Asparagus is a vegetable that belongs to the allium family, which also comprises leeks, onions, chives and shallots. It is native to the Mediterranean and Asia Minor areas, but has since been cultivated in most countries around the world. Contrary to many people’s conception, asparagus is a hardy plant and adaptable to most climate conditions, and indeed, as a perennial that overwinters in the ground, they thrive in places that have winter ground freezes. Asparagus is also a very healthy vegetable, providing good levels of a wide range of nutrients. These include potassium, B vitamins and calcium. And with no fat and virtually no calories, asparagus delivers all these positive benefits without any downside.
Choose a position where your asparagus can stay permanently. They are a perennial plant and, given the right conditions and maintenance, can provide you with crops for years, even decades. Indeed, you won’t be harvesting them until at least the third year after planting, as the root system takes some time to grow strong enough to withstand harvest. Ideally you want to give the asparagus a position in full sunlight. They will tolerate partial shade, but full sunlight produces the most vigorous growth and the healthiest plant. The location also needs to drain well, as standing water will rot the roots.
Asparagus plants like a soil that is well drained and rich in organic matter. They develop very deep roots, so you want to try and make sure the soil is loosely structured for quite a way down the soil profile, enabling the roots to grow well and for moisture to percolate and aeration to occur. The best way to prepare the soil for asparagus plants is to dig a trench of around 75 centimeters and then add lots of organic material to it. This can include compost, manure, worm castings, leaf litter and so on. You can then layer soil over the top. The lower layer of organic matter will draw down the roots of the asparagus plants, making them stringer and more resilient. It will also help keep the pH of the soil balanced. Asparagus prefer a soil of between 6.5 and 7 in pH, so if your soil is acidic consider adding some organic lime along with the organic material.
Asparagus is typically planted either as seeds or seedlings. In either case, ensure you have organic specimens. Plant approximately 40 centimeters apart. This may seem like a lot but it is to prevent the extensive root systems from competing with each other for nutrients. Water the newly planted specimens well, ideally with harvested rainwater. You can also plant asparagus as ‘crowns’. These are nodules with roots already growing and are typically about a year old. Plant in trenches around six inches deep and well composted. Place each crown on a small mound and spread the roots out in different directions to ensure robust growth. Planting crowns will mean you should be able to harvest in the second year after planting rather than the third. However, make sure you source crowns from an organic supplier, and do not use any that are more than a year old, as the shock of transplantation is more severe with older crowns. In all cases, mulch around the plants to help preserve moisture and protect the plants during the winter.
A common companion plant for asparagus is tomato. The tomato repels the asparagus beetle that feeds on the roots, while the asparagus is thought to repel certain nematodes in the soil, which may damage the tomatoes. You should avoid planting asparagus in close proximity to other alliums as, given the similar genetic profile, they will be competing for the same nutrients and inhibit one another’s growth.
Water regularly, as the soil should be well drained. The asparagus plants need more water in their first two years of growth to establish themselves. You may want to consider installing a drip irrigation system.
Compost around the plants each spring to help support growth. The extensive roots of the asparagus plants typically out-compete weeds for nutrients, so they shouldn’t be a problem after the first year or two. After the first frost in winter, or when the foliage of the plants turns yellow or brown, cut the asparagus back to ground level. This will help stimulate growth in the spring. When you cut back the foliage try to avoid letting the berries fall to the ground as they can germinate and your garden bed will have too many plants to be support.
In the third year after planting, you can harvest the spears over a four-week period, while by the fourth the harvesting period can be extended to 8 weeks. Looks for spears with tightly formed tips and thin, strong stalks. As the weather warms up over the harvesting season, more and more spears will appear and you can harvest every other day or so, depending on the number of plants you have. Snap the spears off at ground level.
Like most vegetables, asparagus are best used as soon after harvest as possible. This is when they are at their fresher and so replete with the maximum amount of nutrients and flavor. However, uncooked asparagus spears will keep for up to three days in the refrigerator and still be tasty. However, the spears should really be kept damp, so either wrap in a damp tea towel or, alternatively, place the base of the stems in a jar with about an inch of water in the bottom then cover the tops loosely with a plastic bag. Asparagus can be used raw in salads, but that method means the stalks remain somewhat fibrous and only the tips are generally used. To use all of the spears they should be quickly boiled or steamed, for two or three minutes at most. This softens the stem to make it more appealing but also retains most of the nutrients. The key is to retain the bright green color of the stems – if they start to leach color they are leaching nutrients and flavor. A good tip is that once you have finished boiling or steaming, plunge the spears into ice water to preserve the color and flavor.