Epi hybrid Plant & Photo: Bev and Kermit Bender, USA

Epiphyllums (type Epiphyllum phyllanthus) are epiphytic cacti with flattened leaf-like stems and large white flowers that open at night. Outer petals usually have some color, usually yellow. You may read elsewhere that one Epiphyllum species, E. ackermannii, produces red flowers but that is no longer correct since E. ackermannii has been transferred to the genus Disocactus.

More familiar in collections are the many epis with fantastic colorful flowers which bloom during the day. In the past these have been referred to as Epiphyllum hybrids. In fact these hybrids rarely involve species of Epiphyllum as a parent. They are mostly hybrids of related genera such as Disocactus, Pseudorhipsalis and Selenicereus.

Some have suggested the hybrid epis with colorful flowers should have a name of their own. Nothing has ever been officially decided about that so until a formal name is decided upon, hobbyists and growers alike continue to call them Epiphyllum hybrids .. epis for short.

Epis are frequently referred to as Orchid Cactus. This is not correct since Orchid Cactus are not epiphyllums at all but rather they are found in Schlumbergera or Disocactus which are closely related genera.

While the night blooming white flowered epis are beautiful, people tend to more often grow the hybrids since flower colors are stunning in many shades of pink, red, orange, violet, yellow, etc. It is also more convenient to have day flowering species so one can enjoy the flowers for a longer period of time during daylight. Unless of course you don't mind staying up all night to view the white flowers of night blooming species.

The following are answers to questions I have been asked over the years along with some growing advice which I hope will be helpful.

Why are they called epiphytes?
Plants which in nature grow on other plants are called epiphytes. In the case of epis, the 'host' plants (trees on which epis grow in nature) are used only for support and not as a source of food to the epis.
The word 'epiphyte' is derived from Greek word meaning 'upon a leaf' because when the flowers appear we see them 'on' the 'leaves'. This is misleading because technically epis have stems-not leaves.

How can I know a plant is an Epi when I see it?
Epis usually have flat leaf-like stems (although in some hybrids the stems are 3 angled). In mature plants the stems can be 18 inches to 30 inches long (45cm to 75 cm) and their general habit is to grow new stems from the base of the plant. There are exceptions where a new stem will develop somewhere along an old stem. This will usually happen if the growing tip of an old stem has been damaged or if indiscriminate pruning is done.

Note: It is wise to discourage new stem growth from along the older stems. If you allow them to grow you will soon have a tangled mess of a plant which will need much pruning and when that happens it will leave the plant with a lot of very unattractive, scarred stems. If you nip off the new growth that appears along the stems, as soon as it appears, it will leave a far less serious mark than if you allow the new stem to grow and have to cut it off later.

The average width of the stems at the widest part is usually between 2 and 4 in (5 and 10 cm). There are a few which are narrower than that.
Along the edges of the stems are usually indentations which may be shallow or deep. The shape and depth of some of these indentations adds lots of interest to the overall appearance of the plants. Areoles (little furry tufts out of which the spines grow) can be found along these indentations.
Flowers (often very large) with long tubes are produced at the areoles. A few hybrids have smaller flowers which are no less beautiful than the larger ones.

Where do Epis come from and what is their natural habitat like?
Epis originate from tropical forests of Mexico, Central and South America and the West Indies. Most grow in trees where they tuck their roots into pockets of decaying vegetable matter which settle into nooks and crannies of tree branches. A few Epis may be found lower down near often rocky ground where their roots find their way into rocky crevices where also is found composted dead remains of surrounding vegetation.
Their tropical environment provides them with lots of warmth and high humidity and most important .. shading from full sun. Other plants that can be found growing in the same habitat are orchids, bromeliads, ferns and mosses.

