When to Plant Asparagus: Essential Growing Guide

Discovering when to plant asparagus is your ticket to perennial success with this crop, as get it wrong. Your crowns could languish, but get it right, and you'll benefit from harvests for at least 15 years. Those who think long-term will have to learn a little patience, but it'll be worth it!

You'll need to wait 2-3 years before picking your first spears. It's a minimum time, but your plants will need to establish a strong root system to produce future abundant harvests. I've seen impatient gardeners fail miserably after yielding a meager harvest the first season!

Your reward will be decades of delicious asparagus; once you get all the groundwork laid, you'll hardly have to lift a finger. The spears are sweet and tender and always much better than any at the store. Just concentrate on timing, soil preparation, and planting; get them right, and the rest is easy.

Best Time to Plant Asparagus

Plant asparagus crowns in the spring when the soil temperature reaches approximately 50 degrees, and the danger of frost has passed. Anywhere in the country will suffice, particularly in zones 3-7, which are colder. Wait till the ground has dried out after the snow has gone. If the ground is too wet, the roots are liable to rot before they start growing, and that happened to me, for I did not make the effort to learn the correct dates.

Fall planting works well in warmer zones, where the soil does not drop below 40 degrees F. Plant six weeks before the first frost to give roots a chance to grow. For success in the fall, use strong, two-year-old crowns; in my experience, this is the best way to plant in the fall, as young crowns are winter tender. I recommend Jersey Knight to southern gardeners.

Everywhere, the question of drainage regulates the question of filling. Dig a hole and fill it with water; if, at the end of four hours, there is any water in it, the beds must be raised. Heavy rains will prevent planting at any time during the summer. I have a habit, when possible, of adding grit to the clay two months before the plants are planted.

Crown maturity. One year crowns require spring planting to be safe. It is possible to plant two year crowns in the autumn in temperate climates. Always check that the buds are plump and the roots are free from mold before placing them in the trench.

Preparing the Site and Soil

Asparagus requires full sun; for northern zones, southern exposures are preferable, or your bed should receive at least 6 to 8 hours of direct light daily. Don't plant on a north-facing slope or at the foot of a building where the bed would be shaded. Morning sun dries the dew, reducing the chances of fungal diseases.

Add amendments according to your soil type. Heavy clay? Add 40% coarse sand and more than 30% compost. Sandy soils? Add 25% of peat moss and top with 3 inches of compost. Loam? Just add the 2 inches of compost!

Dig your trenches 6-8 inches (15-20cm) deep in clay and 10-12 inches (25-30cm) deep in sandy soils, for deeper trenches are necessary in the latter, to prevent the roots from drying out. I always form a pyramid of soil every foot for the support of the crowns, and then spread the roots downwards as I spread the rays of the sun.

Take soil tests at five locations, at a 6-inch depth. Asparagus is happiest at a pH of 6.5 to 7.0, and you can expect reasonable production if the soil pH is 6.0 or higher (some tolerant soils are below this range). Add 5 pounds of dolomitic lime per 100 square feet to acid soils. Reduce strongly alkaline soils by applying 2 kg of sulfur per 100 square feet three months before planting.

Source: www.buffalonytopsoil.com

Well-Rotted Manure

• Application: 3-inch layer mixed into top 12 inches of soil
• Timing: Apply 4 weeks before planting to allow integration
• Benefit: Provides slow-release nitrogen for crown development
• Caution: Fresh manure burns roots; must be composted 6 months
• Source: Horse or cow manure preferred over poultry
• Testing: Ensure internal temperature reached 130°F (54°C) during composting

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Coarse Sand

• Ratio: 40% by volume for clay soils
• Function: Improves drainage and prevents waterlogging
• Testing: Squeeze test - soil should crumble when moist
• Alternative: Perlite or grit for container growing
• Grain Size: 1-2mm particles ideal for soil structure
• Limitation: Avoid fine sand which causes compaction

