Asparagus officinalis

An upright, deciduous, suckering herb up to 2m tall with a rhizome growing to 1.5 m by 0.8m.

Attractive herbaceous perennial growing to around 2m tall, with airy feathery foliage (not the true leaves). True leaves are reduced to scales on the stem or spines at branching points. Green stems (up to 25 mm long) act as leaves and are produced in clusters.
Creamy-white male and female flowers are borne on separate plants and reasonably insignificant. After flowering, red berries follow. These berries are approximately 7-9 mm in diameter and contain up to six black seeds.

Good drainage, full sun to light shade, and plenty of mulch are required. Prefers well-drained soil and can grow in very acidic, alkaline and saline (salty) soils. It can tolerate maritime exposure. Avoid planting in frost pockets as spears are tender.

Healthy soil is essential for producing vitamin and mineral-rich vegetables. The use of ample organic material is fundamental to the success of most vegetable gardens, especially those newly created on sandy or clay soils.

Organic material provides food for plants (especially nitrogen and phosphorus). Sandy soils are also improved because the humus holds more water and clay soils are made more easily workable. Organic material for vegetable gardens is usually comprised of farm manure mixed with straw or compost. This can be mixed into the soil, but a no-dig philosophy is preferable, allowing the organic material to breakdown and incorporate into the soil with time.

A green manure crop is another useful way of both improving the soil structure and providing nutrients. Plants, such as mustard, peas and buckwheat, are grown thickly then when mature are dug in to the soil, providing nitrogen and other nutrients as they rot. The addition of a general purpose fertiliser will encourage plant growth and should be applied at the specified rate prior to planting. Two of the more popular organic fertilizers are blood and bone and sheep pellets. Lime should also be applied to the soil every few seasons to improve the soil structure, as well as create a balance of nutrients.

When soil preparation is complete the vegetable garden should be weed-free and of a stable, aerated nature.

Asparagus is a perennial plant and can live for up to twenty years; it benefits from good soil preparation before planting. Removal of all weeds is essential, as this will be extremely difficult once the crop has been planted. Asparagus can be planted as young plants (known as crowns) or grown from seed. Growing from seed is cheaper but more labour-intensive and can take an additional year before the first harvest is produced.

Crowns should be planted in April in a trench 30 - 45cm wide and 35cm deep, with well-rotted organic matter placed in the bottom 15cm of the trench. Some excavated soil should be used to make a 10 cm high ridge along the bottom of the trench and crowns should be placed at 35-45 cm intervals along the trench with the roots spread out as evenly as possible around the centre of the crown. Crowns should then be covered with 10cm of soil which should be gently pressed down and watered.

Tall above-ground stems can be supported to prevent them rocking in the wind and damaging the crowns.
Control weeds by mulching with organic materials, such as straw stable manure or untreated sawdust. Alternatively, using a Dutch or push hoe will discourage weeds from establishing. Careful plant spacing will also help to suppress weeds. The growing season for many spring and summer vegetables can be extended by planting in a glasshouse or under a cloche.

Asparagus plants are winter dormant with edible spears (shoots) produced in spring from underground crowns. Harvest when the spears are 15 - 20cm long. After eight weeks, harvesting should cease and the remaining spears allowed to grow into tall, ferny foliage to sustain the plant. Foliage will die back naturally in autumn.

Good drainage, sun and plenty of mulch are required. Crop rotation can assist in maintaining the fertility of the soil and ensuring the soil remains in balance. This is achieved by rotating different categories of vegetables in a plot of land throughout a cycle of seasons.

Generally, vegetables can be divided into three groups for crop rotation:
1. Root/leaf crops such as carrots, potatoes, radishes, parsnips, beetroot, yams, silverbeet, spinach and lettuce.
2. Vine crops/brassicas including tomatoes, cucumbers, melons, pumpkins, cabbages, cauliflowers and kale.
3. Legumes/alliums including garlic, onions, peas, beans and shallots.

Proper crop rotation will ensure that at any one time one of these three varieties monopolises an area of ground. Root crops such as potatoes can break and loosen the deep soil while legumes will add nitrogen from the air to the soil. Different plants will add or take nutrients to or from the soil at different rates. In addition, crop rotation can help counteract pests and control disease.

Prune foliage in autumn when yellowed to 2.5cm above the soil.

It is important to consider that most of the plants grown in the vegetable garden are produced to be eaten, so it is preferable to avoid chemical sprays to control pests and diseases. Correct cultivation and strict weed control are the keys to ensuring garden pests are kept to a minimum. Companion planting is also a good option and involves placing certain plants beside each other to discourage disease and pests.

Companion plants often emit aromatic odours that discourage pest insects or attract beneficial insects such as bees. Mixtures of plants have proven to be more pest-resistant than large blocks of a single crop.

Edible Garden

Garden asparagus is a widely grown seasonal vegetable that has been cultivated for thousands of years. It is now an economically important crop. This and a few other species of the genus are still harvested from the wild in parts of the Mediterranean. It is depicted on Egyptian tombs dating from the 4th century BC and evidence suggests it was cultivated in ancient Rome.