Ficus Benjamina in danger?

[cap_n_red]

I am brand new to bonsai - I have had this ficus for about a month. It has been doing so well! Happy and healthy as far as I could tell.

It's winter in my region - house at 68. I water an average of once per week, wetting the soil surface, allowing the water to penetrate, and then wetting again until water accumulates in the drip pan. I then empty the excess water.
I also have the ficus under a pictured "Care-X daylight" lamp. I usually have the light on 14-16hrs/day.

As of the last three days, the ficus leaves have been turning brown and dropping! Attached photos. Any guidance on management here? Thank you.

 

[Carol 83]

Welcome to the forum. I think it's underwatered. I keep many tropicals inside for the winter and I generally water every 2 days or so depending on the tree.

 

[ShadyStump]

I have (quite) a few of these, including one in a pot almost exactly like that one.
I concur with the under watering. Everything else should be absolutely great for a benjamina. Try the chopstick trick: stab a wooden or bamboo chopstick or skewer into the soil all the way to the bottom of the pot, nearest the middle you can get it. Leave it there, and use it like a dipstick to check soil moisture. Water when the stick is all but dry.

Even if you start watering just perfectly right now, those leaves look like they're done for. The tree should come back, but it'll be bare for a month or two. You may lose a branch or two, likely nearer the top. Just a heads up. Still, keep at it. Ficus benjamina is one danged hardy tree, so you should be in good shape by summer. Even if it does die, get another and try again. Can't tell you how many trees I've killed, but it doesn't matter. Still at it, and learning every day.

 

[Shibui]

I also suspect dehydration with once a week watering. Your description of how you water sounds thorough, but the water may still not be making it right to the centre of the pot.
If you have accurate scales, try an experiment. Water as normal. Wait a few minutes until the water stops draining then weigh the pot and tree. Now soak the pot in a tub of water for 10-20 minutes. Take it out and allow the water to drain as before. Weigh again. Any difference in weight is the water that soaked into the centre of a dry root ball. If there's no difference in weight, your watering is effective! Even after 40 years of growing bonsai I'm still amazed how dry a pot can be, even after watering and how carefully we need to be to get pots fully wet.

I notice almost all the damaged leaves are up top on the side closest to the grow light. Lower down they still look good. I don't need to use those things but I have read others saying that leaves too close to a grow light will burn. Any chance the light could be too close/too strong for the tree?

 

[cap_n_red]

Thanks everyone for the timely advice.

I wound up soaking and weighing like Shibui suggested. Both pots accepted 100 grams of water. Wow - I didn't have a good grasp on just how much these trees can drink! Good perspective. Will update my watering protocol appropriately and hopefully see some good results.

 

[Shibui]

I wound up soaking and weighing like Shibui suggested. Both pots accepted 100 grams of water. Wow - I didn't have a good grasp on just how much these trees can drink!

This is a really good example of how complex proper watering can be.
That extra 100g is half a cup of water. That water soaked into the dry spaces that were left after the pot was watered and is now available for the roots.
That 100g is not how much the tree uses in one day, though. With inadequate watering, the pot gets gradually drier each day. You water but only partly fill the pot so the tree uses the water you added plus some of the reserve. Each day the pot is a little drier despite you adding water until there's not enough reserve and the tree dehydrates. It may take 3 weeks or more for the deficit to get critical.
You should be able to get by with a good soak every 2-3 weeks and regular watering in between until you get the hang of watering so that water soaks right into the root ball. Knowing the approximate weight of that tree and pot properly wet will allow you to do periodic checks to see how well your watering is doing. You'll be able to skip the soakings when your watering is putting adequate moisture into the soil.