Things You'll Need
Commercial concrete sealer
Concrete planters are both sturdy and attractive. Some cements are high in alkaline, which leaches into the soil and may stunt the growth of plants. Hypertufa planters have high alkaline levels due to the use of Portland cement. Other planters may have clay mixed in with the cement which leaches salt into the soil over time. Also, due to the porosity of some cement, the soil may dry out too quickly. Properly treating then sealing the concrete planters ensures your plants remain healthy.
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Set the planter outside for two weeks prior to planting. Hose it down with water three to five times daily on days it is not raining. This naturally leaches out much of the excess salts and alkalinity.
Mix 1/4 cup vinegar and 1 gallon of water. Soak concrete and hypertufa planters in the solution for 1/2 hour to neutralize the alkaline.
Paint the inside of the planter with concrete sealer. Paint on a single coat and allow it to dry overnight then paint on a second coat and let dry completely.
Fill the container with a well-draining potting mix and replant.
Water daily or as necessary to keep the soil moist but not soggy. Water once weekly with a solution of 1 tbsp. vinegar mixed in 1 gallon of water to wash excess salts from the soil that may accumulate in clay and concrete planter mixtures.
When replacing the soil or plants in the concrete planter reapply a coat of the sealer, which may wear off over time.
Check soil moisture in the planters daily, as they may dry out quickly. Water until it drains from the bottom drainage holes to ensure the bottom of the soil is moist.
Avoid setting the planters out to cure during freezing temperatures. This may cause the planter to crack.