A drainage hole is pretty close to mandatory. Without one you need to be uber careful about watering. I don't trust my own skills enough to not have a drainage hole.

I have a grand total of one planting w/o a drain hole. It's a very shallow penjing arrangement. That it's shallow allows me to easily determine how wet/dry the soil is at the bottom of the 1-1'2" deep tray, which knowledge I consider mandatory. I also use only distilled water, water from the dehumidifiers, or snowmelt to irrigate with to eliminate salt build-up, which is a death sentence in containers w/o holes. Finally, I use fish emulsion fertilizers to help guard against the accumulation of unused fertilizer salts. The planting is in its 5th or 6th year and doing well, but you can see by my outline that you cannot treat a planting w/o a drain hole like traditional container plantings and expect it to be problem free.

Al

Thanks guys!

Also , I see a very tiny fly like insect in my coleus, only on the ones in soil medium in my dish garden. I also have few rooting in water nearby they dont have insects.

What are they? They are black , with common fly like looks, Flies slowly and walks/runs fast underside the leaves and on soil.

I sprayed houseplant insecticidal soap spray...made of seaweed extract, but of no use!

What is it? Is it harmful to kids? How to treat it before they multiply?!!!

You may have fungus gnats and if so they are best treated with BT. BT is readily available as a remedy for mosquito larva and is available as Dunks or a granular form which I think is easier to use for your purpose. Al