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Frost and Succulents: What You Need to Know

Frost and Succulents: What You Need to Know

Depending on how long temps stay below freezing (32 degrees F), “frost tender” succulents may show varying degrees of damage. When moisture in the cells of a vulnerable plant freezes, it expands, bursts cell walls, and turns leaves to mush. In a “light frost,” leaf tips alone may show damage. In a “hard frost,” temps stay below freezing for hours, which can collapse entire plants. Succulents typically don’t regenerate from roots.

Crassulas, aeoniums, euphorbias, and kalanchoes are among the most tender succulents. A few succulents have a built-in antifreeze that enables them to survive temperatures well below 32 degrees F—below zero, in fact.

Should you be worried about your outdoor succulents in winter? It depends on where you live. See “Cold Weather Care for Outdoor Succulents, By Region.”

Your area is frost-free (lucky you!) if…

Agave attenuata grows in gardens, and the plants look like this year-round.

Cold Weather Care for Garden Succulents

Agave attenuata is the first succulent to show damage from frost in winter.

In my garden, this soft-leaved agave is the canary in the mineshaft where cold is concerned. A lot of succulents breeze through a brief frost (less than an hour), but leaf tips of Agave attenuata show damage right away.

Frost and Succulents: What You Need to Know

After a brief exposure to 32 degrees, Agave attenuata will look like this.

Such damage is unsightly but seldom fatal. See the healthy green part of each leaf? Use scissors to trim off the tissue-paper-like frozen tips [see how], cutting each leaf to a point. When you’re done, the damage will be barely noticeable. By summer new growth will have hidden those shorter, trimmed leaves. (Note: Such damage is similar to scorching caused by too much sun and heat, typical of desert climates, and by—believe it or not—wildfire.)

 

Cold Weather Care for Garden Succulents

What about an agave or other succulent that has frost damage only on its leaf tips? Don’t bother to trim them. It’ll lose those oldest leaves in a few months anyway.

Areas of occasional, mild frosts (like inland Southern CA):

Watch the weather forecast, and if there’s a “frost advisory” for your area, before dark go outside and cover your tender succulents. Frost tends to happen after midnight, with temps getting colder toward dawn. Cold air is heavier than warm, and flows down slopes and collects in low spots. Consequently, succulents in swales are more at risk than those atop berms. You may have heard that Christmas lights raise the temperature a few degrees. Yes, if they’re the old-fashioned kind. Those sold nowadays (LEDs) don’t generate heat. The succulents you have to worry about are those out in the open, with nothing above them. I sometimes stand over a succulent and gaze upward. If there are no tree limbs or eaves directly overhead, it gets draped.

I live in the foothills NE of San Diego at 1,500 feet (Zone 9b). And yes, I’ve been outdoors in my pajamas and slippers at 11 pm after hearing the weather forecast on the late-night news, shivering as I throw sheets on vulnerable plants, while my husband holds a flashlight. If frost is predicted for a series of nights, I may leave the plants covered; otherwise, I remove the sheets the next morning. To make sure they won’t blow off, I secure them with clothes pins and rocks. Do NOT use plastic. It doesn’t allow the plants to breathe.

Frost and Succulents: What You Need to Know

Frost cloth protects jades and other vulnerable succulents in my garden. See the video. 

Why cold damages some succulents and not others

A lot has to do with where a particular kind of plant originated. Succulents, which store water in their leaves to survive drought, are mostly from dry, hot climates. But some are from dry, cold climates—and those are the ones that don’t freeze. See my article in the Wall Street Journal: Showy Succulents for Snowy Climates. Among the “hardies” are:

Frost and Succulents: What You Need to Know

Stonecrops (small-leaved sedums), like those above in a Colorado rock garden…

Frost and Succulents: What You Need to Know

sempervivums (hens-and-chicks, above) of which there are numerous species and cultivars; certain cacti, yuccas and agaves (like Agave utahensis, A. montana and A. parryi), and lewisias from the Pacific Northwest.

Related Info on This Site:

Overwintering

How to grow indoors

Cold Weather Care for Outdoor Succulents

Frost damage

 

Learn more in my books:

Designing with Succulents (2nd ed.):
— Cold-Climate Succulent Gardens, pp. 111-113
— Cultivating Succulents in Challenging Climates, pp. 143-148

Succulents Simplified:
— Protection from Frost, pp. 48-50
— Frost Damage, p. 72 and p. 77

I also recommend Hardy Succulents, by Gwen Kelaidis, illustrated by Saxon Holt:

Screen shot 2016-01-05 at 7.59.00 PM

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Four Ways to Overwinter Succulents

These four ways to overwinter succulents give you several options, depending on how cold it gets where you live. Most varieties can’t handle temps below 32 degrees F.

These common winter conditions can lead to damage or death for dormant (not actively growing) succulents:
— soggy soil (causes roots to rot)
— excess rainfall (engorges cells)
— frost (causes cell walls to burst)

Some succulents do have a built-in antifreeze. Those indigenous to the Americas, such as cacti and agaves, or to northern climates like many sedums and sempervivums, tend to fare better than those from Madagascar and South Africa (kalanchoes, aeoniums, aloes and crassulas). But no succulents want a lot of water when dormant, nor high humidity at any time of the year. All prefer well-draining soil, bright but not intense light, and good air circulation.

#1: Cover your plants

If you live where frost is occasional and lasts only a few hours (inland valleys of Southern CA), cover vulnerable, in-ground succulents with bed sheets when there’s a frost advisory for your area. Or use what nurseries do: Pellon nonwoven fabric or Agribon’s floating row cover. These are made of spun nylon, like fusible interfacing without the fusible part. It will protect about 2 to 4 degrees below freezing. For a bit of extra warmth, use C-9 Christmas light strings (the old-fashioned kind).