Why do some stems put out long stringy things and others do not? Should I cut them off?
Those long stringy things are adventitious roots! Do not cut them off. It is quite natural for many epis to produce these roots. If they appear in large numbers, however, this may signal problems exist such as perhaps the plants may be too moist, too dry or in too much shade. The adventitious roots could be reaching for the moisture, light and even food that the plant is not receiving in sufficient quantities through watering, natural light and fertilizer.
When these adventitious roots appear, you should ask yourself if you are giving the plants enough water and/or fertilizer, if there is enough humidity around the plants and perhaps you should check the soil in the pot for signs of pest infestation which might be damaging the roots. Also, although I will tell you later that these plants do better if a little pot-bound, it is just as possible to underpot the plants which can also force roots to be produced along the stems.

Are epis daytime or night-time flowering?
True Epiphyllum species flower at night. Hybrids flower during the day.

When do they flower?
Most hybrids bloom anywhere from about the end of February through April, May and June. A few hybrids bloom later than that as do the true Epiphyllum species.

Are flowers on all Epis the same shape?
No. They are not the same shape. The different shapes of flowers are described as wide, bell-shaped, funnel-form, cup-shaped and irregular. The arrangement of the outer petals and their number are described as:

• Wheel-shaped (with few radiating narrow petals)
• Overlapping with 15 to 20 petals overlapping in two circular rows
• Thick with 5 to 25 petals giving an appearance of three or more rows
• Loose with the petals irregular and not symmetrical. They may be single or overlapping, ribbony or twisting and with textures described as transparent, waxy or shiny, iridescent or with a sheen.
• The edges may be smooth, finely serrated and wavy or crepe-like. Inner petals can be wheel-shaped, overlapping, double and single loose.
• The shape of petals can be narrow, oblanceolate (narrow and tapering to a point), obovate (oval with narrow base), spatulate (spoon-shaped), elliptic (oblong with both ends narrowing down).

How long do the flowers last?
Flowers of most plants last about two days in hot weather and longer in cool weather.

What is bud drop?
When flower buds do not mature but instead drop off the plant, this is called bud drop. This can happen naturally if the plant produces more buds than it can reasonably handle. If the plants drop an awful lot of buds then something is wrong with growing conditions. The first thing to suspect is too much heat around the plant.
Bud drop can also occur if you move the plants too soon after buds begin to form such as taking the plant from the greenhouse into the house-especially if the house is a lot warmer than the greenhouse. To minimize the risk of bud drop, wait to move the plant until buds are well formed. Note I said 'minimize the risk' because it is always better not to move a plant from a location where it has been happy for some time.

Can I preserve the flowers?
If you want to keep a flower beautiful for a special occasion, place an epi flower in a sealed jar and put it in the refrigerator. The flower will often stay fresh for up to one month.

Do the flowers have a fragrance?
Some species have flowers with a fragrance. It is most noticeable in late evening or early morning when the temperature is coolish rather than warm.

What do I do when flower buds form?
When buds begin to show, plants are best kept at a minimum temperature of 50F (10C). It is important to note that too much heat at this time can hinder flowering and even cause the flowers buds to abort. A temperature of around 65F (15C)
Epis should now be in a very bright situation, preferably with some filtered sun and given plenty of water.
On a bright, warm day a light misting with warmish water will be appreciated. It takes a lot of energy for a plant to bloom so when the buds turn into blooms, the plant should be fertilized.

What do I do after the plants have finished flowering?
Do not be tempted to 'twist off' the remains of flowers. Let the flowers dry up and then cut them off with a knife. Don't cut them off too soon. If you wait a while you will see if fruit is going to form. It is interesting to let the fruit develop just to see what it looks like if you haven't seen one before. If you remove the fruit, don't twist it off. Also cut it off with a sharp knife.
Because plants flower at different times, it is impossible to say which month or months in the year when all epis may want to rest. It stands to reason that an Epi that produces an abundance of flowers will have exhausted itself in the process and may decide to have a rest once flowering is over. On the other hand some plants begin to put on new growth right after flowering. Since plants are living things with minds of their own, while we can develop a schedule of sorts for them, we cannot perfectly predict what any plant will do. Regular observation of a plant's condition and growing habits will tell us what the plant needs, when those needs should be met and whether or not it wants to rest.

