The Ficus genus, with more than 1,000 known species, is undoubtedly an extremely popular choice as a containerized tree. It offers candidates which tolerate the "dryer than desert" conditions found in many homes with central heating or A/C, a premier attribute for houseplants, and most are endowed with a high level of natural genetic vigor that makes them forgiving and 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. While the information is aimed at the more popular species of Ficus like lyrata, elastica, benjamina, microcarpa, salicifolia/nerifolia, benghalensis, et al, the cultural wants of Ficus other than the hardy fig are very similar, the greatest variability being light levels – though all respond best to very bright light or even direct sunlight.
Roots and Soil
The roots of some Ficus species are so powerful they have been known to destroy concrete buildings or buckle roads, and can literally be measured in kilometers as they extend underground wherever the water supply is adequate. All species of Ficus grown in containers have greater potential for reaching more of their genetic potential when grown in 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, etc. I grow all my Ficus in a soil mix consisting of equal parts of screened pine or fir bark, screened Turface (Turface is a special type of clay, baked at a high temperature so it's almost like porcelain), and crushed/screened granite. Many other growers use a very popular medium called the 5:1:1 mix. To be fair, I will add a qualifier here: one 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 very 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 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 jeopardy from the several fungal infections that fall under the canopy of the common term, 'root rot'. Reasoning and often well-meaning but erroneous advisers tell us that to avoid the root rot issue, we should not water to the point of soil saturation; rather, we should water in smaller measures to avoid the specter of root rot. 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 (salts) in our tap water and fertilizer solution, accumulate in the soil. As the level of dissolved solids 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 by way of the same mechanism by which moisture is 'pulled' from ham or bacon through use of curing salt. 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 the precautions of regularly flushing the soil with water.
The substrate serves as a foundation for every conventional container planting, and your choice of substrates probably has a greater impact on your effort:reward quotient than any other single factor. Please take a moment to ask for more information about soils. My experience has shown that understanding what properties affect water retention in container substrates, and how they affect it, is the single largest step forward a container gardener can take at any one time. If you're a hands-on grower with a desire to work toward ensuring you're optimizing the opportunity for your trees to realize as much of their genetic potential as possible, you'll almost certainly gain the most traction by working toward eliminating the limitations imposed by a substandard substrate. I've had many thousands of interactions with people who witness their growing experience has been radically changed for the better by adopting a less limiting home for their plants' roots.
Watering
Most Ficus species will tolerate dry soil quite well. If there is a choice to be made between 'a little too dry' and 'a little too wet', come down on the dry side. Allowing the soil to completely dry; however, will result in undue drought stress and likely the leaf loss which accompanies it. Leaf loss isn't usually a life threatening event for healthy trees as their energy reserves are normally enough that the tree can push a new flush of foliage. Still, a new flush of foliage is an expensive affair, considering the energy reserves used represent diminished assets which certainly would have been directed toward increased vitality, an increase in the plant's mass and other metabolic functions. If you wait to water 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. Better still, start using a 'tell' to 'tell' you when it's time to water. You'll find a short piece re using a tell at the end of the information about growing trees in pots.
The best way to water your Ficus is to apply water slowly until the soil is fully saturated and maybe just a bit of water is exiting the drain hole. Wait a few minutes and water again so at least 15-25% of the total volume of water applied in both applications exits the drain. The first watering and the wait dissolves accumulating salts so they can enter the soil 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 suppression of root function which accompanies it, or worse, the potentiality 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 in the growth rate, vitality, and appearance of plants tolerating a substrate vs. the same traits in plants that appreciate (thrive in) a substrate with superior properties.
More about soils as questions arise .... please ask! It's a key factor. When grower's instincts tell them there are problems in the rhizosphere (root zone), more often than not their instincts are well-founded.
Light
Although many Ficus begin life as understory trees and are generally at least moderately 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 have at least 40 containerized Ficus and all bur pumila are in full sun and tolerate it well, at least here in Michigan – YMMV. Even some of the newer cultivars, developed expressly to be extremely shade-tolerant, do best in full sun.
There is a difference between sunburn and heat damage. Sunburn is a chemical reaction that occurs after molecules in the tree's photosynthesizing apparatus have stimulated to a very high state of excitation. As the excitation diminishes a O negative free oxygen radicle is produced. This is the exact same O negative radicle found in H2O2 (hydrogen peroxide). It oxidizes the first organic molecule it comes in contact with, often that is the pigment chlorophyll, and bleaches the pigment to a silverish color which gradually turns brown or black. This is technically called photo-oxidation but we commonly refer to it as sunburn.
