Flower tip rot (blackening of the base of a tomato) is every gardener’s nightmare. You come to the garden full of expectations of beautiful fruits, but you find dry, sunken, dark brown to black spots on the tips.<\/p>\n\n\n\n
The good news: It is not a contagious disease that spreads from plant to plant like mold. It is a physiological disorder caused by a lack of calcium in the fruits.<\/p>\n\n\n\n
Here is a complete guide on how to properly fight flower tip rot and save your crop.<\/p>\n\n\n\n
Why does it happen? (Myth vs. Reality)<\/p>\n\n\n\n
Many people think: “My tomatoes are turning black; the soil lacks calcium, I need to add it.” However, in most cases, there is enough calcium in the soil. The problem is that the plant cannot transport it to the fruit.<\/p>\n\n\n\n
Calcium is transported throughout the plant along with water through transpiration (evaporation of water from the leaves). If this water transport is disrupted, calcium reaches the leaves but not the tip of the fruit. The cell walls at the tip of the tomato break down, leading to black rot.<\/p>\n\n\n\n
Main causes:<\/p>\n\n\n\n
Irregular watering: Alternating between extreme drought and overwatering.<\/p>\n\n\n\n
High temperatures and dry air: The plant closes its stomata to prevent water loss, which stops the transport of calcium.<\/p>\n\n\n\n
Overfertilization with nitrogen or potassium: Too much nitrogen leads to lush leaf growth, which depletes all the calcium. Conversely, too much potassium or magnesium blocks the uptake of calcium by the roots.<\/p>\n\n\n\n
Damaged roots: Burying too deeply near the stem.<\/p>\n\n\n\n
How to properly combat rot?<\/p>\n\n\n\n
If spots have already appeared on the fruit, they cannot be saved (they can be removed to prevent weakening the plant). However, immediate action is needed to protect the rest of the crop.
\u2026 First aid: Foliar fertilization (immediate action)<\/p>\n\n\n\n
Since calcium is absorbed slowly through the roots, it must be supplied directly to where it is lacking.<\/p>\n\n\n\n
Buy a liquid calcium fertilizer (e.g. Wuxal Calcium, Formit or an organic alternative).<\/p>\n\n\n\n
Spray it on the leaves and young fruit.<\/p>\n\n\n\n
Important: Spray early in the morning or evening, never in direct sunlight, as this will burn the leaves. Repeat the application every 7\u201310 days until the problem is resolved.<\/p>\n\n\n\n
Regular and deep watering (the basis for success)<\/p>\n\n\n\n
Tomatoes need stability. Water them less frequently but thoroughly (directly to the roots) so that the soil can absorb the water well, rather than just lightly misting the surface daily. The soil should never dry out so much that the plant droops.<\/p>\n\n\n\n
Mulching (retaining moisture)
Spread a layer of mulch (grass clippings, straw or wood chips) around the tomato stems. Mulch helps maintain consistent soil moisture and protects the roots from overheating and sudden changes in temperature.<\/p>\n\n\n\n
Avoid nitrogen deficiency<\/p>\n\n\n\n
Once the tomatoes start to bear fruit, reduce the use of nitrogen-rich fertilizers (such as undiluted, fermented chicken manure or \u201cchicken manure\u201d). Instead, use a balanced fertilizer, ideally one specifically formulated for tomatoes and peppers (which are also sensitive to nitrogen deficiency).<\/p>\n\n\n\n
Greenhouse shading
If you are growing tomatoes in a greenhouse, good ventilation is essential during the summer heat. At temperatures above 32\u00b0C (90\u00b0F), the plant becomes stressed and can no longer absorb calcium. You can also shade the greenhouse with a special net or lime in the summer.<\/p>\n\n\n\n
Prevention for next year
Liming in the fall: If the soil is proven to be acidic, apply dolomite lime in the fall. You can add a handful of ground eggshells to the planting hole (they work slowly but have a long-lasting effect) or a little garden lime.<\/p>\n\n\n\n
Choosing a variety: Elongated, fleshy tomatoes (such as San Marzano or “Bull’s Heart”) are more susceptible to blossom end rot than classic round or small cherry tomatoes. If you struggle with this problem every year, try changing the variety. Are you having problems with rot on a particular variety this year, or did it appear for the first time because of a heat wave?<\/p>\n","protected":false},"excerpt":{"rendered":"
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