Christmas cactus stem rot

Christmas Cactus (Schlumbergera spp.)-Stem and Root Rots

Cause Several organisms can cause lower stem and root rots on these holiday cacti including Fusarium oxysporum, Pythium spp., and Phytophthora sp. The OSU Plant Clinic has found Fusarium.

Fusarium survives in the soil as thick-walled, dormant chlamydospores, which germinate in response to exudates from nearby plant roots. Hyphae then penetrate the roots, colonize the cortex, and move into the xylem tissue. The fungus can attach wounded or non-wounded plants. Small spores, microconidia, are produced and carried up into the plant.

Both Pythium and Phytophthora are oomycetes and are strongly favored by abundant moisture especially in poorly drained potting media. They can survive in dust, planting media, or soil particles on greenhouse floors, flats, and pots. Wood benches can also be a reservoir. Spread can also occur via movement of infected plants. Damaged plants are more easily infected. Pythium can enter roots damaged by high-soluble salts, either from over-fertilization or from letting the rooting medium dry out, even for short periods, during propagation.

Symptoms

Fusarium – Water-soaked lesions first occur with reddish-brown margins. The tissue then dries to a paper-thin tan. Upper portions of the plant wilt when cut off from functioning roots.

Pythium – Feeder roots become brown and soft rotted where the cortex easily separates from the vascular system. The plant wilts in later stages of disease development.

Phytophthora – Plants collapse and show brown lesions at the base of the plant.

Cultural control

  • Do not overwater plants.
  • Provide good drainage for plants in containers.
  • Avoid reusing pots or trays from a previous crop for propagation. If pots must be reused then wash off all debris and soak in a sanitizing solution or treat with aerated steam for 30 min.
  • Remove all dead and dying plants from the production area being careful not to contaminate healthy plants or areas.

Chemical control Focus on cultural controls first. Labels may still list old Zygocactus name. Rotate among fungicides from different groups with different modes of action.

To control Fusarium only:

  • Empress at 1 to 3 fl oz/100 gal water can be used for cuttings or seedlings. Group 11 fungicide. 12-hr reentry.
  • Heritage at 0.2 to 1 oz/100 gal water plus a non-silicone-based wetter sticker. Group 11 fungicide. 4-hr reentry.
  • Insignia SC at 6 to 12 fl oz/100 gal water. Do not use with organosilicate-based adjuvants. Use preventively only. Group 11 fungicide. 12-hr reentry.
  • Orkestra at 8 to 10 fl oz/100 gal water. Group 7 + 11 fungicide. 12-hr reentry.

To control Rhizoctonia only:

  • Cleary’s 3336 EG at 8 oz/100 gal water as a drench after transplanting. High rates in combination with mancozeb may damage plants. Group 1 fungicide. 12-hr reentry.
  • Heritage at 0.2 to 1 oz/100 gal water plus a non-silicone-based wetter sticker. Group 11 fungicide. 4-hr reentry.
  • Medallion WDG at 1 to 2 oz/100 gal water. Use with oils or adjuvants may damage plant. Group 12 fungicide. 12-hr reentry.

To control Pythium and/or Phytophthora only:

  • Alude at 5 to 10 fl oz/100 gal water applied as a soil drench at a rate of 25 gal solution/100 sq ft. Use only once per month. Can also be used as a foliar spray at 26 to 54 fl oz /100 gal water at 14- to 21-day intervals. Group P7 fungicide. 4-hr reentry.
  • Fosphite at 1 to 2 quarts/100 gal water. Do not use copper products within 20 days of treatment and do not use spray adjuvants. Group P7 fungicide. 4-hr reentry.
  • Heritage at 0.2 to 1 oz/100 gal water plus a non-silicone-based wetter sticker. Group 11 fungicide. 4-hr reentry.
  • MetaStar 2E at 0.5 to 2 fl oz/100 gal water at transplanting, and see label for media incorporation. Group 4 fungicide. 48-hr reentry.
  • Subdue MAXX at 0.5 to 1 oz/100 gal water at transplanting. Group 4 fungicide. 48-hr reentry.

