How to feed tomato plants in containers?

Tomato plants grow well in containers, provided the pots are large enough and the plants are kept well-watered and fed. Tomato plants grown in an open garden pull nutrients as needed from the soil. In containers, tomato plants often need more frequent feeding, as the nutrients in smaller quantities of soil deplete quickly. Feed these tomato plants at least once every 10 to 14 days. This is assuming you are using liquid or granules, rather than fertiliser spikes (these are left in the soil).

1. Use a good starter fertiliser, mixed in with the potting soil, when you first plant tomatoes. If you've already planted them in containers, add a water-soluble starter fertiliser to the top 2.5 cm (1 inch) of soil and water it in well. When water starts seeping out of the container base, you've watered deeply enough. If you are using a liquid fertiliser, apply it carefully to avoid splashes and follow mixing directions and application directions fully.
2. Fertilize the plant again in two weeks. This time, use either another water-soluble liquid or granule fertiliser (for tomatoes) or add a tomato fertiliser spike to the pot. Fertiliser spikes release fertiliser gradually over time (up to two months) -- these may be more convenient if you have a very busy schedule. No matter which kind of fertiliser you use, water the soil well so the fertiliser travels down towards the plant roots where the plant can use it.
3. Continue fertilising the plant every two weeks (unless you use spikes), until the first fruit blossoms appear. When this occurs, start fertilising every week throughout the rest of the growing season.

Tomatoes are heavy feeders. They are greedy and like lots of food. Use tomato fertilizer wisely and your plants will reward you.

Why container watering impacts feeding

Tomatoes in pots and containers require frequent watering or they will dry out. But watering leaches nutrients out of container plants. So you need to be especially vigilant to include tomato fertilizer in your container gardening plan to get best results.

Try these top tips for fertilizing tomatoes in pots

• Add a slow-release fertilizer (like Osmocote) to your containers when planting. Nutrients will disperse over time.
• Try grass clippings. They do double duty as mulch. Apply a couple of inches to the soil surface of your containers.
• One easy way to fertilize tomatoes is to mix a small amount of soluble, balanced tomato fertilizer (like Miracle Grow for Tomatoes) into water. Fertilize and water at the same time.
• When it comes to fertilizing tomatoes in pots, little and often is better than a lot, less often. Tomatoes like regular feedings of small amounts of fertilizer rather than infrequent, large doses. Some gardeners swear by weekly feedings or even more often. Others say every two weeks is enough. Take time to find out the best schedule that works for your plants. There are plenty of variables including tomato variety, container size, plant size, your weather, and potting mix type.
• You’ll know you’re feeding plants too much when they produce more leaves than fruit. If production is low or foliage starts to yellow, you’re probably not feeding enough.
• A good fertilizer to use on container tomatoes should have more phosphorus (the middle number in a fertilizer’s 3-number series) than nitrogen (the first number in a fertilizer’s 3-number series). Too much nitrogen can mean lots of leaves and few fruit.
• Avoid feeding tomatoes at the peak of the day or when weather is really hot – say, when temperatures are over 90-95 degrees. Extra nutrients are hard for plants to digest in the heat.