By Russell T. Nagata
By Russell T. Nagata
University of Hawaii at Manoa
College of Tropical Agriculture and Human Resources
Komohana Research and Extension Center
Happy April Fool’s Day! On this day for jokesters and fools, my real story is on plastic, clay and other containers able to hold soil for growing plants. Pot, or container, gardening is perfect for those who don’t have a large yard, live in an apartment or condominium, have more than enough rocks to open a gravel pit, and for those who like the convenience pot gardening brings.
Gardening in pots and containers also has the benefit of being higher above the ground; raising the pots on stands makes it easier for those who are restricted in bending or kneeling. Along with pots and containers, raised beds are becoming very popular, and commercially made frames are available.
For the best results, start with selecting the proper-sized pot or container for the plants you wish to grow. Containers come in all sizes and reflect the ingenuity and artistic passion of the creator. While plastic, clay and ceramic pots are most common, many other items are used, including old wine barrels, used metal and plastic storage drums, tires, washing machine tubs, bathtubs and toilet bowls.
Plastic pots can be purchased in various sizes, including those that can hold 20 or 30 gallons of media. The effect of pot size will reflect how large a plant you can grow, stability of the pot with the plant, and the frequency between watering and nutrient management. For example, when planting tomatoes, a small patio-type plant can be grown in a two- or three- gallon container. Larger tomato vines will need larger pots up to 20 or more gallons of planting media to grow to maximum size. Larger containers also provide a good anchor for the plant so the wind can’t blow the pot over.
Raised beds are made of many different materials. The benefit of raised beds are that you can make garden plots of any size, any shape, and as deep as you want. Commercially available raised beds are made from wood and recycled plastic made into boards and logs. Homemade raised beds are constructed from concrete blocks either dry stacked or mortared together, lumber, used 6-inch or larger diameter PVC or metal pipes and used corrugated iron roofing. Old concrete guardrail posts also make great frames for raised beds, but they are very heavy and difficult to move. When constructing raised beds, consider the width of your garden bed, unless you will step into the plot. For most individuals, normal reach is two to three feet, making maximum garden width four to six feet wide, if accessible from both sides.
It is best to use a high quality potting soil mix when planting in pots or containers. These types of mixes normally have low incidence of diseases and plant parasitic nematodes, which can greatly reduce plant vigor. These soils also have good drainage characteristics, yet are able to hold in moisture so you are not constantly watering. Potting soil made with a mixture of peat, perlite, or cinders and vermiculite also works well. A one-inch layer of gravel or cinders on the bottom of the pot can help excess water drain from the pot. For raised beds, well drained soil high in organic matter should be used. Remove all large rocks and other debris while filling the raised bed to help in digging and cultivation later on. A half-inch hardware cloth screen works well to eliminate large material going into your bed.
Maintaining consistent soil moisture is best for plants, and the best way to achieve this to have the proper container size for the plant you wish to grow. A large plant in a small pot will deplete all of the moisture very quickly and result in frequent watering to maintain plant growth. If your plant consistently requires more than one watering a day, your pot is definitely too small. With proper sizing of your container you should be able to water every two to three days under normal conditions for a mature plant. Young plants may go for a week or more before requiring watering. For raised beds that drain too slowly or do not hold moisture very well, the addition of compost can help.
If you are in a windy location and grow plants that are upright and have large leaf surface area that catches the wind — such as eggplant and tomato — staking of the pots or plants may be necessary to keep them from constantly blowing over. Individual pots can be staked to a metal pipe, pole or rebar that is driven into the ground. If you have numerous pots in one location, you can drive poles at each end of the row to attach a wire or bar on which you can secure your plants.
For more information on this and other gardening topics, please visit the CTAHR electronic publication website at http://www.ctahr.hawaii.edu/Site/Info.aspx or visit any of the local Cooperative Extension Service offices around the island. I can be reached at russelln@hawaii.edu.