Garlic (Allium sativum) is one of the 20 most important vegetables in the world, with an annual production of ≈25 million tonnes (World Atlas, 2017). Garlic is thought to have originated in an area from China to India to Egypt to the Ukraine (U.S. Department of Agriculture, 2019). China dominates the world garlic industry (Lipka, 2011), producing more than 80% of the world tonnage (World Atlas, 2017). Although the United States is the world’s largest importer of fresh garlic (Boriss, 2006), it is also a valuable crop for U.S. growers. Garlic sells for as much as $2 to $4 per pound in the United States, with a potential value between $1400 to $3200 per acre (Bachman and Hinman, 2008). Total value of U.S. commercial garlic production was $138.5 million in 2014 (Boriss, 2006). California produces ≈85% of the garlic grown in the United States (Walters, 2008); Nevada, Oregon, and Washington also grow significant acreage (Boriss, 2006; Ford et al., 2014; Walters, 2008), with New York ranked fifth in U.S. production with more than 300 acres (Cornell Cooperative Extension, 2019). Garlic has a higher nutritional value than other bulb crops (Naruka and Dhaka, 2001) and Americans consume an average of 2 lb of garlic per person each year, an amount that has steadily increased since the 1920s (Boriss, 2006).
Garlic is a perennial that belongs in the Amaryllidaceae family. All parts of garlic are edible except for the roots and the paper-like covering that encloses each clove (Encyclopedia Britannica, 2016). All garlic used for culinary purposes is from the species A. sativum, which has two subspecies, A. sativum ssp. ophioscorodon, known as hardneck (or bolting) garlic, and A. sativum ssp. sativum, known as softneck (or nonbolting) garlic (U.S. Department of Agriculture, 2019). Hardneck garlic is easily identified when it produces a long flower stalk, commonly referred to as a scape. The scapes are edible when cut from the plant while tender and no longer than 16 inches or more than one-quarter of an inch in diameter (Bachman and Hinman, 2008). In fact, scape removal improved bulb yield from 5% to 15% in a Minnesota study, depending on the amount of organic matter in the soil (Rosen and Tong, 2001). Hardneck garlic is more flavorful and the skin can be peeled from the cloves more easily (Frederick et al., 2014); therefore, it is favored by gourmet chefs. The mild hardneck scapes are also edible (Frederick et al., 2014). Softneck garlic is easier to grow and is the type of garlic usually found in grocery stores. Softneck garlic typically has a shelf life 6 to 8 months compared with a 2- to 4-month shelf life for hardneck garlic (Frederick et al., 2014). Hardneck cultivars have a single layer of six to eight cloves arranged around the flower stalk (Walters, 2008). Softneck cultivars have cloves arranged in three to six layers around each other, totaling ≈12 to 25 cloves per bulb. They are sometimes braided after harvest because they do not have the flower scape growing up the center (Walters, 2008). The outer layer tends to have larger cloves, whereas the inside layers of cloves become progressively smaller (Bachman and Hinman, 2008). Elephant garlic (Allium ampeloprasum ssp. ampeloprasum) is a type of leek (A. ampeloprasum). It is grown by several southwest Missouri producers and consumers using the same practices as those used for true garlic cultivars. Consumers also like elephant garlic because of its large cloves, which makes food preparation simpler. Elephant garlic has larger bulbs at maturity than true garlic; in fact, one clove can weigh as much as an entire bulb of true garlic (Boyhan et al., 2012).
Because plants are typically sterile, garlic is vegetatively propagated by dividing bulbs into individual cloves (Bandara et al., 2000; Meredith, 2014). The best planting densities in a study performed in Mexico were between two and four plants per square foot (Castellanos et al., 2004). Each clove should be planted with the basal plate down. Mechanical planting is sometimes used, but proper orientation of the cloves cannot be guaranteed. When planted upside down, growth tends to be uneven and slow; therefore, ultimately, yield and quality can be reduced (Castellanos et al., 2004). Because garlic is a high-value crop and uses large amounts of nutrients, growers should devote their best soils to growing it (Bachman and Hinman, 2008). Pennsylvania State University Extension specialists recommend applying the equivalent of 75 lb/acre of nitrogen at planting, 25 lb when the plants are 6 inches tall, and 25 lb at ≈1 May (Ford et al., 2014). The use of border rows is sometimes recommended because a significant “border effect” may exist at a field edge, thus causing plants to grow differently than other plants in the research project (Davis et al., 2017). Mulch is often recommended because garlic is a poor competitor with weeds. Garlic emerged sooner, started to grow faster, and had greater yields and bulb diameters when black plastic was used instead of bare soil/wheat (Triticum aestivum) straw mulch in Illinois (Walters, 2008). Instead of black plastic, other types of mulch such as straw can be used (Volk et al., 2004). Garlic harvest begins when the lower one-third of the leaves begin to brown and dry, and bulb size will double during the last stages of growth (Volk and Stern, 2009). Garlic bulb formation will stop when soil temperatures increase to more than 90 °F (Bachman and Hinman, 2008). The entire plant is pulled or dug from the ground. Bulbs are then typically air-dried before use (Bratsch et al., 2009).
