Low Desert Almanac

Citrus Care Calendar

Watering, feeding, pruning and freeze protection for citrus in the Phoenix area, month by month, following University of Arizona Extension guidance.

Yard & Garden

What does my citrus need this month?

Pick a month

The four jobs

Watering

How long to wait between irrigations, by the season the month sits in.

Feeding

Which of the year’s three nitrogen applications falls in this month, and for which trees.

Pruning

Whether the month is in the pruning window, and what to take off if it is.

Freeze protection

What the month asks you to do about frost, or what to leave alone.

Watering, feeding, pruning and freeze guidance come from the University of Arizona co-operative extension’s citrus publications: AZ1151, AZ1671, AZ1455 and AZ1222. The frost figures come from NOAA’s climate normals for Phoenix Sky Harbor.

Citrus in

December

Four jobs, every month of the year. The extension publications give intervals and windows; this page arranges them onto a calendar.

Watering

21 to 30 days apart. The tree is close to dormant and over-watering now is a common way to lose one to rot.

Source: AZ1151

Feeding

No feeding. The next application is January, the first third of the new year.

Source: AZ1671

Pruning

No extensive pruning. Wait for February, unless a limb was broken by wind or fruit.

Source: AZ1455

Freeze protection

The month the whole year’s frost work is for. A cover over the canopy and an incandescent light under it is the standing method AZ1222 gives; the same publication notes that frosts here are usually calm, clear and short, which is why protection so often works.

Source: AZ1222

What the month normally does

0.1 nights below 32 °F · 6.8 nights below 40 °F

Normal nights per month, Phoenix Sky Harbor, 1991–2020. NOAA NCEI . The outlying valleys run colder than this.

How much cold each group takes

What survives a winter is the top of the tree, and citrus divides into four groups on that basis. Find your tree’s group before you decide how much winter work it needs.

Group Examples What the publication says
The most cold hardy Trifoliate orange Survives to 5 °F. Grown here as a rootstock more often than as a fruiting tree, and named for that reason. AZ1222
Quite cold hardy Kumquats, Satsuma mandarins Described by AZ1222 as quite cold hardy, which puts them well outside the range a normal Arizona winter reaches. Limes, by contrast, AZ1001 calls "extremely frost sensitive". AZ1222
Partially cold hardy Sour orange, tangerines, tangelos, sweet oranges, navel oranges, grapefruit May survive to 20 °F without significant damage. This is the group almost every Valley orange and grapefruit tree belongs to. AZ1222
Least cold tolerant Lemon, lime, citron Will suffer at least some damage below 25 °F. This is the group to cover first, and the group most often lost to a December night. AZ1222

When a freeze is forecast

The four methods the extension gives, in its own order of usefulness. What they are working with is described below them, and it is the reason protection works as often as it does here.

Cover the tree

A blanket, burlap or frost cloth over the canopy, brought all the way to the ground where it can be, with the cover removed during the day. The cover holds the warmth the soil gives off through the night, so covering the ground as well as the leaves is most of the benefit.

Add a heat source, but not an LED

A single incandescent bulb under the cover is the long-standing method. It has to be an incandescent: the point is the heat the lamp throws, which an LED does not.

Keep the soil moist

Moist soil holds and releases more heat overnight than dry soil. Watering ahead of a cold night is a hedge, not a cure, and it works best combined with a cover.

Run water over the canopy

A continuous spray of water can hold tissue near 32 °F by releasing heat as it freezes, but only while the water keeps flowing. It must stay on until the air temperature is above roughly 37 °F, and stopping early is worse than never starting.

Most Arizona cold events are frosts (calm, clear and dry, with cold air pooling overnight) and sub-freezing temperatures rarely last more than a few hours or drop below 20 °F. True advective freezes, carried in on wind, are rare here, and the publication is candid that protection against those usually fails. The practical consequence is that a cover and a light work here far more often than they would in Florida or Texas. AZ1222

Feeding, by tree size

Split the year’s nitrogen into three equal applications. Oranges, mandarins, tangelos and grapefruit are fed in January–February, March–April and May–June. Lemons and limes take the first two on the same dates and the third in August–September instead, which keeps late growth off a tree that would otherwise carry soft wood into a frost. Grapefruit and pummelo take half the chart amount annually; lemons and limes take about ten per cent more.

Tree Actual nitrogen a year
Newly planted, after it has established and started growing None to 0.13 lb of actual nitrogen a year
Small: 2 to 3 ft tall, trunk up to 1.25 in, canopy up to 9 sq ft 0.25 to 0.50 lb a year
Medium: 4 to 8 ft tall, trunk 1.25 to 4 in, canopy 16 to 64 sq ft 0.75 to 1.00 lb a year
Large: 10 ft or more, trunk 6 to 10 in, canopy over 64 sq ft 1.25 to 1.50 lb a year

Feeding figures from AZ1671 .

