Liquid seaweed can provide valuable nutrients to apple trees and stimulate growth in positive ways. Improperly timed seaweed sprays, however, can be detrimental to apple tree growth and fruit production. Understanding how liquid seaweed impacts apple trees and how tree needs change through the growing season helps ensure successful use of liquid seaweed with apple trees.
Liquid seaweed, also known as liquid kelp or kelp extract, contains major plant nutrients such as nitrogen, phosphorus and potassium. However, its main benefit comes not as a fertilizer but as a growth stimulant. Liquid seaweed is rich in plant growth hormones and micronutrients that boost apple tree growth. When applied to apple tree foliage, trees absorb these beneficial compounds directly where they need them most. Liquid seaweed sprays can improve crop yield and quality, while they stimulate root development. This increases an apple tree's ability to take up nutrients directly from the soil.
Timing Seaweed Sprays
Liquid seaweed applications benefit apple trees most when done in early spring. When soils are still cool, nutrients are not readily available to trees and other plants. Spraying just when blossom buds begin to show green -- before apples begin to bloom -- will stimulate growth and provide nutrients at a critical time. After your apple tree is done blooming and its petals drop, you can spray the tree again within 10 to 14 days from the petal fall. Do not spray your apple tree with liquid seaweed any later in the season. Late sprays can delay fruit coloring. They also promote tender new growth, susceptible to winter damage, which decreases cold hardiness of your tree.
When applying a liquid seaweed solution, use a sprayer that will deliver a fine mist to wet foliage completely. Use most liquid seaweed extracts at a rate of 1 to 2.5 ounces of extract to 1 gallon of water. Follow the manufacturer's instructions on your product's label. Even though this is a natural product, wear protective eyewear, gloves and protective clothing when spraying apple trees. Clear the area of children and pets. Don't be tempted to apply extra product; too much liquid seaweed can inhibit growth. Apply the spray in early morning when apple tree foliage will absorb it quickly and dry well before the sun gets warm. Always check the forecast. If rain is expected within 24 hours, postpone your spray.
When Not to Spray
When spraying apple trees -- with liquid seaweed or any other product -- one of the most important things to know is when not to spray. Never spray your apple tree with liquid seaweed when the tree is in bloom. Among the many benefits of liquid seaweed is the product's ability to control and kill some insect pests. If sprayed while your tree is blooming, liquid seaweed could possibly harm the beneficial insects pollinating your apple tree.