Notes: chlorothalonil inhibits root growth.

A healthy, blooming Thanksgiving cactus (Schlumbergera truncata). Source: Peter coxhead, W

In general, home gardeners do pretty well with Christmas cactus, both the real thing (Schlumbergera x buckleyi) and its close relative, Thanksgiving cactus (S. truncata), which I’ll call “seasonal cacti” in this article. (Read When your Christmas Cactus Blooms Too Early to know how to distinguish between the two.) In many homes, they come to bloom twice a year, in November/December and again in February/March. And they live for decades with only minimal care. But sometimes you start to notice that all isn’t right. The “leaves” (stem segments) go from shiny, green and plump to dull, thin, shriveled, soft and sometimes even reddish. What’s going on?

Not a Leaf in Sight

The flat growths on seasonal cactus are stems, not leaves. Source: Julie Weisenhorn. University of Minnesota.

Banish the word “leaf” from your vocabulary when thinking about seasonal cactus. They have no leaves at all or rather, no longer do. Way back when they sprouted as seedlings, and that can be 40 or more years ago, they did bear exactly two cotyledons (seed leaves), but ever since, they’ve been getting along strictly using their stems. The flattened green stem segments link together like a chain, eventually forming an arching, hanging plant and even later, turning brown and woody (at least the very oldest stems do). Being green, stem segments carry out photosynthesis like a leaf would and keep the plant fueled in energy. But still, stem segments just aren’t leaves.

Limp, shriveled segments show that this Christmas cactus is in serious trouble. Thughorse, garden.org

When stems become soft and shriveled, it’s essentially because they are thirsty: not enough moisture is reaching them. Logic would seem to suggest they simply need to be watered more, but that’s not necessarily the right thing to do.

Lack of Water or Too Much?

There are two main reasons why moisture fails to reach the stems, especially the last segments. Either the soil is too dry or the roots are damaged … and the latter can actually be caused by too much water!

If the Soil Is Too Dry

Seasonal cacti will often keep blooming even when they’re suffering from severe root damage. Source: zensero, home-design

If the soil is too dry, that’s easy enough to see or, at least, to feel. Touch it. Your fingers will easily feel the dryness. So, if dry soil is causing the shriveled stems, yes, watering is the obvious solution. Not just a light watering, but a deep, thorough watering, so that the whole root ball is thoroughly moistened.

Sometimes, when potting soil is very, very dry, it repels water, so when you water the plant, moisture no longer penetrates the soil, but runs off immediately into the saucer below. This is especially common in hanging baskets, which we tend to water more lightly than we should, fearing any surplus water will pour out of the saucer onto the floor. As a result, the poor plant never gets enough moisture and is constantly drought-stressed.

If that’s your diagnosis, don’t just water the plant, soak the root ball. Plunge the pot into a sink or pail water of tepid water and let it soak for 10 to 15 minutes. Then let it drain thoroughly. Once rehydrated, the soil will become water-receptive again and you can water normally in the future … unless you allow it to dry out too once again.

How Often Should I Water a Seasonal Cactus?

Water your seasonal cactus when the soil is dry to the touch. Source: homedepot.com

Seasonal cacti are not desert plants and don’t need to be kept dry like desert cacti. Although quite forgiving of irregular care, they do prefer “even moisture” throughout the year. Just follow the golden rule of watering: water deeply, enough to moisten the entire root ball, then allow the soil to dry before watering again. It works every time!

When Soil Remains Wet

If your plant shows shriveled stems, but the soil is still moist to the touch, it’s obvious the problem is not related to underwatering. The situation is, in fact, much more serious. This occurs when the roots are dead or dying!

There are many reasons why the roots can be in such bad shape. Here are the two main ones.

