Question
I recently aquired some new plants, specifically, some streptocarpus and a rex begonia.  The leaves on the strep are arching down over the pot and curling backwards.  My rex begonia's leave are also curling backwards creating dome shaped leaves. I am also having a problem with the rex's leaves turning brown and dry on the edges. I realized that other plants I have had in the past, such as herbs, have had the same problem.  Whenever you look at a healthy plant from just about any species, the edges of the leaves are always slightly cupped upwards, rather than downwards.  I have no idea what could be causing this, and I haven't found help for this problem anywhere else. My streps and rex are very young plants with about 3 well-developed leaves on each plant, and I have only had them about a month. I grow most of my plants in a west-facing window right now, which only gets about 3-4 hours of direct sunlight because of other buildings, trees, etc. My rex grows in a north-facing window. I follow constant feed directions, using a balanced fertilizer. I water when the soil is dry to the touch, and use moist pebble trays to help with humidity.  Thank you for any help.
Jennifer Wilson

Answer
Hi Jennifer,

It is not uncommon for young leaves on a Streptocarpus to have a hump-backed shape. The leaves usually flatten out as they mature. Inadequate light - Streps are sun lovers - and inadequate water may also cause the Strep leaf curling you described. You can experiment a bit by keeping your Streps a little more moist and providing a little more light, if possible. Also, be sure temps are always above 60 degrees F.

The Rex Begonia leaves should not be curled into hump-backed shapes. That is almost assuredly a sign of drought stress. You may be waiting a bit too long in between waterings or perhaps you are not watering thoroughly enough. Paradoxically, if your Rex is in too large a pot, it is possible that the soil is staying moist for too long and the roots are slowly rotting and not absorbing water properly.

The dry, brown edges are often a symptom of underwatering and/or too much mineral salts in the soil. The excess minerals can build up if your local tap water is on the hard side. If so, switch to filtered, distilled or rainwater. Too much fertilizer is another source of mineral buildup. Fertilizing is overrated and unncessary in most instances. I suggest that you stop fertilizing altogether.

Please let me know if any of this is unclear or if you have any additional questions.

Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

You can E-mail me directly at: [email protected]

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