8 Super Useful Tricks for Growing Asparagus From Seed

Asparagus is a perennial vegetable crop that will reward your efforts year after year. Growing asparagus from seed is very rewarding but requires plenty of patience. However, planting asparagus seeds is often more cost-effective than buying mature crowns. In this article, you’ll discover how to grow asparagus, where to plant asparagus, and many more helpful tips and tricks for starting an asparagus patch in your home garden.

Asparagus plants need two to three years before they’ll be ready to harvest. On average, growing ten to twenty asparagus plants per person in the household will provide a sufficient harvest once the plants mature. The primary advantage of planting first or second-year asparagus crowns is harvesting asparagus spears sooner. Raising asparagus from seed adds one to two years to the expected harvest time. Read on to learn everything you need to know about planting asparagus seeds and cultivating a productive asparagus crop.

Best Tricks for Growing Asparagus from Seed

Getting an early start is critical when growing asparagus from seed. On average, germination takes about three weeks. Asparagus seedlings should grow indoors for 12 to 14 weeks before getting transplanted. Once your seedlings are approximately 12 inches tall, plant them deeply in the soil. How deep to plant asparagus depends on how well your garden soil drains (see details below). In addition, proper plant spacing is vital for an abundant asparagus harvest.

Male asparagus plants produce more edible spears than their female counterparts, which use a considerable amount of their energy for seed production. Remove all female plants from your asparagus patch for higher yields. They produce red berries in late summer or fall.

Jersey Knight and Jersey Giant are among the best asparagus varieties to grow from seed. Developed by the expert plant breeders at Rutgers University in New Jersey, they produce a large harvest and are more likely to be male. Heirloom asparagus varieties like Martha Washington and Mary Washington are known for being highly resistant to common plant diseases, such as asparagus rust, but not for having male-dominant seeds. If you want to add some diversity to your veggie garden, try planting a colorful heirloom asparagus variety like Purple Passion, which is disease-resistant and male-dominant.

Seed Starting Supplies

• Seedling tray, peat pots, or cardboard egg carton
• Seed starter soil mix
• Humidity dome
• Seedling heat mat
• 2-4 inch pots
• Compost
• All-purpose organic fertilizer

Planting Asparagus Seeds

Plant asparagus seeds between mid-January and early February, depending on your area’s last frost date. Fill a seedling tray, peat pots, or a cardboard egg carton with seed starter potting mix. It’s helpful to pre-saturate the soil to avoid displacing the tiny asparagus seeds after planting.

The ideal soil temperature for germinating asparagus seeds is between 70°F and 85°F (21-30°C). The top of the refrigerator is often warm, making it an excellent location for germinating vegetable seeds. Alternatively, consider purchasing a seedling heat mat from your local garden supply shop.

Soak the asparagus seeds in water for 12 to 24 hours ahead of your desired time. Doing so helps to break down their protective outer coating, which helps them germinate faster. Then, plant the seeds a quarter-inch deep and cover them lightly with soil. Keep them consistently moist, but don’t let the soil get soggy. Covering the seedling tray with a humidity dome or a sheet of plastic wrap helps retain moisture. To reduce the risk of mold and avoid disturbing the seeds, place a shallow tray of water underneath your seed starting tray to allow the soil to absorb moisture through the drainage hole at the bottom.

How to Grow Asparagus From Seed Indoors

Since asparagus seedlings have such a lengthy germination and growth period, it’s best to plant asparagus seed indoors in late winter or early. Grow the seedlings indoors until the last danger of frost for your region has passed, and you can transplant them outside in your garden.

When you notice the seedlings’ roots emerging from the drainage holes at the bottom of your seedling tray, transplant them into 2-4 inch pots. The plants usually take about one month to reach this size. Peat pots are beneficial because you can transplant them directly into the ground and avoid disturbing the seedlings’ delicate root systems.

To prevent your asparagus seedlings from becoming elongated or “leggy” while growing indoors, make sure they get plenty of bright light. For best results, place them on a sunny windowsill and rotate the tray or pots a quarter-turn once or twice every week. Alternatively, supplement natural lighting with LED or fluorescent grow lights. Asparagus seedlings require at least six to eight hours of light per day.

