Do you know the difference between a radish and a turnip? While both root vegetables belong to the mustard family, turnips (Brassica rapa) are larger, sweeter, and milder than your typical radish.
Turnips are about the size of a tennis ball and are most commonly white or yellow. Parts of the root that are exposed to sunlight may turn bright purple. The tender greens that top the round root are also edible.
This article will allow you to explore each one of the turnip growth stages and enable you to learn how to grow these often underrated vegetables in your own garden.
Conditions for Growing Turnips
Turnips are biennial vegetables that typically need two growing seasons to reach maturity. However, most turnips are grown annually and harvested during their first year.
You can grow turnips in USDA Zones 2 to 9 and similar climates. Since turnips have an annual life cycle, they will die off during the year’s first hard freeze and will not return the following spring.
Though turnips are cold-sensitive, they also don’t enjoy hot temperatures. For this reason, most turnips are planted in the early spring or late summer. Turnips need about two months to fully mature, so this timing gives them plenty of time to grow while being protected from either too-warm or too-cold conditions.
I always keep in mind when growing root vegetables that soil quality is paramount. Compacted, rocky soil can lead to deformed turnips. Whether growing your turnips in the ground, raised beds, or containers, work the soil to a depth of at least 8 to 12 inches.
Select a planting location that receives full or partial sun. Ideally, your turnips should receive morning sun and afternoon shade. This will help keep the soil cool and delay bolting (i.e., early flowering).
I recommend aiming for 1 inch of water per week when growing turnips. Dry soil produces turnips with stronger (but not necessarily better) flavor profiles. Consistently moist soil produces the best flavor. Note that poor-draining soil is likely to cause issues with root rot.
Turnip Growth Rate
Turnip greens usually grow 12 to 14 inches tall at harvest time. This means that the average turnip can grow 1.5 inches per week throughout its lifetime. Of course, the actual growth rate of any given turnip will vary greatly based on temperature and irrigation.
The leaves of a turnip are the easiest to track regarding growth. What we care about most, however, is the root. Turnip roots don’t fill out considerably until the greens are nearly full-grown.
Once well-established, a turnip can go from a thick taproot to a round bulb 2 to 4 inches in diameter within 14 to 21 days.
Growth Stages of Turnip
Most turnips are direct-sown from seed. It takes 40 to 60 days on average for turnips planted in this manner to mature and be ready to harvest.
As with all garden vegetables, certain factors can affect the days required for maturity. For example, I recommend starting fall turnips at least 70 days before your area’s earliest potential frost date. This allows plenty of time for the turnips to develop before any risk of frost damage.
1. Seed Germination
All turnips sprout from tiny, easy-to-grow seeds. The best way to start turnips at home is by directly sowing the seeds wherever you want the turnips to grow.
Turnip seeds will germinate in soil temperatures from 40 to 85 degrees F. However, temperatures above 60 degrees F are ideal for germination and early growth. The soil also needs to be moist for germination to occur.
The first germination stage is water imbibition, when the seed absorbs moisture from the soil through its protective seed coat. Once the seed contains enough water, cell division begins inside the seed embryo.
This cell division eventually leads to the seed coat splitting, revealing the radicle or the seed’s first root. The seed’s hypocotyl, primary shoot, and cotyledons, or embryonic leaves, followed shortly after.
You won’t have to wait long to see progress! According to Cornell University, turnip sprouts can emerge within 4 to 7 days when grown from seeds and kept in the right environment.
Turnip seedlings emerge with two bean-shaped leaves called cotyledons. Cotyledons develop as part of the seed’s embryo and contain vital energy that the young turnip can use to support its early growth.
These two cotyledons are unique. All other leaves on the turnip plant are considered adult or ‘true’ leaves. Most turnip seedlings develop their first adult leaves within a few days of sprouting.
Beneath the soil’s surface, the turnip’s radicle develops into an enlarged taproot that grows incredibly fast. This root can grow more than an inch per day during the first few days of seedling development! Smaller root hairs branch off the taproot to access moisture and nutrients within the soil.
3. Vegetative Growth
Turnips have elongated, slightly frilly leaves that emerge from the crown of the plant in a loose rosette pattern.
Vegetative growth can feel like a waste of time and energy for those looking to enjoy a tasty turnip root. But healthy top growth is crucial if the turnip is going to develop that thick taproot you crave.
A turnip root is essentially a dense cache of stored energy. That energy comes from the leaves photosynthesizing and collecting resources for the turnip to use later in its life cycle (assuming we don’t get to it first). This is why the turnip must go through a vegetative growth stage before focusing on root development.
4. Root Development
This is the growth stage you’ve probably been waiting for. Once the turnip has a nice set of healthy leaves and has spent 30 days or more collecting and storing energy from the sun, it switches gears into root development. During this stage, the top portion of the taproot swells to be several inches in diameter.
A turnip left to its devices will eventually flower in its first or second year. Turnips use the energy stored in their taproots to send out a tall flower stalk and produce seeds.
Since a turnip uses the energy in its taproot to produce flowers, it should come as little surprise that bolting can ruin the quality of the turnip bulb itself. Taproots of turnips that have already begun to flower tend to be small, tough, and poor in flavor.
When a turnip flowers earlier than expected, it is called bolting. Bolting is typically triggered by high temperatures or long daylight hours. This is a big reason why turnips are planted during cool weather.
Turnips boast small, yellow flowers with four petals, each typical of members of the mustard family. Flowering turnips resemble mustard, radishes, and other close relatives.
6. Seed Production
Turnip flowers may reproduce via self- or cross-pollination. If you want to save turnip seeds from your garden to plant in future years, remember that cross-pollinated seeds tend to be healthier with better genetic diversity.
The seeds form in thin, green seed pods like bean pods. Pods should be left to turn brown and dry on the plant before collecting the seeds. Just note that the seeds will eventually pop out of the pods on their own if left a few days too long.
When to Harvest Turnips
Knowing when to pull turnips from your garden often requires trial and error. Most gardeners I know just use their hands or a dull trowel to check the size of their turnips, harvesting when the root has reached a suitable size. Use a garden fork to leverage the turnips from the soil when they are ready.
I highly recommend tracking the number of days that have passed since planting. Check the turnips’ size according to when the particular variety is said to mature.
Turnips harvested with intact greens are typically picked when the roots are about 2 inches in diameter. Meanwhile, topped turnips are usually left to develop until the roots are 3 inches long.
Harvesting Turnip Leaves
Some gardeners grow turnips for the nutritious greens rather than for the plump bulb. Turnip greens can be harvested at least 4 to 6 inches tall. Cut the leaves 1 inch above the crown of the turnip (the point where the leaves emerge from the plant). Doing this will encourage more leaves to grow in their place.
FAQs Growing Turnip
What is the life cycle of a turnip?
Turnips are biennial vegetables that complete a life cycle over two years or growing seasons. However, most gardeners grow turnips as annuals. Harvesting turnips in their first year prevent flowering and preserve the quality of the nutritious taproot.
- Cornell University Turnip seed germination
Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.