Asparagus
Asparagus officinalis
Asparagaceae · asparagus family
Origin · temperate Europe · Mediterranean · Western Asia
- Matures
- 24–49 months
- Harvest
- Over a period · Perennial
- Sun
- 6–8+ hrs
- Spacing
- 12 in
Planting window
When to sow, by microclimate — foggier blocks run a different calendar than sunnier ones.
| Jan | Feb | Mar | Apr | May | Jun | |
|---|---|---|---|---|---|---|
| Foggy | ● | ● | ● | |||
| Sunny | ● | ● | ● |
| Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|
| Foggy | ● | |||||
| Sunny | ● |
Sunlight
How well it does at each level of direct sun per day.
Soil depth
Root room it needs — useful for sizing raised beds and containers.
Soil pH
The soil acidity it grows best in — most crops sit just below neutral, so this mostly matters for heavily amended or long-reused beds.
- Preferred range
- pH 6.2–6.8
Spacing
Room each plant needs — along the row and between rows — for sizing beds.
- In-row
- 12 in
- Between rows
- 36–60 in
Growth habit
The shape it makes in the bed and how tall it gets — what tells you whether to give it a trellis, a stake, or just room.
- Habit
- Upright
- Mature height
- 3–5 ft
Stands on its own; the tallest types appreciate a stake in wind.
Growing in containers
Whether it does well in a pot, planter, or window box — the SF balcony-and-deck question, weighing its footprint, form, and staying power, not just root depth.
Better in open ground — it wants more root room, spread, or staying power than a pot gives.
How to start it
Sow it where it grows, or raise it under cover and set it out — and how far ahead to start the seedlings if it's the latter.
- Usually
- Direct-sow
- Start indoors
- 10–12 weeks ahead
Sown straight into the bed it will grow in.
Getting started
How it goes in the ground — how deep to sow or set it, and the soil temperature it needs to wake up. The cold-soil floor is the real limiter for direct-sowing in a foggy SF spring.
- Started from
- From crowns
- Ideal soil temp
- 65–85°F
- Set depth
- 4–6 in
Sprouts between 50–95°F; happiest around 65–85°F.
Watering & feeding
How thirsty and how hungry it is — the water it wants and how much feeding the bed needs to keep it producing. In the fog belt even a thirsty crop drinks less than it would inland.
- Water need
- Low
- Feeding
- Moderate feeder
Gets by on less — water deeply, then let it dry out between; forgiving of a missed day.
A balanced feed worked into the bed at planting usually carries it through the season.
Once the crown is established this deep-rooted perennial gets by on little — water through the fern season, then ease off. A moderate feeder that appreciates compost worked in each year.
Pests & diseases
What tends to trouble this crop — what it is, what you'll see, and what to do about it, least-toxic first.
Asparagus beetles are the one pest that defines this crop — they scar spring spears and bleach the summer ferns. The two crown diseases are the reason siting matters more here than for an annual: a bed is in for 15+ years, so Phytophthora crown and spear rot, which follows saturated soil, is the real risk in an SF winter — plant on the best-drained ground you have and resist watering an established bed through the rainy season. Fusarium arrives on infected crowns rather than from your soil, so buy from a reputable supplier and pick resistant varieties (UC 157, Jersey Knight).
Pests4
Asparagus Beetles
- What it is
- Larvae are dark green-gray grubs about 3/4 inch (9 mm) long when full grown. Asparagus beetle adults may be bluish black beetles with a red prothorax and yellow spots and red borders on wings. Spotted asparagus beetles are reddish orange beetles with black spots.
- What you'll see
- Adults chew the growing tips of spears in spring leaving brown stains, scars, or blemishes. Larvae may chew ferns, causing them to appear bleached.
- What to do
- Remove spears promptly. Handpick beetles or wash eggs, larvae, and adult beetles off with a strong stream of water. Clean up debris and remove and destroy ferns by proper pruning in late fall to reduce overwintering sites for adults. Applications of a pyrethrin spray may be effective against larvae when they are young.
