows at 3 to 4 weeks
White or strawberry clover, sown into the alleys once the brassicas are established and thinned. Rake in lightly and water. The canopy fills in as the crop bulks up.
Keep it low and off the shoulders
Clip the clover if it starts crowding the root crowns. Both crops sit partly above ground and need light on their leaves right up to frost to build sugars.
Other brassicas, and the reason is clubroot rather than competition. Turnips, rutabaga, cabbage, kale, broccoli, radish and mustard all host Plasmodiophora brassicae, and its resting spores are close to permanent.
University of Maryland Extension reports that clubroot spores can survive in soil for 10 to 20 years, with enough dying off within 5 to 7 years to make that a workable rotation. NC State Extension recommends rotating infested ground away from brassicas for a minimum of 4 to 7 years.
Which makes a lot of standard companion advice actively bad. Planting radish among your turnips as a flea beetle trap crop does work behaviourally, but on ground with any clubroot history you are feeding the pathogen to save some leaves.
Soil pH is your other lever. UC Agriculture and Natural Resources found that keeping soil pH above 7.2 to 7.3 through liming suppresses clubroot symptoms, though it does not kill the pathogen. That is above the pH 6.2 to 6.8 these crops otherwise prefer, so it is a trade you make only where clubroot is confirmed. Our soil pH guide covers how to move it without overshooting.
Common Mistake to Avoid
Do not use mustard or radish as a trap crop in a bed you plan to grow brassicas in again. Both are clubroot hosts. The NCAT guidance on trap cropping is sound where clubroot is absent, but on infected ground it trades a leaf problem you can live with for a soil problem that outlasts your tenancy.
Beyond brassicas, the honest answer about tomatoes, pole beans and strawberries is that the warnings are folklore. What is real is phenology: those are warm-season crops that want soil these root crops find far too hot. It is a timing mismatch, not antagonism.
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Read the Free GuideAnything that is not a brassica and does not shade the crowns. That is a broader list than most charts suggest, and the selection logic is simple.
Clover and other low legumes between rows, for the pest effect above. Alliums such as onions, leeks and garlic, which occupy a narrow vertical column and share none of the brassica pests or diseases. Carrots and beets, which root deeply on a similar cool-season schedule. Lettuce and spinach in the gaps early on, harvested before the roots need the space.
Flowering borders around the outside rather than inside the bed. NCAT notes sticky traps and border plantings as continuous barriers for flea beetles, which is a perimeter strategy, not an interplanting one. The same principle we applied to the wider companion planting chart: keep the primary crop's spacing intact and put the helpers at the edges.
After frost, not before. Both crops convert starch to sugar when exposed to cold, which is why a turnip pulled in September tastes sharp and the same variety in November tastes sweet. Leave them in the ground through the first few light frosts.
Washington State University puts rutabaga storage at 32°F (0°C) with 95 to 100% relative humidity, keeping up to 6 months. Oregon State Extension gives a more forgiving home range of 32 to 40°F (0 to 4.4°C) at 90 to 95% humidity, with tops cut to about 1 inch (2.5 cm) and roots packed in barely moist sawdust so they do not touch.
Turnips keep less well. University of Alaska Fairbanks Extension puts them at about 38°F (3.3°C) and 90 to 95% humidity for roughly 3 months, packed in moist sand or sawdust. Plan to eat the turnips and store the rutabaga.
Key Takeaway
Humidity is the variable people get wrong. These roots need 90% or higher, which a dry basement will not give you. A crate of barely damp sand in an unheated garage beats a bare shelf indoors, and a dirt floor holds humidity better than concrete.
Other brassicas, above everything else. Cabbage, kale, broccoli, cauliflower, radish and mustard all host clubroot, and its resting spores persist in soil for 10 to 20 years. Grouping them concentrates the disease and forces a 4 to 7 year rotation later. Beyond that, avoid tall crops that shade the root crowns late in the season, since both turnips and rutabaga need leaf light to build sugars before frost. The frequently repeated warnings about tomatoes and pole beans are not supported by research, though those crops do want much warmer soil.
Half an inch (1.3 cm), the same as rutabaga. University of Illinois Extension recommends sowing 3 to 20 seeds per foot of row at that depth, then thinning to 2 to 4 inches (5 to 10 cm) apart once seedlings reach about 4 inches tall. Sowing deeper slows emergence through cool autumn soil, and shallower risks the seed drying out before it germinates. Rutabaga wants slightly wider rows at 14 to 18 inches (36 to 46 cm) and thinning to about 4 inches, because the roots get considerably bigger.
Roughly 60 to 100 days depending on variety and how large you want the roots, with baby turnips ready considerably sooner. Rutabaga takes longer, around 90 to 100 days. The practical rule from Illinois Extension is to sow rutabaga about 100 days before your first hard frost, then sow turnips 3 to 4 weeks after that so both mature into the same cool autumn window. Washington State adds that soil should reach at least 50°F (10°C) before you seed, since germination is poor below that.
The measured evidence says yes for aphids and caterpillars. University of Hawaii trials found significantly fewer lepidopteran eggs and caterpillars on clover-undersown broccoli than on bare ground, and fewer insect contaminants at harvest, with no yield reduction recorded. NCAT summarises similar aphid reductions in clover living mulch. The trials are in broccoli and cabbage rather than root brassicas, so treat it as promising rather than proven for turnips. Sow the clover after the crop is established, not alongside it.
After. Cold exposure triggers conversion of stored starch into sugars, which is why post-frost roots taste sweeter and less sharp. Extension guidance for both crops is that they tolerate several light frosts in the ground, and rutabaga in particular is routinely left out into late autumn. The limit is a hard freeze: much of the rutabaga root sits above soil level, so it is more exposed than a carrot or parsnip and should be lifted before the ground freezes solid.
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