How this works

Method

Why citrus is the one tree that asks for something every month

Most of what grows in a Valley yard can be left alone for long stretches of the year. Citrus cannot, quite. It is evergreen, so it holds its leaves through winter and has to be hardened off for the cold rather than dropping everything and hiding. It fruits over months rather than weeks, so it is carrying a crop through the heat. And it is grown here at the edge of what the climate will support: an orange is comfortable in the Valley but a lime is not, and the difference between the two is a matter of about 5 °F on the coldest night of the year. All of that adds up to a tree that wants something in every month, not much in some of them, but something.

The four jobs this page tracks are the four the University of Arizona’s co-operative extension writes about: watering, feeding, pruning and freeze protection. Each comes from its own publication (AZ1151 for irrigation, AZ1671 for fertiliser, AZ1455 for pruning, AZ1222 for cold), and each publication gives intervals and windows rather than a page a month. Arranging them onto a calendar is this site’s work, and the page says so rather than implying the extension published it this way.

The year has a shape, and it is not the shape people expect

The watering interval is the clearest place to see the year turn. Through December, January and February a mature tree on flood irrigation is watered every three to four weeks. The interval shortens through spring, holds at about two weeks through May and June, tightens to ten days to a fortnight through the worst of the summer from July to September, and then opens out again as the nights cool. The tree is not being managed by a calendar; it is being managed by how fast it is using water, and the interval is the readable consequence of that. Watering on a fixed weekly schedule year-round is the single most common way to get this wrong, in both directions: too much in winter rots roots, too little in July drops fruit.

Feeding has a shape of its own, and it is the shape that catches people out. The year’s nitrogen is split into three equal applications, but not all citrus takes them at the same time. Oranges, mandarins, tangelos and grapefruit take theirs in the spring and early summer, finishing by June. Lemons and limes take the first two at the same dates but delay the third to August and September, which keeps the last push of growth off a tree that would otherwise carry soft wood into the frost. Either way, nothing is fed between October and December. A late nitrogen application is a gift to a frost.

Pruning is a timing problem more than a skill problem

The whole of the pruning advice comes down to when. The window is February through April, and both ends of it are load-bearing. Before February, the tree is still exposed to frost and a cut forces the tender regrowth a cold night will kill; after April, the summer sun does the damage instead, because a citrus canopy is thin and the wood beneath it has never seen direct light. Cut a limb in June and the exposed bark can sunburn and die back. So the extension advises against discretionary pruning from May through the middle of October, and against doing much of it at all from November through January. A broken limb comes off whenever it needs to (that is repair, not pruning), but everything else waits for the spring window.

Freeze protection, and why it works here

This is the half of the year the calendar is really organised around, and the reason it works is a property of the Valley’s winter rather than of any clever technique. Arizona cold events are mostly frosts (calm, clear nights when the ground radiates its heat away and cold air pools in the low spots), and they seldom last more than a few hours or drop below 20 °F. A true advective freeze, the kind carried in on wind, is rare here, and against one the extension is candid that protection usually fails. But against an ordinary frost night, a cover and a light work far more often than not.

The methods follow from that. A blanket or frost cloth over the canopy, brought down to the ground where it can be, holds in the warmth the soil gives off. A single incandescent bulb under the cover (incandescent, not LED, because the point is the heat the lamp throws) adds a few degrees. Moist soil holds and releases more heat overnight than dry soil, so watering ahead of a cold night is a hedge. And a continuous spray of water over the canopy can hold tissue near 32 °F by releasing heat as it freezes, but only while the water keeps flowing; it has to stay on until the air is above roughly 37 °F, and stopping early is worse than never starting. Which of these matters most depends on the tree: an orange in the middle of the metro area is rarely at risk, and a lime on the cold side of a house is the one the cover is for.

Sources

Where this came from

Every figure this tool uses was read from the source named above on 11 October 2026. Anything still waiting on a check is listed in the site's data notes rather than shown here as if it were settled.

Limits and assumptions

Read this

Before you rely on this

This tool works from climate normals and published guidance, not from live weather. It describes a typical day for the month or date you chose, which is useful for planning and useless as a forecast.

