The first big vegetable of the season, asparagus, is also among the most beloved. The tender spears arise from perennial roots in spring while the weather is still chilly, and more buds keep coming until the warm days of summer, when the fronds are left to grow into head-high branches.
Asparagus is easy to grow in climates where the plants get a nice winter chilling, but sometimes things don’t go exactly as planned. From companion plants for asparagus to when to clean up old asparagus stems, here are our six most-asked questions about growing asparagus.
1. It feels like spring outside. Why is my asparagus not growing?
Assuming nothing terrible has happened below ground, the plants are probably waiting for days to get warmer. Research from Michigan State University in the northern US showed that dates for asparagus emergence can vary by three weeks, and that emergence depends more on daytime temperatures than soil temperatures. Cold spring weather can slow spear emergence while warmer temperatures coax the spears to life. In most temperate climates, the asparagus harvest season runs from three weeks before the last spring frost date to three weeks after.
2. My plants have grown well for two years. The first spears are coming up, but some are spindly and they don’t look like the pictures online.
Don’t get me started. Many of the photos online show purchased asparagus spears that have been stuck into a pile of soil by the photographer. Real asparagus emerges erratically over a period of six weeks, and some individual plants produce larger or smaller spears than others. Once harvesting begins it’s important to pick asparagus every other day, or daily in very warm weather.
3. What are good companion plants for asparagus?
It depends on the age of the asparagus. The first two years after planting, strawberries make good companion plants for asparagus by filling open space that might otherwise go weedy. Garlic makes a good edging plant. As asparagus matures, the tall fronds shade out low-growing strawberries, so it will be better to mulch between plants and use annual flowers like calendula along the bed’s edges. Cherry tomatoes or tomatillos make good companion plants for asparagus when properly sited. In summer in the Northern Hemisphere, asparagus foliage leans to the east, while the vining branches of cherry tomato and tomatillo pull to the west. When cherry tomatoes or tomatillos are planted on the east side of mature asparagus, the two crops support each other and mingle into a happy mass.
4. Do you need to cut asparagus spears when harvesting, or can you snap them off? How should I store the harvested spears?
Asparagus spears naturally snap at the point where they become brittle and tough, so snapping works just fine. A knife requires two hands and poses a risk to nearby emerging buds, so is simply unnecessary.
You can save up dry spears in a plastic bag in the refrigerator, or place them in a jar with the cut ends in 2 inches (5cm) of water. It is best to postpone washing and trimming until just before asparagus is cooked, because the tips can absorb water that can lead to rotting (hence the upright jar storage of purchased asparagus). Before discarding the tough bases of asparagus spears, use a vegetable peeler to remove the skin on the lower section of the stem. Chances are good that the inside of the stem will be tender and delicious.
5. I am moving to a new garden. Can I dig and move my asparagus, or should I start over with new plants?
Asparagus plants can be dug and moved in spring or autumn, but it is a huge undertaking because the roots are so extensive. Another concern is that an established asparagus planting could host common soil-borne diseases, while dormant crowns or seedlings carry a much lower risk. Why not start your new bed with a clean slate? A productive asparagus bed is also a nice personal legacy to leave behind.
6. Should I clean up old asparagus stems in autumn, winter or spring?
If your asparagus is troubled by asparagus beetles, you can interrupt their life cycle by cutting old foliage close to the surface and composting it in late autumn. However, in cold climates it is often best to leave the brown foliage on the bed until early spring to hold snow and insulate the crowns from the ravages of winter. Do clean up old asparagus stems in late winter, pull out any weeds, and mulch to protect the soil from erosion. If you have miscanthus or other large ornamental grasses, you can use the pruned tops as convenient spring mulch for asparagus.