Nutrients for Kratky Strawberries

Garden fertilizers assume the soil will supply part of what a plant needs. In water there is no soil, so the nutrient has to be complete: nitrogen, phosphorus and potassium, plus calcium, magnesium and trace elements such as iron.

Any complete hydroponic nutrient will grow strawberries. Many Kratky growers use a dry three-part recipe made of a fruiting-crop formula, calcium nitrate and Epsom salt, because it is inexpensive and keeps well. Bottled liquid nutrients are easier to measure and work just as well.

Strawberries are sensitive to salt, so they prefer a weaker solution than tomatoes or peppers.

• Young plants: start at about half the strength on the label.
• Established plants: many growers run an EC of roughly 1.0 to 1.5 mS/cm.
• No meter? Mix at half to three-quarters of the label rate and watch the plant.

Brown, crisp leaf edges are the usual sign the solution is too strong.

Plants take up water faster than they take up nutrients, and water also evaporates. In a container that is never drained, the remaining solution gets steadily more concentrated as the level falls. This is the main reason strawberries in Kratky containers need more attention than lettuce.

• Top up with plain water or a weaker mix, not full-strength solution, so the concentration comes back down.
• If you have an EC meter, measure before and after and aim for your target range.
• Leave an air gap under the lid every time.
• Every few weeks, empty the container and start with fresh solution. This resets both the strength and the balance between nutrients.

Most tap water works. Very hard water raises pH and adds its own minerals, so you may need more pH adjuster. If your tap water is heavily chlorinated, letting it stand overnight before mixing helps.

• Masterblend for Kratky Strawberries: Mixing Ratios Explained
• What EC Should Kratky Strawberries Be?