This characteristic is not common but some (not all) Philodendron species are known as myrmecophytes that are plant species that live associated with a colony of ants.  Myrmecophytes possesses specialized organs that exude a sweet liquid or provide shelter or food for the ants. These Philodendron species often possess extrafloral nectarines or tissue from which the ants can draw nourishment.  The plant benefits by the protection from predators that try to eat the plant's leaves that is provided by these often fierce ants.  An extra-floral nectary can be born on the stems and the leaves as splotches with the color of a purple/reddish wine stain known as being vinaceous.   Although nectaries secrete sweet liquids to attract pollinators an extrafloral nectary does not produce its liquid for the purpose of pollination.  You will read more later in this article about insect pollinator attractants.  This characteristic should not alarm the home grower since the ant species attracted are not found in a home setting outside the tropics.

Species compared to hybridized Philodendron.

Although there are a very few natural Philodendron hybrids found in nature (such as Philodendron 'Marijke' (photo below, left), many Philodendron commonly sold at nurseries are hybridized plants and are not species.  The majority of hybrid names are simply made up and almost no information can ever be reliably found.  You'll just have to believe what a grower tells you and that may often be incorrect since scientifically accurate information on hybrid plants is rarely available.

Hybrid Philodendron are created when the pollen from one species is applied to the spadix of another species at the time the plant is ready to reproduce.  The pollen of a hybrid may be applied to the spadix of another hybrid creating a further confused hybrid.  (An explanation of the spathe and spadix that are parts of the inflorescence of an aroid is found later in this article.)  The resulting seeds (if the hybrid even produces seeds since many are sterile) are not a species, but a hybridized  form.  Some hybridizers enjoy seeing just what they can create and after a period of time you have no idea what the parents may have been.  As a result, there is no way of knowing if the new hybrid prefers wet conditions, drier conditions, grows in the ground or high in the trees.  Although hybrids can be beautiful, my preference is to grow only Philodendron species that can be traced back to their natural habitat and better understood.
 

Growing and watering Philodendron.

The common advice on most garden websites is to allow a plant to dry between watering that is often not good advice.  Anyone that has asthma knows the difficulty of getting air out and then drawing it back in.  Even though plants release oxygen into the air through their leaves they draw fresh oxygen into the plant through their roots.  A potted plant is much like your lungs and if you can't bring in fresh oxygen you will soon cease to live.  As a result the top layer of a potted plant's soil should not be allowed to dry since that dry soil prevents the intake of fresh air!  Once the soil dries it creates a "blanket effect" to hold in the stale moisture and keep out fresh oxygen.  Once the soil dries the moist layer below cannot easily breathe in order to re-oxygenate the soil that soon becomes anoxic. Anoxia causes root rot,  The dry upper layer actually prevents the capillary effect of the wet surface evaporation when damp soil is exposed to air.   When you pour water in the air inside the soil is displaced so the oxygenated air inside has left the pot. If the upper soil layer completely dries the "lungs" of the pot cannot work and can no longer continue to draw in another breath of fresh air. 

The entirety of the soil needs to remain evenly damp so the roots of the plant can continue to draw in fresh oxygen.  Otherwise, root rot is likely to begin.  Since most people don't want to bother with ever watering their plants, many people go into a garden store and a very rich potting soil that stays soggy all the time.  Despite the belief that are giving the plant "rich" soil to make it thrive they may be dooming their Philodendron specimen to death.  Philodendron species can literally drown in mucky soil due to a lack of oxygen! 

For some unexplained reason many growers believe the rich soil makes a Philodendron grow better!  Typical "potting soils" just don't work for the vast majority of Philodendron species since , most grow in trees, not in soggy soil.  A Philodendron species' roots are designed to collect rain water during the wet season and suffer through the dry season.  But even in the dry season a Philodendron sp. can collect enough water from the humidity around their exposed roots to survive.   

Although house plant growers commonly believe tropical plants do not need water in winter that belief is simply a myth. Tropical plants live in very humid conditions and are capable of gathering water directly from the air even during the drier portions of the year when it doesn't rain on a daily basis. 

The photo to the right is of our personal collection of rain forest plant species that includes almost 100 Philodendron specimens.  We water every week of the year averaging four days a week in summer and three days per week in winter.  As can be seen in the photo the plants love water.

Despite the belief of far too many growers, growing plants is not just about the water content of the soil!  The advice to water only once a week and keep the top two inches of the soil dry is not always good advice!  Many aroids and other plant species grow in very wet soil! 

Instead it is about the fast flow of water through the soil or the lack thereof that causes a lack of oxygen, anerobic fermentation and saprophytes that turn into pathogens.  Saprophytes are organisms including fungus or bacteria that grow on and draw nourishment from dead or decaying organic matter that often includes soggy wet soil. The pathogens attack the roots and cause them to rot so all of the advice to "slow down on the water" is really about how to control the pathogens.

Fermentation and saprophytes often occur in muddy soil that will not not allow the roots to breathe but they don't necessarily occur in water which is why we can cause a plant that is about to die to grow new roots in clean water.  As a result, it is necessary to use soil mixes that allow the roots to breathe and will not remain soggy. I've attempted in many threads to explain the necessity of mixing proper soil for plants but the advice is often ignored since it requires some "work" on the part of the plant's keeper. The reason plants rot is not the amount of water given to the plant! These are rain forest plants and are literally drowned for months at a time!

