Whether you're an avid gardener or just starting out, learn everything you need to know about root vegetables like potatoes and carrots, and how to take those tasty bulb vegetables like onions and garlic from seed to your table.
Featured Expert: Dr. Frank Williams, BYU Professor of Plant and Animal Science.
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Root and Root-like Vegetables
Root and root-like vegetables
Examples of these vegetables are potatoes, beets, carrots, sweet potatoes, parsnips, radish, turnips, and rutabaga.
With these vegetable we eat something other than the fruit-we eat the food storage organ of the plant.
Cut the potatoes in fairly large pieces, each piece containing one or two eyes. It's best not to have several eyes on a piece as too many shoots will develop, thus cutting down on the yield.
Gently work the seed piece into the soil 1-2 inches underground.
New potatoes are ready in two months. They are small and do not have a hard skin.
They are mature when the skin is tough (plus they will store longer)
Suberization is a step potatoes go through that prevents them from rotting as quickly. Suberization is Mother Nature's process of depositing the waxy-fatty substance suberin in the skin cells and turning the skin cork-like. When the suberization process is complete, since the skin is less permeable, weight loss is minimized, quality losses are minimized, rot is minimized, and disease resistance is maximized.
Potatoes intended for long-term storage should not be harvested until the vines have been dead for at least ten to fourteen days.
When doing a complete harvest, dig all the potatoes outward a distance of 1 ½ - 2' from the plant.
The major challenge is controlling insects; common pests include the potato bug, slugs, snails, and wire worms.
Snails and slugs feast on most plants, especially young, tender transplants, leafy vegetables and succulent plant parts.
Both the adults and larvae of the Colorado Potato Beetle feed by chewing the leaves and terminal growth of plants.
Damage is seen as shallow to deep holes in the potatoes, caused by wireworms burrowing into the tuber while feeding. Wireworms bore perpendicularly or diagonally to depths up to 0.5 inch, but do not tunnel all the way through the tuber.
The potato flea beetle feeds on leaves and stems resulting in many small holes in the leaves. Most damage is caused by the larvae, which hatch from eggs scattered by adult females in the soil around potato plants. The larvae feed on roots, underground stems, and tubers.
The fungus, which causes the potato late blight, infects leaves, stems and tubers. It is best known for causing the devastating crop losses that resulted in the Irish potato famine.
Plant seeds 1/4 to 1/2 inch deep (no more than two or three seeds per inch) in early spring. Later sowings may be planted 1/2 to 3/4 inch deep when the soil is dryer and warmer. Space rows 12 to 18 inches apart.
Thin carrot seedlings when they're about 5cms (2 inches) tall to a space of 2cm (a little under an inch). Then thin again when the plants are 15cms (6 inches) tall with 5cm (2 inches) between them.
Fertilizer
Use 1 pound of nitrogen worked into the soil in the spring. Other than that carrots need very little fertilizer.
Planting
Carrot seeds are so small, a teaspoon holds 2,000 seeds. Most instructions will tell you to sow six seeds per inch, but that's easier said than done.
Here's a good idea to help make carrot planting easier. Mix the seeds with clean builders or sandbox sand to facilitate even distribution over the prepared seedbed. The goal is to spread about 3 to 4 seeds to the inch in either the traditional row, or scattered over a designated area.
Carrot seeds can take up to 3 weeks to germinate. You can soak the seeds in water for 6 hours before planting to help speed up germination.
This site offers some helpful hints on planting carrots.
Make your own liquid seed tape with water and cornstarch: To one cup of lukewarm water, stir in cornstarch one teaspoon at a time until the mixture resembles Cream of Rice--before it cools to rubber. Add your carrot seeds and fill a clean, plastic shampoo bottle with the mixture. Now you just squeeze out lines of seeds!
To harvest, dig gently around the carrots, hold the tops close to the ground, pull up, and twist the plant gently by its stem.
A light frost will force carrots to store more sugar.
Pests and challenges
Pests and diseases are not a huge problem with carrots.
The aster leafhopper is a consistent problem for carrot growers in the upper Midwest.
Aster yellows is caused by a plant pathogenic micro-organism, that is carried from plant to plant by sap-sucking leafhoppers.
