Ficus Trees in Containers IV
Previous threads about how to approach long term care of Ficus in containers have reached the limit of 150 posts 3 times. I have been tending to more than 30 of my own Ficus trees covering at least 8 species in containers for more than 20 years, and teaching others in the community how to manage their containerized trees for the long term for 12-15 years. I'm also called on regularly to repot/rejuvenate large trees owned by others, so my experience with the genus is extensive, even to the inclusion of Ficus carica - the hardy fig.
The information I am supplying comes from knowledge gleaned from diligent pursuit of the physiology of woody plants, and in many cases from the pursuit of information specific to various Ficus species. In order that I might be proficient at maintaining trees in containers over the very long term, I have also spent a considerable amount of time and effort gaining a command of other plant sciences, with soil science, soil/water relationships, and nutrition getting special attention. My habit is to share information, particularly information I have verified via my own practical experience and observations, which run to more than 20 years of maintaining healthy Ficus specimens in containers, as previously mentioned.
In short, I'm not here to reinforce what you don't have to do; rather, I'm here to help you get more from your container gardening experience by helping you learn how to give your trees the best shot at growing to their potential by helping you reduce or eliminate factors that are limiting to growth and vitality.
From the family: Moracea (relative of mulberry)
Native: India, other tropical - subtropical regions
The Ficus genus
with more than 800 known species, is undoubtedly an extremely popular choice as a containerized tree. It tolerates the "dryer than desert" conditions actually found in many or most centrally heated homes reasonably well, and is endowed with a natural genetic vigor that makes it easy to grow. There is however, much myth and misconception regarding the care of this plant and the reasons it reacts as it does to certain cultural conditions. I would like to talk a little about the plant and then offer some specific information regarding its culture. I will primarily address Ficus benjamina - the 'weeping fig', but the commonly grown Ficus elastica - rubber tree, has the same cultural preferences. In fact, we can virtually lump all the Ficus species commonly grown as houseplants into a single group in all areas except light preferences. We need to make allowances for some of the fig species that won't tolerate direct sun as well as benjamina and elastica, and we may as well expand that exception to the variegated cultivars of benjamina and elastica as well.
is one of the species of Ficus commonly referred to as a strangler fig. It often begins its life in duff, in the crotch of a tree, or high on a branch as a seed deposited in the droppings of a bird or other tree-dwelling animal. After the seed germinates and as it grows, it produces thin aerial roots that often dangle in the moist air or attach themselves to the host trunk, while gaining nutrients and moisture from the air, leaf litter, and the bark of the supporting tree. It does not actually parasitize the plant it grows on, it only uses it as support. This relationship is termed epiphytic, or the tree an epiphyte. Those familiar with the culture of orchids and bromeliads will recognize this term.
After the aerial roots have formed and extended, and when they finally reach the ground, the tree begins a tremendous growth spurt, sending out more roots and developing a dense canopy that eventually shades out the supporting tree at the same time the roots are competing for nutrients in the soil and compressing the trunk and branches of the support tree to the point of stopping sap flow. Eventually the supporting tree dies and all that is left where it once stood, is a hollow cavity in the dangling Ficus roots that have now thickened and self-grafted to become the trunk. It is easy to see how many of the trees in the Ficus genus have come to be called by the name 'strangler figs'.
Roots and soil
The roots of some Ficus species are so powerful they can destroy concrete buildings or buckle roads, and can be measured in miles as they extend underground in search of water. When we consider the young tree and its ability to obtain sufficient moisture from just the surrounding air and bark surface of the support tree by way of aerial roots, we can draw an important conclusion: All species of Ficus prefer well-aerated and fast draining soils. In this regard, they are actually no different than any other tree you would endeavor to grow in a container, so try always to use a soil that guarantees an ample volume of air in the soil and excellent drainage for the intended interval between repots. This can be accomplished by using a soil whose primary fraction is comprised of large particles (like pine bark) combined with ample volumes of perlite or other inorganic ingredients like Turface, pumice, Haydite, crushed granite, or others. I grow all my Ficus in a soil mix consisting of equal parts of pine or fir bark, Turface (a calcined clay product), and Gran-I-Grit (crushed and screened granite). To be fair, I will add a qualifier here: the cost of the potential for superior growth and added vitality when using these fast (draining) well-aerated soils comes in the form of you needing to be prepared to water more frequently as the soil particle size increases. Roots are the heart of the plant, and the rest of the plant can do nothing without the roots' OK - the top just THINKS it's in control. Take care of the roots, and if your other cultural conditions are favorable, your plants will thrive.
