The best soil for azaleas in pots is a combination of organic materials. Group the pots together and surround with bales of straw or other insulating materials. Unlike outdoor azaleas and rhododendrons, indoor azaleas are not frost hardy and are therefore not suitable, in frost-prone areas, for permanently planting in the garden when their period of flower is over.However, they can be kept and grown on as pot plants for flowering in future years.. Winter Protection for Azaleas. How to Water Rhododendrons. Encore Azaleas growing in containers will require closer attention to soil moisture. Watering Encore Azaleas In Containers. Use your finger to check the soil, and when it is dry to a depth of a finger length or so, water until water runs from the holes in the bottom of the pot. Transplanting the plant into a bigger pot ensures vigorous and sustained azalea growth. Growing indoor azaleas as houseplants. Cut back on water by about one-third during the autumn months to toughen the plant for winter, then water thoroughly after the first two or three hard freezes. Cultivation notes. Wait a few minutes and repeat. Move plants to the most sheltered area near the building. Water these plants whenever the soil is thawed and dried. You may be able to successfully overwinter the plants on the balcony. Well draining but moisture retentive soil. You want the water to rest below the interior pot (the cotton rope will draw water into the pot, providing the plant with hydration). Some reviewers note they marked the fill line with tape or a marker, since there’s no indicator line on the pot itself. Add water to the exterior pot, being careful not to overfill. This way you will know that the water has infiltrated the soil effectively. You realize you need a little bit of know-how to fertilize or prune your plants -- but you probably consider watering a cinch. Characteristics of Good Soil for Azaleas in Pots. During cooler months, Encore Azaleas growing in containers will not require as much water. Check plants throughout the winter and water thoroughly whenever the soil is thawed and dry. Azalea winter care begins in fall, when you should slow down and eventually stop irrigating your plants. Check soil moisture regularly and provide water if the top inch or two of the soil is somewhat dry to dry. Most pot-grown azaleas are sold in 6-inch pots, according to the University of Minnesota. Water azalea regularly. Water azaleas with a generous soak so that there is a trickle emerging from the base of the pot. At the hottest times of year I recommend watering the azalea at least twice per week. Although you should water azaleas as frequently as required to keep the soil moist. Select a pot, choosing one that holds a minimum of 5 gallons--the bigger, the better--and has drainage holes on the bottom. 1/3 Peat moss will provide the correct soil pH and 2/3 of either leaf mould, compost or manure provides the optimal soil moisture balance, structure and nutrients for azaleas to grow in pots and containers. Pour 1 inch of gravel into the bottom of the pot.