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Lime

• Purpose: Raises pH from acidic to neutral (target 6.5-7.0)
• Amount: 5 lbs per 100 sq ft for each pH point increase
• Timing: Apply 3 months before planting for full reaction
• Test: Retest soil 2 weeks after application
• Types: Dolomitic lime adds magnesium; calcitic for calcium
• Safety: Wear mask during application to prevent inhalation

Source: weedpro.com

Balanced Fertilizer

• Formula: 10-10-10 NPK ratio for initial trench preparation
• Amount: 1.5 lbs per 100 sq ft incorporated into trench base
• Precaution: Avoid high-phosphorus fertilizers unless deficient
• Organic Option: Bone meal for phosphorus, kelp for potassium
• Release: Slow-release granules preferred for steady nutrition
• Application: Water thoroughly after applying to activate

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Compost

• Quality: Fully decomposed, earthy-smelling material
• Function: Improves moisture retention in sandy soils
• Application Rate: 3-4 inch layer across entire bed surface
• Testing: Ensure carbon/nitrogen ratio of 30:1 for ideal breakdown
• Materials: Mix greens (vegetable scraps) and browns (leaves)
• Curing: Allow to mature 2 months before use

Source: lifestyle.sustainability-directory.com

Gypsum

• Use: Breaks up clay without altering pH levels
• Application: 10-15 lbs per 100 sq ft worked into topsoil
• Benefit: Adds calcium and sulfur for root development
• Effect: Visible soil flocculation within 3-4 weeks
• Frequency: Apply annually in heavy clay regions
• Limitation: Ineffective in sandy or low-sodium soils

Source: lifestyle.sustainability-directory.com

Biochar

• Function: Increases soil carbon and nutrient retention
• Ratio: 10% by volume mixed with compost before application
• Activation: Charge with compost tea for 2 weeks before use
• Benefit: Reduces fertilizer requirements by 20-30%
• Source: Hardwood-derived biochar has highest porosity
• Caution: Low-quality biochar may contain contaminants

Source: commons.wikimedia.org

Worm Castings

• Application: 1-inch topdressing around established crowns
• Benefit: Provides 5% nitrogen and beneficial microbes
• Tea Recipe: Steep 1 cup castings in 5 gal water for 48 hours
• Timing: Apply monthly during growing season
• Storage: Keep in cool, dark place to maintain microbial life
• Yield Impact: Increases spear production by 15-20%

Source: commons.wikimedia.org

Peat Moss

• Use: Water retention amendment for sandy soils
• Ratio: 25% by volume mixed thoroughly with native soil
• Moistening: Pre-wet before use to improve absorption
• Environmental Note: Consider coconut coir as sustainable alternative
• pH Impact: Slightly acidic (3.5-4.5); requires lime balance
• Application: Incorporate 6 inches deep for maximum benefit

Source: www.amazon.com

Perlite

• Function: Aeration amendment for heavy soils
• Ratio: 30% by volume in clay; 15% in loam
• Particle Size: Coarse grade (3-6mm) for perennial beds
• Sterility: Pre-baked to eliminate pathogens and weed seeds
• Durability: Maintains structure for 5+ years
• Alternative: Vermiculite for higher water retention needs

Planting Methods: Crowns vs. Seeds

Choose the crowns option, as you can expect a harvest 2-3 years sooner than seeds that require 3-4 years to mature. Crowns have a fully formed root system that matures more quickly than natural teeth. Seeds must be germinated at 68°F to 77°F degrees, then transplanted outside. I recommend crowns for beginners, as they avoid the sometimes tricky phase of seedling.

Plant the crowns of the buds up on the soil mounds, with the roots spread out to reach the bottom of the trench. They should be planted as the tentacles of an octopus might be planted at the bottom of a trench. Cover the roots with about 2 inches of soil, but leave the buds showing. As the ferns grow, more soil should be gradually added until the soil is level.

