Dear Garden Problem Lady

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I have an indoor bonsai ficus tree that I love, that the kids gave me for Mother’s Day, and about two weeks ago it had a total collapse and shed every single leaf. At first it looked as though shoots might be coming up, but now it looks all bare and brown. At the bottom of the trunk there is a little white growth – mold of some kind? Have I over-misted?

How beautiful and various these indoor bonsais are! It could survive over-watering, but try a fungicide and pray. Or – poor soil, thus poor drainage, could cause root rot – hence leaf loss. Or it may lack light. It needs five hours daily of direct or indirect sunlight. 

Our Japanese maple looks green but it used to be a red tree. Quick googling leads me to understand that red Japanese maples are sort of hybrid trees, and that if the tree turns green it is because the green roots are taking over. What can I do?

This could depend on your tree’s cultivar. Japanese maples have more than 700! Some healthy ones produce more chlorophyll in their leaves to survive too much shade during summer. They turn back red next spring with more sun. Others, to get more sun, may have sent up shoots from below the graft (many red Japanese maples have been grafted onto green tree roots), so it’s a matter of trimming off those shoots. Check your cultivar’s name and description before you start to worry about your tree.

What should I do – and when – to overwinter my first dahlias?

You can overwinter dahlias fairly easily. After the first frost has blackened the foliage, cut off all but two to four inches of top growth, and carefully dig tubers up without damaging them. Allow tubers to dry for a few days in a frost-free place, out of direct sunlight. Once dried, remove any excess soil, leaving one to two inches of stem. Store tubers in a ventilated box or basket. Place slightly moistened sand, peat moss or vermiculite in the bottom of the box and store in a cool, dry location at 45 and 55 degrees F. Check tubers periodically through winter for rotting and drying out. If the tubers appear shriveled, mist them lightly with water. If any start to rot, trim the rotted portion of the clump so it won’t spread. The tubers are fragile, handle gently. When warm weather arrives, after all danger of frost, plant the tubers.

Mr. Houseplant will speak at the next Zoom meeting of the Capitol Hill Garden Club on Tuesday, Oct. 13, at 7 p.m. Please email [email protected] at least 24 hours in advance for access code.