Learn how to perform a home DIY soil test for alkaline or acidic soils and what you need to know about minerals in your water.
How Do I Fix Blossom End Rot on My Tomatoes?
For the past three years, I’ve had blossom end rot on all my tomatoes. I’ve read that this isn’t a virus, but that it’s a problem with too much or not enough water, or watering at the wrong time. I’ve also been told to add lime or to water with a mixture of powdered milk or Epsom salt. I’ve taken all of this advice with no success and am at a loss. Do you have any suggestions?
A lot of gardeners have problems with blossom end rot. If you reach out on any garden forum, people will overwhelmingly tell you to put eggshells in your soil. But here’s the catch: Those eggshells have to decompose first, so that trick only works well for the following year!
Several different factors can cause blossom end rot:
- Poor calcium in the soil
- Overwatering or under-watering
- Over-fertilizing
- Soil pH
- Root damage
- Plant variety
- Time of year
Since the cause is often a calcium imbalance, people think adding calcium should solve the problem. Eggshells, shellfish, and lime contain calcium, and so does well water. If you have limescale on your faucets, there’s a good chance your plants receive enough calcium through the water, which is more usable than materials that have to decompose first. So if you’ve amended your soil with calcium, you can disregard calcium imbalance as the cause. You can also speed the decomposition of calcium-containing organic products by adding beneficial microbes to your soil. My favorite method is pouring whey from my cheesemaking onto the soil. Calcium and probiotics, all in one!
Inconsistent watering can also cause blossom end rot. Too much water will damage roots, keeping the plant from taking up necessary calcium. If the plant doesn’t receive enough water, it can’t transport the calcium. To solve this, use mulch and monitor your watering. If you use weeper lines or driplines, water for the same amount of time every day that it doesn’t rain so your water use is consistent. If you can feel damp soil less than an inch below ground level, you don’t need to water yet.
Over-fertilizing, specifically with nitrogen, magnesium, and phosphorus, can make blossom end rot worse. That’s not great, because nitrogen makes plants grow, phosphorus makes them bloom, and magnesium helps them absorb calcium. So the trick is balancing the fertilizer. That’s why I like to combine compost and microbes: Together, they tend to provide more balance than most chemical fertilizers. Epsom salts, composed of magnesium sulfate, could actually be making the problem worse.
Home DIY Soil Test
And I hate to tell you this, but that garden lime could also be a problem. Yes, soils need calcium. But growing tomatoes prefer soil that’s on the acidic side, and lime is alkaline. Here’s a simple DIY soil test for acidity: Measure equal amounts of soil into two canning jars so they’re not quite half-full, then pour in enough distilled water to fully drench the soil with at least an inch of water over it. (Don’t use tap water or well water for this. Only use distilled water, so it has a neutral pH.) Shake the jars well. Now, add 2 tablespoons of baking soda to one of the jars. Pour about 1/4 cup of vinegar into the other. Lean close and listen. If the one with baking soda fizzes, your soil is acidic; if the one with vinegar fizzes, your soil is alkaline. Of course, you can send your soil in for testing or buy kits that’ll give you a more precise measurement. For alkaline soils, add elemental sulfur, compost tea, coffee grounds, waste coffee, stale beer, or that nice cheesemaking whey. For acidic soils, try a little bone meal when you transplant tomatoes to add calcium while also supporting root growth with potassium.
Damaged roots don’t transport calcium well. Tomato roots can take more abuse than other plants, but they do have limits. Digging too close to the plant, overwatering, or planting in restrictive containers can all cause root problems.
Some varieties of tomatoes, peppers, and eggplants are just more susceptible. I find that paste-type tomatoes succumb first, as do longer semi-hot peppers, such as Anaheims. Read a few reviews – the kind people aren’t paid to write – to learn if a variety tends to get blossom end rot. I love ‘Sunrise Sauce,’ a new orange F1 determinate paste tomato, because only the first tomato from each plant gets blossom end rot in my garden.
Why the first tomato? Sometimes, blossom end rot is just temporary. It’s common to find it on the first fruits but not get it again. Calcium uptake can be different depending on the plant’s maturity, the season, and more. This can worsen when gardeners apply high-nitrogen fertilizers when their plants are still small. But when people claim they sprinkled eggshells beneath their tomatoes and that solved the problem, they most likely weren’t going to get more blossom end rot anyway. Because, as I said before, eggshells must decompose before they work. If you keep getting blossom end rot after those first few tomatoes, then you have other problems to address.
There isn’t a one-size-fits-all solution for blossom end rot. I recommend sending a soil sample this fall, because that will give you specific results on exactly what your soil needs – if it even needs anything at all. In the meantime, do the canning jar soil test and look at your watering techniques to see if you can improve something now. Some gardeners apply foliar treatments, which put calcium directly on the leaves so it absorbs faster, but most of these aren’t organic. If an organic garden is your priority, then ask your garden center if it has organic foliar treatments.
