When to Fertilize Garlic: A Season-Long Schedule

On this page (11)

Fertilize garlic at four points — a base dressing before planting, a green-up top-dress as spring growth starts, a phosphorus-leaning feed at bolting, and a potassium push as the bulbs swell — and treat foliar sprays as a supplement, not the main course. The schedule below is built from Chinese field videos, which give rates per 亩 (mu); we convert those to square feet before you use any of it, and then set the lower-input US extension schedule beside it.

Affiliate links: we may earn a commission at no extra cost to you. Details.

First, the units — and the intensity gap

Two conversions to hold in your head:

• 1 亩 (mu) ≈ 667 m² ≈ 1/6 acre ≈ 7,175 sq ft.
• 1,000 sq ft ≈ 0.14 亩, and 1 斤 = 0.5 kg.

Those conversions matter because Chinese field rates assume intensive production — beds, film, flush irrigation, high inputs. A US backyard bed is a lower-input system, so the converted numbers below are the intensive end of the range, not the default for a raised bed. The extension schedule at the end is the low-input reference.

The conversions are ours: 1,000 ÷ 7,175 = 0.139, multiplied by the Chinese rate. They are rounded approximations, not exact equivalents.

1. Base dressing, at planting

The extension guides put a complete fertilizer down before planting, worked into the bed ^{9, 10} — that is the foundation the rest of the season sits on. The Chinese videos in this article start their clock at green-up, so there is no field rate here; use the extension base rate.

2. Green-up: the first spring feed

The Chinese source is specific about why plain urea is not the answer at green-up: growth needs nitrogen, but phosphorus demand peaks at bolting and potassium demand peaks from bolting into bulb swell — and urea itself has to convert in the soil (this account says about four to five days) before the roots can take it up, which is slower in a cold spring ¹. The recommendation is a compound NPK fertilizer, calcium ammonium nitrate, or a microbial product rather than urea alone ¹.

For a garden bed, a balanced water-soluble NPK is the simplest way to hit that green-up target: a water-soluble NPK for spring green-up.

Timing: the first green-up watering comes after the spring equinox and before Qingming, when the daily mean is around 7 °C; the field rate is 40 斤 (20 kg) of compound fertilizer per 亩, or 50 斤 (25 kg) of calcium ammonium nitrate, or about 10 kg of a microbial agent ¹.

If the plants come out of winter yellow and weak, a second video uses urea at 5 kg/亩 plus potassium dihydrogen phosphate at 3 kg/亩, flushed with the irrigation water; for normal-looking plants, a soluble NPK at 10–15 kg/亩 ². Converted: 0.7 kg urea and 0.42 kg KH₂PO₄ per 1,000 sq ft, or 1.4–2.1 kg of soluble NPK.

3. Bolting: phosphorus peaks

At bolting, phosphorus demand is at its peak, and potassium demand runs from bolting into bulb swell ¹. The field method is "feed the roots, supplement the leaves": a high-potassium fertilizer at the root zone plus potassium dihydrogen phosphate sprayed on the canopy, with the potassium credited for moving photosynthate into the bulb ⁴.

The foliar rate at bolting is 150 g/亩 of potassium dihydrogen phosphate in 15 kg of water, sprayed evenly — and again before bulb swell ³. Converted, that is about 21 g per 1,000 sq ft, at a spray concentration of 1%.

4. Bulb swell: the potassium push

When the bulbs start to swell in early May, the field rate is a high-nitrogen, high-potassium fertilizer at about 30 斤 (15 kg) per 亩, or a tank mix of potassium dihydrogen phosphate at 2 kg/亩 plus urea at 5 kg/亩, dissolved fully and flushed with the water ¹. Converted: 2.1 kg per 1,000 sq ft for the first, or 280 g KH₂PO₄ plus 0.7 kg urea for the second.

5. Foliar feeding: the supplement

Foliar feeding is not a replacement for the soil feeds; it is for the moments when root uptake lags. The clearest window in the videos is the three-leaf stage, just as the seedling moves off the mother clove and its roots are still shallow: per 亩, 100 ml of a 42% high-nitrogen fertilizer plus 100 g of 99% potassium dihydrogen phosphate in 20 kg of water, sprayed evenly ⁵. If you scale it, keep the ratio — 100 ml : 100 g : 20 kg.

Before winter, at five or six leaves, another video sprays 50 g/亩 of potassium dihydrogen phosphate in 15 kg of water, aimed at root growth and cold hardiness ³. We list only the fertilizer ingredients; the videos also add growth regulators, which are not fertilizer and are not covered here.