If you could visit a rain forest you would quickly learn the soil is composed of leaf litter, decaying wood, compost, animal droppings and the charcoal left behind when a part of the forest burns. If we'll just listen to Mother Nature we can all make our plants grow as they do in nature. That is precisely what I attempt to explain when I recommend mixing soil, not just buying a bag at the store. Over time we've arrived at a soil mixture for most of our aroid species which duplicates the rain forest. We use this mixture on the advice of the aroid keepers at the Missouri Botanical Garden in St. Louis. The goal of this mix is to allow the roots to freely find places to extend and grow without constantly finding wet places where they will rot. This mix will remain damp but drain quickly and as you can see from the photo above will make the plants thrive.

Rather than using a rich, soggy soil and watering only once a week (or less), use a soil that holds moisture well but drains quickly.  With the help of botanical garden researchers we've developed a soil mixture for most of our Philodendron sp. that works great.  People who visit our artificial rain forest are often amazed at the size of many of our specimens that grow much faster and larger than they often do in a home.  

The exact mixture is not critical but we use a soil mixture composed of approximately 30% soil, 20% peat, 40% orchid bark with charcoal , 10% Perlite and some finely cut and shredded sphagnum moss works well.  We also make our own compost and add it in place of some of the peat and bark  when available. We often add extra hardwood or aquarium charcoal to help purify the soil and sometimes volcanic rock.   We often add extra hardwood charcoal to help purify the soil and sometimes volcanic rock  The  charcoal is used to increase drainage but also to take advantage of the tiny air spaces in the charcoal for growing beneficial microbes.  It helps with water retention, as well.  If you have some good compost feel free to add it.  Small pieces of charcoal can be purchased from any good orchid supply.  If you are concerned about your soil remaining wet just add more orchid mix, cypress mulch, Perlite and sphagnum moss. 

We grow many different Philodendron species in this basic mixture and some of our specimens have reached their adult or near adult size and regularly produce a spathe and spadix (inflorescence).   The goal of our mixture is to cause the water to flow through the soil quickly, remain slightly damp, but never soggy.  The roots of our plants attach to the bark just as they do in nature on the side of a tree.  Most growers call a mix similar to the one we use a "jungle mix".

Temperature?  All Philodendron species are tropical.  That means they just can't tolerate cold temperatures for extended periods and in most cases a freeze will kill the plant.  Some do not appreciate the temperature of an air-conditioned home for long periods of time!  As a general rule, don't allow the temperature around your Philodendron specimens to drop below 12.75C (55 degrees F) if at all possible.   It is best to keep them below 90 degrees F which is not particularly difficult if you grow them in some form of shade or filtered light.  Some species will tolerate short periods of cold, such as Central Florida.  But most won't survive anywhere outdoors north of Zone 9.  Zone 10 is best!  Many will simply die if exposed to a freeze.  Since most demonstrate much faster growth when the temperature is in the 80 to 88 degree range you may find your specimen will appreciate being allowed to live outdoors during the spring, summer and portions of the fall.

Humidity is extremely important!  Do everything possible to keep the humidity high around your Philodendron most of the time.  These species live in a jungle that can have a humidity level near 100%!   If you live in a climate that has a low humidity you'll need to provide a method of giving the aroid more humidity.  In our rain forest the humidity is always high (85% or higher) due to the pond in the center of the room and frequent overhead misting!  Some growers keep their Philodendron near a swimming pool to allow for a constantly high humidity.   Air circulation is equally important since the air is almost always moving in the rain forest.

Proper light for Philodendron species.

Have you ever noticed your Philodendron "weeping"?  It is not uncommon to see water dripping from the leaf tips.  Although many growers assume the liquid is a result of dew it would be unlikely to observe dew forming inside a home on a house plant.   Even the droplets of water seen on grass in morning are frequently caused by guttation, rather than dew.

Aroids and other plant species possess glands known as hydathodes that are capable of producing a clear liquid through a process known as guttation. The word guttation is derived from the Latin word gutta "gut-TA" meaning droplet.  Excess moisture in the leaf blade normally transpires through pores of the leaf blade and is evaporated by heat and wind.  During periods of low temperatures and still air motion the water just accumulates at the leaf's tip.  Although sometimes called "sap" on plant discussion websites guttation is just the watery liquid that comes out of the plant and is common especially at night.

During the heat of the year the warmth of the sun pulls the water inside the stem (base of the plant) through the petiole (support of the leaf blade) to the lamina of the leaf so the blade is filled with water.  Natural evaporation causes the water to be raised upwards.  When evaporation is not "pulling" the water out of the plant as a result of the lower natural temperatures during fall and winter the water inside the blade has no place to go and must find a method of escape since the petiole and stem are already filled. The water just seeks the easiest route out of the plant and chooses a gland. The weight of the water builds pressure pushing downward on the petiole toward the stem and finally builds to a point where the plant is simply forced to release the liquid through the leaf.  

Guttation commonly happens at night when the transpiration rates are naturally low.  It is possible for guttation to occur when the hydrostatic pressure is insufficient to prevent the flow of water into the xylem. The xylem is a plant tissue of various cells that is capable of transporting water and other substances including salts to the leaves.  Guttation frequently occurs in tropical plants when high humidity inhibits the natural transpiration or the loss of water vapor inside the plant to the outside air.

Guttation often occurs through the hydathodes that are found on the leaf tips of many Araceae (aroids). A hydathode is a modified stoma which is normally involved in photosynthesis that must secrete water as a result of the pressure of the excess water. The hydathodes of Araceae are commonly localized in the leaf tip but may be found elsewhere on the leaves.
 

Philodendron reproduction.