Foliar Feeding with Food from the Sea

In the 1950s, scientists used radioactive isotope "tracers" to prove that plants can absorb nutrients through their leaves and stems ("foliar feeding") just as easily as through their roots.  In an old Organic Gardening article, Supercharge your Plants with Seafood Sprays (July 1997), Vicki Mattern observes that while feeding the soil is the cardinal rule in gardening organically, foliar feeding has its place and she lays out the why, what, when and how.

WHY?  Increases yields & makes nutrients available to plants more quickly than other kinds of fertilizers

• If your plants are suffering obvious nutrient deficiencies, such as stunted growth, strangely colored leaves, etc.
• If your plants are in danger of unusual stress -- light frost (studies have shown that seaweed sprays can provide an extra 2 to 3 degrees of frost protection), drought, intense heat, flooding, etc.
• When your plants are at their most critical stages of growth: 1) setting buds (just before they bloom) and 2) at fruit set (when you see tiny fruits beginning to form).  Studies have found that seaweed sprays can boost strawberry yields up to 133%, tomato yields up to 37%    
• Research has also shown that seaweed sprays can suppress disease (botrytis on strawberries); reduce the number of pests (red spider mites on cucumbers and apples); increase the shelf life of many crops.

WHAT?  Fish, Seaweed or a Blend of Both

• "Fish-only" brands provide:  1) high amounts of nitrogen -- the food necessary for all stages of plant growth, especially for leaf formation,  2) phosphorus -- essential for the formation of plant roots, flowers and fruits and  3)  potassium -- helps plants absorb nutrients, makes them more vigorous and able to resist diseases.
• Seaweed based fertilizers supply  1) the big three nutrients (N, P and K) although not in the great amount that Fish does.  2) micronutrients and plant growth compounds, vital to a plants' health.  Land-based fertilizers do not easily provide these benefits.  NB: In his book Seaweed and Plant Growth (Clemson University, 1987), Dr. Senn, who is professor emeritus of horticulture at Clemson U, reports that seaweed contains at least 70 plant-friendly trace elements, including boron, copper, iron, manganese and zinc.  He adds that  the plant growth compounds also present in seaweed (cytokinens, betaines, giberellins, etc.), speed up the process of flowering and fruiting and increase plant survival during drought and other times of stress.

WHEN?  Morning!

• "It's best to foliar feed in the morning," advises Dr. Senn, explaining that "plants are hungry then, just like people." 
• As the day progresses, the cells on the surface of a plant's leaves close up to reduce moisture loss.  When those cells are closed, they are less receptive to liquid nutrients than in the morning when they're wide open.

OMRI approved fish & seaweed fertilizer

HOW?  Simple spray bottle with diluted seaweed and/or fish fertilizer.

• Every 2 weeks, feed the foliage of your plants with a combination of fish and seaweed like Neptune's Harvest for a well-balanced "meal".
• Look for seaweed that comes from cold waters, especially the waters off New England and Norway.
• Ascophyllum nodosum is considered "the cadillac of seaweeds" according to Dr. Senn.