Growing Our Garlic

The Site

The land is being converted from pasture previously used for sheep and beef farming. It appears to have been intensively grazed over the years, which has led to compaction. There are a number of perennial weeds present, such as yarrow, Californian thistle and couch. The total area to be used for garlic production is just under 1ha, however, not all of it will be used for growing crops as some is needed for tracks, the existing hay shed and storage of resources.

The Soil

Located on a silty river terrace, it is a sedimentary soil type. It is a loam with good texture, neither too open nor too heavy, so has the potential to provide the fertile, free-draining soil that garlic requires. An initial soil test in January 2020 found that it had a pH of 6.3 with 11.1% organic matter. Most nutrients tested for were considered to be in the medium range, with the notable exception being an Olsen Phosphorus level of 8mg/L (medium range of 25-50mg/L).

The Climate

There are many microclimates in the Taihape area and the closest official weather station is Waiouru which, at 823m above sea level, is often very different to Taihape, situated about 400m lower. The annual sunshine hours for Palmerston North (closest available) are around 1700 hours. The mean annual rainfall recorded in Waiouru is 1033mm but Moawhango is on the dry side of Taihape, so rainfall is less than what is officially recorded for Waiouru/Taihape. The driest months are usually January and February, just after garlic is harvested. Mean temperatures for January, recorded in Waiouru, range from a high of 19.7 degrees C down to a low of 7.9 degrees C, while those for July range from 8.4 degrees C to 0.5 degrees C. The main season for frosts is from April to October, but frosts can happen at any time of the year.

The garlic patch is fairly open and sunny, with no shading from the north. Being in a valley means that direct sunlight may be reduced at the start and end of each day, due to hills on the east and west sides. However, being in the valley also provides some protection from strong winds.

Site Preparation

The garlic is being grown with a 3 year crop rotation, so the site preparation is being staggered year by year. In spring, a subsoiler is used to break up compaction, followed by cultivation to break up the dense pasture on the surface. This area is then sown in a diverse mixed species cover crop to help rejuvenate the soil life. After the cover crop is terminated by mowing and a shallow power harrow, occultation is used to suppress regrowth of the pasture and any weeds. By late summer, the tarps are lifted so the beds can be hand weeded in preparation for planting. Hand weeding is necessary to remove persistent perennial weeds like couch. Paths between garlic beds are covered with woolly dags, a waste product from the farm, with weedmat on the top. This is effective for helping to control the couch. Wider vehicle tracks are left in grass and mown.

The following amendments are added to beds prior to planting garlic:

Reactive Phosphate Rock (RPR) to address the low phosphorus levels.
Dolomite Lime to add calcium and magnesium, as soil analysis showed magnesium to be on the low side (0.98 me/100g).
Aged sheep manure (available from the farm), to boost nitrogen and feed soil life.
Agrisea Soil + slow release seaweed granules, as a biostimulant.
Humates, as a biostimulant and soil conditioner. Straw, bought from a local farmer, is used as a mulch to protect the soil surface immediately after planting.

Beds with significant amounts of couch are prepared for planting by hand using a garden fork to ensure thorough removal of couch. Beds with few perennial weeds can be prepared with the two-wheel tractor using the power harrow attachment to loosen the top of the soil. Beds may also be broadforked for better aeration if needed.

Planting

Garlic cloves are selected from whole bulbs within a few days of planting and planted by hand, using a Japanese hoe if needed. The garlic is planted into 1.5m wide beds, with 6 rows per bed. Rows are spaced 24cm apart, with 15cm on each edge. 3 rows are planted from each side of the bed, with a 63cm reach required to plant the inner-most row. This can be done without having to walk on the beds. The cloves are spaced at 15cm apart within the row. This spacing is used as the standard as it is wide enough to allow the bulbs to develop to their maximum size. Sometimes a closer spacing may be used for very small cloves or bulbils that are not likely to grow as large. String lines are used to ensure rows are straight and a measuring stick ensures spacing is even. Garlic cloves are planted with the root end down and growing tip up, to a depth that covers the top of the clove with a few centimetres of soil. Here is a video to show how we plant.

The timing of planting varies with the different varieties. Planting season starts in April with the Turban and Asiatic varieties. These are followed in May with Artichoke types. Then in June to July, the late season varieties, such as the Creole, Marbled Purple Stripe and Silverskin groups. A spring planting in August to September is also possible with the Creoles, e.g. 'Ajo Rojo', and Silverskins, e.g. 'Printanor' or 'Kakanui'.

Cultivar Selection

From our observations in previous seasons, it appears that garlics in the Turban group are the best suited for avoiding garlic rust in the Moawhango Valley location, primarily due to the earliness of their harvest time. Garlic rust has been observed in the crop every season, starting in mid to late December. As the Turbans are harvested in early December, they are out of the ground and curing before the rust gets the chance to take hold. Mid season varieties, such as the Artichokes, get a medium amount of rust on foliage before they’re ready to harvest and the late season varieties, such as the Silverskins, are the most affected by the time they are harvested in mid January.

The Turban types also seem superior with respect to a problem known as secondary sprouting, or 'witches brooming'. This occurs when the cloves divide twice within one growing season, and is thought to often be due to unusual temperature fluctuations which mix up the garlic’s normal vernalisation processes. In the 2021 growing season, the worst affected variety was the 'Ajo Rojo', a Creole, followed by the 'Takahue', an Artichoke, and to a lesser degree in the Silverskins. The Turbans, however, appeared to be completely unaffected by the unusually warm temperatures that were experienced in August 2021.