Meredith (2014) stated that garlic is usually planted in the fall and harvested ≈9 months later unless the winters are exceptionally severe. Fall plantings provide garlic an opportunity to establish a root system, but not so much time that growth aboveground is exposed to winter cold. Plants go dormant during the colder months of winter and resume growth in the spring (Volk et al., 2004). Spring regrowth begins in mid-March in the upper midwestern United States (Walters, 2008). In southwest Missouri, fall-planted garlic tends to sprout before the ground freezes and often overwinters with the foliage aboveground. The formation of bulbs and cloves depended on daylength and soil temperature according to a project performed in Canada (Bandara et al., 2000). According to Kamenetsky et al. (2004), short days are required for both dormancy induction of axillary buds and clove formation. Most published research reported higher yield and quality when garlic was planted in the fall, although results varied on whether garlic grew better when planted in early fall vs. later in the fall. The most beneficial time to plant garlic in Oregon is from September through November according to Bubl (2015). Garlic planted in early- to mid-October in Virginia had higher yields than garlic planted later in the fall (Bratsch et al., 2009). In Egypt, one study indicated that a later fall planting resulted in higher yields (Foda, 1977), but another study concluded that yields were higher when garlic was planted early in the fall (El-Zohiri and Farag, 2014). A second study performed in Egypt found that garlic cultivars with different bulb skin colors (red or white) varied in yield based on planting date, although the garlic on the final planting dates had the lowest yields (Youssef and Tony, 2014). The findings of Youssef and Tony (2014) agreed with the results of research conducted in Virginia that indicated that garlic planted earlier in the fall had higher yields than garlic planted later in the season (Bratsch et al., 2009). Similar trends were seen in Bangladesh (Islam et al., 1998; Rahim et al., 2003). A study performed in Brazil found that cultivars differed in production based on fall planting dates but, in general, a larger percentage of bulbs emerged when planted on the earlier dates (de Resende et al., 2011). Yields were also higher in Brazil when garlic was planted in late February rather than on the traditional planting dates in mid-March to mid-April (Pinto et al., 2000). February is a late summer month in Brazil, whereas March and April are early fall months.
A few studies have examined yields when garlic was planted in the spring. Fall planting resulted in better yields than spring planting in Saskatchewan, Canada (Waterer and Schmitz, 1993). Spring-planted garlic can develop successfully if it is planted in March or April in Virginia (Relf, 2015). Spring-planted bulbs that received preplant chilling of ≈39 °F for 45 to 60 d were larger and had more cloves than bulbs that received no chilling or a longer chilling period in Canada (Bandara et al., 2000). Large vegetative plants that developed under cool temperatures and a short daylength had the highest yields, and early planting resulted in larger yields in Bangladesh (Raham and Talukda, 1986).
Average yield per acre of garlic varies by location in the United States. Lee Farms LLC (Truxton, MO) owner R. Lee (personal communication) reported he gets yields of 4000 to 5000 lb/acre in Missouri. C.L. Stewart (personal communication) of Cornell University reported yields of 8000 to 10,000 lb/acre in New York.
Despite studies involving planting dates for garlic in other areas, no such work has been reported for garlic in Missouri. Missouri growers traditionally plant garlic in the fall, from mid- to late-October. The project was initiated after a local grower claimed that garlic yields are larger if planted in early- to mid-September. The objectives of this study were to evaluate yields of two garlic cultivars and elephant garlic planted on four dates in the fall and in early spring at two locations in southwest Missouri in 2016–18.