The adult Carrot Rust Fly emerges in early spring, eggs are laid at the base of the carrot and the newly hatched larvae burrows into the soil and feeds on side roots of the host plant.
Grubs of the carrot weevil feed on the exterior or burrow into carrots. They usually cause damage near the top of the carrot.
Young carrot seedlings are weak and grow slowly. It is essential to keep weeds under control for the first few weeks. Keep weeds out in the early stages so the nutrients go the vegetables and not the weeds. Weed carefully by hand so as not to disturb the young carrots.
Planting carrots in the late summer, so they are ready to harvest in the fall, is ideal because a little bit of frost stores some sugar in them.
To produce sweet and orange carrots, make sure the roots are completely covered by soil.
A sandy loam soil is ideal for growing carrots.
Soil that contains rocks and organic matter is not good for carrots. When the root runs into a rock or piece of organic matter it causes the carrot to split.
If the soil is too wet it can cause carrots to crack.
Water carrots consistently to prevent cracking.
Raised beds and containers are ideal for growing carrots.
If your soil contains high amounts of organic material or rocks, the ideal thing may be to dig a little trench six inches wide and a foot deep and fill it with sand and grow your carrots there.
Mix carrot seeds with sand to make them easier to space when planting.
You can speed germination by soaking seeds in water for 6 hours prior to planting.
Keep them moist until they sprout. Then water on a regular basis or as needed when the soil dries down ½ - 1 inch.
Try to get carrots so they are 1 - 2 inches apart.
Use compost and wood ash to control pests.
Keeping weeds out of carrots is very important.
Other Root Crops
Beets
Table beet (also known as garden beet, blood turnip or red beet) is a popular garden vegetable throughout the United States.
Beets are ready to harvest after 40 - 50 days, or when they reach 1-2 inches in diameter.
Beet greens are cooked or served fresh as greens.
Radish
Radish is a cool-season, fast-maturing, easy-to-grow vegetable.
Parsnips
Parsnip is considered a winter vegetable because its flavor is not fully developed until the roots have been exposed to near-freezing temperatures for 2 to 4 weeks in the fall and early winter.
Parsnips left in the ground after the first frost are sweeter and can be harvested all winter long.
Bulb Vegetables
Some examples of bulb vegetables are chives, garlic, leeks, onions, and scallions, shallots.
What will work for the climate you live in? See what your neighbors are growing.
The day-length is very important for onions but less important for garlic. You will need to learn which varieties will do well in the area where you live in relation to the day length.
Choose varieties appropriate for your area by checking with your area Extension Service.
Tips on bulb vegetables from Frank Williams
A bulb is nothing more than a compressed plant.
Onion
More onions are consumed than any other vegetable. It is one of the oldest of all cultivated plants and now grows in many different forms and in almost every area of the world.
The onion is adapted to a wide range of temperatures and is frost-tolerant.
Choose a garden site that is in full sun and has a well-drained soil with pH of 6.0 to 6.5. Apply lime and fertilize according to soil test results. Many gardeners plant onions in a raised bed rich in well-rotted compost, manure, and other organic matter.
Apply a general fertilizer by working it into the soil a few days before planting.
Sunlight and space
Sunlight 6-8 hours a day.
To produce dry onions, plant the smaller sets 1 inch deep, with 2 to 4 inches between sets. Allow 12 to 18 inches between rows.
Planting
You can buy onion sets or seeds.
Sets will mature a little earlier in the season but seeds will also mature very well.
Space seeds or starts 6 to 8" apart from each other in a row.
Spacing between rows is just enough to be convenient to walk between them.
Seeds can be sown directly into the garden, covered with one-fourth inch of soil and should sprout within 7- 10 days.
When you are using transplants they should be planted as soon as possible.
Onion plants are hardy and can withstand temperatures as low as 20o F. They should be set out 4 to 6 weeks prior to the date of the last average spring freeze.
Watering
Water once every three or four days during germination and then taper off to once a week.
Let them dry out a little after the harvest so they don't rot when stored.
Pests and Challenges
Onion Thrips have rasping-sucking mouthparts and feed by rasping the surface of the leaves and sucking up the liberated plant fluid. They feed under the leaf folds and in the protected inner leaves near the bulb.
Bulb mites damage bulbs by penetrating the outer layer of tissue and allowing rotting organisms to gain entry.