Ways to overwinter succulents

In my YouTube video, Frost Protection for Succulents, I show how I do this in my own garden. In the foothills NE of San Diego at 1,500 feet, it’s subject to cold air that settles in inland valleys. 

Also:
— Don’t peel away dry leaves attached to a succulent’s trunk or stem. They protect it from temperature extremes (cold and hot).
— Keep succulents on the dry side. Cells that are turgid are more likely to burst when the liquid within them freezes and expands.
— Move cold-sensitive succulents beneath a deck, tree or eaves. Such structures help to keep heat from dissipating and protect leaves from falling ice crystals.
— Or place pots against walls, hardscape, boulders and/or shrubs that absorb and slowly release the day’s heat. South- and west-facing exposures do this best.

If you live in Zones 8 or lower, grow tender succulents as annuals or in containers that you overwinter indoors. These members of my Facebook community graciously shared their winter set-ups:

#2: Outdoors, Temporary Greenhouse

Candy Suter, Roseville, CA (near Sacramento): Midwinter nights may drop into the 20s F but seldom go lower than 25 F. Candy moves her succulents into a small walk-in greenhouse (center) or a gazebo (right), which she covers with 5mm plastic to hold in warmth. She anchors the plastic along the bottom, secures the seams with duct tape, and adds a small heater with a fan on the coldest nights.

Ways to overwinter succulents

#3: Indoors, shelves with lights

Pat Enderly of Virginia Beach, VA: Midwinter lows average 32 F. Pat brings her plants indoors and tucks them into shelving units she purchased online. Each shelf has a waterproof tray, and each unit is lit by two T5 bulbs. “They do a wonderful job of keeping my succulents from etiolating (stretching),” Pat says, adding that the lights, on timers, stay on from 7 am to 7 pm daily. Pat moves her succulents indoors in Sept. and Oct. and takes them outside in April.

Ways to overwinter succulents Ways to overwinter succulents

#4: Climate-controlled greenhouse

Tenaya Capron of Buffalo, TX: Although average midwinter lows hover above freezing, occasional winter lows may drop into the single digits. Tenaya and her husband built this 24×20 free-standing greenhouse, which they outfitted with exhaust and overhead fans, an overhead heater, and double sliding barn doors on either end. I love the library ladder, don’t you?

Ways to overwinter succulents

Find more info in my book, Designing with Succulents (2nd ed.):
— Cold-Climate Succulent Gardens, pp. 111-113
— Cultivating Succulents in Challenging Climates, pp. 143-148

Related Info on this Site:

Temporary greenhouse


Succulent FAQs, Basics

How to keep succulents happy


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How to Grow Succulents Indoors

If you’re wondering how to grow succulents indoors, basically you need to outfit a basement, sun room, spare room or alcove with tables and shelves that can withstand moisture, plus lights and a fan that run on timers. Fortunately succulents need very little water. Dribble a little at the base of each plant every three weeks or so, enough to hydrate the roots but not so much it puddles on the floor. Don’t fertilize succulents when they’re dormant (growth slows to a standstill, usually in winter).

Move potted succulents indoors when temperatures drop into the 30s. Clean the pots’ exteriors and check for pests. Keep them above 32 degrees F but not higher than 60 (cold is necessary for flowering later on). Keep a fan running to enhance air circulation, and a dehumidifier if the air is moist.

Place your succulents near a window. Maximum sun exposure is on the south and west sides of your house. The farther north you live in North America, east will provide bright light, but not enough for crassulas, echeverias and aloes to maintain their red hues.

Don’t set plants near heaters or furnace vents. They’ll cause the soil to dry out and your plants to desiccate.

Install grow lights. Situate indoor succulents beneath lights that stay on six hours daily. Fluorescent is fine and economical. Experts in growing succulents in gray-sky climates recommend T-5 grow lights. If your plants stretch toward light (or flatten their rosettes to expose more of their surface area), add more lights or move the plants closer to the ones you have.

Agrobrite FLT44 T5 Fluorescent Grow Light System, 4 Feet, 4 Tubes, about $120 on Amazon.

 

No room? Go vertical. Create a “light island.” There are shelving units designed for indoor plants. Each shelf has a waterproof tray, and each unit is lit by two T5 bulbs. The lights, on timers, stay on from 7 am to 7 pm daily. Shown below is arguably the ultimate indoor plant-shelf unit. Made of lightweight, powder-coated aluminum, it has adjustable lights with energy-efficient, full-spectrum bulbs; plastic drip trays; and wheels for easy positioning. Three shelves provide 18 square feet of growing space. From Gardener’s Supply Co.; about $600. 

Get a timer which automatically turns the lights on at, say, 7 a.m. and off eight hours later. I like this one, below, because it has multiple outlets:  Titan Apollo 14, about $26. 

Watch the temperature. If it falls below freezing (32 degrees F) many succulents may show long-term damage (or die). This indoor thermometer is digital and also has a humidity gauge. But what I love about it is that it keeps daily high and low temps for 24 hours!

AcuRite 00613 Humidity Monitor with Indoor Thermometer, Digital Hygrometer and Humidity Gauge Indicator, about $12 on Amazon.

Watch for pests. Succulents in cramped conditions are at risk of mealy bugs, spider mites and other pests. At the first sign of infestation, spray with 70% Isopropyl alcohol. Isolate infested plants so pests don’t spread, and clean the surrounding area.

Related info on this site: Overwintering

 

How to keep succulents happy