Garlic harvesting time

Hard neck garlic harvest in Nova Scotia typically happens the first week of August, although with how hot this summer has been (Table 1), some varieties are a bit ahead of schedule.

Table 1. Degree day accumulations as of July 26, 2021.  All data are taken from the Kentville weather station, based on a start date of March 1, and calculated using the single sine method.

 

Fig. 1. This garlic from mid-July, isn't quite ready to
harvest. Note how the wrapper leaves aren't yet snug
around the cloves.

I have blogged about garlic harvest timing in the past, and if you haven't come across it before, I strongly recommend giving it a read!  The number of green leaves left is a good tell, but if your garlic is super healthy, or super sick, it might not be the best barometer (Fig. 1).  You can find the blog post by typing "garlic" into the search bar on the right of the NS Vegetable Blog, or for direct access, click here.  

By mid-August my car usually smells of garlic from all the samples of unhappy garlic I've collected from growers.  This is often the result of poor post-harvest management.  August in Nova Scotia, when growers are trying to cure their garlic, is often a muggy month, providing poor drying conditions. 

Fig. 2. Relative humidity and temperature.

You NEED good air circulation and ideally low relative humidity (less than 70%) in your curing space otherwise you run the risk of disease running rampant.  If your garlic is taking more than three weeks to cure, it is likely your relative humidity is too high.  There are cheap sensors available from Canadian Tire or Amazon to measure relative humidity and temperature.  If you are serious about growing garlic, I strongly recommend you get one.  Some of the nicer sensors even upload it to a web portal (Fig. 2) so you can check on it from the comfort of the couch. Move the sensor around your drying space to see if you can find any "dead" space with low air movement and higher relative humidity.  Those are the areas where disease is most likely to rear its ugly head.  It is best to try and move some fans to around to get rid of this dead space.

Fig. 3. Unhappy garlic - Penicillium (blue) and
Rhizopus stolonifer (white and black fungus). 

Did you know you could submit samples to 
Perennia's Plant Health Lab?  This service
is often free for registered farms.  Reach out to
me, Rosalie Gillis-Madden, if you have a vegetable
sample you want to submit to the Plant Health Lab.

It shouldn't need to be said that diseased garlic should not be used for seed.  Advanced growers with smaller plantings sometimes earmark particularly healthy plants in the field before harvest as candidates for seed stock.    To read more about garlic storage, post-harvest diseases, and planting stock considerations, check out Perennia's factsheet.

Fig. 4. Garlic storage, post-harvest
diseases, and planting stock considerations
fact sheet.

Garlic harvest!

Wrapper leaves snug around cloves.

Garlic harvest is upon us, and if you haven't already started harvesting your garlic, now would be the time to start planning it.  Different varieties will mature at different times, so it's always good to check on bulb development of few bulbs of each variety.  One way to determine harvest-readiness is by looking at the number of green leaves.  Each leaf corresponds to a wrapper leaf around the bulbs.  Wrapper leaves protect the cloves from light, moisture, heat, etc.  For best storability, it is suggested to harvest with five to six green leaves.  That way, if a wrapper leaf or three is lost in harvesting and cleaning, there will still be two to three wrapper leaves around the bulb to protect it from storage rots, desiccation, etc.

Stem and bulb nematode damage

Green leaves should be used as a guideline, but not a rule.  Sometimes on a particularly healthy plant, the leaves can remain green despite harvest-readiness.  Alternatively, if there is heavy thrip damage, high stem and bulb nematode populations, etc. the leaves can brown prematurely.  It is always best to pull a few bulbs and check to see how the cloves are filling the wrapper leaves.  Give the bulb a squeeze, and if there is any give, then the garlic isn't quite ready yet.  You should also cut the bulbs in half perpendicularly to the stem.  Each clove should be tight in the wrapper leaves.  If the wrapper leaves seem a little loose around the cloves, then wait a little longer to harvest.  The cloves in harvest-ready garlic will also start to pull slightly away from the stem, especially in hardneck varieties. 

Cloves starting to pull away from stem.

Hardneck varieties (Allium sativum var. ophioscorodon) produce scapes.  Hardneck types, as a general rule of thumb, produce larger cloves, but have a shorter storage life, which can be greatly influenced by harvest timing.  If you leave harvest for too long, the wrapper leaves will start to decay, and the cloves will continue to grow and pull away from the stem and the bulb will split open, rendering the bulb unmarketable.  Softneck varieties (A. sativum var. sativum) do not produce a scape, and typically have a longer storage life.

Garlic harvested too early might not have fully developed its yield potential or flavour profile, and will tend to shrivel when cured.  Late-harvested garlic is more likely to have poor storability, particularly the hardneck varieties, as the wrapper leaves start to deteriorate, exposing cloves.  It is often better to harvest a little early than a little late.

Target harvest for early in the morning on a dry day for best results.  Do not leave garlic in the sun for long as it can scald, and the cloves will quickly deteriorate.  Handle garlic gently as it is sensitive to bruising.  The higher the moisture or relative humidity when you are drying your garlic, the slower the garlic will dry down and cure, resulting in high disease potential.

Post-harvest handling can dramatically affect garlic quality and storability.  Recent research from Cornell University suggests that root trimming does not have any impact on bulb quality, weight, or disease incidence.  Washing garlic post-harvest, while resulting in good looking bulbs initially, ultimately resulted in more discolouration after drying and curing.  For more details about post-harvest handling of garlic, check out Cornell's Garlic Post-Harvest Study.

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Garlic harvest and postharvest

Garlic growers are harvesting their crop these days.  In general garlic may be harvested when the leaf tops begin to discolor and dry.  If the bulbs are immature when harvested they will tend to shrivel when cured.  If harvested too late, the bulbs may be discolored and the outer papery covering will break down exposing the individual cloves.  Garlic is ready for harvest when the cloves are fully segmented but the bulb is still tightly encased by an intact outer skin.

Given wet weather and increased humidity, curing and postharvest storage are critical in the production of quality garlic.  Garlic must be cured for several weeks prior to storage.  Under very humid conditions, the bulbs can also be cured on racks in forced air dryers at low temperature and low humidity.  The bulbs must be thoroughly dried before placing in long term storage.  Mold growth can be a problem if garlic is not cured properly before storage.
 

 

When properly cured, garlic keeps well under a wide range of temperatures.  Store cured garlic in open-mesh sacks in a dry, well-ventilated storage room.