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GARLIC GROWING GUIDE
The ten stages of growing garlic
Garlic is generally a low maintenance crop. It does not need a lot of effort, but it be can be affected by pests and disease than many other vegetables. Thus, garlic does need some attention while growing and these are some key aspects to consider.
In addition to preparing the soil before planting it is good to have a fertiliser regime while the plants are growing which consists of at least two phases. Nitrogen is important for leaf growth and is needed early on in leaf growth. Phosphorous is important for root development in the later phase of the plants' life.
The first stage is for leaf growth where nitrogen is important. In mild winter climates garlic will grow up to 12+ leaves, while in colder climates less than 12 leaves are produced. Regular monthly fertiliser applications up until the maximum leaf number is obtained will support good leaf health. We apply a general organic fertiliser or blood and bone during this time.
It is important to keep a regular fertiliser regime (monthly) during except over winter if the day temperatures are below 12°C. In winter rainfall leaches out the nutrients, while in spring the soils are beginning to warm - cold soils do not aid in nutrient uptake. So it is best to maintain a good regular balance of fertiliser just after planting and when the soils warm up in spring.
The second stage is bulbing which occurs once the plant nearly reaches the maximum number of leaves before maturing. This is called the transition stage for the plant. At this point, potassium is important for root development as the plant is putting its energy into bulb growth. We apply a general organic potash during this time.
Once garlic cloves are in the ground it is worth considering whether to use mulch on top of the soil, particularly to suppress weeds. While we at Gourmet Garlic do not top cover (we use mulch on farrow beds though) others use mulch in different locations around the country. Often mild to cool winter areas, particularly near the coastal areas need not apply mulch unless the garlic is affected by salt spray or other local conditions. It is best not to apply mulch in wet climate areas.
Mulch moderates the soil temperature, and reduces the effect of extremes like snow. In saying that garlic originates in cold extremes and our young garlic shoots in the deep south have no problem surviving with a foot of snow covering them in winter. Few places in the country experience permafrost for weeks on end, unlike some in Siberia, Canada and other northern hemisphere higher latitudes.
Mulch retains moisture, suppresses weeds and adds nutrients to the soil. It also has its disadvantages in that it can also keep the soil temperature damp and cool during spring, slowing growth and it can foster disease, moulds, pests. It is better to apply mulch after winter for adding nitrogen and reducing weeds. In spring it can suppress the weeds and conditions are warmer reducing the chances of mulch being a cold waterlogged mat. Choose the mulch that holds the least amount of water, overseas sugar cane mulch fits this criteria.
There is a bit of an art to using mulch. Mulch should not be too heavy or dense, it should be light and fluffy for shoots to pop through - generally 2-10cm of depth is a good guide. There are a variety of mulch options such as hay, straw, grass clippings and a mix of chopped up leaves. Choose a mulch source with few weed seeds.
We do not recommend using black plastic weedmat. The soil can rise above 50 degrees a few centremetres down into the soil stressing the roots and culturing disease. It is better to use this material it for the side linings of beds.
If you live in a windy area and are using light mulch such as hay or dried leaves, consider wetting it to reduce its movement around the garden. Mulch is normally removed in spring and if it gets waterlogged it may prevent garlic shoots from rising to the surface. Some growers apply mulch once the shoots are several centimetres high.
Garlic should never be allowed to dry out, but should never be saturated ... it should be moist not wet. Roots are shallow (although can descend 60cm) but can still need deep watering. Watering is relatively intuitive often a finger test of dampness is all that is needed. If in doubt purchase a cheap moisture plunger or dig down beside the plant to spade depth and test soil conditions. If the leaf edge is beginning to yellow this is one possible first sign that the plant is deficient in moisture.
The most ideal time to water is morning during sunny and warm conditions allowing the plant to dry out and reducing the risk of disease. It is not best practice to water (via a overhead method) in the evening or night as this will result in prolonged leaf wetness which can encourage disease and rust spores.
Some places in winter and early spring, like here in the deep south need no or very little additional water in winter or early spring. Of course, those with sandy soils, warmer winters or dry and windy places will need a watering regime to achieve ideal soil moisture conditions even in winter. In these places (particularly without mulch) it might be necessary to water every day or every second day.
