According to almanac tradition, sweet potatoes are a root crop, and root crops go in during the third quarter of the Moon, between full moon and last quarter. The traditional days for 2027 that also fall in a fruitful or semi-fruitful sign are May 23-24 (Moon in Capricorn), June 19-21 (Moon in Capricorn) and June 24-26 (Moon in Pisces). No effect of the Moon on sweet potatoes has been proven.
What the tradition says about planting sweet potatoes
Gardeners who practice planting by the moon sort crops by what the edible part does. Leaves go with the first quarter, fruit and seed with the second, and anything that grows underground with the third. Sweet potatoes are classed as roots, so the almanac rule is to plant them between the full moon and the last quarter. That is tradition, handed down in farm almanacs, and nothing more.
| Quarter | Moon phase | Crop type in almanac tradition |
|---|---|---|
| 1 | New moon to first quarter | Leafy crops that bear above ground (lettuce, spinach, cabbage, broccoli, celery) |
| 2 | First quarter to full moon | Above-ground crops that bear seed inside the fruit (tomatoes, peppers, beans, squash, corn) |
| 3 | Full moon to last quarter | Root crops, bulbs, perennials (potatoes, carrots, garlic, onions, beets). Sweet potatoes belong here. |
A fourth quarter, from last quarter to new moon, is set aside in the same tradition for rest: weeding, pruning, turning the soil and composting. Planting is not assigned to it.
Many almanacs add a second filter, the sign the Moon is passing through. This convention labels Cancer, Scorpio and Pisces fruitful, and Taurus, Libra and Capricorn semi-fruitful. The remaining signs are labeled barren, although sources differ on Virgo, Sagittarius and Aquarius. The dates on this page use the quarter rule together with a fruitful or semi-fruitful label.
The astronomy is worth knowing too. The Moon’s phase cycle lasts 29.53 days, so the third quarter comes around once per cycle. Its tidal pull at the Earth’s surface is about 1.1 millionths of a meter per second squared at its strongest, roughly one ten-millionth of gravity. That is far too small to move anything as small as a seed or a root, and no effect of the Moon’s phase or sign on germination or yield is established. The figures come from the NASA Moon Fact Sheet. If you follow the custom, you follow it as a tradition.
Traditional sweet potatoes planting days, 2026 and 2027
The table lists every month with traditional days for root crops, with the Moon’s sign on each run of days. All times are Eastern (ET).
| Month | Traditional days for sweet potatoes | Moon sign |
|---|---|---|
| May 2027 | May 23-24 | Capricorn |
| June 2027 | June 19-21 June 24-26 |
Capricorn Pisces |
The months shown are those when gardeners in much of the country plant sweet potatoes. Your state may start earlier or later, so only the rows that fall inside your own state’s window count. A row outside it is not a planting day for you, whatever the Moon is doing.
Each day is read at noon ET, and the Moon changes sign during the day. Treat the first and last day of every run as soft edges. If you want to stay well inside a window, the middle days are the firmer choice. On June 19-21, for instance, June 20 sits between the other two.
Capricorn carries the semi-fruitful label in this convention, and Pisces the fruitful one. Both qualify under the almanac rule used here. Gardeners who prefer the biodynamic system of Maria Thun sort days differently. That system calls Taurus, Virgo and Capricorn root days, so its list would not match the table above. The table follows the older almanac convention only.
Planting twice in one month, on both June runs, is also possible. The tradition has no rule against it, and the table simply shows the third-quarter days from two different lunar cycles. Whether a second planting suits your plot is a question for your state calendar, not for the Moon.
Check your state first: when to plant sweet potatoes where you live
The order of decisions matters more than the dates. Start with your state’s planting calendar for sweet potatoes, because that calendar decides whether anything can go into the ground at all. The Moon comes second, and only if you want it. Following the custom means choosing among the days your state has already opened. It never means planting on a day outside that window because the table lists it.
Frost dates and soil temperature are what set the calendar of the place. This page does not give figures for either, because they differ from one county to the next and the pages built for them are more careful than a lunar table can be. When to plant sweet potatoes where you live covers the sweet potato timing in detail. For a broader look at your region’s calendar, the state guides collect the local information in one place.
A short routine keeps the two sources apart:
- Find your state’s planting window for sweet potatoes on the linked pages.
- Look at the rows in the table above and keep only those that fall inside that window.
- Within those rows, pick a day in the middle of a run rather than at its edge.
If no row fits, you have not lost anything. The tradition has no rule that outranks the state calendar, and a gardener who plants on a plain calendar day is still planting on a day your state’s guidance supports. If the Moon does not line up this year, the next listed month or a later year gives another chance. For a look at the waning half of the cycle in general, there is a separate page on planting in a waning moon.
A fair way to try it
Nobody can say from this page whether the custom does anything for your sweet potatoes. A home gardener can still test it on their own plot with a plain side-by-side comparison. The steps are short:
- Split the planting in two. Plant half on a traditional day from the table and half on an ordinary day inside the same week, so both batches go in under the same local conditions.
- Label both halves clearly, with a stake or tag showing the date and which group each belongs to.
- Keep notes on emergence of new growth for each group, then record the harvest from each one separately.
- Repeat in a later season if you can, and keep the notes from every year in one place.
One season will not settle anything. Weather, soil and the plants themselves vary from year to year, and a difference between two small groups can come from any of them. A result in a single year tells you very little. Several years of notes from the same plot at least give you something to look at.
That is the only way a home gardener can judge the tradition for their own garden. It asks for two labeled rows and a notebook. It does not need a belief in the Moon, and it does not need a verdict from anyone else.
Questions about planting sweet potatoes by the moon
Does the tradition say to plant sweet potatoes in a waxing or a waning moon?
Waning. According to almanac tradition, root crops go in during the third quarter, which runs from the full moon to the last quarter, and that is part of the waning half of the cycle. Above-ground crops are assigned to the waxing half, in the first and second quarters. The tradition treats the fourth quarter, also waning, as a resting period instead of a planting one.
What if the traditional day falls on a frost?
Plant according to your state calendar and leave the traditional day aside. The Moon has no standing against the local calendar, and a table row that does not match your window is not a planting day for you. Look for the next listed run that does fit, or skip the custom this year. The state pages linked above are the place to check your own dates.
Do I need to follow the Moon sign as well?
No, but many almanacs add it, and the dates in the table above use it. A gardener who follows only the quarter rule has a wider set of days to choose from, because the sign narrows the list. Gardeners who plant by Maria Thun’s biodynamic calendar use a different sign grouping and call Taurus, Virgo and Capricorn root days. The two systems do not give the same days, and neither has been shown to affect a crop.