Should I ever prune epis and how do I do that?
Pruning or cutting back should not be necessary. Healthy branches will produce flowers for several years. However, if the areoles along a stem look dead or lifeless or a stem has become unsightly for some reason, it is better to remove that stem. Always remove it from the base of the plant. Never cut half a stem off since the half left on the plant will produce new shoots usually near the cut end and eventually ruin the overall appearance of the plant. New growth should always be encouraged from the bottom of the plant for best appearance.

Potting: What pots should they be planted in and what size?
The use of plastic pots rather than clay pots helps to keep the soil cool and moist which epis enjoy. An added advantage to plastic pots is that roots don't stick to the inside of plastic pots as they do to the insides of clay pots which can result in many broken roots when re-potting. This is important since epis don't like to have their roots disturbed too much when being re-potted.
As mentioned earlier, epis in their natural habitat put down their roots into smallish pockets of decaying material. They should therefore never be grown in pots bigger than they need to be comfortable. They are happier if slightly under-potted. Being a little root-bound appears to encourage better flowering. At the other extreme if the pot is much too small the plant may stop growing. Potting on to the next size pot should only be necessary every two or three years.
After re-potting, do not water for a week or so to give any injured roots a chance to heal.
Plants with a pendant habit are suitable for hanging baskets. As stems grow they fall over the sides of the pot. When hanging these up in the greenhouse keep in mind the plants do not like high heat and full sunshine which is often found high up in a greenhouse. If you must hang the plants there make sure enough shading is provided.
On the greenhouse bench, you can reduce the space needed for each plant by using a small fan type trellis (or other type support) inserted into the soil in the pot at the back of the plant. Stems are then placed upright against the trellis and secured to it with a piece of soft material such as the stretchy tape used for tying up outdoor garden plants. For added stability the trellis can be screwed to the plastic pot. It is obviously easier to do this before you put a plant in its pot .. but it can also be done without disturbing a plant by simply screwing the support on the outside of the pot. It is probably better to do that with any plant that is well established as you don't want to risk injuring roots by pushing the trellis down into the soil. Epis have a shallow and fibrous root system which is easily damaged.

Soil: What soil should I use?
The soil for Epis must contain some organic matter. It needs to have a slightly acidic reaction. Leafmold is the best organic matter to use and oak leafmold the very best of all. A little well aged manure is also helpful. If you don't have access to these types of organic matter, the addition of horticultural peat to a good, sterilized houseplant potting soil will fit the bill. Coarse sand or grit must be added to this for drainage.
If you plan to use compost in the soil mix - remember that a little goes a long way.
Never use ordinary outdoor garden soil. There is too big a risk of introducing bugs and other problems which can attack epi roots causing serious damage. In any case most outdoor garden soil is far too heavy for any houseplants even with the addition of products to lighten its weight.

Can you suggest a basic mix?
A basic mix might be:

• 50% sterilized houseplant potting soil low in peat. If it is high in peat depending on how peaty the soil is you may not need to add more organic matter.
• 30% organic matter (leafmold, compost, peat)
• 20% Coarse sand or grit or horticultural perlite to encourage drainage. I personally won't use perlite because eventually it washes up to the top of the soil. I use No. 2 chicken grit.
• A big helping of common sense**
• A little bonemeal is optional.

What about watering?
Epis should never be allowed to totally dry out. On the other hand they will rot at the roots if the soil is always soaking wet. After thorough watering, excess water must drain off quickly through the pot drainage holes so the soil is left moist and not soaking wet. Yes, there is a difference between soaking wet and moist. I always use the comparison of a sponge that has been soaked (soaking wet) to one that has been wrung out (left moist) to explain the difference. If the water drains out of the soil well, it is left moist. If it doesn't drain well the soil will be soaking wet.

How much light do these plants need?
When sun reaches Epis in their natural environment, it is filtered down to them through the branches and leaves of the trees. They are never subjected to full sun. However, it is interesting to note that plants growing in very dense trees will be found growing high up in the trees where more light is available to them than would be available further down the tree. This tells us that while epis don't want full sun, they nevertheless need very bright light. In fact, if an epi is grown in too much shade, flowering will be poor or the plant may not flower at all. When you see recommendations for growing Epis in the shade, therefore, this does not mean you should put the plants in a dark area under the greenhouse bench.

