Blossom End Rot in Squash: Why it Happens and How to Fix It
Blossom end rot is the last thing you’d expect on your squash. You go to harvest the vegetables, only to find brown, black, and mushy spots on their bottoms! Don’t worry; this condition isn’t a disease. Join seasoned grower Jerad Bryant to learn how to fix it.
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My zucchinis had blossom end rot one year. I noticed mushy spots on the bottom of the veggies that slowly spread over time. I cut the ends off and ate the zucchini, but I had to solve the problem in the garden to prevent the rest from rotting.
Though squash blossom end rot often stems from a calcium deficiency, the reason for this deficiency varies. Perhaps there’s not enough calcium in the soil, or there’s not enough moisture. More often than not, end rot occurs because there’s too much or not enough water near the squash roots.
To understand the condition, we’ll take a look at how it works and what crops it affects in the home garden. Don’t worry if your squash has symptoms of end rot; we’ll solve the problem in no time!
What Is Blossom End Rot?
Blossom end rot (BER) is a physiological condition that affects fruiting crops. It’s not a disease, nor does a pest cause it. It happens because of improper growing conditions that deprive crops of the nutrients they need to thrive.
Squash Blossom End Rot
This condition occurs when squash lacks the nutrients to form taut skin and firm flesh. As the vegetable enlarges, it begins to rot near the bottom. Black, leathery skin forms and spreads. As the rot spreads, fungal and bacterial diseases may invade the squash and cause further damage.
Instead of letting the rot spread, it’s good to catch the condition early. When you apply corrections early in the growing season, there’s plenty of time for the squash plants to produce more healthy harvests.
Alongside squash, this rot affects tomatoes, peppers, eggplants, and vine crops like pumpkins. Prevention is the ideal way to keep it out of the garden, but this rot will occasionally occur despite your best efforts. Don’t fret—dealing with the rot is a rite of passage for home gardeners!
Lookalike Conditions
It’s easy to confuse squash blossom end rot with other skin disorders, like sunscald or cracking. You’ll know what it is by the location where it occurs. This rot starts on the bottom of the fruit or vegetable and works its way upwards.
Scalding occurs anywhere the sun hits the skin, and cracking occurs on the top or along the sides of the squash. If you notice multiple squash with the same black spot on their ends, it’s likely squash blossom end rot.
Why It Happens
This physiological condition often occurs because of a lack of calcium. The skin lacks the nutrients it needs, leading to sunken spots, brown flesh, and rotting symptoms. Keep it at bay with regular watering and a proper fertilizing regimen.
Moisture Imbalance
Many gardeners assume they have a calcium deficiency when the cause is watering infrequently or too frequently! Garden crops need plenty of water to thrive during the hot summer months. Too much and not enough water prevent the roots from taking in calcium.
Calcium moves from the soil into the squash when the vegetable needs it. This action relies on water movement in the plant. When the leaves transpire and release water, the roots pull calcium up from below ground.
If the soil is too dry, the squash vine transpires less and takes in less calcium. Similarly, when the ground is waterlogged, squash roots cannot take in sufficient water or calcium.
The key isn’t watering all the time; it’s watering when the vines need moisture most. Consistent watering is ideal. Let the soil surface dry a bit, then water deeply to ensure the roots take in enough water and calcium.
Calcium Deficiency
If you’ve been watering consistently and the rot symptoms continue appearing, the issue may be a calcium deficiency. Calcium is crucial for proper squash formation. Without it, you’ll also notice deficiency symptoms in the leaves, like crinkles, chlorosis, and dark leaf veins.
Fortunately, garden supply companies make calcium fertilizers that help ease the symptoms. Some have magnesium and sulfur in them, while others are purely calcium.
Too much calcium may also cause growing issues. If you’re unsure how much is in your soil, consider using a soil test. Many local universities and Master Gardener programs offer cheap soil testing a few times a year. The test will tell you how much calcium is present, so you can determine how much to add.
Excess Fertilizer
Occasionally, too much fertilizer causes squash blossom end rot! Excess nutrients early in the growing season lead to excess leafy growth at the expense of flowers, fruits, and stems. This leafy growth holds calcium, preventing it from being accessible while the squash is forming.
This leads to low calcium levels in the soil, which causes the rot as the squash begins to form. Too much nitrogen, magnesium, potassium, or sodium promotes excess leafy growth at the expense of flowers and squash later in the growing season.
Growers who use compost tend not to overfertilize, as compost feeds the earth slowly over time. Consider switching from fertilizing to mulching with soil amendments, like compost and leaf mold.
How to Fix It
So, you’ve got squash blossom end rot and you want to fix it. Let’s solve the issue! It’s easy enough once you know what’s going wrong.
Water Regularly
Regular watering tends to make the problem go away. Most growers struggle with keeping their garden moist under the hot summer sun, and consistent moisture is difficult to achieve.
Some regions may need irrigation once or twice a week during the summer, while others need daily watering to stay moist. Use the finger test if you’re unsure of the soil moisture levels. Stick your finger in the dirt about an inch down and feel if it’s wet.
If it’s wet underneath, wait a day or two before checking the soil again. If it’s dry, add plenty of water to soak the ground and moisten the roots.
Apply Calcium Fertilizer
After applying consistent irrigation, if rot still appears, it’s a good idea to test the soil for calcium. Deficiencies are rare, though they do occur in certain soils where lots of crops grow annually.
To fertilize, add one regular dose of organic calcium fertilizer to the soil. Water it in well, and splash the fertilizer off the leaves and stems to avoid burning them. After two weeks, apply another regular dose if the rot is still appearing on new squash.
Instead of fertilizer, or in conjunction with it, consider adding compost. Compost feeds the soil with nutrients, and it insulates the roots and prevents water evaporation. It’ll maintain regular moisture levels and feed hungry squash roots.
Leach Excess Fertilizer
If too much fertilizer is the issue, it’s important to leach out the nutrients before they cause problems in your squash crop. Many nutrients are easily washed away with water in a process called leaching.
To leach excess fertilizer from the ground, set a hose on a low trickle near the roots. Let the hose water the site for an hour or longer, and move it as necessary to ensure all parts receive plenty of moisture.
Water pushes nutrients deeper into the ground, and it washes them away. Watch for symptoms of excess fertilizer after leaching the site, and repeat the process as needed.