BachmanJ.HinmanT.2008Garlic: Organic production. 14 Dec. 2019. <https://www.attra.ncat.org/attra-pub/summaries/summary.php?pub=29>
BorissH.2006Commodity profile: Garlic. 9 Feb. 2020. <https://aic.ucdavis.edu/wp-content/uploads/2019/01/agmr-profile-Garlic-2006B.pdf>
BoyhanG.E.KelleyW.T.GranberryD.M.2012Production and management of garlic elephant garlic and leek. Univ. Georgia Coop. Ext. Circ. 852. 9 Feb. 2020. <https://extension.uga.edu/publications/detail.html?number=C852&title=Production%20and%20Management%20of%20Garlic,%20Elephant%20Garlic%20and%20Leek>
BratschT.MorseR.ShenZ.BensonB.2009No-till organic culture of garlic utilizing different cover crop residues. 9 Feb. 2020. <https://www.pubs.ext.vt.edu/2906/2906-1389/2906-1389.html>
BublC.2015Get your garlic on: A primer on planting growing and harvesting. 9 Feb. 2020. <https://extension.oregonstate.edu/news/get-your-garlic-primer-planting-growing-harvesting>
CastellanosJ.Z.Vargas-TapiaP.OjodeaguaJ.L.2004Garlic productivity and profitability as affected by seed clove size, planting density and planting methodHortScience3912721277
Cornell Cooperative Extension2019Cornell vegetable program. 9 Feb. 2020. <https://cvp.cce.cornell.edu/crop.php?id=14>
DavisR.F.HarrisG.H.RobertsP.M.MacDonaldG.E.2017Designing research and demonstration tests for farmers’ fields. Univ. Georgia Ext. Bul. 1177. 9 Feb. 2020. <https://secure.caes.uga.edu/extension/publications/files/pdf/B%201177_4.PDF>
de ResendeJ.T.V.MoralesR.G.F.ResendeF.V.FariaM.V.de SouzaR.MarcheseA.2011Garlic vernalization and planting dates in GuarapuavaHortic. Bras.29193198
Encyclopedia Britannica2016Garlic. 9 Feb. 2020. <https://www.britannica.com/search?query=garlic>
FordT.G.BogashS.OrsolekM.KimeL.HarperJ.2014Agricultural alternatives garlic production. 9 Feb. 2020. <https://www.extension.psu.edu/garlic-production>
FrederickP.HlubikB.LeviantE.2014Growing garlic in the home garden. 9 Feb. 2020. <https://njaes.rutgers.edu/fs1233>
IslamM.N.RahimM.A.AnawarH.R.M.M.1998Effects of date of planting and different germplasms on the growth and seed bulb yield of garlicBangladesh J. Seed Sci. Technol.24554
KamenetskyR.BarzilayA.RabinowitchH.ShafirI.ZemahH.2004Environmental control of garlic growth and florogenesisJ. Amer. Soc. Hort. Sci.129144151
LipkaM.2011Do you know where your garlic comes from? 9 Feb. 2020. <https://www.bostonglobe.com/business/2011/12/18/you-know-where-your-garlic-comes-from/KxPYsrCkZ5VdJK5LzROmCO/story.html>
MeredithT.J.2014The complete book of garlic: A guide for gardeners growers and serious cooks. Timber Press Portland OR
NarukaI.S.DhakaR.S.2001Effect of row spacing and nitrogen fertilizer on growth, yield, and composition of bulb in garlic (Allium sativum L.) cultivarsJ. Spices Aromat. Crops10111117
PintoC.M.F.MaffiaL.A.CasaliV.W.D.BergerR.D.CardosoA.A.2000Production components and yield loss of garlic cultivars planted at different times in a field naturally infested with Sclerotium cepivorumIntl. J. Pest Mgt.466772
RahimM.A.ChowdhuryM.N.A.AnwarH.R.M.M.AlamM.S.2003Effect of planting dates on the growth and yield of garlic germplasmAsian J. Plant Sci. Info.22171174
RelfD.2015Onions garlic and shallots. Virginia Coop. Ext. Pub. 426-411. 9 Feb. 2020. <https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/426/426-411/426-411_pdf.pdf>
RosenC.J.TongC.B.S.2001Yield, dry matter partitioning, and storage quality of hardneck garlic as affected by soil amendments and scape removalHortScience3612351239
U.S. Climate Data2019aClimate Joplin—Missouri. 9 Feb. 2020. <https://www.usclimatedata.com/climate/joplin/missouri/united-states/usmo0457/2016/1>
U.S. Climate Data2019bClimate Springfield—Missouri. 9 Feb. 2020. <https://www.usclimatedata.com/climate/springfield/missouri/united-states/usmo0828/2016/1>
U.S. Department of Agriculture2019Taxon: Allium sativum L. 9 Feb. 2020. <https://npgsweb.ars-grin.gov/gringlobal/taxonomydetail.aspx?id=2368>
VolkG.M.SternD.2009Phenotypic characteristics of ten garlic cultivars grown at different North American locationsHortScience4412381247
World Atlas2017The top garlic producing countries in the world. 9 Feb. 2020. <https://www.worldatlas.com/articles/the-top-garlic-producing-countries-in-the-world.html>
YoussefN.S.TonyH.S.H.2014Influence of planting date on the performance of new garlic genotype grown under El-Nina governorate conditionsNat. Sci.12112119
El-ZohiriS.S.M.FaragA.A.2014Relation planting date, cultivars and growing degree-days on growth yield and quality of garlicMiddle East J. Agr. Res.311691183