Roses love to eat. Like people, roses love seafood served on a regular basis and seaweed, the seafood of roses, can be found in abundance in coastal New England. With so much coastline, there is no shortage of seaweed which can be used as mulch, soil conditioner, and a winter cover for roses.
While seaweed is a low-analysis fertilizer, more or less equivalent to that of farm manure, it is a teeming stew of micronutrients, hormones, vitamins, trace minerals, enzymes, amino acids, and growth stimulants, which are directly available to plants. Seaweed contains all the major and minor nutrients, as well as most of the trace elements, including manganese, iron, boron, zinc, copper, and a chelating agent known as mannitol, a simple sugar that makes micronutrients already in the soil available to the rose. Coastal rose gardeners can mulch their rose beds freely with fresh seaweed without concern for salinity. Anecdotal evidence indicates no ill effects to the soil from salt with moderate seaweed use. It conserves soil moisture and controls weeds but brings no weed seeds or plant diseases with it to the garden. University of Rhode Island researchers report that seaweed usage may result in increased plant resistance to mites and aphids and some diseases and maybe even to cold temperatures. When used as a winter cover and turned into the soil in the spring, it decomposes quickly, stimulating soil microorganisms that, in turn, break down nutrients into forms that plants can absorb. As an organic amendment, it enhances the soil’s ability to hold moisture, helps prevent wide swings in pH, and improves the tilth of the soil.
Seaweed is readily available for harvest. Just head to the beach with a rake and basket and help yourself. I have discovered several quiet, out-of–the-way, seaside nooks around my part of southern New England where I gather good seaweed. There is one special stash where the seaweed is superb and lies knee-deep at the high water mark. All I have to do is bag it up and toss it into the truck. I can attest, however, that fresh seaweed has the distinct aroma of low tide, so be sure to bring it home in someone else’s car.
If seaweed collection is not an option, there are seaweed concentrates, extracts, and liquid products that can be found in garden centers and catalogs. I use a liquid product called Response, a non-toxic seaweed-based fertilizer that sprayed directly on the foliage keeps my leaves green and healthy. It can also be applied into the soil as a drench.
I use seaweed liberally in my garden as a mulch – sometimes mixed with horse manure – and a winter cover. I like liquid fish emulsions and seaweed extracts, too, and use them as part of my liquid fertilizer program. These are all available in local garden centers. I add these products to water-soluble fertilizers like Miracle-Gro or Magnum Rose, adjust the dosages of everything, and feed weekly. What could be more New England than using products from the ocean to make plants grow?
However you do this, be sure to put seafood on the menu in your rose garden and enjoy the results.