Springtime’s not complete until gardeners have potted up planters and containers at entry doors, garage fronts, decks and patios. Several tips can increase success and make container grown plants flower more abundantly.
- Containers should preferably have one or more drainage holes in the bottom. If no drain is possible, watering must be done very carefully to avoid water ponding in the interior from overwatering. If a container has a drainage hole, pebbles, rocks or other materials do not need to be added to the base for “drainage.” Research has shown that this layer of change can actually impede drainage. When water reaches the layer of change, it pauses, over-saturating the soil above before passing down into the layer of rocks. The recommendation to avoid rocks or pebbles in the bottom interior is different from the past common practice.
- Begin with high quality potting mix. Miracle Potting Mix works well, as do the custom blends recommended by locally-owned garden centers. Moisture Control Potting Mixes contain materials that retain moisture, which can be valuable in hanging baskets or planters exposed to hot, dry, or windy sites.
- Potting mixes in containers can be re-used from year to year, if it was a high-quality mix to begin with. We’ve used the same mix in pots for five or more years. Each year remove about 1/4 of the old mix, add fresh, and mix well. To recharge the nutrient level of old mixes, Osmocote slow-release fertilizer granules can be added, following label directions.
- You can often tell the quality of potting mixes by lifting the bags. Poor mixes are often very heavy and wet.
- High quality mixes like Miracle Gro Mix are very dry in the bag. Wet the mix before using by adding water to the bag and mix well. Or dump the bag in a wheelbarrow, wet down, and blend until the potting mix is nicely moistened. Young plant roots don’t like to contact bone-dry soil when transplanting, and very dry mixes are difficult to water after planting, if not pre-moistened.
- When selecting plants to go into a planter, consider the idea of adding a thriller, a filler, and a spiller. A thriller is an eye-catching focal point plant for the container’s center. A filler is a plant that will spread out and fill the gaps around the thriller. A spiller is a vining or trailing plant that will spill over the edge of the container, softening the container’s edge and giving extra color over the containers sides.
- If containers are planted to be immediately “full-looking,” they can become quickly overgrown and overcrowded. Allow enough room between plants so they can develop, unless you’re needing immediate full effect for an event like graduation open house. Containers that are packed full in spring will need remedial pruning by mid-summer to prevent the planting from going downhill if plants struggle in competition with each other.
- Container-grown plants are totally dependent on us to provide water and nutrition. Fertilize at least every two weeks with a water-soluble fertilizer like Miracle Gro. If Osmocote slow-release fertilizer is used, fertilize at half-strength with Miracle Gro.
- “Deadhead” planters by removing the spent, dried blossoms immediately as flowers wither. This is very important to prevent the formation of seedpods. Deadheading flowers encourages continued flowering.