May 16, 2015

1 - Wax begonia plants are succulent plants and subject to overwatering problems when first planted.

Yard and Garden May 16, 2015

Q.
All of my front porch potted flowers, except my wax begonias, are thriving (photos e-mailed). Even my geraniums, which you cannot see in the picture, because they are hanging in a basket, are doing well. However, though still alive, I have not noticed any growth with the begonias since I planted them about three weeks ago. Further, there is a brownish coloring appearing around the edges of the leaves.

The plants get the afternoon sun in southeastern New Mexico and I give them a good dousing with the hose when I get home from work. However, I think I may be overwatering the begonias. Do they require less water than other popular flowers? Thanks.

-Tim H.

A.

Tim, thank you for the photographs, they are good photographs and very helpful. Begonias (and geraniums) are succulent plants and can indeed suffer from overwatering. Based on the pictures, that is one possibility for your problem.

Your pictures show that the plants have many flowers. An old recommendation is to choose bedding plants with few or no flowers since the energy of the plant is directed at producing flowers instead of growth. The bedding plants may have been treated with plant growth regulators to keep them compact and encourage flowering. Since people prefer to purchase plants with flowers to be sure they have the flower colors that they prefer, this makes sense, but the growth inhibition may continue for a while after transplanting. This may be part of the situation with your begonia plants. While these plants are growing more slowly, their water requirements are less. With succulents like the begonias, this may contribute to an overwatering problem. The other plants are not succulents and do not appear to be as strongly inhibited (except the geraniums that are not in the photographs, but they are probably larger and perhaps not treated with growth inhibitors or as strongly affected as begonias).

I think I can see the exposed edges of peat pots in the close up picture of the pot containing the wax begonias. I do not see that in the pots with the other plant species (but then there is no close up picture of those). The exposed edges of the peat pots can serve as wicks drying during the day and exposing the plant roots to accumulated salts (minerals left as the water evaporates). The browning edges of the wax begonias may be due to salt burn mediated by the exposed peat pots. This salt damage to roots can result in root death and root rot. There appear to be some symptoms of drying in some of the leaves of the begonia plants. This may be due to loss of roots, even when the potting soil remains moist. Once again the succulent nature of the wax begonias can enhance the problem with root loss and development of root diseases.

Reduce watering a little, perhaps watering some in the morning and then a little more in the evening, to see if this will help the plants. Continue watering the other plants as you have been watering since they are growing well.

Wax begonia leaves have an interesting characteristic of developing a frosty, glazed (dull green) appearance when the plants are in need of water. Let that be a guide to direct your watering. The begonias and geraniums, more than the other bedding plants, can tolerate and even benefit, from a little drier growing conditions. Do not begin fertilizing until the plants have established their roots and begun growing more foliage.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

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