Can I grow epis under Artificial Light?
Yes. Epis can be grown successfully under grow lights. The plants should be positioned so that the lights are about 12 inches above the tallest stems. Lights should be kept on for the same length of time as natural daylight occurs out of doors, changing with the seasons of the year. More on this a little later.
If you grow the plants under lights, it will do them the world of good if you put them in a shady spot outside in late spring and summer to enjoy the fresh air and natural light for at least a few months of the year. To minimize infesting the plants with outdoor pests, don't put the plants on the ground but rather put them on a bench or a table well away from outdoor soil. More on the outdoor situation later.

What Temperature, Humidity and Ventilation do epis need?
Epis do well in temperatures between 45 and 70F. They run a high risk of damage if the temperature drops below 40F. If it goes higher than 70F some humidity must be provided by misting and/or keeping a container of water nearby which evaporates into the air adding humidity around the plants. 50% humidity is best but the plants will tolerate less than that for a while.
Ventilation is important. Don't ever cram the plants together, even for the winter months, so that air cannot circulate in and around the stems. If air cannot circulate freely you will be creating a good breeding ground for fungal infection.

Should I put epis outside in spring and summer?
Where should they go in winter months?
Epis benefit greatly by being put out of doors in a shady place in spring and summer. The heat in a greenhouse can become too much for them in the middle of summer. If grown in the house, a period out of doors is a good idea so that the plants can have some much needed fresh air. That being said .. it is often reported that once plants are put outside they encounter all sorts of problems such as spots on the stems, rotting stems, etc. While it may he handy to hang the plants from tree branches, that is where I believe the problems occur. Outdoor trees and their leaves often have all sorts of problems such as bug infestations, fungi, etc. which transfer down to the epis hanging there. I recommend not to hang the plants from trees in your yard but rather put them in a place well away from other overhanging outdoor plantings. Do not put the plants on the bare ground which invites a host of creatures to invade the pots through the drainage holes. Slugs in find epis a tasty treat!
You should also provide some rain protection so that you can continue to control the amount of water the plants receive. An unexpected dump of rain for several days could be too much for the soil in the pots to handle and rotting roots could result. If your rain water is fairly pure, however, an occasional rain watering is beneficial.
If you must grow the plants in a heated house in winter, put them in the coolest room of the house where they receive natural daylight and no artificial light after sundown. A cool period in winter along with long, dark nights not interrupted by artificial lighting will (in my own experience) encourage flower buds to form.

How much water do they require?
Unlike many other cacti, the biggest danger to epis is under watering them. Established plants should never be allowed to dry out completely. When you water the plants, water them thoroughly so that the water flows freely out through the drainage holes. Allow the soil mix to almost dry out before watering again. If you don't have a water meter to check moisture in the soil, do as I do. Go out into the garden and find a flat stone to place on top of the soil in each pot. Every few days lift the stone. If there is moisture under the stone you do not need to water. If the spot is dry, it is time to water thoroughly again.
If plants are grown in the home where there is winter heating, extra care is needed to see that the roots don't totally dry out. Sometimes in winter we tend to forget about our plants because they are resting and not performing. It is really not good to keep the plants through winter in a hot room in the house but if you have no cool room in which to put them near a bright window, make sure the roots don't go dry or the plants will either be damaged or set back and the next season's flowering will either be poor or totally curtailed.
The ideal over-wintering of these plants is in a cool greenhouse at around (45-50F). Here they may go through an entire winter on only one or two waterings and misting is not required except on a sunny day when sun warms the greenhouse. Cooler temperatures along with reduced light intensity (compared to spring and summer) and shorter days all mean the soil will not dry out nearly as fast as it does in spring and summer.