Consider using a drip system. Sprinklers can wet leaves which encourages garlic rust and other diseases to take hold.
It is also important to know when to stop watering. Yes, for garlic the 2-4 weeks before harvesting it is necessary to stop. At this point bulbs are drying out and are vulnerable to excess moisture. Rainfall or continued watering up to harvest time can cause storage rot plus the bulb wrapper can split and be stained. Note that once bulbing begins (8-10 weeks before harvest), the plants immune system becomes inactive and they are more prone to basal or root rot diseases.
Even with using mulch, persistent weeds can still break through the soil seeking any available light.
Wild garlic evolved in the cold mountains of Central Asia. They had little competition in their arid homeland and as a result grew only a few slender leaves which are unable to be replaced. As a result, garlic does not tolerate completion from weeds.
It is necessary to keep on top of weeds as soon as they rise out of the soil. Weeds not only shade the garlic leaves but also drain nutrients from the soil and can cause premature bulbing.
It is good practice to regularly weed and give garlic the best chance to grow large heathy bulbs.
The scape is a flower stem and is mostly associated with hardneck garlic types. Before harvesting, hardneck garlic typically sends up a scape which normally curls then straightens before the garlic is harvested (softneck garlic can scape when stressed). Semi-bolting hardneck types (creole, turban, asiatic) in milder-winter areas do not necessarily produce a scape.
The garlic plant puts energy into forming the scape so many growers remove them to direct the plants resources into developing the bulb. We have found there is a direct correlation of bulb size and scape removal of around 10-30%. We remove the scape before they begin to curl, before they are longer than 20cm tall.
If removing the scape, do so on a dry day so the break can heal cleanly without introducing infection and disease. When you see the firm stalk rise up from the middle of the leaves snap (not pull) it off the stalk by hand (if the scape is small) or with secateurs below the umbel before it widens. If the scape is pulled, it may result in the pseudostem becoming weak and will let water down into the bulb. More information is available on our garlic scape page.
While garlic is a pretty hardy plant, it can be affected by range of pest species (nearly 100) and the first warning signs once planted are irregular 'roguing' growth. A garlic grower should be regularly inspecting the garlic growth to find the first signs of irregular growth early.
Garlic is one of the most susceptible annuals to disease for three main reasons. Firstly the cloves and bulbils are clones of the plant so unlike seed it can carry forward and accumulates disease to future generations. Secondly bulbs grow in the damp soil and for a long time where they are exposed and vulnerable to a whole range of soil borne diseases. Thirdly there are few infield treatments to cure many garlic diseases. For bacterial and viral issues there is almost no treatment options, while fungal issues only has limited options. The best method is crop rotation, raising the soil, planting good stock and removing rogue shoots early.
The first sign is the plant having smaller, yellowing or shriveled leaves compared to others in the bed. It is worth inspecting plants regularly to catch these rogue sick plants as they will never grow into healthy ones. Also, be careful to remove them including the surrounding soil before disposing. To leave sick plants in the soil increases the disease and affects soil health and nearby garlic.
Most fungal issues can be reduced by practicing crop rotation (recommended 3+ years), choosing good planting stock, having good watering practices and planting a variety of garlic groups known as polyculture. Once shooting begins look out for the warning signs of disease or other non-uniform growth.
While it is handy to have early season garlic like turbans and asiatics, the mid to late harvesting garlics are generally are less prone to seasonal pest and diseases as the season warms up.
Garlic produces roots first, before sending out shoots. In mild-winter climates where cloves are planted shallower, shoots are likely to appear 1-2 weeks after planting. In such climates where the daytime temperature is above 12°C then leaf growth will continue through winter. In colder climates it can take up to six weeks for leaves to appear.
In colder climates only 3-6 leaves will initially grow before the plant goes into dormancy. Once spring arrives and temperatures exceed 14°C, then leaf growth resumes. Note that standard purple stripe and sometimes the porcelain garlic group has an 'alien' early growth form where they lie flat with the ground. Porcelain is also known to be the most susceptible to having viruses.
The three main categories of garlic problems, having diseases, unusual growth or affected by pests. Our page on common garlic problems discusses the main garlic diseases encountered by growers in NZ, the irregular growth that an occur and common pests.
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