Heat damage, on the other hand, is destruction of tissue by high temperatures. The layer of air that surrounds leaves is called the 'boundary layer'. The leaf surface absorbs light energy and turns it to heat (a passive solar collector). The boundary layer is an excellent insulator that traps heat in the leaf. This is the main reason direct indoor sun can become a problem – not sunburn (other than in unacclimated plants). Utilization of a fan in rooms that allow direct midday sun to plants disrupts the boundary layer so heat can dissipate into surrounding air, and in most cases allows you to give your plants sun that would otherwise cause heat build-up problem. Procede carefully until you're on sound footing.
I have often read anecdotal assertions that Ficus 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.
An aside: brighter light to interior branches and in particular, good air movement, are important considerations if you want to stimulate back-budding. Air movement increases water loss by transpiration which increases the size of transport vessels and the o/a volume of water/nutrients in the nutrient stream. Brisk air movement is also an important plus that helps keep insect herbivory at a minimum.
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.
Temperature
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 can 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. So even though your tree might survive a month of temperatures in the 40s, it will not like it.
It is prudent to select a location free from cold breezes for your tree. Even short exposure to cold drafts can cause shedding of leaves. The mechanism that causes shedding from cold drafts is roughly the same mechanism that causes shedding from a reduction in light. Same effect – different cause.
Some Ficus can tolerate temperatures as low 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*
Humidity
The leathery leaves of trees in the genus are blessed with a waxy cuticle which helps to limit moisture loss, making the plant suitable to a moderately wide range of indoor humidity levels, even though Ficus prefers humidity levels above 55-60%. 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 enough to replace that being lost to the air through transpiration. The fast (free draining) substrates 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 60 seconds. For the rest of the 1,339 minutes in the day – not so much. For small plants, a humidity tray may marginally effective, but a room humidifier can really be helpful. I keep my winter grow area at 55% RH.
Fertilizer
A fertilizer's NPK RATIO is different than its NPK percentages. Ask about this if you're still confused after reading on.
3:1:2 RATIO soluble fertilizers like Miracle-Gro 24-8-16 or 12-4-8, and Dyna-Gro's Foliage-Pro 9-3-6 (all 3:1:2 ratios) are good choices. I especially like Foliage-Pro 9-3-6 because it provides all the essential nutrients in the approximate ratio at which the plant will use the nutrients, and provides favorable ratios between nutrients, each to the others. Also, it derives 2/3 of its nitrogen from nitrate sources and does not utilize urea, which tends toward producing coarser growth and long internodes as opposed to the fuller and more compact plants fertilized with nitrate N present. Because I use very fast-draining and highly aerated substrates, I can fertilize at very low doses, every time I water, which I do during the winter. During the summer, I fertilize every weekend when mean temperatures are no higher than 80*. 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. No one can give reliable fertilizing advice (other than reliable generalities) unless they know something about the substrate your plant is in and your 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.
Defoliating
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 defoliate 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 radical. Ficus is better able to adapt to an increase in photo load than a decrease.
Repotting
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 potential 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. I might get push-back on this point, but undoubtedly it will be from growers who have never included repotting as part of their care regimen. I've probably done full repots on over a thousand Ficus for 30 years, and maybe 2 or 3 have died close enough to the repot date to make me suspect the stress of repotting MIGHT have had an impact on loss of viability. The Ficus benjamina in the image sequence below has been repotted several times. It was grown from a pencil thick cutting I acquired somewhere along the way. This was a severe root pruning session because the tree is a bonsai candidate.
It is pretty much universally accepted among nurserymen, that you should pot up at or before the time where the condition of the root/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.
This ^^^ is what a very healthy ficus root system looks like.
I'm not suggesting anyone who decides to root prune their tree should go as far as shown in the images. I provided the images to help dispel the idea roots are a mysterious part of plants that if tampered with will surely cause instant death.
Plants age differently than people (ontogenetically as opposed to chronologically). That being so, their tissues tend to retain their ontogenetic vigor. Of the tissues that make up your tree, those with the most potential vigor will be located in the root to shoot transition zone. When the tree is healthy, cutting roots back hard, and in some cases cutting the entire tree back hard, has a very significant rejuvenating effect. Arborists and nurserymen all understand cutting a tree or shrub back hard creates an explosion of growth - rejuvenation pruning.
