Garlic Issue - Ask Extension
We have what is to us a rather perplexing issue and would appreciate any advice you could give us. We have been growing garlic for 45 years and never...
Knowledgebase
Garlic Issue #938302
Asked July 07, 2026, 10:14 AM EDT
We have what is to us a rather perplexing issue and would appreciate any advice you could give us. We have been growing garlic for 45 years and never had this problem before.
*Raised bed 8” and added new dirt 3 years ago
*Recently:
*Tilled in compost (straw + grass clippings) 8/1/25
*Planted garlic 10/15/25 (We purchase garlic seed, do not use grocery store produce)
*Added manure 5/1/26 (Black Kow)
*Looked fabulous until mid-May 2026 – 2“of heavy rain followed by several days of more rain. Stalks turned brown within 2 weeks (top to bottom)
*Dug up 6/8/26 – garlic very small. Ground hard as a rock (in the past, ground has been very friable.) Noticed small dots of clay in the soil.
*We don’t know if it is nutrient deficient or if the rain caused all of this. Will adding more compost alleviate the situation? The garlic bed is enclosed in a chicken wire/pvc cage to keep the deer from trampling it, so if a tarp over the top during heavy rains would help, we can do so.
Thank you in advance for any guidance you can provide.
Cuyahoga County Ohio
Expert Response
Hello,
Large amounts of rain could have created the proper environment for fungal disease to develop in the garlic plants. Garlic does not do well in wet sites and unfortunately, during heavy rain periods, a tarp will not keep the soil from becoming waterlogged. Humidity can also encourage fungal disease infection.
White rot and botrytis neck rot are two common fungal diseases which occur in garlic. Pests such as bulb mites and nematodes also can infect garlic.
The most accurate method of assessing the problem would be to send a sample of the garlic to a university-based diagnostic lab. In Ohio we have the C. Wayne Ellett Plant and Pest Diagnostic Lab (PPDC) run by OSU. The lab examines diseased plant material and writes an assessment of the lab results along with recommendations for remediation.
I have listed a link for the PPDC website below. The website contains all the information that you need to know if you would like to send in plant samples to them.
It would also be a good idea to conduct a soil test of the garden bed. Garlic grows best in a soil with the PH measurement of 6.0-7.0. A soil test will give you the PH number as well as any nutrient or mineral deficiencies. The soil test results will give suggestions for soil amendments, if needed. I have listed a link below for OSU Factsheet HYG-1032 which explains how to conduct a soil test as well as a list of labs that OSU recommends for soil testing.
On the list of your site prep and fertilization schedule you mention adding Black Kow in May. On the package directions it instructs users to work the product into the soil two weeks before planting. It's possible that the timing of adding Black Kow to the garden bed after the plants were established may have had a negative effect on them. The addition of nitrogen in May is not generally recommended for garlic.
In the article from Iowa State that I listed below, it recommends fertilizing with an all purpose 10-10-10 fertilizer 3-4 weeks after the plants emerge in the spring. They also advise to add the fertilizer as a side dressing, placed 4 inches away from the garlic. Your fertilization rate and amounts depend on your garden size and the results of the soil test.
To summarize here, a soil test and plant sample test would be helpful if you plan on growing garlic next year. Make sure that your site is not compacted soil or heavy clay. Crop rotation to another bed is recommended if it turns out that there is a disease or insect issue with the garlic.
Please write back if you should have more questions.
Thanks for asking Ask Extension.
Betsy B. - MGV
https://yardandgarden.extension.iastate.edu/how-to/growing-garlic-home-garden
https://cfaes.osu.edu/fact-sheet/growing-garlic-garden
https://extension.umn.edu/vegetables/growing-garlic
https://extension.umd.edu/resource/garlic-bulb-mites/
https://extension.umaine.edu/agriculture/garlic/maine-garlic-pest-field-notebook/
https://u.osu.edu/vegetablediseasefacts/garliconions/garlic-bloat-nematode/
https://cfaes.osu.edu/fact-sheet/soil-testing-horticultural-needs
https://ppdc.osu.edu/
https://blackkow.com/vegetable_gardens
Large amounts of rain could have created the proper environment for fungal disease to develop in the garlic plants. Garlic does not do well in wet sites and unfortunately, during heavy rain periods, a tarp will not keep the soil from becoming waterlogged. Humidity can also encourage fungal disease infection.
White rot and botrytis neck rot are two common fungal diseases which occur in garlic. Pests such as bulb mites and nematodes also can infect garlic.
The most accurate method of assessing the problem would be to send a sample of the garlic to a university-based diagnostic lab. In Ohio we have the C. Wayne Ellett Plant and Pest Diagnostic Lab (PPDC) run by OSU. The lab examines diseased plant material and writes an assessment of the lab results along with recommendations for remediation.