Small gray flies lay eggs in the soil surface near the germinating plants. Larvae, or onion maggots, feed on the developing seedling and, in the case of the onion maggot, on the expanding bulb.
Damage caused by leafminers is primarily cosmetic in green bunching onions.
Bacterial soft rots are characterized by softening and water soaking of one or more of the inner fleshy scales of the bulb.
The most striking symptom of pink root is, as the name indicates, pink roots. Infected roots first turn light pink, then darken through red and purple, shrivel, turn black, and die.
Plants affected by basal rot show progressive yellowing and dieback from the tips of leaves.
Weed control is a very important aspect in growing onions successfully.
Tips on growing onions from Frank Williams
Onions contain a gas that reacts with the water in our eyes producing mild sulfuric acid, which causes tears.
Onions are a biannual plant. It takes two years to get the large onion. The first year the seed is planted and a small onion is harvested and allowed to dry. The next spring the small onion set is planted and grows into a large onion.
To produce large bulb onions, plant the sets in early spring.
To have a good continual crop of green onions, plant the seeds throughout the spring at 2-week intervals.
Onions should be planted about 3 inches apart in rows 1 foot apart.
Onions are very site sensitive. The taller the tops are before the onion bulb begins to form, then the larger the onion will be.
Onions are very sensitive to day length. Be sure to plant the variety of onion that is adapted to your climate and day length.
Onions can be harvested at any stage. If you want to store them, harvest them after the tops fall over.
If you harvest onions when the tops are still green, you cut the tops off, and put the onions in storage, the bulb will begin to grow.
In order to store onions they must be cured, or dried down, in a warm dry place. Curing is complete when the neck is tight and the outer scales are dry.
Garlic
Garlic is one of the oldest cultivated plants, and thought to have originated in Southwest Asia.
Warm climates are good, but garlic will grow almost anywhere. It tolerates cold winters and short growing seasons if planted at the right time and with minimum care.
Day-length is important with garlic, because the size of the bulb is partly dependent on above-ground conditions (not as much as with onions, however).
Space the cloves 6 to 8 inches apart from each other. Spacing depends on a number of factors. Close spacing results in high yield but smaller bulbs, while spacing farther apart will result in lower total yields but larger bulbs.
Garlic is not easy to grow because their watering needs are more stringent.
The most critical stage for irrigation is during bulbing. Lack of irrigation or rainfall during this stage will result in smaller bulbs and earlier maturity.
Garlic needs to have consistent water so the soil stays moist, but not too moist or there will not be adequate amounts of oxygen in the soil.
Soil should not dry down more than 2" during the growing season.
If the garlic bulbs are left in the ground over winter, let them go to seed the following season. At the top of the seed stalk the bulbs will produce 10 to 15 tiny bulbs that you can plant.
If garlic is stored, it won't re-sprout because the top of the clove is closed. This also prevents bugs from crawling in.
Onion Thrips have rasping-sucking mouthparts and feed by rasping the surface of the leaves and sucking up the liberated plant fluid. They feed under the leaf folds and in the protected inner leaves near the bulb.
Small gray flies lay eggs in the soil surface near the germinating plants. Larvae, or onion maggots, feed on the developing seedling and, in the case of the onion maggot, on the expanding bulb.
Bulb mites damage bulbs by penetrating the outer layer of tissue and allowing rotting organisms to gain entry.
Damage caused by leafminers is primarily cosmetic in green bunching onions.
Bacterial soft rots are characterized by softening and water soaking of one or more of the inner fleshy scales of the bulb.
Plants affected by basal rot show progressive yellowing and dieback from the tips of leaves.
Tips on growing garlic from Frank Williams
Harvest garlic when the top has dried down.
Garlic are a little harder to grow, but can grow most anywhere with a little care.
Don't plant garlic in a real wet soil.
Other Bulb Vegetables
Chives
The chive plant is the smallest member of the onion family.
You can start chive plants from seed, purchase a plant or two, or ask a neighbor for a division from their chive plants.
Leeks
Leeks like lots of moisture, so they do not do real well in a dry climate.
Leeks can be harvested when they are pencil-sized and used as you would scallions. When larger, harvest them for soup and savory pies.
Shallots
Shallots are often considered the gourmet member of the onion family.