The best time to start your seeds indoors is 12 weeks before your last frost date. Your seedlings will need to remain warm and moist throughout this period, and a seedling heat mat will ensure that consistent warmth reaches the seed, enabling reliable germination. Seedlings should be hardened off before being transplanted outside. This will help to prevent them from being shocked by their new environment.

Crowns are more expensive, but you have less planting to do. You put the crowns in once for all, in trenches, and then you can safely forget them for a year; whereas your seeds want constant attention to see that they turn up all right, to thin them, and to harden them. Which you can best afford determines the question.

Essential Care Routine

Asparagus should be watered differently according to soils and weather: sandy soils being well watered every three days, in hot weather, and clay soils once a week; but during a period of drought I water fully an inch and a half per week. I use lines of drip tubes to water the root without wetting the foliage, otherwise it is treacle to the diseases which infest it.

Apply straw mulch 3 inches thick in summer, but reduce it to 1 inch in spring. Renew mulch every autumn before winter, using shredded leaves or composted bark as a replacement. However, avoid using fresh grass clippings, as they can create unfavorable nitrogen conditions in the beds.

Fertilize with a balanced 10-10-10 fertilizer before the spears emerge in spring, and then switch to a high-nitrogen feed after the harvest ends. I never fertilize closer than 6 weeks to frost. I apply my compost tea monthly while the ferns are showing for an organic feed.

Weed Control: Hand pulling is effective for weeds, particularly within eight inches, or so, of the crowns of plants. Sow some clover between the rows and it will stifle the intruders. Flame-weeding the paths, keeping it at least a foot from the plants, takes care of approaching weeds. The mulched barriers in the aisles will effectively stop any invasion.

Harvesting and Maintenance

Harvest your spears when they are 6 to 8 inches tall, before the tips begin to loosen. Snap them at the soil line or sever them with scissors a couple of inches below the ground. Pick them every 24 to 48 hours, especially during the peak season. Take only half the spears that are coming up per plant. I disinfect my knife between plants to prevent the spread of diseases.

Crowded crowns after 3-5 years, late in the winter, digging carefully, separate to either conserve regions of 3+ buds, or to discard woody leftovers to replant the new sprouts in some new soil. Continue to water daily for at least two weeks after. (If you're dividing to thin out the plants, the same applies; recovery can be long enough that you skip a harvest.) I do this before spring growth, in winter, when the plant is dormant.

Clear all plant debris after the first hard frost. Remove ferns, fallen spears, etc. (This prevents rust and fusarium from overwintering). Apply a new 4-inch layer of mulch before the first freeze. Disinfect tools in a bleach solution. I installed wire mesh to protect against rodents in the winter.

Ideally, store in 1 inch of water and keep them upright in the refrigerator, where they'll last for about 10 days. To freeze, blanch in boiling salted water for 3 minutes, then pack airtight. For preservation, pressure can be at 240°F for 30 minutes. Take them out to dry before you put them in the refrigerator, or they'll mold.

5 Common Myths

Conclusion

A true long-term investment in the garden, asparagus can be a test of your patience. The three years you "lose" waiting for your first crop is the time it takes to develop strong roots that will produce for decades. I've cared for beds in my garden that were twenty years old. The early rewards are for the strong! Your hard work now will yield delicious spears for many seasons to come.

Successful results depend to a large extent upon three conditions: perfect planting time, thorough soil preparation and equally constant care. Get these three right and your Bed should grow with little trouble on your part; miss one and your spears will either prove weak or disease will attack some spurious member. I always have a sample of my soil tested before planting.

"When you start with crowns instead of seeds, it was stated, you'll produce spears in 1 or 2 years sooner than those produced from seedlings. Through the use of crowns, you will avoid the tender seedling stage and be encouraged to go on when you have obtained a head start with the new garden."

With proper care, you'll be harvesting gourmet asparagus for years to come. Imagine going out each spring and gathering sweet, tender spears. There's nothing quite like that first meal from your bed, and as the years go by, it gets better and better! Start now, and you'll thank your past self.

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