Put fertilizer on tomato plants only when their soil or growing medium needs it. A soil test, the product label and the plant’s growing conditions are better guides than a homemade “fruit booster.” Adding phosphorus, Epsom salts, aspirin or several feeds together does not reliably turn flowers into tomatoes.
First identify what is limiting the crop
Separate three situations: a small, poorly growing plant; a leafy plant with few flowers; and a plant that flowers but fails to set fruit. They do not necessarily need the same treatment. Check light, moisture, root health, variety and recent weather alongside fertility.
Before buying anything, write down what is already in the bed or pot: compost, manure, slow-release fertilizer and liquid feeds all contribute nutrients. Keep the labels so you can avoid applying several products for the same purpose.
Choose fertilizer from evidence
University of Minnesota Extension recommends using soil-test results for phosphorus and potassium decisions and warns that excess nitrogen produces leafy growth and delays fruiting. A product marketed for tomatoes can be convenient, but its name does not establish that your garden needs its nutrient ratio.
Read the three numbers on the package as nitrogen, phosphorus and potassium information. Match the application to the recommendation and measured growing area. Do not substitute a tablespoon-per-plant recipe from another product: formulations differ.
For containers, check whether the potting mix already includes fertilizer and for how long. Use a feed intended for that growing situation at its labelled rate. Keep drainage working and avoid applying concentrated fertilizer to a severely dry, stressed root ball.
Compost, worm castings and liquid organic feeds
Mature compost can be part of soil preparation. It is not a precisely measured substitute for every nutrient, and adding more each time flowering slows is not a diagnosis. Worm castings likewise vary; compare their analysis, cost and intended use rather than assuming they contain everything tomatoes need.
Fish-based fertilizers and seaweed products differ substantially. Some are nutrient sources, while others have very low nutrient concentrations. Read the analysis and directions rather than treating “organic” as a promise that unlimited use is harmless.
There is no need to brew a bucket of compost tea or combine multiple products as a default fruiting treatment. This guide does not recommend homemade foliar mixtures or promise disease prevention from them. Keep the care routine simple enough that you can tell what changed.
What about Epsom salts?
Epsom salt supplies magnesium and sulfur; it is not a complete tomato fertilizer. Use a confirmed need and appropriate advice before adding it. Nebraska Extension explains why routine applications are unnecessary in many vegetable gardens. A repeating spray schedule is not justified merely because tomatoes are flowering.
Aspirin and blossom-set sprays
Do not use crushed aspirin as a routine substitute for diagnosis or a labelled plant treatment. The earlier claim that a homemade aspirin spray reliably increases yield or prevents blight is not a dependable gardening recommendation.
A blossom-set product is also not an all-purpose cure. Check its exact label, permitted crop and intended conditions before considering it. If flowers are dropping during unsuitable weather, review Maryland Extension’s fruit-set guidance. Do not assume spraying can correct every temperature or pollination problem.
Blossom-end rot needs a different response
A dark, sunken patch at the blossom end of a fruit is not proof that you need a stronger flowering feed. Calcium delivery to developing fruit can be disrupted by moisture and root problems. Maintain even moisture and use testing to assess soil amendments. Existing damaged tissue will not heal after a spray. See Minnesota Extension’s tomato disorders guide.
Keep the productive parts of the plant
Support vines and use pruning appropriate to the cultivar; suckers are capable of fruiting. Keep healthy foliage rather than stripping it away to “send nutrients to fruit.” If the plant is already growing well, the most useful next step may be steady care and observation rather than another product. Record applications and harvests so next season’s decisions are based on results.