Common Issues You Should Know About Before Growing Asparagus

The perennial asparagus is an excellent vegetable to add to your garden. The plant stays productive for well over 15 years in the right conditions, and it can serve as an ornamental with its ferny and colorful shoots. But unlike other vegetables, getting it to establish in the soil can be challenging. In fact, asparagus is one of the most difficult vegetables to grow in your garden. For all its longevity and productivity, the veggie requires specific growing and care conditions before and after planting, and throughout its long years. And once it's growing successfully in the garden, you need to watch out for the pests who, just like you, find its spears extra delicious.

Asparagus diseases are another hurdle that could diminish your harvest or, worse, end the plant's life prematurely. There are several of those infections and you'll have to identify them and take precautions or look out for the early symptoms and act quickly to save your plants. This might all seem intimidating, especially if this is your first time growing the crispy veggie. But there's no need to feel discouraged. This article sheds light on the common issues you might come across when growing asparagus, as well as how to fix or prevent them before they even happen.

Harvesting asparagus is another aspect of the plant that is fraught with problems. Since the spears are literally the young stalks that turn into ferns and support the crown, the risk of overharvesting is high. Overharvesting not only impacts the vegetable's growth, but also reduces the harvest over the next season. Another problem has to do with harvesting too early. If you don't allow the plant to fully develop first, cutting those delicious spears could lead to depleted sugar reserves in the plant, which affects its quality and leaves it vulnerable to pests and diseases.

To prevent these problems, you should allow your asparagus enough time to establish before you begin harvesting the spears. This depends on how you started your plants. For asparagus grown from seeds, the recommended time to start harvesting is after three years. If you started it from crowns, then harvesting can begin in the second year. The first harvest season should be limited to just two to three weeks to protect the plants. In the spring, cut the spears when they're between 6 to 8 inches long. A healthy plant will replace the cut spears with thick new ones. But after six to seven weeks of harvesting, the new spears grow as thin as a pencil or less. That's your cue to end the harvesting season.

Winter isn't kind to many perennials, and asparagus is no exception. Cold weather could damage the roots and cause the stalks to turn soft and brown. Asparagus is susceptible to damage when the temperatures drop to the low-20 degrees Fahrenheit. In warm climates where the winter is mild throughout, wintering the vegetable isn't necessary. But if you live in a cold region where frost is a regular threat, then you need to prepare your asparagus bed for the coming winter.

You can start wintering the asparagus when the leaves turn yellow and fall off in autumn. Cut back the fronds to about 2 or 3 inches from the ground. The next step is to cover the bed with a thick layer of organic mulch, such as sawdust, wood chips, or straw. Usually, 4 to 6 inches of mulch will protect the plant against cracking when unpredictable weather causes the soil to freeze again after thawing. Keep in mind that mulching could slow the growth of the asparagus in the spring. So, if you get a thick snow covering in the winter, you don't need to mulch the beds. After the last frost, inspect the plant and remove any stalks damaged by the cold.

Beetles love asparagus so much that three species target its spears relentlessly and two of them are named after the vegetable. Those two are the common asparagus beetle and the spotted asparagus beetle. They both have a quarter-inch-long, oval-shaped body with two antennae. However, the common beetle has a dark blue body with cream blotches, while the spotted beetle has a reddish-orange body with 12 black spots. Both the larvae and adult common asparagus beetles feed on the ferns of the plant. Meanwhile, the larvae of the spotted beetle feed on the berries, while the adults feed on the buds and young spears. The third beetle is the Japanese beetle. It's a flamboyant bug, about 1/3 of an inch long, with a bright green head and bronze wings. It feeds on and strips off the leaf-like parts of the stem.

One way to manage the two asparagus beetles is to pick them up by hand and drown them in a bucket full of soapy water. They're most active in the afternoons, so that's the best time to look for them. Keep an eye out for the piles of brown eggs on the stems and dispose of them in the same way. Another option is to invite ladybugs to your garden — their larvae feed on the eggs and larvae of the asparagus beetles. You can keep Japanese beetles out of your garden by planting geraniums or use pheromone traps to control their infestation.

Yellow-striped armyworms are about 1.5 inches long with yellow, black, and red stripes along their backs. They only feed on the ferns of the asparagus, so their damage is mostly limited. But the same can't be said about cutworms, which come in two flavors. White cutworms are translucent worms the same size as armyworms. They attack the asparagus from early spring to June, causing a lot of damage to the tips of the spears. Dark cutworms have brown stripes on their backs and feed on the base of the asparagus. Their damage ranges from distorted spears to slowed-down growth.

To get rid of cutworms, don't let weeds grow in or near the asparagus bed. Another effective method is to clear out debris where the grubs take shelter. Since the worms are active at night, pick them up and drown them in a bucket. If you have a large infestation, consider spraying them with a pesticide that contains permethrin. As for armyworms, letting nematodes in the soil is an effective natural remedy to control the pests. Bacillus thuringiensis pesticides can be used to eliminate small worms, although they don't work against large ones.

Asparagus rust is another fungal disease that impacts the plant's appearance, growth, and productivity. It's caused by the Puccinia asparagi fungus and mostly affects the ferns of the vegetable. When the ferns are infected, small green lesions emerge which soon join to form large ones. Sometimes they will appear on the stems as well. When the lesions mature, they turn rust-colored and release spores that infect the ferns again in a continuous cycle. Before the winter, the rust-like spores turn black and prepare to overwinter. Infections often lead to a weakened crown and reduced spear production. Rust often spreads during humid conditions and dry soil.

One of the best ways to combat rust is to harvest spears in the spring regularly. This removes the spores from the plant, which limits infections and breaks the cycle of reinfection and overwintering. Cutting and disposing of infected ferns before the spring is recommended to prevent the spread of the disease. If asparagus rust is a threat in your area, select rust-resistant varieties, such as the Millennium strain. Also, spacing the rows in the bed at least 6 feet apart helps improve ventilation and reduce infections.

Cercospora blight is also a fungal disease, and it also causes serious damage to the ferns of the asparagus. The result is fewer spears to harvest and a sickly plant overall. The first signs of an infection are gray oval lesions with reddish edges. They spread up along the ferns, causing them to turn yellow, stop producing spears, and go dormant. If the disease isn't treated, it will eventually cause the death of the asparagus. The fungus is active in the summer months and prefers hot and humid conditions.

Keeping the asparagus plant dry, especially the ferns, is a recommended way to prevent infections. Try to water the plants in the early morning to allow the sun to dry out excess moisture throughout the day. Other prevention strategies include removing and burning old ferns, either in the early spring or late fall. Do the same for any infected plant parts. This will break the cycle of infections and eliminate the fungal spores wintering on the ferns. You might also spray the plants with fungicides to control infections.