  • The month rows are this site’s arrangement of the four extension publications onto a calendar. The publications give intervals and windows, not a page per month, so reading them side by side is our arithmetic. For anything on the edge of a decision, open the publication named beside it rather than trusting the arrangement.
  • The watering intervals are for a mature tree three years or older, irrigated by flood or basin. A tree on drip or micro-sprinkler needs its intervals closer together than these, a newly planted tree needs more water far more often, and a tree in sand or gravel takes the short end of every range while one in clay takes the long end. The intervals are a starting point, not a schedule.
  • The cold-hardiness figures describe the top of the tree (the scion) and the temperatures at which each group can be expected to take damage. Whatever a citrus is grafted onto can change how the tree comes back, but the figures here are about the wood above the graft, as the publication gives them.
  • The frost figures beside each month are twenty-year climate normals for Phoenix Sky Harbor, and a normals record is an average rather than a forecast. Sky Harbor is also the warmest part of the metro area: normal nights below 32 °F are rarer there than in the outlying valleys, which run several degrees colder on a clear winter night and freeze more often.
  • A normal number of cold nights says nothing about a particular winter. The 1991–2020 stretch behind these figures includes winters that froze hard and winters that barely dipped, and the record cold night in the Valley’s history sits well below anything an average would suggest. The frost article is where the extremes are.
  • Feeding advice is about nitrogen, split into three equal applications across the year, and it describes amounts rather than brands or products. A complete fertiliser supplies the other nutrients alongside the nitrogen, and a soil test is a better guide than a chart if you want to know what a particular tree or a particular soil actually needs.
  • This is a calendar for citrus in the low desert, the Valley and the country around it. Citrus grown at higher elevations, where the winter is longer and colder, is working with a different set of numbers, and the freeze guidance in particular does not transfer.
  • The three fertiliser applications are evenly spaced by design, so a month that falls between two of them is described as between two of them rather than as a month to feed. That is the publication’s shape, not a gap in the calendar.
  • Nothing here covers pests and diseases. Citrus in the Valley deals with a handful of its own (citrus leafminer, aphids, thrips, the odd root rot), and those are a separate question from the four jobs on this page.

Questions

Short answers
When do I actually cover a lemon tree, and when can I stop?
Lemons and limes are the least cold-hardy citrus the Valley grows, and the extension’s figure is that they suffer damage below about 25 °F. That makes them a December-to-March tree to watch, with early December and late January the two coldest stretches in the twenty-year record. The practical rule is to keep a cover and an incandescent bulb to hand from late November through the middle of March, and to act on the forecast rather than the calendar: cover when a frost is predicted, and take the cover off again in the morning. The reason protection works here is that Valley cold events are mostly calm, clear frosts that last a few hours, not a wind-driven freeze that would laugh at a bedsheet.
Why is there no feeding at all between October and December?
To keep soft growth off the tree going into winter. Nitrogen pushes new leaves and tender wood, and tender wood is exactly what a frost kills. The year’s nitrogen is split into three equal applications: the first two in the spring for every kind of citrus, and the third in either May–June or August–September depending on what you are growing. Lemons and limes take their last third in August and September; oranges, mandarins, tangelos and grapefruit take theirs in May and June. Either way the feeding stops by September so the autumn flush hardens off before the first cold night. A late feeding is a common way to lose a tree that would otherwise have come through.
Can I prune in June? The tree is huge.
The extension’s guidance is not to prune citrus between May and the middle of October, and the reason is the sun. A citrus canopy is thin and the bark underneath it has spent its life in shade; cut a limb in June and the wood that is suddenly exposed will sunburn and can die back. Pruning is a February-to-April job, and April is the last month of it. Winter pruning is possible outside the forbidden window, but the publication still advises against doing much of it from November through January, because pruning at that time forces new growth that the frost will catch. If a limb is broken by wind or loaded with fruit, take it off whenever it needs to come off: the rule is about discretionary pruning, not about repairing damage.
How often should I water, and does it change through the year?
It changes a great deal, and the year has a clear shape to it. A mature tree on flood or basin irrigation is watered every 21 to 30 days in the cool months of December, January and February, every 14 to 21 days through the spring and autumn, every 14 days in May and June, and every 10 to 14 days through the hottest stretch from July to September. A tree that drops its fruit in August is usually one that was kept on a July interval through a hot, dry spell. Two things override all of it: drip and micro-sprinkler systems need the intervals closer together than flood irrigation does, and a newly planted tree needs water far more often than any mature-tree figure suggests.
My orange tree has been fine for years. Do I really need to do anything in winter?
Probably less than you fear, and the reason is the Valley’s winters rather than luck. An orange belongs to the group the extension calls partially cold hardy (able to take about 20 °F without significant damage), and the twenty-year record at Sky Harbor has almost no nights below 32 °F at all, let alone below 20. So a mature orange in the middle of the metro area is rarely at risk. Two things change the picture. A tree outside the urban core (out past the fringes, where cold air pools) sees more and harder frosts than the airport figures suggest. And a tree that was fed late and went into winter with soft growth is more vulnerable than the figure implies. The protection is worth setting up for a lemon or a lime; for an established orange it is a hedge against an unusual night.