Carrots and parsnips are root vegetables that do well in cooler conditions. Carrots are one of the most popular garden vegetables and come in colors beyond the traditional orange, including purple, red, yellow, and white. Parsnips are close relatives of carrots and have a more subtle, sweeter, nuttier flavor. Both are great additions to the Iowa vegetable garden.
Carrots and parsnips grow best in the cool temperatures of spring and fall. Depending on variety, carrots are ready to harvest 50 to 60 days after planting. Parsnips are a long-season crop that takes 100-120 days to mature enough to harvest.
In Iowa, plan to plant carrots in early April and sow staggered plantings every 2 to 3 weeks through summer. The last practical planting date for carrots in Iowa is August 1st. These plants benefit from succession planting. By staggering the plantings, you have some carrots coming into maturity each week rather than an entire crop all at once.
Learn about suggested carrot varieties for your garden in this article: What are some good carrot varieties for Iowa?
Parsnips are planted in early to mid-spring and remain in the garden until frost in the fall. The frost is important to help the long roots to develop good flavor. The longer the parsnips stay in the ground in the fall, the sweeter they will be. These cold-hardy plants will even tolerate staying in the ground over winter and harvested early the following spring. Just be sure to dig them in the spring before they send up a flower stalk as the flavor declines if the plant is allowed to bolt in spring.
Carrots and parsnips grow best in moist, well-drained soils that are not compacted. Loamy, sandy soil is ideal to allow uniform root development. When soils are heavy, rocky, or compacted, roots are often smaller and irregular in shape. If soils are not ideal, grow these root crops in raised beds or amend the soil with compost to improve soil conditions. Cultivars that produce shorter roots will also perform better in less-than-ideal soils. Containers are not a good option for growing carrots or parsnips because they do not provide enough room for the large tap roots to form. Grow in full sun, providing at least six hours of direct sun a day.
Sow carrot or parsnip seed directly in the garden ¼ to ½ inches deep in rows 18 to 24 inches apart. Do not sow seed indoors in containers for transplanting as they do not transplant easily. Seedlings can be slow to germinate, taking as long as three weeks to emerge, especially when soil temperatures are cold. After the seedlings emerge and are 3 to 4 inches tall, thin the planting so the remaining plants are 2 to 4 inches apart. To thin, cut the top off unwanted seedlings at soil level, rather than pulling the young plant so as not to disturb the surrounding soil.
The seed is very small and difficult to evenly plant in rows. Because of this, thinning after plants emerge is important. Pelleted seed is available for easier planting. Pelleted seeds have an inert, clay-based material coating the individual seeds, making them larger in size and easier to plant in well-spaced rows. Carrot seed is also sometimes available in a seed tape comprised of a paper strip embedded with evenly spaced seeds. Pelleted seed and seed tapes are more costly but require much less thinning after germination saving you time and effort.
Some gardeners plant radish and carrot seeds together. The radish germinates quickly to mark the row and helps to prevent soil crusting that can hinder carrot germination. The mix of seed helps distribute carrot seed more evenly, reducing the amount of thinning that needs to be done. When the radish matures in 3 to 5 weeks, it is harvested, giving the carrots more room to develop and grow.
Carrots and parsnips do best in cool, moist, but well-drained soil conditions. Provide consistent moisture throughout the growing process. Plants need an inch of water a week provided by the gardener if not provided by Mother Nature. Drought stress will cause carrots to become misshapen, small and develop a tough, fibrous texture with a bitter flavor.
These root crops need moderate levels of fertilizer. A complete fertilizer, such as 10-10-10, can be applied to the garden at a rate of 1.5 lbs per 100 square feet prior to planting. Apply a second application of fertilizer as a side dressing along the row when the carrot tops are 6 to 8 inches tall. Well-composted manure can also be utilized to improve soil fertility. Because carrots are frequently consumed raw, it is important not to use fresh manure as it can contain disease-causing microorganisms. Additionally, fresh manure will reduce or stunt root development because of its high nitrogen levels.
Cultivate lightly to remove weeds without disturbing the roots. Weed management, especially before and just after germination, is important. An organic mulch like grass clippings, clean straw, or coco mulch can also help reduce weeds, conserve soil moisture, and moderate soil temperatures.
As these root crops grow, some varieties will push the top of the root up and out of the soil. When observed, mound or hill soil over the shoulders to prevent the tops from turning green.
Carrots and parsnips grown in compacted or heavy soils produce stunted, forked, or twisted roots. Excessive nitrogen or overcrowding may produce plants that are all tops with lush foliage but little or no root development. Inconsistent moisture can cause the roots to split or crack.
Crusting of the soil surface and dry soil conditions may result in poor germination. This is particularly true of summer plantings. Crusting may be prevented by lightly covering the seeded row with vermiculite, sawdust, or peat moss. During dry weather, gently water the row to promote germination.
Some people develop a rash from contact with the leaves or roots of parsnip, especially on bright sunny days. When weeding, thinning, or harvesting parsnips, it’s best to wear gloves, long sleeves, and pants.
Carrots and parsnips are relatively disease and insect pest free. Occasionally, carrot weevil or root maggots may be a problem, but these issues are not common. Good cultural practices such as using compost to improve drainage, keeping gardens free of weeds, and fall clean-up can often prevent any significant insect or disease issues.
Carrots can be harvested anytime they reach a usable size. For most varieties, this is 6 to 8 weeks after planting when the roots are ¾ inch or more in diameter. Water the garden the day before harvest or harvest after a rain. Push a garden fork into the soil alongside the row to loosen the soil to more easily pull the carrot without breaking the root.
Leave parsnips in the ground as late into the season as possible. Cold soil temperatures help increase the sugar content in the roots giving them a better flavor. Parsnips can also be overwintered in the garden and harvested early the following spring. As with carrots, irrigate the day before or harvest after rain. Push a garden fork into the soil alongside the row to loosen the soil to more easily pull the parsnip. Roots are often 10 to 12 inches long, so digging and loosening them with a garden fork is needed to prevent root breakage during harvest.
Carrots can be used fresh or cooked. Parsnips are typically cooked. Because they are sometimes eaten raw, clean and wash carrots and parsnips after harvest and again before eating as a practice in safe produce hygiene. Store roots in the coldest part of the refrigerator (ideally at 32°F and 95 to 100% relative humidity) for up to three months. Before storage, cut off the foliage to within ½ inch of the roots. Surplus can also be canned or frozen.