Before I go on
I would like to say there is a very important relationship between your choice of soil, your watering habits, and a very common and serious problem that too often goes completely undiagnosed. That problem is a high level of soluble salts in the soil. When we choose soils that hold water for extended periods, we put our trees at risk for the fungal infections that cause root rot. Reasoning tells us that to avoid the root rot issue, we should not water to the point of soil saturation; rather, we often feel that watering in sips to avoid the specter of root rot is the wise alternative. This strategy though, puts us squarely on the horns of a dilemma. If we don't/can't water copiously on a regular basis, the soluble salts, i.e.,all the dissolved solids in our tap water and fertilizer solution accumulate in the soil. As the level of salts in the soil increases, the plant finds it increasingly difficult to absorb water and the nutrients dissolved in water. If the salt level gets too high, it can actually 'pull' water OUT of cells in exactly the same fashion that curing salt 'pulls' moisture from ham or bacon. This 'reverse osmosis' causes plasma to be torn from the walls of cells as they collapse, killing cells and tissue. The technical term for this is plasmolysis, but we more commonly refer to it as fertilizer burn. Fertilizer burn can occur whether or not we use fertilizer. The salts in our tap water alone, can/will eventually build to the point where water uptake is impossible, unless we actively take precautions.
Your soil is the foundation of every conventional container planting, and your choice of soils probably has a greater impact on your effort:reward quotient than any other single factor. Please take a moment to learn more about soils. My experience has shown that understanding how soils work and how to tell the difference between a good and a not so good soil is probably the single largest step forward a container gardener can take at any one time. Find more about soils here.
Ficus b. will tolerate dry soil quite well. Allowing the soil to completely dry; however, will result in undue drought stress and accompanying leaf loss, an expensive affair, considering the plant will call heavily upon energy reserves to replace lost foliage - reserves that might better have been directed to other functions and growth. If you wait just until the soil feels dry to the touch at the drain hole before watering, your tree will be free from the effects of drought stress. Soils feel dry to the touch when their moisture content is somewhere between 40-45%, but Ficus can still extract water from soils until moisture content drops to about 25-30%, giving you a 10-15% cush AFTER the soil feels dry. Use a finger or a sharpened wooden dowel stuck deep into the soil to check for moisture content. A wooden skewer or chopstick used in similar fashion is also a useful tool, and feeling the soil at the drain hole and withholding water until it feels dry there, is also a good way to judge. Water meters are rather ineffective, They actually measure EC (electrical conductivity). To illustrate: Insert a clean probe into a cup of distilled water. It will read 'DRY'. Add a little table salt of fertilizer, it will read 'WET'.
Though I try never to water my Ficus with cold water, I have never been able to verify that cold water has any negative impact on our houseplants ..... and I've asked a good number of horticulture's upper crust about any potentially negative effects, always receiving a shrug. The best way to water your Ficus it to apply water slowly until you estimate the soil is almost wet enough that water is about to appear at the drain hole. Wait a few minutes and water again so at least 10-15% of the total volume of water applied exits the drain. The first watering dissolves accumulated salts in the soil and allows them to go into solution. The second watering carries them out of the container. We already illustrated the importance of using a soil that allows us to water in such a manner without having to worry abut root rot. If you feel you cannot water in this manner without risking lengthy soil saturation and the possibility of root rot, your soil is probably inappropriate for the plant. Lest anyone complain at that observation, I would point out there is a difference between the growth and vitality of plants that are only tolerating a soil vs. the same traits in plants that appreciate (thrive in) a medium with superior properties.