What do I do about fertilizing?
If you have just repotted a plant into fresh soil mix and the mix is adequate as outlined earlier, you don't have to add fertilizer for about 6 months. After that ...
From early spring through fall months, feed the plants at least once a month with a balanced houseplant fertilizer (20-20-20 is fine) with trace elements - taking care to dilute the fertilizer to one quarter the recommended strength. Diluting the fertilizer will ensure you are not feeding the plants with too much nitrogen which you would be doing if you mixed it at full strength. Too much nitrogen will encourage growth of stems at the expense of flowers.
Do not fertilize your plants in late fall and winter months.
Do not fertilize plants that are sickly.
I prefer to use a liquid fertilizer for all my plants rather than a granular one because a liquid fertilizer will immediately mix well with the water and be readily available to the plants' roots. Some recommend using a bloom booster fertilizer a few weeks before flowering, also at quarter strength.

When do the plants actively grow?
Epis begin active growth in later winter or spring and many put on new growth in early fall. Then there are my own plants which often put out new shoots in the middle of winter! As I said before, we can set a schedule but the plants do what they want to do when they want to do it and not when we think they should.
In nature a resting period is brought about by a long dry spell or cold period and during these conditions growth stops. It follows therefore that if there is a period of cooler weather or short days and colder weather, it is important not to try to stimulate growth. Let the plants rest through that period as they would in nature. That means water only enough to prevent the roots from drying out and do not fertilize.

How do I get seeds from my own plants?
True species come true from seed. Epi hybrids do not. For hybrids, only cuttings will produce a duplicate of the original plant.
To get true seed a flower must be pollinated with pollen from another individual of the same species. If all the plants in your collection came from cuttings of the same plant, which means they are all part of the same individual, there is no point trying to pollinate the flowers.
The procedure is simple. The ripe stigma is liberally dusted with pollen from a freshly opened flower. The trick is to know when the stigma is ripe. Sometimes the stigma is ripe and receptive when petals collapse and it is left sticking out of the faded flower and sometimes it can even be ripe before the buds open. If the pollen 'takes' the ovary remains green and attached to the plant after the rest of the flower fades. If it doesn't take, the entire flower fades and eventually drops off.

Tell me about fruits and seeds
If plants are growing in a greenhouse many flowers will be pollinated by bees and fruits will form on the stems as a result. One fruit is produced per areole. Fruit will only mature if the seed has been fertilized. If it is not fertilized the partially developed fruit will fall off.
There is a wide variety of color, surface texture, spines and flavor of epi fruits. Yes, the fruits are edible. Although I must warn you if you are tempted to taste them that some fruits have a very unpleasant, acrid taste. On average fruits take about a year to ripen. Some ripen much earlier and some later. When the fruit is ripe the color usually changes to red but sometimes also to yellow. A few varieties remain green. The best way to determine if a fruit is ripe is by feeling it. When it becomes slightly soft it is ripe.
If you plan to sow the seeds, try to be patient if you are waiting for a fruit to ripen because seeds from pods that are not ripe will take a very long time to germinate .. if ever. Seeds of epis are often disappointing in their low rate of germination which is another good reason to propagate from cuttings.
When the pods are cut open you will see shiny black seeds embedded in a soft pulp. Seeds and pulp are removed from the fruit. There is no really quick way to separate the two. Try putting both in a jar of water and let them soak overnight. The water will separate much of the pulp from the seeds. Next day drain off the water and spread the seeds on a piece of kitchen paper towelling. Let them dry in a warm place. Seeds can then easily be flicked off the paper into a container. Most if not all of the dried pulp will remain stuck to the paper. Do not try this on Kleenex from which, for some reason, the seeds and pulp refuse to let go.
When sowing seeds, strong light promotes germination. Sow the seeds on the surface of the soil. Do not cover them. If you cover the seeds with soil they could take up to two or three years to germinate, if ever! Germination should happen in three to five weeks.

