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GARLIC GROWING GUIDE
The ten stages of growing garlic
Before planting it is necessary to select your site, prepare the soil, consider pre-cooling bulbs (more on this below) and cracking your cloves from the bulb.
Soil preparation is probably the single most important aspect of growing great garlic. It is often overlooked. An important point is that there is a big difference between dirt and soil. 'Dirt' is potential soil, while 'soil' is rich in nutrients, alive with biological diversity and deep in organic matter.
Garlic likes plenty of sunshine, so find a site that receives plenty of full sunlight. We have run several trials over the years and have found that shady parts of our beds reduce bulb size by 20-30%. It is important that over the winter months and early spring that the young plants get plenty of morning light. This will help the plant dry out quickly which reduces the chances of getting leaf diseases. Garlic does not like strong wind, so plant in a sheltered area.
Ideally, soil preparation should begin 1-2 years before planting. If you can't wait to build soil consider adding a good quality compost to your garden beds. The bed should not have had Allium species (garlic, shallots, chives, leek, onions, spring onions or chives) growing in it for the past couple of years. We operate on a three-year rotation - growing only once every three years in the same soil. This will reduce the risk of soil disease and nutrient depletion.
Root, leaf and fruit plants require different nutrients and create different soil biological diversity. If you are replanting your bed following the growing of a garlic crop it is best to next grow a leaf crop (eg. spinach, lettuce, broccolli), followed by a fruit crop the year later (eg. tomatoes, beans, peas) before replanting garlic. While it might be impractical, ideally Allium species should not be grown in the same bed for three years.
Keep in mind that good garden soil has a ratio of 25% air, 25% soil solution (water and nutrients) and 50% soil particles (a mix of clay/sand/silt). Add too much water or have too much of one type of soil particle and your garden produce will be less productive.
Garlic is a long-period root crop. Unlike many seasonal crops taking three months to grow, garlic is in the soil for 7-9 months. So the soil must be healthy and in an optimal state before planting and during the seasons for leaf development and bulbing stages. If you have brought in new planting stock consider placing it in quarantine bed for a year or two to isolate from other garlic where bulbs have potential to import disease or pests.
Soil should be deep (ideally >40cm) for roots to penetrate well into the ground. Soil should also be friable looking crumbly, not caked nor a fine powder. It takes years to build and maintain your soils with rich compost, however, this can be quickly remedied using purchased good quality organic compost. Try to avoid using plastic bagged compost or manures as some growers find they get poor germination results.
Being a root crop, having optimal soil conditions sets the bulb up to be healthier and stronger from the outset. Before planting it is best to loosen the soil to break up clumps and reduce compaction with a fork and aerate the soil. This will help with water, oxygen and nutrients penetrating deep into the pores of the soils.
It is important not to over turn your soil as this will mix up the natural layers (horizons) of the soil profile and ultimately upset the delicate soil biota. The 'L' or the living layer is the top horizon of soil and the most biologically active with worms, slugs and snails. It sits on the 'O' or organic layer which is mostly decomposed organic matter. The 'A' layer or active soil which contains decomposed matter and mineral particles is below this.
Care needs to be taken of healthy garden soil. Healthy soil is teeming with biological life which is hard at work breaking down larger organic matter, fixing and cycling nitrogen, and even working directly with the garlic roots.
The soil biota consists of megafauna (worms, slugs, snails >2mm in size), mesofauna (0.1-2mm such as mites), microfauna (<0.1mm such as nematodes, roundworms and protozoa such as flagellates that live in fine water pores), and microorganisms which make up the most abundant and diverse of the soil communities such as bacteria, yeast, fungi, and algae. Take care of the soil and the garden will provide for you.
Garlic prefers free-draining soils, not too wet but moist. Raised beds only 30cm high can make a massive difference in the success of your crop particularly if you have a wet season. Soil borne fungal, bacterial and viral diseases can cripple your plants if they are in a water-logged soil.
If you live in a wet area and if your garlic is not in raised beds then consider raising the garlic beds slightly higher than the surrounding soil. At Gourmet Garlic we mound our soil up by 10cm and between beds have a free draining mulch layers as pathways. If you are in an extremely wet area consider raising each row by 30cm above surround soils.
If you have clay soils which retain water then dry and become solid in spring then extra effort is needed to break up the clay and mix it with organic matter. As for sandy soil which holds little moisture and nutrients, it's worth also undertaking a soil building programme of organic matter with composting.
While garlic can survive in nutrient deficient soils, for healthy and large bulbs, garlic needs a nutrient rich soil with a relatively neutral pH (around 6.5 -7.0pH). You can buy a cheap pH and soil moisture tester from most hardware stores or garden centres. Add elemental sulphur (it will not readily leach) if the soil is too alkaline or lime if the soils is too acidic.