Watering that goes with the feed

• After planting: soak the planting furrow through once, and water again three to five days later — uneven watering is the main reason the video gives for patchy emergence ⁸.
• Before winter: the antifreeze watering should be late rather than early — wait until the five-day average temperature is below about 5 °C, when the plants have gone dormant ⁶.
• The winter-water question: a field already watered before the film went on does not need a winter watering — extra water lowers soil temperature, dulls the film's light transmission, can spread rot bacteria, and leaches fertilizer. A field that shows fertilizer burn does need water, and generously ⁷.

The US extension schedule, for comparison

This is the lower-input counterpart to the field calendar:

• Maryland: fertilize before planting in fall, again in April, and if needed in late May ⁹.
• Utah: side-dress ½ lb of 21-0-0 per 100 sq ft in mid-April, and ¼ lb in late May ¹⁰.
• Minnesota: top-dress as shoots emerge, then again two to three weeks later; avoid nitrogen after the first week of May, and stop watering two weeks before harvest ¹¹.

Same crop, same stages, roughly — but fewer applications and smaller amounts per area. That is the difference between a field calendar and a garden one.

FAQ

Can I use urea alone at green-up?

The Chinese source argues against it: nitrogen is part of the answer, but phosphorus and potassium are timing-specific, and urea needs days in cold soil before it converts ¹.

How big is a 亩?

About 667 m², roughly one-sixth of an acre, or about 7,175 sq ft — so 1,000 sq ft is about 0.14 亩.

Do I need foliar feeding at all?

It is a supplement for when root uptake lags — at the three-leaf stage, or before winter ^{5, 3}; the soil feeds are the main course.

Next steps

• When to plant garlic in fall — the zone calendar, so the base dressing goes down at the right time.
• The grow-garlic hub — the pillar page, from clove to bulb.
• How to plant garlic step by step, curing and storing, and mulching — companion guides, linked once they publish.

As an Amazon Associate, Garlicly earns from qualifying purchases.

Sources

1. 康达农资, 年后大蒜返青肥，尿素，复合肥，硝酸铵，用那个好 (135 s, 2024-01-03): https://www.bilibili.com/video/BV1qC4y1i7fz — green-up feed, NPK demand by stage, field rates.
2. 三农木雨听风, 给大蒜追肥，选择复合肥还是尿素？ (83 s, 2025-10-26): https://www.bilibili.com/video/BV1QVszzVEUn — yellow/weak stand rate vs normal stand rate.
3. 睢阳农科, 大蒜要想获得高产，用对磷酸二氢钾很关键 (141 s, 2022-11-16): https://www.bilibili.com/video/BV18P411g78v — potassium dihydrogen phosphate windows and rates.
4. 农人-阮方兵, 大蒜抽苔期怎么追肥? 蒜头才能结的大? (213 s, 2025-04-16): https://www.bilibili.com/video/BV16QoTY6ECb — bolting-stage high-K feed, root plus foliar.
5. 睢阳农科, 大蒜叶面肥，这个时间喷施，防黄叶干尖产量高 (87 s, 2024-10-15): https://www.bilibili.com/video/BV1q22ZYSE4s — three-leaf-stage foliar recipe.
6. 爱华生活记, 大蒜越冬前，浇封冻水有什么用？什么时间浇最好？4个作用很重要 (317 s, 2023-02-16): https://www.bilibili.com/video/BV1n24y1p7Aj — antifreeze watering timing.
7. 农业技术分享2022, 大蒜要不要浇越冬水？ (142 s, 2022-10-27): https://www.bilibili.com/video/BV1gg411h7xS — when winter water is unnecessary, when it is needed.
8. 农民云飞V, 大蒜啥时候可以浇水？大蒜为啥会出苗不齐？ (173 s, 2024-10-02): https://www.bilibili.com/video/BV1wz4uepEw2 — after-planting watering rhythm.
9. University of Maryland Extension, Growing Garlic in a Home Garden (updated 2023-08-22): https://extension.umd.edu/resource/growing-garlic-home-garden
10. Utah State University Extension, How to Grow Garlic in Your Garden (published 2020-05): https://extension.usu.edu/yardandgarden/research/garlic-in-the-garden
11. University of Minnesota Extension, Growing garlic in home gardens (reviewed 2026): https://extension.umn.edu/garden-and-home/yard-and-garden/gardening-in-minnesota/growing-garlic