When planting in a planter, consider the type of planter, flowers and soil--and whether you need to move the planter. Terracotta allows oxygen to flow freely through the plants roots. The pots can be soaked in water so the flowers retain moisture longer. Plastic doesn't allow oxygen to move through the roots, and the non-porous pot retains moisture too long, possibly causing root rot. If you are planting in an extra large pot, can you lift it if it needs to be moved? Plant your flowers in such a way that they will thrive in their new home.
When planting flowers in a wooden planter, consider the longevity of the wood. Wood eventually rots after years of water exposure; never plant directly on the wood. Use a plastic planter that will fit in the wooden one, or use small pots for individual flowers. The advantage to using small pots is that you don't have to worry about compatible plants. Plants that need watering everyday can be placed with ones that need it just once a week.
Follow these tips from Reader's Digest when planting flowers in an extra large pot with no hole: To lighten the pot, use light potting mix containing vermiculite and peat moss. First, fill the pot one-third to one-half full with foam packing peanuts. Some of the packing peanuts dissolve in water, therefore, test a few before putting them in the pot. Fit a piece of landscape fabric between the soil and the foam to keep the materials separated. Fill the pot with potting mix and plants. Make sure to purchase compatible flower plants--plants that have the same watering and fertilizing requirements. Although you're providing space for drainage, evaporation occurs slower than in a pot with a drainage hole. Do a feel test on the soil before adding more water.
Many planters made out of ceramic, plastic, and even metal are now available available in gardening centers. These planters don't allow oxygen to flow through the roots and soil of the plants, therefore, water doesn't evaporate as readily. However, you can still successfully grow flowers in these planters by following a few tips: In the absence of a drainage hole, line the bottom of the pot with some pebbles or gravel; use pebbles for the small pots and gravel for the large pots. Always feel the soil first for moisture before watering the flowers.
Terracotta planters are the best material for growing plants of all kinds. Oxygen circulates freely throughout the soil and roots of the plants. The porous material can be soaked in water, keeping thirsty plants moist for a longer time. When planting in terracotta pots, there's no need to add any drainage materials.