Aphids
- What it is
- Aphids have soft pear-shaped bodies with long legs and antennae and may be green, yellow, brown, red, or black depending on the species and the plants they feed on. A few species appear waxy or woolly due to the secretion of a waxy white or gray substance over their body surface.
- What you'll see
- Low to moderate numbers of leaf-feeding aphids aren't usually damaging in gardens or on trees. However, large populations can turn leaves yellow and stunt shoots; aphids can also produce large quantities of a sticky exudate known as honeydew, which often turns black with the growth of a sooty mold fungus.
- What to do
- Before planting vegetables, check surrounding areas for sources of aphids and remove these sources. On the other hand, these aphid-infested weeds can sometimes provide an early source of aphid natural enemies.
Cutworms
- What it is
- Cutworms are dull brown caterpillars ranging in length from 1 to 2 inches when fully grown. They curl into a C-shape when disturbed.
- What you'll see
- Cutworms feed on blossoms and leaves of many ornamental plants and attack most garden crops. They clip off seedling stems near or just below the soil level.
- What to do
- Cutworms are pests mainly in the spring. Destroy crop residues; keep garden weed-free in winter.
Snails and Slugs
- What you'll see
- Snails and slugs feed on a variety of living plants and on decaying plant matter. They create irregular holes with smooth edges on leaves and flowers by scraping with their rasp-like tongues.
- What to do
- It will not be possible to eliminate some shelters, such as low ledges on fences, the undersides of wooden decks, and water meter boxes, so make a regular practice of trapping and removing snails and slugs from these areas. The survivors congregate in the remaining shelters, where you can more easily locate and remove them.
Diseases2
Fusarium Wilt on Asparagus
- What you'll see
- Mature plants infected with Fusarium gradually decline in productivity and growth. Spears are weak and spindly. Reddish brown vascular discoloration, which may extend into the crown, is present at the base of infected stalks. Crowns and belowground portions of stems exhibit reddish flecks or sunken brown lesions.
- What to do
- Fusarium wilt is introduced on transplants. Once in the soil, little can be done to prevent it from infecting other plants. Plant resistant varieties. If direct seeding, use clean seed.
Phytophthora Crown and Spear Rot on Asparagus
- What you'll see
- Soft, water-soaked lesions on shoots near the soil line elongate rapidly and become light brown. The affected side of the spear becomes flattened, and the shoot becomes extremely curved and may even collapse. Infected crowns display yellow orange colored tissue that may appear waterlogged and fibrous.
- What to do
- Most common in wet years. Avoid prolonged saturation of the soil and provide good drainage. Irrigate only as much and only as often as necessary. Plant in Phytophthora-free soil and use disease-free transplants.
Harvest & storage
How to tell it's ready to pick, and how to keep it once it's in.
- Keeps
- DaysBest eaten within a few days of picking.
- Ready to harvest
- Snap or cut 5-8 in spears at the soil line while the tips are still tight, before they fern out.
- Storing
- Highly perishable — stand or wrap the spears and refrigerate; best within a few days.
Culinary use & nutrition
What it's for in the kitchen, and the nutrients a 100 g raw serving is a notable source of.
In the kitchen
- Boiled / steamed
Nutrition highlights
- Excellent source
- Vitamin K, Copper
- Good source
- Folate, Thiamin, Iron, Riboflavin
Share of the Daily Value in a 100 g raw serving (USDA FoodData Central).
Pollinators & wildlife
What this crop offers the garden's wildlife once it flowers — often the payoff for letting a bolting plant stand.
- Bees
- Honeybees and natives — bumble, mason, and sweat bees — working the flowers for pollen and nectar.
The reward for stopping the harvest: once you let the spears fern up, the plants hang small greenish bell flowers along the stems in early summer and honey bees work them steadily. Cut the bed to the ground instead and there is nothing to visit.
Sources
Growing data on this page is drawn from UC Master Gardeners, Marin County, UC Master Gardeners, Contra Costa County, and the other references on our sources page.