  • Soil kept too moist. If the potting mix is constantly wet, oxygen can’t reach the roots which, unable to breathe, start to die. Then root rot sets in. This is a disease caused by various pathogens—Pythium, Phytophthora, Rhizoctonia, Fusarium, etc.—whose spores lie dormant in most soils, ready to spring into action whenever root cells start to suffer. The disease then spreads from the dying roots to living ones, killing them in turn. Obviously, without roots or with fewer roots, the plant can no longer correctly hydrate itself, even if the soil is soaking in moisture, and its stems begin to shrivel. It reminds me of The Rime of the Ancient Mariner: “water, water everywhere, nor any drop to drink!”
  • Mineral salt buildup. Over time, usually over several to many years, salts accumulate in any houseplant’s potting soil. They’re present in small quantities in the water you apply and in even greater quantities in fertilizer. When they increase too much, there comes a point where the soil contains more salts than do the roots. Water will then flow from the plant into the surrounding soil to dilute the concentration (this is called osmosis) rather than from the soil into the plant. As a result, the roots lack water and start to die. Often, the accumulation of salts in the soil is accompanied by a whitish or yellowish crust on the rim of the pot or even on the stem of the plant. Epiphytic plants such as seasonal cactus are especially susceptible to mineral salt damage.

Change the Soil to Save Your Plants

If you suspect that mineral salt buildup is causing the problem, the easiest solution is to repot.

Repotting will help this shriveled Christmas cactus recuperate. Source: Zanes Wildflora

Unpot the plant and remove as much of the old soil as you can. If the roots are rotten (they’ll smell like rotten potatoes), prune them off. Prune out any rotting stems as well. Now repot into a clean pot (with drainage holes, of course). Note it need not be a larger pot. In fact, if the plant has lost roots, it’s often best to repot it into a somewhat smaller one. Any potting mix that drains well (houseplant soil, cactus soil, orchid mix, etc.) will be suitable.

Water well to moisten the soil initially, then modestly for the coming months, only when the soil is dry to the touch. Usually, the plant will readily produce new roots when given fresh potting soil and its health will begin to improve. Still, you have to be patient: it may take several months before you see a clear improvement.

Take a Few Cuttings

Also, whenever a seasonal cactus is looking a bit off, it’s always wise to take cuttings in case you fail to revive the original plant.

Take backup cuttings of wilting seasonal cacti. Source: laventanadejaviruli.blogspot.ca

For best results, choose stems with at least three segments (four or five would be even better). To remove them, twist the stems rather than cut them: they will separate quite naturally at the base of a segment.

Insert the cuttings into a small pot of slightly moist potting soil, completely covering the lower segment in mix. Keep the mix slightly moist until new growth appears and that can take several months.

Backup Plants

One of the reasons I suggest combining taking cuttings together with any other rescue method for a declining seasonal cactus is that sometimes very old specimens don’t respond well to repotting, even when you’re doing it to save their life. They seem stuck on their old ways and prefer to die slowly rather than accept a change for the better … like some older humans, by the way. The cuttings thus become your “backups.”

Good luck saving your Christmas and Thanksgiving cacti!

10 Facts About Christmas Cacti

If you’re lucky, you could receive a Christmas cactus as a gift this holiday season. This common house plant blooms during the Christmas season, but its long green arms are attractive throughout the year. With cultivars in a rainbow of colors, it is a plant worthy of appreciation. These 10 facts about Christmas cacti will help you to care for your plant if you’re given one this holiday season.

1. It’s called a “cactus”, but thrives in cool temperatures. Christmas cacti need to be kept away from heat sources. Purdue University Extension Service, states that a Christmas cactus will blossom longer when exposed to only cool temperatures. For best results, put your Christmas cactus in a cool place — away from heaters and fireplaces — without frequent drafts. Big changes in temperature can cause the cactus blossoms to drop before they open. Optimal temperature for Christmas cacti is 68 degrees F.

2. Christmas cacti need light to bloom. According to Purdue University Extension, keeping your Christmas cactus plants in a sunny location indoors is the key to prolonged blooms. However, if you move them outside during the summer, you’ll have the most success with a partially shaded location, as too much direct light can burn the leaves.