It is important to have ideal soil nutrient conditions in the soil before planting as garlic is a heavy feeder. Garlic grows roots almost immediately after planting and is in the soil longer than any other vegetable. Initially, garlic needs nitrogen-rich soil so consider sources of nitrogen to mix into your soil in preparing the bed.
Some growers use a cover crop of nitrogen fixers, while home gardeners might add their own compost of grass clipping, seaweed, worm juice, aged manures or other available organic fertiliser. There are a few organic fertilisers available in hardware stores and garden centres too to assist with increasing your soil's essential nutrients. These semi-commercial garlic growers use no artificial nitrogen inputs with great results. They prefer natural additives like guano, bonemeal, and sheep pellets.
Aged manures can be good to add to soils before planting, providing not too much is applied. Ensure that the manure is not too nitrogen rich. Nitrogen-rich chicken manure for example might need a stand down time or be mixed into the soil well before planting (at least two months) to ensure the garlic roots are not burned on contact. Note that many manures will contain seeds and will introduce unwanted weeds.
We use organic fertilisers to cure imbalances. Generally, soil organic matter and micro-organisms are far better at curing imbalances although taking time to break down and release their blend of nutrients via natural processes. Consider applying blood and bone, matured animal manure, potash, gypsum and other organic material.
Nitrogen is important for leaf growth which is needed early on in growth, while phosphorous is important for root development in the later stages of garlic maturity to get good bulb sizes.
Garlic needs cool winter temperatures of 5-10°C for 1-2 months for the bulb's development. In most parts of the country this is a normal winter temperature.
In the warmer northern climates of NZ with their milder winters natural vernalisation might not be achieved. In this case growers may choose to artificially vernalise their bulbs before planting by placing them in the warmest part of the refrigerator for 2-3 weeks before planting.
Most garlic cloves are ready to plant in autumn. You might discover some of your cloves in the bulb are beginning to sprout. Normally, if you can see exterior shooting, then the plant is past the ideal planting time. Ideally the yellow-green sprout inside the clove should be about halfway up internally within the clove. If you are unsure you can cut a clove lengthways and see its development and then add it to a meal.
Before planting cloves it is necessary to separate them from the bulb. Cracking bulbs should be undertaken on the day of or the day before planting as cloves can dry out once bulb wrappers have been removed, which might help diseases, encourage the swelling of roots and begin sprout growth. So crack on the day!
Only the bulb wrapper (skin) needs to be removed, not the clove skin. It is important to separate all cloves from the bulb. The divisions in the basal plate can sometimes be very difficult to detect. We find the softneck silverskins and artichoke types the most challenging to crack. What appears to be single cloves can be several closely joined. You can often see a fine crack in the basal plate of the clove which is the dividing line between cloves.
The small and often misshapen cloves in softnecks will grow regular shape bulbs but they will be smaller. Save the tiny ones for eating. In cracking, look for the large bulbs with large cloves which will put the most energy into the early stage of growth. Growers have found that large cloves from large bulbs provide the most success at harvest with good, healthy-sized bulbs.
Cloves should be firm. Ensure that you check each clove for any disease such as mould, rotting or other imperfections. If there is any doubt, throw them out (the entire bulb not just the individual infected clove as the disease can be spread). Sometimes, particularly for the cracking hardneck bulbs, the clove skin may tear. These can still be planted providing there is no bruising or they have not been cut by fingernails. Take care not to damage cloves that have been cracked/popped before planting.
There is an art in cracking. Do not crack bulbs from the base as this can damage root buds in the basal plate making the clove less vigorous. One of the best ways to crack involves three steps:
1) Run your thumbnail around the false stem above the clove tips to break the bulb wrapper
2) Grab the false stem and twist it vigorously
3) Apply pressure down and out to break and remove the bulb wrapper
Ensure cloves are put in a breathable container or bag with good air circulation until it is time to plant. It is important to avoid them sweating, heating up and getting mould. Store for planting away from heat, out of direct sunlight and at room temperature.
Some growers sterilize their cloves before planting. This is because the clove may have come in contact with a leaf disease from bulb skins or have had mites infecting the clove. This will result in the best start for strong growth for the garlic clove in the germination stage. While at Gourmet Garlic we do not pre-treat cloves, we would do if we were having problems with diseased plants.
Growers may choose to sterilise the clove to reduce fungal problems. There are a few options. If the clove has not shooting then some growers soak cloves for 2-3 minutes in a hospital grade chorine bleach (Sodium hypochlorite) before rinsing in water. If cloves are shooting then add 1 part bleach to 3 parts water and use the same technique.
Alternatively some growers use a teaspoon of bicarbonate of soda or potassium carbonate per litre of water to dip cloves in before planting. Some users also use neem oil. These are considered less effective than the bleach treatment. Some growers use a 5% alcohol (vodka) and water mix to sterilise cloves from infection and pests before planting.
In addition some garlic growers elect to give the cloves an added benefit by soaking them in a seaweed solution (1 teaspoon of solution per litre of water) for less than 12 hours to enhance root growth.
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