More about soils as questions arise .... please ask!
Although many Ficus begin life as an understory tree and are generally quite shade tolerant, most actually spend their life struggling through the shaded understory until they eventually reach the forest canopy, where they finally find full sun and can begin to come into their own. We should give Ficus all the sun they will tolerate. I grow all varieties of Ficus b. in full sun, and they tolerate it well - even some of the newer cultivars that are supposed to be extremely shade-tolerant.
I have often read anecdotal assertions that Ficus b defoliates at the slightest change in light levels (or temperature). I have found this to be only partly true. Any trees I have moved from a location with a lower light level to a brighter location have not suffered leaf loss (abscission). Instead, they have rewarded me with more robust growth and back-budding. If the change is reversed, so the tree is moved from high irradiance levels to a dimmer location, leaf loss is probable, but even then it depends on both the suddenness of the change and the difference between the two light levels. It might be interesting to note that trees that are being grown out, or allowed to grow unpruned, are most likely to suffer loss of interior leaves when light levels are reduced. Trees in bonsai culture, or properly pruned trees where thinning has occurred to allow more light to the trees interior are less affected.
Indoor supplemental lighting is a broad subject, but if you have the ability to provide it, your trees will definitely show their appreciation. Brighter light = smaller leaf size, shorter internodes, and superior ramification (finer branching), not to mention a marked increase in overall mass.
Expect the most robust growth characteristics when the plant is kept in a temperature range between 60-80* F. Actual root temperatures above 90-95* should be avoided because they impair root function/metabolism and slow or stop growth. Temperatures below 55* should also be avoided for several reasons. They slow photosynthesis to the degree that the plant will necessarily call on stored energy reserves to power metabolism and keep its systems orderly. This essentially puts the tree on 'battery power' - running on its energy reserves. After exposure to chill and subsequent return to more favorable temperatures, the plant does not quickly recover the ability to carry on normal photosynthesis. The time needed for the plant to recover its normal photosynthesizing ability is more appropriately measured in days, than hours. Leaf loss can also occur as a result of exposure to chill, particularly sudden chill.
It is prudent to select a location free from cold breezes for your tree. Even short exposure to very cold draughts can cause leaves to abscise (fall/shed). The cool temperatures slow or halt the flow of auxin (a growth regulator - hormone) across the abscission zone at the base of each leaf petiole (stem) which allows an abscission layer to form and causes leaves to fall. Chill also stimulates an increase in abscissic acid (also a growth regulator - hormone) which is also a player in leaf loss.
Benjamina can tolerate temperatures as low as the mid-30s for brief periods if the exposure to chill is gradual, but it should be noted that even though there may not be any readily visible impact on the tree, the tree will always be in decline at temperatures below about 55* because of the impact on the tree's inability to carry on efficient photosynthesis. Sudden and large temperature drops can cause varying degrees of chill injury in the plant, caused by phenolic compounds leaking from cells, which shows up looking much like freeze damage. Severe injury could occur in plants that were growing at 80-85* and were subjected to sudden chilling to temperatures as high as 45-50*
Benjamina's thick, leathery leaves with waxy cuticles help to limit moisture loss, making the plant suitable to a wide range of indoor humidity levels, even though it prefers humidity levels above 50%. When humidity levels are blamed for leaf loss or necrotic leaf tips and margins, it is likely the blame has been misplaced. Those pesky high salt levels in soils, most common in late winter, can make it difficult and in extreme cases impossible for the plant to absorb water to replace that being lost to the air through transpiration. The fast soils that allow copious watering, which flushes the soil of salts regularly are actually much more important/beneficial than maintaining ultra high humidity levels. Misting is very effective ..... For about 30 seconds. Forget the misting please, it is ineffective. For small plants, a humidity tray may marginally effective.