3. The Christmas cactus is native to Brazil. These epiphytes (a plant that grows on top of another plant non-parasitically) are at home in the Brazilian rain forest, among tree branches, discloses Clemson University Cooperative Extension. Since they are tropical plants, they thrive in humid conditions.

4. Christmas cacti need their beauty sleep. The horticulture experts at the Cheyenne Botanic Gardens recommend setting your Christmas cactus in a room where you never turn the lights on at night. In order for the flower buds to set, Christmas cacti need 14 hours or more of continuous darkness per day. However, after the flower buds have set, the plants can withstand light at night.

5. Unlike the other Christmas favorite, Poinsettia, Christmas cactus is not toxic to dogs and cats. Poinsettia is famously poisonous to dogs and cats. However, the ASPCA, reassures that if Fido or Fluffy nibbles on a Christmas cactus, she should not experience irritation or vomiting like she would from the sap of the Poinsettia.

6. Christmas cactus can live for 20 to 30 years. Can you imagine passing a living, flowering plant on to your children or grandchildren? The Old Farmer’s Almanac tells us Christmas cacti can live for 20- 30 years when properly cared for. If you provide long nights starting around October 1, you can force the Christmas cactus to bloom year after year. Cool night temperatures also encourage it to bloom.

7. Overwatering will kill Christmas cacti, but they like to be misted on a daily basis. An Oregon State University Extension Service horticulturist recommends watering a Christmas cactus only when the soil is dry to the touch. Instead, gardening expert and radio host Walter Reeves, the Georgia Gardener, suggests misting the leaves of the Christmas cactus daily, to maintain the desired level of humidity around the plant.

8. 5 diseases commonly infect Christmas cactus. Penn State University Extension experts provide a handy fact sheet outlining the plant diseases that most often affect Christmas cacti. Their list includes basal stem rot, botrytis blight, impatiens necrotic spot virus, phytophthora root rot, and pythium root rot.

9. Fungus gnats, flower thrips, and root mealybugs are the pests that most often infest Christmas cacti. Avoid overwatering, the biggest culprit in attracting pests to Christmas cacti. Preventive care, such as discarding infested plants, is another recommended tactic. Pesticides are available for commercial growers, though home gardeners may not be able to get their hands on them.

10. By the way, that Christmas cactus you are buying is probably not actually a Christmas cactus. Surprise! According to U-Mass Extension Service, “Most commercial cultivars of holiday cactus are actually Schlumbergera truncata, commonly known as Thanksgiving cactus or Zygocactus. True Christmas cactus is an interspecific hybrid of Schlumbergera truncata and Schlumbergera russelliana that originated about 150 years ago in England. It’s a common houseplant but not often grown commercially.”

For expert advice on plant care and selection, consult a qualified landscaper.

Updated December 27, 2018.

Disease in Christmas cactus

I have many holiday cactus of many types, including several generations of plants I have grown from seed so I really am looking to solve this problem in my plants!
To begin with: I have a jade plant that began to occasionally develop discolored leaves that would drop off. I did not think too much of it. Then one of my two true Christmas cacti (grown from cuttings of plants that have been in the family for generations) began to develop similar symptoms. Some of the smaller branches would develop a pale pink or white color to the base of the segments and then would eventually drop off. This plant is now almost dead as more and more branches have discolored and then dropped off. These sections do not look wilted, moldy, rotten, ect. They simply drop off.
It seems to be spreading which has me very worried. The other Christmas cactus has many discolored branches and a few have dropped off, and some of my other plants have discolored branches but are not losing any branches yet.
I cannot figure out what is going on to make these apparently healthy plants suddenly die back like this. These is no obvious fungus, no stem or root rot, no insects as far as I can tell (I even looked them over with a magnifying glass). The plants are in the same spot and cared for the same as usual, they have been healthy and good bloomers there for a long time.
The pictures are
1) jade plant leaves – the top one is a diseased leaf that fell off, the bottom one is a healthy leaf I picked
2) A Christmas cactus branch that fell off showing the discoloration on the base of each segment
3) An old picture of this Christmas cactus in bloom – thats what it looks like healthy\
Thank you for any help!
Oh and I almost forgot – the jade plant did have a problem with mealybugs a few years back which I treated with insecticidal soap and which I am pretty sure was cured. I don’t see any actual signs of mealybugs on any of the plants now.