Choosing a Location for an Asparagus Patch

Finding a suitable location for your asparagus bed is essential because, once established, these perennial vegetables will return for up to 20 years. The north or east side of your garden is ideal for growing asparagus from seed. Once fully mature, asparagus fronds can grow up to four or five feet high, so make sure they don’t shade other sun-loving plants.

Select a location that gets full sun and has nutrient-rich soil that stays consistently moist but also drains well. Late spring frosts will damage emerging asparagus shoots, so avoid planting in exposed or low-lying areas. Asparagus plants develop deep roots, and they grow best in deep, loose soil free from obstructions. Ensure your planting site isn’t too rocky and doesn’t get water-logged or soggy for long periods.

To prepare your asparagus bed, begin by removing all weeds. Next, mix in a four-inch layer of compost, well-rotted manure, or other soil amendments with a rototiller. Loosen the soil to a depth of 12 inches so the asparagus plants develop strong root systems. If you don’t have a well-draining spot in your garden with appropriate soil, consider planting asparagus in raised beds.

Transplanting Asparagus Seedlings

Transplant your indoor-grown asparagus seedlings in the spring after the last danger of frost. Before transplanting, harden off your baby plants for seven to ten days by leaving them outdoors for progressively longer periods. That way, the seedlings can gradually adjust to exposure to the elements, and the risk of losing them to transplant shock is lower.

There are several different techniques for transplanting asparagus seedlings. Either dig individual holes six to eight inches deep or create long trenches. Plant each row three or four feet apart and leave eight to ten inches between each plant to give the plants plenty of room to develop. Planting the seedlings close together will result in thinner spears. To encourage your asparagus to grow thicker spears, give them more space. Since asparagus crowns already have an extensive root system, the plant spacing should be about 18 inches.

Be careful when handling the seedlings, and avoid damaging their roots when removing them from the pots. Using peat pots is helpful because you can bury them in the soil, and they will naturally compost themselves. Add one tablespoon per plant of phosphorus-rich fertilizer to the bottom of the hole or trench, and gently place the asparagus seedling in the bottom. Cover the root ball and the base of the stem with two to three inches of compost and soil.

As the plants grow taller, keep filling in the planting holes or trenches by covering the crown with more compost and soil. However, be careful not to smother the plants, adding only one or two inches of soil at a time and leaving at least three inches of the stem above ground. Once you’ve filled the hole or trench, create a small mound around the plant’s base to facilitate better drainage and prevent water from pooling up.

Ideal Growing Conditions for Asparagus Plants

Asparagus plants grow best in full sun. The plants can tolerate partial shade but produce a larger harvest if they get at least six or more hours of direct sunlight daily. In addition, they prefer a neutral to slightly acidic soil pH level.

In addition to adding all-purpose organic fertilizer or compost to your asparagus bed in early spring, the plants greatly benefit from supplemental phosphorus. Bone meal, fish emulsion, rock phosphate, or composted manure also help keep the soil rich in phosphorous and other essential nutrients to promote strong, healthy roots. Fertilize your asparagus patch each year in early spring and late fall with an organic, all-purpose fertilizer or compost.

Apply two inches of mulch around the asparagus patch to help retain soil moisture and suppress weed growth. Use lightweight materials like grass clippings, leaves, or straw to avoid blocking or smothering the emerging asparagus shoots.

During the first three years, refrain from harvesting any asparagus spears. Doing so allows the plants to focus their energy on growing robust root systems. Instead, concentrate on building a balanced soil environment and keeping the bed free of weeds. For a larger asparagus harvest in the future, pull out the female plants after they’ve flowered and can be identified by their red berries.

Your asparagus patch may become less productive over time. If you start getting a diminished crop, refrain from harvesting that season to allow the plants to store more energy. Then, in late fall when the plants have gone dormant, dig them up and divide the roots. Use a clean, sharp knife to separate the asparagus crowns into several pieces with plenty of healthy roots attached. Crown division is a straightforward and efficient method for regrowing asparagus.

Harvesting Asparagus Spears

The shoots will be ready to harvest in the third year after planting asparagus from seed. Wait until the asparagus spears grow between six and ten inches tall before collecting them. Although it may seem tempting, remember that cutting first or second year asparagus spears can either kill the plants or significantly stunt their growth.

Harvest mature asparagus spears for six to eight weeks, from late May or early June through July. Use a clean, sharp knife or a pair of garden clippers, or snap off the asparagus spears manually at the soil level.

