How to Grow Parsnips (Pastinaca sativa)

By Erin Marissa Russell

Mention parsnips to many gardeners, and you’ll get a confused expression or a shrug of the shoulders—at least in some parts of the world. Although they’re more prevalent in Europe and northern parts of the United States, these white root vegetables just aren’t that well known to most of us, either as a garden plant or for their potential on the dinner table. But if you’re one of those gardeners who is familiar with parsnips, you know just how delicious they are as well as how rewarding they can be to grow.

As root vegetables, parsnips are cultivated mainly because people are interested in what’s underground: the edible root of the parsnip, which can reach sizes of 15 inches tall by three or four inches wide. Like carrots, the parsnips are widest at the top, from which fernlike greens emerge, while the root below tapers to a point. But despite their resemblance to carrots, parsnips are a member of the parsley family,k along with hemlock, celery, and caraway.

Parsnips are technically biennial plants (meaning they have a two-year growth cycle), but they’re normally treated like annuals. Gardeners dig parsnips up before they develop the second year’s foliage. If parsnips weren’t harvested at that time, they would produce yellow blossoms in their second year.

Parsnips are a hardy cool-weather crop that needs the temperature to get close to freezing during their growth period to trigger their salts to transform into sugars. This conversion results in the parsnip’s renowned delicate sweetness, Parsnips taste best if you harvest them just after a hard frost.

As tasty as parsnips are, it makes sense that they would develop a defense mechanism or two. The delicate fronds of greenery are harmful to skin. Handling your parsnip plants without protective gardening gloves can result in phytophotodermatitis, which causes a sunburn-like response to the sun’s UV rays. However, the edible root of the parsnip plant does not irritate skin.

Often, gardeners grow “free range parsnips,” leaving them out in the garden all winter. Doing so simply gives the parsnip more time to mature while the weather is cold. If you decide to go this route, cover your plants with a layer of much, and harvest in spring right after rising temperatures thaw the ground.

Varieties of Parsnips

There are so many varieties of parsnips on the market, from hybrids to heirlooms. Choose any that interest you, or choose more than one and experiment to find your favorite. Here are just a few to get you started.

Avonresister: Resists branching and forking as well as canker. Parsnips are sweet and aromatic with smooth skin. You may need to order from another country if you are an American gardener.

Cobham Improved Marrow: This late-maturing species produces very sweet parsnips. Known for strong germination, resistance to canker, and smooth skin regardless of soil type.

Gladiator: Gladiator parsnips, which are imported from England, grow quite large at 10 to 12 inches long. Known for smooth skins without imperfections and sweet, earthy tasting parsnips that perform well in various climates. Can be stored in the soil without turning woody

Growing Conditions for Parsnips

Gardeners in USDA Hardiness Zones 2 through 9 can grow parsnips. Choose a spot in the garden for your parsnips where they’ll get full or partial sun. Parsnips perform best in rich, heavy soil that is sandy or loamy, either neutral in pH level or slightly acidic. (Not sure what the pH level is in your garden? Learn how to find out when you read our article “How to Test pH in Your Soil.” Avoid planting parsnips in areas recently treated with manure, as doing so can cause your parsnips to fork.

How to Plant Parsnips

Parsnips have a rather long growth period, between 100 and 120 days, so plant fresh seeds absolutely as soon as it’s possible to work the ground in spring. Parsnip seeds have a tendency to become unviable quickly, so it’s imperative that you plant fresh ones.

Like carrots, parsnips need the soil to be loose so they aren’t impeded as they work to develop those tasty roots below the ground. That’s why you’ll need to prepare the soil where parsnips will grow by tilling or working the top 12 to 15 inches. Spread 2 to 4 inches of well rotted compost over the surface of the soil, then mix the compost down through the top 9 to 12 inches.

Plant your parsnip seeds one inch deep, with two seeds per inch. Cover them with a fine layer of soil, and firm it down to keep the seeds in place.Situate your rows of parsnips about 20 inches apart. Water the area after planting your parsnips.

They’ll begin to germinate in two or three weeks or even longer, which is a quite slow sprouting time. So when your parsnips don’t come up right away, take heart, In all likelihood, they just need a bit more time. However, if time doesn’t resolve the issue, keep in mind that parsnip seeds germinate best when the weather stays between 50 and 70 degrees Fahrenheit.

Keep the ground where your parsnips have been planted consistently moist, and do not allow a crust to develop on the surface of the soil. The tiny seedlings may not be able to break through if the area dries out to this point. Radishes planted among the parsnips can function as a marker crop and also prevent a crust from forming over the soil.

Weed the parsnip bed meticulously as your seedlings are coming up to prevent invasive plants from choking your parsnips out, but take care not to pull up your parsnips. Once your seedlings are fairly well established, thin them so that there’s between three and six inches of space between your plants.

