Grow It Eat It: Maryland's Food Gardening Network

Happy Roots

Water
The limited volume of growing medium available to container vegetable plants makes it critical to keep the root system moist at all times.

Watering needs will vary depending on container size, ambient temperature, wind, sunlight, and humidity. You can count on watering most container vegetable plants daily during the summer months. The growing media should always be moist, but not soggy. Add water slowly until you see it drain out the bottom (except for “self-watering” types.)
Use a watering can or nozzle on the end of a hose that produces a soft stream of water. Be careful not to use hot water! It can burn leaves and young roots.
Eating quality and yield will be greatly reduced if plants are allowed to wilt due to a lack of water. Drought stress will kill feeder roots and slow plants down.
Water-holding polymers can be purchased and mixed with growing media to help containers retain moisture. Although effective, these products are not necessary for success.
Small containers dry out more quickly than large containers. Use a saucer to catch excess water.
Large, mature plants need more water than seedlings and young plants.
Micro-irrigation with soaker hoses and drip emitters is efficient, convenient, and relatively inexpensive. You can water all of your containers automatically using a series of drip emitters on a timer.

Fertilizers
Regardless of the growing media used you will need to fertilize plants regularly. University of Maryland researchers were able to double pepper production when 5-gallon buckets containing 100% compost were fertilized, at planting, with a slow-release fertilizer. This occurred because nitrogen is usually the limiting nutrient. This highly soluble nutrient is required in large quantities by vegetable crops and is easily lost in the water that drains from the bottom of your containers.

The questions “how much” and “how often” to fertilize will depend on many factors— type of fertilizer, plant needs, type of container, etc.
Even “quick” crops like leaf lettuce or broccoli raab that mature in 35-45 days may need to be several times.
Long-season crops like tomato, cucumber, eggplant, and pepper may need to be lightly fertilized every 2 weeks or so, to produce a continuous harvest.
Soluble fertilizers in liquid or powder form are very convenient to use and effective because the nutrients are immediately available. They are mixed with water and poured around plants according to label directions.
Liquid sea kelp and fish fertilizer, and compost tea are excellent organic fertilizers that you mix with water and apply around plants.
Blood meal, composted chicken manure, nitrate of soda, cottonseed meal and alfalfa meal, and worm castings are all dry organic fertilizers that you can mix into growing media at planting and re-apply as needed.
Many non-organic fertilizers are available for container gardening. They are usually either fast-acting soluble “plant foods” that are mixed with water, or pelletized slow-release fertilizers that are relatively expensive but can provide nutrients for 2-4 months.
NOTE: never add lime, wood ashes, or gypsum to any commercial growing media or compost. Lime is already added to commercial soil-less mixes. Compost, either commercial or backyard, has a pH of 6.8-7.5 (a soil pH of 6.2-7.2 is a good range for most vegetable plants.) And always follow fertilizer label directions.

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For more information, contact Jon Traunfeld, University of Maryland Extension Specialist

Last updated: 01/7/2011