The ideal time to repot a Ficus, is not early spring or winter when the tree is weak. Ideally, repot when the tree is healthy, has much in the way of energy reserves, and in the month prior to its most robust growth. June and July are prime months for most of the US. Trees have weak periods and strong periods during the growth cycle. Doing heavy work like hard pruning and repotting are best done when trees are strong and photosynthesizing ability is peaking. Thinking of the summer solstice and Father's Day are an easy way to remember when to repot Ficus. 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. I'll look forward to it.
Remember - potting up a root bound plant is a half measure, and ensures the plant has a much limited opportunity to realize its genetic potential; whereas, a full repot, which includes a change of soil and root pruning, ensures the plant WILL be free of limitations associated with root congestion until such time the root/soil mass can again be lifted from the pot intact (approximately). 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, potted-up plant - root work being the difference.
Pests
Ficus trees suffer from some pests. Most common are scale, followed closely by mites, thrips, and less often, mealybug. 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. Ask about the use of neem because factors like pH levels and water hardness need consideration in order to avoid alkaline hydrolysis and loss of effectiveness. There are options other than neem oil.
Common disorder
Oedema (edema), a physiological disorder, is common, and almost always associated primarily with water-retentive substrates and/or over-watering. Suspect it if you see corky patches most prevalent on the underside of the leaves, usually preceded by wet, bumpy patches which can initially 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 questions you would like to ask or points you would like to have clarified. It is great fun visiting and helping people who are devoted to improving their ability to provide for their trees.
I truly hope you have found some value in this offering. Thanks for reading to the end.
Al
Using a 'tell'
Over-watering saps vitality and is one of the most common plant assassins, so learning to avoid it is worth the small effort. Plants make and store their own energy source – photosynthate - (sugar/glucose). Functioning roots need energy to drive their metabolic processes, and in order to get it, they use oxygen to burn (oxidize) their food. From this, we can see that terrestrial plants need plenty of air (oxygen) in the soil to drive root function. Many off-the-shelf soils hold too much water and not enough air to support the kind of root health most growers would like to see; and, a healthy root system is a prerequisite to a healthy plant.
Watering in small sips leads to avoid over-watering leads to a residual build-up of dissolved solids (salts) in the soil from tapwater and fertilizer solutions, which limits a plant's ability to absorb water – so watering in sips simply moves us to the other horn of a dilemma. It creates another problem that requires resolution. Better, would be to simply adopt a soil that drains well enough to allow watering to beyond the saturation point, so we're flushing the soil of accumulating dissolved solids whenever we water; this, w/o the plant being forced to pay a tax in the form of reduced vitality, due to prolong periods of soil saturation. Sometimes, though, that's not a course we can immediately steer, which makes controlling how often we water a very important factor.
In many cases, we can judge whether or not a planting needs watering by hefting the pot. This is especially true if the pot is made from light material, like plastic, but doesn't work (as) well when the pot is made from heavier material, like clay, or when the size/weight of the pot precludes grabbing it with one hand to judge its weight and gauge the need for water.
Fingers stuck an inch or two into the soil work ok for shallow pots, but not for deep pots. Deep pots might have 3 or more inches of soil that feels totally dry, while the lower several inches of the soil is 100% saturated. Obviously, the lack of oxygen in the root zone situation can wreak havoc with root health and cause the loss of a very notable measure of your plant's potential. Inexpensive watering meters don't even measure moisture levels, they measure electrical conductivity. Clean the tip and insert it into a cup of distilled water and witness the fact it reads 'DRY'.
One of the most reliable methods of checking a planting's need for water is using a 'tell'. You can use a bamboo skewer in a pinch, but a wooden dowel rod of about 5/16" (75-85mm) would work better. They usually come 48" (120cm) long and can usually be cut in half and serve as a pair. Sharpen all 4 ends in a pencil sharpener and slightly blunt the tip so it's about the diameter of the head on a straight pin. Push the wooden tell deep into the soil. Don't worry, it won't harm the root system. If the plant is quite root-bound, you might need to try several places until you find one where you can push it all the way to the pot's bottom. Leave it a few seconds, then withdraw it and inspect the tip for moisture. For most plantings, withhold water until the tell comes out dry or nearly so. If you see signs of wilting, adjust the interval between waterings so drought stress isn't a recurring issue.
Thanks again for taking a look.
Al
