All plants

Turnip

Brassica rapa subsp. rapa

Brassicaceae · cabbage family

Matures
30–75 days
Harvest
Once · Annual
Sun
4–8+ hrs
Spacing
2–6 in
Botanical engraving of Turnip

Planting window

When to sow, by microclimate — foggier blocks run a different calendar than sunnier ones.

JanFebMarAprMayJun
Foggy●●●●●●
Sunny●●●●●
JulAugSepOctNovDec
Foggy●●●
Sunny●●
Well-suitedMarginalNot suited

Sunlight

How well it does at each level of direct sun per day.

<2 hrsNot suited
2–4 hrsMarginal
4–6 hrsWell-suited
6–8 hrsWell-suited
8+ hrsWell-suited
Well-suitedMarginalNot suited

Soil depth

Root room it needs — useful for sizing raised beds and containers.

6–10"Not suited
10–15"Marginal
15–18"Well-suited
18–24"Well-suited
Well-suitedMarginalNot suited

Spacing

Room each plant needs — along the row and between rows — for sizing beds.

In-row
2–6 in
Between rows
12 in

Growth habit

The shape it makes in the bed and how tall it gets — what tells you whether to give it a trellis, a stake, or just room.

Habit
Low mound
Mature height
12–18 in

Low and self-supporting — no staking needed.

How to start it

Sow it where it grows, or raise it under cover and set it out — and how far ahead to start the seedlings if it's the latter.

Usually
Direct-sow
Start indoors
4 weeks ahead
Direct-sowWell-suited
TransplantWell-suited

Sown straight into the bed it will grow in.

Well-suitedMarginalNot suited

Getting started

How it goes in the ground — how deep to sow or set it, and the soil temperature it needs to wake up. The cold-soil floor is the real limiter for direct-sowing in a foggy SF spring.

Started from
From seed
Ideal soil temp
60–95°F
Sow depth
0.5 in
Time to emerge
1–3 days

Germinates between 40–105°F; happiest around 60–95°F.

30°F110°F
IdealWorkable

Pests & diseases

What tends to trouble this crop — what it is, what you'll see, and what to do about it, least-toxic first.

Pests5

Aphids
What it is
Aphids have soft pear-shaped bodies with long legs and antennae and may be green, yellow, brown, red, or black depending on the species and the plants they feed on. A few species appear waxy or woolly due to the secretion of a waxy white or gray substance over their body surface.
What you'll see
Low to moderate numbers of leaf-feeding aphids aren't usually damaging in gardens or on trees. However, large populations can turn leaves yellow and stunt shoots; aphids can also produce large quantities of a sticky exudate known as honeydew, which often turns black with the growth of a sooty mold fungus.
What to do
Before planting vegetables, check surrounding areas for sources of aphids and remove these sources. On the other hand, these aphid-infested weeds can sometimes provide an early source of aphid natural enemies.
Source
Armyworms
What it is
Armyworm larvae feed in groups, which distinguishes them from other vegetable pests such as corn earworms and loopers. Markings on newly hatched armyworms are usually hard to distinguish from those of other caterpillars; older larvae have distinct lengthwise stripes.
What you'll see
Armyworms may feed on the crowns of seedlings. On larger plants, armyworm caterpillars skeletonize leaves.
What to do
Handpick. Virus diseases, parasites (Hyposoter and Trichogramma), and general predators may be effective on caterpillars.
Source
Flea Beetles
What it is
Their small size, enlarged back legs, characteristic shot-hole damage, and habit of jumping when disturbed make flea beetles easy to identify. There are numerous flea beetle species.
What you'll see
Adults feed mostly on leaves, leaving tiny pits or small holes at their feeding sites. Flea beetles feeding together can cover leaves with bleached, pitted areas or ragged holes.
What to do
Remove debris in the fall to remove any overwintering beetles. Reflective mulches applied very soon after planting and before plants become infected can be helpful.
Source
Harlequin Bug
What it is
Harlequin bugs can be confused with Bagrada bugs, an invasive species, but are much larger and lack the white markings characteristic of Bagrada bugs. Harlequin bugs may also be confused with stink bugs.
What you'll see
Harlequin bugs suck fluids from plant tissue. They leave yellow or white blotches on areas of leaves where they have been feeding; heavy infestations can cause plants to wilt, turn brown, and die.
What to do
Handpick bugs or their eggs. Destroy old cole crop plants and mustards because they provide breeding areas.
Source
Loopers
What it is
Loopers are green caterpillars with several white stripes down their backs. They arch their backs as they crawl, this looping movement giving them their name.
What you'll see
Loopers eat irregular holes in leaves, most often older leaves. They may also bore holes in lettuce and cabbage heads or damage fruit.
What to do
Handpick. Apply Bacillus thuringiensis or spinosad; they are effective against loopers, especially when caterpillars are small.
Source

Sources

Every figure above is backed by these.