My begonia bedding plants from market packs tend to rot where the stem meets...
My begonia bedding plants from market packs tend to rot where the stem meets the roots before they take root. I was advised to plant them slightly high to avoid the problem which did not make much of a difference. Even where they have not died off they are not what I would call thriving. There is mulch in the beds but not covering or crowding the plants. More information - they get about 3/4 day of sun, they are getting minimal water, usually just from rain, I see no evidence of bugs or slugs, and I have been trying to grow them in the same bed for five years. My standard of comparison for what they should be is plantings of begonias by landscapers in front of business where they are thriving and near the size of soccer balls already. I can follow up with a picture if that would be helpful.
St. Mary's County Maryland
If the stems are rotting your begonias are just too wet. It may be that they just need to dry out from our recent weather.
You should press your finger into the soil near the plant and see how moist it is. If this has been a continual problem for you we would guess that perhaps the soil in your bed may not be well-draining. You could amend the soil throughout (before planting next year) with some organic matter such as peat moss or compost.
The larger plants nearby probably started as carefully cultured, well-branched plants in 4 inch individual pots, and they may also have have been fertilized, either with a slow-release granule (like Osmocote) added to the soil, or with each watering in the nursery. This type of planting can be costly for homeowners, but your plants can catch up eventually with good care under proper cultural conditions.