Care for Parsnips

While your parsnip plants are growing, provide them with water each week if less than an inch or rain has fallen. Make it a point to regularly examine your parsnip bed for weeds and remove any you find. Inconsistent hydration is one of the few things parsnips will not tolerate, so be sure to provide them with plenty of water. And because parsnips take so long thntgo mature, weeding the area where they are growing will be more of a chore than it usually is with other crops.

Garden Pests and Diseases of Parsnips

The biggest challenge gardeners of parsnips will face is keeping them steadily hydrated. Though they can experience issues with the pests and diseases listed below, these are relatively rare.

Alternaria: Alternaria blight is a fungal infection with three strains. Aside from the version that affects parsnips and carrots, called black rot of carrot or Alternaria dauci/Alternaria radicina, there is also Alternaria brassica or Alternaria brassicicola—affecting plants in the Brassica family —and the strain affecting tomatoes, Alternaria alternata, also called Alternaria stem canker. Although Alternaria can strike at any time in a plant’s life cycle, it is most common when they are flowering and fruiting. The disease is spread via infected seeds and presents as stunted growth in the seedling stage or as damping off.

If your plants have been struck by Alternaria, you’ll see stunted growth along with yellow or brown spots on foliage up to three quarters of an inch across that spread out in darker and darker widening rings. Quarantine or destroy any affected plants; they cannot be eaten, used in compost, or fed to animals.You can prevent Alternaria from returning or avoid it altogether by improving air circulation around plants—allow plenty of room between plants, weed thoroughly, and stake your plants.

Aphids: There are many types of aphids, which vary in size and color, but all are tiny and tend to appear on the underside of leaves. Aphids feed on plants by sucking the moisture out of their foliage, resulting in leaves that are misshapen, distorted, withered, or puckered. Fight aphids off with a homemade spray of one liter warm water, four or five drops of dish soap, and a tablespoon of neem oil.

Aster leafhoppers: Prevalent throughout southern Canada and the midwestern United States, aster leafhoppers feed on plants and spread the disease aster yellows. The insects are tiny at a fifth of an inch and are thin, shaped like wedges, and light green with six white spots on their heads. The smaller nymphs have wings, but adults do not.

Carrot root fly: When carrot root flies strike, you’re most likely tof first notice them as white maggots, though the first stage of their life cycle is laying eggs in soil near plants. The maggots tunnel through root systems and eat them. Infested plants have foliage discoloration to red, followed by wilting. Affected vegetables are edible, although the insects will have gotten to them first, making them unattractive.

You can deter the carrot root fly from your parsnips by companion planting with alliums that have a strong scent (garlic and chives) or spreading your parsnips throughout the garden instead of using one large bed to hold them all.

Cercospora: This fungal disease is also called both leaf blight and leaf spot. Cercospora can take out an entire crop during any stage of its life cycle. On plants like parsnips that have thin leaves, it causes the margins of leaves to curl inward, withering as it spreads toward the stems. As the disease progresses, foliage begins to appear gray and fuzzy from the presence of spores. Once a decent amount of the foliage is covered in gray (which can happen in a matter of days), the plant is what gardeners call “blighted” and must be destroyed. Prevent cercospora by improving air circulation around plants, avoiding infected seeds, and not letting soil get too wet or splashing foliage with water.

Leaf miners: Leaf miners appear as eggs on the underside of foliage and larvae that eat squiggly tunnels through leaves, They must be managed quickly when an infestation occurs. Fight leafminers with the predatory wasp Diglyphus isaea.

Parsnip canker: All modern parsnip plants, except for the “Tender and True” variety, are immune to this disease. Red-brown canker sores appear on foliage near the top of the parsnip root when parsnip canker strikes. The infection spreads on wind, and plants are most at risk when the weather is cool and wet. Prevent parsnip canker by choosing resistant plants and seeds, clearing the garden of debris from weeds in the parsley family, avoiding damage from carrot rust flies, and covering the shoulders of parsnips and carrots to protect them.

How to Harvest Parsnips

By the middle of fall, your parsnips should technically be ready to harvest. However, their flavor is so much improved by overwintering in the soil that you should wait until after a hard freeze to dig them up. You can harvest your parsnips any time until the middle of January.

To harvest the smallest specimens, just use a trowel or fork to loosen the area around the parsnip, then pull it up. However, most of the parsnips will have to be dug up so they will not break. You may need to dig quite deep to reach the end of the parsnip, which can go on for a six-inch taper and cling to the soil very tightly.

How to Store Parsnips

Parsnips you do not store in the ground (which is the best option) should not be put into the refrigerator. Instead, fill a large wooden box with alternating layers of parsnips and dry sand or peat. Shut the box with a tight lid, and store it in a cool, dry location with plenty of ventilation.

Parsnips are fairly easy to grow (especially when the gardener is armed with all the information you’ve gained here. And in addition to being delicious, they’re very healthy for you. Parsnips are an excellent source of B6 and calcium. Even if you weren’t previously familiar with this underappreciated vegetable, take a chance and plant some parsnips this spring.