I prefer any 3:1:2 ratio soluble fertilizer like Miracle-Gro 24-8-16 or 12-4-8, and I especially like Dyna-Gro's Foliage-Pro 9-3-6, because it provides all the essential nutrients in the approximate ratio the plant will use and in favorable ratios to each other. Alternately, a 1:1:1 ratio fertilizer like MG 20-20-20 is suitable. Because I use fast soils, I can fertilize at very low doses, every time I water. How YOU can/should fertilize is something we should discuss. It can change by season, and also varies based on soil choice and watering habits.
There is no question that in addition to offering greater potential for growth and vitality within the limits of other cultural factors, fast draining, well-aerated soils also get the nod for greatly increasing the grower�s margin for error in the areas of watering and fertilizing.
Leaf loss in Ficus is probably the cause of more conjecture than any other aspect of its culture, so even though I have mentioned it above, I will reiterate. Even though it is widely held that Ficus b. defoliates at virtually any cultural change, with changes in light and temperature most often cited, it is not so. The plant tends to defoliate when there is a fairly abrupt change in light levels - from bright to dim, or after exposure to sudden chill, but the plant does not tend to defoliate when the cultural conditions of light and temperature move from unfavorable to favorable, i.e. from dim to bright or from cool to warm/appropriate - unless the change is markedly radical.
First, I draw a major distinction between potting-up and repotting. Potting up can be undertaken at any time. It involves moving the plant to a slightly larger pot and back-filling with fresh soil, with a minimal amount of root disturbance. Much to be preferred to potting-up, is repotting. Repotting, which has a substantial rejuvenating effect, includes removing all or almost all of the old (spent) soil and selective root-pruning. It is by far the preferred method and probably the most important step in insuring your trees always grow at as close to their potential genetic vigor as possible. Repotting as opposed to potting-up is the primary reason bonsai trees are able to live in small containers for hundreds of years while the vast majority of trees grown as houseplants are lucky to survive more than 5 years without root work
It is pretty much universally accepted among nurserymen, that you should pot up at or before the time where the condition of the roots/soil mass is such that the roots and soil can be lifted from the container intact. Much testing has been done to show that trees left to languish beyond this point will have growth and vitality permanently affected. Even when planted out, growth and longevity of trees allowed to progress beyond this point is shown to be reduced.
The ideal time to repot a Ficus, is when the plant has good vitality and in the month prior to its most robust growth. June and July are prime months for most of the US. HOW to properly repot is beyond the scope of the initial post, but I am sure the subject will be covered in detail as questions arise.
Remember - potting up a root bound plant is a stopgap fix, and ensures the plant has no opportunity to grow to its genetic potential within the limits of other cultural factors; while fully repotting, which includes a change of soil and root pruning, ensures the plant WILL have the opportunity within the limits of other cultural factors. Strong words, but to repeat the illustration: the bonsai tree is capable of living in a tiny pot, perfectly happy for hundreds of years, while we struggle to squeeze 5 years of good vitality from a root bound plant - root work being the difference.
Ficus trees suffer from some pests. Most common are scale, followed closely by mites and mealies. I have always had good luck with neem oil as a preventative and fixative. We can discuss infestations and treatment as it arises, but so it gets included in the original post, I use only pure, cold-pressed neem oil, such as that packaged by Dyna-Gro in the black and white container. The beneficial active ingredient in neem is azadirachtin, the effectiveness of which is greatly reduced by steam and alcohol extraction methods, which brings us full circle to why I use the cold-pressed product.
Oedema can sometimes be an issue as well;. Suspect it if you see corky patches on the leaves, usually preceded by wet, bumpy patches that usually go unnoticed.
This is a long post, and took a long time to compose. I hope it answers most of your questions, but somehow, I cannot help but hope there are a few lingering that you would like to ask or points you would like to have clarified. It is great fun visiting and helping people who are devoted about improving their abilities to provide for their trees.
Here is a link to the previous thread, which is packed with good information.
Additionally, you can find more detailed information about tending trees in containers for the long term here.
I'll leave the link to more information about container soils again - because it's soo important.
I truly hope you have found some value in this offering. Thanks for reading to the end.