I have listed a link for the PPDC website below. The website contains all the information that you need to know if you would like to send in plant samples to them.
It would also be a good idea to conduct a soil test of the garden bed. Garlic grows best in a soil with the PH measurement of 6.0-7.0. A soil test will give you the PH number as well as any nutrient or mineral deficiencies. The soil test results will give suggestions for soil amendments, if needed. I have listed a link below for OSU Factsheet HYG-1032 which explains how to conduct a soil test as well as a list of labs that OSU recommends for soil testing.
On the list of your site prep and fertilization schedule you mention adding Black Kow in May. On the package directions it instructs users to work the product into the soil two weeks before planting. It's possible that the timing of adding Black Kow to the garden bed after the plants were established may have had a negative effect on them. The addition of nitrogen in May is not generally recommended for garlic.
In the article from Iowa State that I listed below, it recommends fertilizing with an all purpose 10-10-10 fertilizer 3-4 weeks after the plants emerge in the spring. They also advise to add the fertilizer as a side dressing, placed 4 inches away from the garlic. Your fertilization rate and amounts depend on your garden size and the results of the soil test.
To summarize here, a soil test and plant sample test would be helpful if you plan on growing garlic next year. Make sure that your site is not compacted soil or heavy clay. Crop rotation to another bed is recommended if it turns out that there is a disease or insect issue with the garlic.
Please write back if you should have more questions.
Thanks for asking Ask Extension.
Betsy B. - MGV
https://yardandgarden.extension.iastate.edu/how-to/growing-garlic-home-garden
https://cfaes.osu.edu/fact-sheet/growing-garlic-garden
https://extension.umn.edu/vegetables/growing-garlic
https://extension.umd.edu/resource/garlic-bulb-mites/
https://extension.umaine.edu/agriculture/garlic/maine-garlic-pest-field-notebook/
https://u.osu.edu/vegetablediseasefacts/garliconions/garlic-bloat-nematode/
https://cfaes.osu.edu/fact-sheet/soil-testing-horticultural-needs
https://ppdc.osu.edu/
https://blackkow.com/vegetable_gardens
Can you comment on the addition of compost and what to look for should we add some? We never had this issue until we added the dirt when we raised the bed an additional 6". We do see spots of clay in this new dirt. Thank you.
On Wednesday, July 8, 2026 at 04:56:35 PM EDT, Ask Extension wrote:
Hello,
Composted manure is fine as long as you add it when you plant the seed in the fall and when the leaves are emerging in the spring, at 4"-6" high. So the timing is important. It should not be added later than early spring. For any fertilizer, follow the package directions for the correct amount. Follow up with another layer of straw and grass mulch after amending the soil in early spring.
The results of a soil test will also help you determine your amounts and ingredients in compost and fertilizer amendments.
Bits of clay are not detrimental as long as it's not compacted in a solid mass which hinders root growth and drainage.
In May when the garlic starts setting scapes and they start to curl, cut them off. This gives the plant more energy for bulb formation.
Having the plants examined by a lab may indicate if excess moisture played a factor in creating a development issue with fungal disease. Excess rain is definitely a red flag for garlic problems.
If the period of heavy rains were followed by drought in your area, then supplemental watering would have been needed. One inch of water per week is recommended through June.
The folks at the Cuyahoga County Extension office may also help you with additional information about growing garlic.
Thanks for reaching out.
Betsy B.- MGV
https://u.osu.edu/ohiovictorygardens/2020/11/02/growing-garlic/
https://hort.extension.wisc.edu/articles/garlic-allium-sativum/
https://cuyahoga.osu.edu/
Composted manure is fine as long as you add it when you plant the seed in the fall and when the leaves are emerging in the spring, at 4"-6" high. So the timing is important. It should not be added later than early spring. For any fertilizer, follow the package directions for the correct amount. Follow up with another layer of straw and grass mulch after amending the soil in early spring.
The results of a soil test will also help you determine your amounts and ingredients in compost and fertilizer amendments.
Bits of clay are not detrimental as long as it's not compacted in a solid mass which hinders root growth and drainage.
In May when the garlic starts setting scapes and they start to curl, cut them off. This gives the plant more energy for bulb formation.
Having the plants examined by a lab may indicate if excess moisture played a factor in creating a development issue with fungal disease. Excess rain is definitely a red flag for garlic problems.
If the period of heavy rains were followed by drought in your area, then supplemental watering would have been needed. One inch of water per week is recommended through June.
The folks at the Cuyahoga County Extension office may also help you with additional information about growing garlic.
Thanks for reaching out.
Betsy B.- MGV
https://u.osu.edu/ohiovictorygardens/2020/11/02/growing-garlic/
https://hort.extension.wisc.edu/articles/garlic-allium-sativum/
https://cuyahoga.osu.edu/