Q. A few of my Christmas cactuses get white, scaly stuff every summer. What is it, and how can I eliminate it?

A. Those are scale insects, and they can kill cactuses of all types.

Because Christmas cactus doesn’t have spines, you have the advantage of being able wipe off the insects with cotton swabs dipped in rubbing alcohol. For other cactus, use a systemic insecticide that is labeled for scale on cactus.

Q. I planted three American beautyberries next to my house last fall. They were all doing well, but about two weeks ago, one of them started drooping. Now it looks dead.

I can’t find anything online about any particular insects or diseases. Where should I turn? Can I plant another one where this one died?

A. I’ve grown American beautyberries for 40 years, and I grew up with them all around me in the woods in Brazos County. As you hinted, I have never seen an insect or disease bother this plant.

The plant in your photo either got broken by a hose being pulled over it, etc., or it got way too dry, if only one time.

I would see no problem in replanting with another.

Q. We have a healthy live oak tree that was fully grown when we moved here 45 years ago. Because of rain, erosion and time, its roots have become exposed. Would it damage the tree if we put black plastic to control growth of weeds and grass about 3 feet around the tree, then covered the plastic with rocks?

A. The exposed roots likely have nothing to do with rain or erosion.

Live oak roots are always quite the soil surface. As the trees get older, the roots grow up and out of the soil farther and farther. It’s all just part of the majesty of the trees.

Plastic probably wouldn’t hurt in a limited area, but you could just as easily (and a lot more tidily) apply a glyphosate-only herbicide to kill the weeds, then mow. More grass won’t grow up through the river rock or other decorative stone you would use to cover the soil.

Q. What would cause my marigolds to have beautifully green leaves but almost no flowers?

A. Shade is the likely culprit. They must have full sunlight.

The other possibility would be if you have allowed seeds to fall to the ground, you might have some inbred plants (not the original hybrids) that are slow to come into flower.

Q. A local lawn service treated my St. Augustine for brown patch and gray leaf spot. They told me to apply a quarter-inch of peat moss or compost. What should I do and when? How much should I apply?

A. That’s an unusual batch of information. First, brown patch is a fall disease that causes the blades to die at their bases. It won’t show up in hot weather.

Chinch bug damage leaves large brown patches in summer. They’re always in full, hot sun, and you can see the black bugs in the dying grass. An insecticide will eliminate them.

Gray leaf spot is a summer fungus that causes gray/brown lesions on the leaf blades and runners, but peat moss won’t help it. Discontinue nitrogen applications until September to lessen it. Nitrogen causes it to accelerate.

Peat moss is applied in April or May to stop the take-all root rot fungus. TARR is not active in summer. You will need a 1-inch layer of peat if you find that disease.

Q. I need a low-maintenance evergreen screen for 33 feet along our property line. Its maximum height should be 6 to 7 feet, width no more than 4 feet. Hopefully it will be fast-growing. I prefer nonthorny.

A. The 4-foot width is the difficult part of all that, because that means it needs to be somewhat upright. That would rule out great plants such as Sea Green juniper, glossy abelia and the fairly uncommon but very pretty Italian jasmine.

Willowleaf holly is probably the best option. It will grow taller than 7 feet, but not by much, so pruning is possible.

Dwarf Burford holly would fit perfectly into the size range, but it is slower to mature. You always could start with larger plants.

Regular nandina (the old-fashioned heavenly bamboo) would be good, although you would want to prune out the tallest canes to the ground each winter so new, vigorous canes would regrow. That keeps the plants from becoming leggy.

Q. Why is my live oak shedding gobs of leaves now?

A. Many trees are doing that. They produced tons of leaves following the cool, wet weather this spring. Once it started to turn hot and dry, they couldn’t sustain all that growth, so they started dropping those leaves.

Leave a Reply

Your email address will not be published. Required fields are marked *