How do I take stem cuttings?
Cuttings are best taken in spring and summer. They may root at other times but rooting is not as good or as fast as in warmer weather and in fall and winter you run a bigger risk of the cuttings rotting.
Cuttings of newer growth usually root faster than cuttings of much older stems. Cuttings of complete stems make the best cuttings although smaller section cuttings will also root.
Sever the stem from the plant. Then take another cut on the bottom of the cutting to about a 1/8 inch below an areole. Allow the cutting to dry and callous over well for about two weeks and then insert into a pot of mix pushing it down about a half inch into the soil.
If the cutting rots, take it out of the soil and make another cut to healthy tissue again just below an areole and try again.
Cuttings may be dipped in rooting hormone powder but I have tried cuttings with and without rooting hormone and I have found no advantage to using the powder. Others may have a different experience. If you do use rooting hormone powder, be aware that you must dust off all the excess because according to the manufacturers of these products, too much rooting hormone will actually inhibit rooting.
If it happens you have a cutting that keeps rotting all the way to the growing tip of the stem, believe it or not you can root the small cutting that's left - upside down! It will take a lot longer for the upside down cutting to grow and produce new shoots but eventually it will and the new shoots will grow the right way up.
Do not take stem cuttings immediately after flowering because this is when the plants have spent a lot of energy on flowering. Give them time to recoup that energy and wait to take cuttings for two or three weeks after flowering has finished.
Cuttings can take anywhere from three to six weeks to root. During the time the cuttings should be kept in a warm, bright, humid place.
When taking cuttings to begin new plants, don't brandish the knife carelessly. Trim the plant with a view to keeping its appearance unspoiled. Don't take so many cuttings that you have only a sad skeleton of the plant left. You can prune a plant to death if you are not careful.
All cuttings should be staked to avoid the need to push the cutting too much into the soil where moisture can cause rot. The stake should be removed as soon as the roots are sufficient to take the weight of the cutting and support it.
Another way to root a stem is to take a stem with adventitious roots (while leaving it on the plant) and pin it down into another pot of soil. The roots will go down into the soil. The stem can be severed from the main plant when roots have sufficiently established themselves in the soil so as to support the new plant.
You should label every cutting. If you are taking multiple cuttings you can easily forget which plant had which color flower. To save time while propagating from cuttings, you can write on the stem itself with a ball point pen (careful not to press too hard to break the skin) and this will last quite a long time. Then when you have more time you can write out proper labels and insert them in each pot.
Larger plants can be divided by splitting the plant root system down the middle into two pieces with roots on each plant portion. Allow the two separated plants to dry for a couple of days before potting up and then don't water for about two weeks. During this time keep the plant in a cool, shady place to prevent the roots drying out too much before watering is started again. If weather is very hot, mist the stems to provide humidity.

Can I graft epis?
Yes you can. Grafting can be used to create an interesting standard plant by grafting epi stem cuttings on to a tall growing columnar cactus. The result is a fountain of epi stems cascading over the top of the columnar cactus. Opuntias and selenicerei are often suggested as good stocks for epis. Selenicerei are especially recommended for grafting epi seedlings. Stocks are the plants onto which we graft other plants. The plants we graft on to the stocks are called scions.
As soon as seedlings are big enough to handle they are big enough to graft. For Selenicereus and other stocks, cut the tip off the stock and place the seedling, after cutting off its own base, on to the stock. There should be no need for weights as the seedling should stick to the stock without pressure. For more on cactus grafting in general (too long to go into here) see our how-to booklet entitled Cactus Grafting Made Easy.

What pests do I look out for on epis?
Mealy bug, scale and fungus gnats are the worst culprits. Slugs love epis if plants are left out of doors.
Mealy bug are whitish insects that leave a cottony residue. These can be removed by hand if you find only a few. They can also be controlled by spraying the stems with an insecticidal soap. I find this a drawback because unless thoroughly washed off later, it leaves a sticky residue. I prefer to use a spray of water to which I add a couple of tablespoons of isopropyl alcohol. The alcohol dissipates quickly without harm to the plant but kills off the pests it touches.