Leave any asparagus spears that grow taller than ten inches to mature fully. Doing so allows the plant to generate enough energy for the following growing season. Stop harvesting asparagus when the fronds begin flowering.

If desired, cut your asparagus back to approximately six inches above the soil level in late fall. However, leaving the fronds standing over the winter can help to protect the crowns from freeze damage. Additionally, mulching your asparagus bed in the fall helps to insulate the root systems during cold weather.

Companion Plants for Asparagus

Companion planting aims to create a healthy and resilient garden ecosystem. Different types of plants have natural properties that can either help or harm their neighbors. When planning your garden layout, it’s essential to keep these relationships in mind. Companion planting also attracts beneficial insects like pollinators and predators to your garden to help your plants flourish.

Asparagus grows well alongside plants in the nightshade family, like tomatoes, peppers, and eggplants. Nightshades have high concentrations of solanine, a naturally occurring chemical that repels asparagus beetles. In return, asparagus plants deter root-knot nematodes, which feed on and damage the nightshades’ roots.

Basil and parsley also ward off asparagus beetles, as well as other insect pests like carrot flies, tomato hornworms, squash bugs, and whiteflies. Herbs like cilantro, comfrey, and dill repel spider mites and aphids. Marigolds and nasturtiums repel aphids and harmful soil nematodes while attracting beneficial insects.

Plant early-season veggies like beets, lettuce, and spinach between your asparagus rows to keep weeds down. Then, when the leafy greens start bolting around mid-summer, plant another crop of lettuce and spinach under the shade of the tall asparagus fronds.

There are also some plants to avoid growing close to your asparagus patch. Alliums like chives, garlic, leeks, and onions stunt asparagus growth. In addition, potatoes also inhibit the growth of asparagus plants because they’re both heavy feeders and compete for deep root space in the garden. Similarly, avoid planting root crops like carrots, turnips, and sweet potatoes next to asparagus.

Most Common Pests and Diseases for Asparagus Plants

In general, asparagus plants are remarkably low-maintenance. Nonetheless, they occasionally suffer from problems with insect pests or plant diseases. However, rest assured that it’s usually possible to resolve the issue using natural methods. Healthy plants are less vulnerable to pest and disease attacks, so be sure to give them the proper amounts of light, nutrients, and water.

Asparagus beetles, aphids, and spider mites are some of the most prevalent asparagus pests. To eliminate a severe insect infestation, spray all parts of the plants with insecticidal soap, horticultural oil, or neem oil. Using companion plants to attract ladybugs, lacewings, and other beneficial predatory insects to your garden is an excellent form of natural pest control.

Asparagus rust is a fungal disease that can be prevalent in humid regions. The symptoms include orange blisters on fronds and spears, yellowing leaves, and overall plant dieback. Fungal rust is often caused by overwatering. Remove the diseased plants as soon as possible, and treat the rest of your asparagus bed with organic sulfur fungicide.

Fusarium wilt is one of the most severe plant diseases for asparagus. The signs include reddish-brown discoloration of the stems and spears that appear weak and spindly. Unfortunately, there’s no known effective treatment once the plants become affected by fusarium wilt. Pull out the affected plants straight away to stop the spread of this fungal plant disease. Planting a disease-resistant asparagus variety like Jersey Giant, Jersey Knight, or Apollo is the best way to prevent fusarium wilt. Also, minimize plant stress by not harvesting asparagus spears for more than six to eight weeks per season and keeping weeds under control. If you’d like to learn more about fusarium wilt, check out this article from the University of Massachusetts Amherst Center for Agriculture, Food, and the Environment.

Although asparagus is a slow grower and must grow for several seasons between planting seeds and the first harvest, it’s worth the wait. Homegrown asparagus is much healthier and tastier than the store-bought alternative, and it’s a low-maintenance perennial vegetable that will reward your efforts for many years to come. Growing asparagus from seed is more cost-effective than planting asparagus crowns. Plant asparagus where it will get plenty of sunlight and grow in rich, moist, well-draining soil to enjoy a bountiful asparagus harvest each spring.

Have you ever tried growing asparagus from seed in your home garden? Feel free to share your success stories or ask any questions you may have in the comments below! If you enjoyed learning how to grow asparagus from seed, please share this gardening guide with your fellow green thumbs.