Cucumber Fertilizer 8-16-36 | Chelated Micronutrients | Hydroponics, Soil & Foliar Application

Everything is measured per plant, so multiply by your plant count. In containers: 1 gallon of water per plant at every stage — ½ tsp (2.8 g) while vining, ¾ tsp (4.2 g) at flowering, 1 tsp (5.6 g) once fruit sets — every 2–3 weeks. In hydroponics: 1.4 g per plant at vining, 2.8 g at flowering, 4.2 g at fruiting, then top up water to hit your target EC. In-ground beds are the exception — they're fed by area (about 70–105 g per 100 sq ft), so plant count doesn't change the amount. The calculator above will size it exactly for your grow.

Cucumbers are extremely heavy potassium feeders during fruit fill. Potassium supports water pressure inside fruit cells, activates enzymes that move sugars from leaf to fruit, and contributes to cell wall strength and firmness. Adequate potassium can also help reduce the stress conditions that sometimes contribute to cucurbitacin accumulation and bitterness — though bitterness in cucumbers is also influenced by genetics, heat, irregular watering, and overall plant stress. 36% soluble potash is sized for peak demand rather than average demand, so plants have what they need at the moment of heaviest pull.

In hydroponic systems, keep pH between 5.8 and 6.2 across all stages. In soil, aim for 6.0–6.5. pH directly governs nutrient availability — outside these ranges, key nutrients like iron and phosphorus become locked out even when present in solution. For a deeper look at how pH interacts with nutrient uptake, see Sulfate vs Chelated Fertilizers.

Cucumber bitterness is caused by cucurbitacin compounds that accumulate mainly in response to plant stress — heat, irregular watering, poor nutrition, and variety genetics all play a role. Good nutrition can help reduce one of those stressors:

• Adequate potassium supports water balance within fruit cells
• Controlled nitrogen helps avoid excessive vine stress
• Balanced micronutrients help reduce the overall stress load that can trigger cucurbitacin production

Combine good nutrition with consistent watering (avoid letting plants dry out), choose low-bitterness varieties where available, and supplement with Cal-Mag Plus during fruit development. No fertilizer can fully offset varietal genetics or severe environmental stress.

Yes — greenhouse trellised cucumbers are the standard reference profile for these rates. Feed per plant: about 1.4 g at vining, 2.8 g at flowering, and 4.2 g at fruiting, adjusting water to hold your final measured EC in range. Monitor EC closely — greenhouse plants under sustained light pressure can be more sensitive to EC drift than outdoor plants. Increase Cal-Mag support during rapid growth periods and adjust based on variety (European seedless types typically run higher EC than standard slicing types).

Container cucumbers feed in two phases, both measured per plant. At potting, mix about ½ teaspoon (2.8 g) per plant thoroughly into the media. Then switch to a liquid feed in 1 gallon of water per plant: ½ teaspoon (2.8 g) while vining, ¾ teaspoon (4.2 g) at flowering, and 1 teaspoon (5.6 g) once fruit sets — every 2 to 3 weeks. The water stays at one gallon; only the fertilizer amount steps up. Apply to moist media and water in with plain water right after. Containers and coco media drain quickly and benefit from routine Cal-Mag Plus support for calcium and magnesium. The Guided Plan tab in the calculator above will build a full staged container schedule for your exact number of plants.

Feeding frequency depends on your method. In hydroponic reservoirs, feed at the full fruiting rate (about 4.2 g per plant) and replace the solution every 7 to 14 days, monitoring EC between changes. In soil, side-dress at first fruit set and repeat every few weeks as fruiting continues. In containers, run a liquid feed every 2 to 3 weeks, stepping up to the fruiting rate. Across all methods, fruiting is when potassium demand peaks, so this is the stage to stay consistent — and to pair with a separate calcium source like Cal-Mag Plus for firm fruit.

No. Calcium and concentrated phosphate react to form insoluble calcium phosphate, which precipitates out as white cloudiness and makes both nutrients unavailable. Always pre-dissolve each product separately in warm water, then add them to the reservoir in order: calcium source first (pre-dissolved Calcium Nitrate if used), then Cal-Mag Plus stock, then the 8-16-36 solution last. Adjust pH after everything is fully dispersed. Never combine calcium sources and concentrated 8-16-36 in the same stock tank.

Calcium and phosphorus are chemically incompatible in concentrated solution. When mixed, they form insoluble calcium phosphate that precipitates out and becomes unavailable to plants. Since this formula contains 16% available phosphate (P₂O₅), calcium has to be supplied separately. Cucumbers need consistent calcium for cell wall integrity and firm fruit development — use Cal-Mag Plus 2-0-0 and/or Calcium Nitrate 15.5-0-0 as companions throughout the season.

The fertilizer is hygroscopic, meaning it absorbs moisture from the air. Keep the bag sealed tight between uses and store in a cool, dry place out of direct sunlight. If it clumps from moisture exposure, simply break it up — efficacy is not affected. For long-term storage, double-bag inside a sealed plastic tub.

Yes. This formula works for all cucurbit crops including watermelons, cantaloupes, honeydew, squash, pumpkins, and gourds. All cucurbits share similar nutritional needs — high potassium for fruit quality, enhanced phosphorus for flowering, and controlled nitrogen to avoid excessive vine growth at the expense of fruit. Apply at the standard cucumber rates listed in the Application Rates tables; large sprawling vines take the full rate, compact bush types take the low end.

Both are high-potassium, water-soluble formulas built on the same chelated-micronutrient backbone, but the macronutrient ratios are tuned to different crops. Cucumber 8-16-36 runs a 4.5:1 K to N ratio with controlled nitrogen suited to trellised cucurbit vines. Tomato Fertilizer 4-18-38 runs a higher 9.5:1 ratio with even lower nitrogen, ideal once nightshades like tomatoes, peppers, and eggplant are flowering. If you're growing cucumbers, melons, squash, or other cucurbits, 8-16-36 is the right base. For fruiting nightshades, reach for the tomato formula instead.

Stop foliar feeding 7 days before harvest and rinse fruit before use. In soil, taper or skip the final scheduled side-dress as the last fruit ripens. In hydroponic systems, many growers run plain pH-adjusted water for the last week to finish clean. This is general best practice for flavor and shelf life, not a fix for a specific problem — a clean finish simply tends to produce better-tasting, longer-keeping fruit.

No. Cucumber Fertilizer 8-16-36 is a synthetic water-soluble specialty fertilizer formulated from solution-grade mineral salts — not an OMRI-listed organic input. It's CDFA registered and independently lab tested. Growers who need OMRI-listed inputs should look at Bone Meal, Blood Meal, and other organic amendments instead.