Never spray the stems of epis with insecticides which can damage the stems and/or kill the plants.
If mealy bugs are on the stems chances are they are also in the soil mix. It is best to knock the plant out of its pot to check to see if the bugs are present in the soil. If they are you will see masses of white whispy stuff like cotton wool adhering to the soil and sometimes to the insides and bottom of the pot.
If you find mealy bugs in the soil try a soak with soapy water which often kills the bugs or if the infestation is really bad, I'm afraid you have to unpot, remove as much soil from the roots as possible, wash the roots and the plant under warm soapy water, rinse well with warm water and repot into fresh soil mix. Sterilize the old pot so that no trace of bugs can transfer to the next plant you put in it. Epi roots will not appreciate this treatment but the pests can cause far more damage if not dealt with.
Scale are small round usually tan colored insects which hide under a hard shell. These can easily be removed by hand if caught in their early stages. These too can be treated with insecticidal soap and sometimes the isopropyl alcohol treatment will work on them too.
If you summer your plants in the garden, remember that slugs love epis and can do tremendous damage in a very short time. Do not put the plants on the ground giving slugs easy access not to mention other garden pests which might be very difficult to get rid of.
Fungus gnats are real pests and are attracted by the moist organic matter in the soil. You must get rid of these or they will spread to all your plants. Add a little insecticidal soap to the water when you do a thorough watering through the soil. I have found adding a little isopropyl alcohol to the water helps deter them too. Do not overdo the addition of peat or other organic matter to the soil which attracts these gnats. A top dressing of small grit over the soil helps to deter these unwanted pests.

Are there any other problems with these plants?
Yes. Here are a few and I hope you never encounter them!

Fungus and bacteria
Epi hybrids seem subject to a number of fungal and bacterial diseases sometimes showing up as black rot. Not much is known about why this happens or how to cure the problem. Infected plants should be destroyed at once before the problem(s) spreads to other plants. The best control is to give your plants the growing conditions they prefer and to make sure the areas where they grow are really well ventilated. The addition of a small fan in a greenhouse can work wonders. Don't, however, aim the fan at the plants. Drafts and chills should be avoided.

Spots or Holes on Stems
Spots on stems or holes in them can sometimes appear. These are usually due to a drastic difference in temperature from day time to night time with rapid cooling in the evening. The plants and flowers are not really affected by these problems. You cannot avoid the occasional spot or hole unless you can provide a perfectly controlled environment and most of us just cannot do that.
Some spots may appear on stems which have come into contact with spines on other cacti or other Epis. These are harmless. They just ruin the look of the stems. It is wise to keep your epis from coming in contact with other plants with spines or thorns. And of course avoid having them so close together that they tend to puncture each other.
Sunken spots on stems creating a mottled effect may be caused by improper feeding or forcing by too strong fertilizers.

Sunburn
Plants that have had too much sun will take on a yellow look. If moved to a shadier place they should regain their green color in time.
A bad sunburn may not kill the plant but will scar the stems permanently.

Withered Stems
A stem will wither when it has literally almost flowered itself to death. After a rest period and attention to watering, the stem may return to normal. If it doesn't, remove it.

Dieback
If stems die back it is a sign that either the root system is damaged or the plant is not getting enough food either from spent soil or from lack of proper fertilizing.

Dried sunken areas on stems
These are an indication of root rot.

Dried sunken areas on stems with yellow/orange discolored blotches
This is a sign that soil is too soggy or roots have been badly disturbed in the repotting process.

Of general interest
Cuttings of stems left in a dry place have been known to root perfectly well after as long as a year without being potted up.
Epi stems don't signal a lack of water by shrivelling as some cacti do.
When young, epi seedlings are cylindrical and covered with whitish spines. They will not flower until this stage has been passed and the mature flattened stems are produced. When the flattened stems appear, it is thought to be a good idea to take them as cuttings because it is said they will flower earlier than if left on the seedling roots.

Epiphyllum species (night flowering)
According to The Cactus Family by Edward F. Anderson (2001) the following are the species of Epiphyllum which are night flowering:
Epiphyllum anguliger
E. cartagense
E. caudatum
E. columbiense
E. costaricense
E. cranatum and var crenatum, var kimnachii
E. floribundum
E. grandilobum
E. guatemalense
E. hookeri
E. laui
E. lepidocarpum
E. oxypetalum
E. phyllanthus
E. pittieri
E. pumilum
E. rubrocoronatum
E. thomasianum
E. trimetrale

Many species previously known as epiphyllums have been transferred to other genera including Disocactus, Hatiora, Pseudorhipsalis, Rhipsalis, Selenicereus, Schlumbergera.