Garden Notes

Autumn golds

By Abigail Higgins - September 28, 2006

Now we are officially in fall. The magic of the wild garden that is the Vineyard in autumn is all about us. Deepening color in foliage and the abundance of golden grasses studded with aster and goldenrod create a tapestry of sometimes overwhelming beauty.

Some Island gardens will have experienced frost already; thankfully our vegetable patch is not one of them. I have, however, cleared out some areas where zucchini and lettuce were grown that are no longer producing. These need a cover crop; a conversation with a friend last week brought up the subject, so I shall write a bit about them.

Cover crops are also known as living mulches, green manures, or catch crops: all these terms describe in some way what the practice of cover cropping does for a garden or field. "Covers" the soil surface, supplies organic matter and benefits like "manure," prevents soil erosion by "catching" wind and water. In the past I have usually by habit gone along with winter rye as a cover crop in our vegetable garden. Other cover crops are available to try however, and just a quick perusal of mail order catalogues should pique one's interest.

Photo by Susan Safford

One of the growing areas of inquiry in cover cropping is that of disease suppression. It has been discovered that cover cropping with members of the mustard family can put allelochemicals in the soil that closely resemble chemical fumigants! For example, oilseed radish works to control several types of nematodes (which are soil-borne pests that impair the quality of crops growing where they occur.) It can be sown in fall, at a rate of two pounds per hundred square feet.

Hairy vetch is another fall-sown cover crop with disease suppression aspects. It is sown to sanitize soils where tomato crops are grown, and is a component in many cover crop mixes. Use it in tandem with winter rye at the rate of .75 lb hairy vetch per 1,000 square feet to 1.75 lb. winter rye per 1,000 sq. ft. The nitrogen fixing ability of the legume complements the nitrogen catching ability of the cereal. In spring, turn these under before they grow too high, or mow them first then turn under, at least three weeks before planting.

I found no consensus about cover cropping of vineyards. Up to about four years from date of planting there is a danger, from cultivating, to new root systems of recently planted vines; but there is also a danger from the competition of perennial weeds becoming established during that interval. Inter-row planting of white clover is a possibility. Obtain UC/ANR publication number 3338, "Cover Cropping in Vineyards: A Grower's Handbook," for further data.

In response to a casual conversation about the edibility of dahlia roots: I have not been able to turn up more than passing references to their having been eaten by the Aztec people at the time of the Spanish invasion of Mexico. It is known that they were eaten, but that seems to be the extent of it. The decorative aspects of dahlias are what impressed the Spaniards; they were whisked away to the royal botanical collection in Spain and jealously guarded. We are still jealously guarding dahlias for their decorative qualities, which is why some gardeners exert themselves to such a degree in the digging and storing of prized varieties. With new cultivars being introduced all the time, there are thousands upon thousands of named dahlia cultivars - one never knows when a beloved cultivar will be pushed off the stage of trade.

The sandplain tapestry. Photo by Susan Safford
The sandplain tapestry. Photos by Susan Safford
However, sooner in the frost-prone gardens and later near the shore or in the higher elevations, we shall be digging and storing dahlia tubers, so we might as well discuss that. Once the plants have bloomed, tag, or confirm the labeling, because they will be impossible to ID when blackened by frost. It is only after frost that dahlias are dug, as the plant's energy is supposedly sent down into the tubers and they will then store well.

Cut off the tops with loppers and set the tubers to dry and cure a few days where they cannot be damaged by further frost. At this point the tubers may be hosed off or left with soil clinging. Individual clumps can be placed in sections of newspaper, the corners brought up around the neck of the clump, and a piece of twine or rubber band used to secure the paper and the ID tag. Place the wrapped clumps in a carton, close it up, and store in a cool, frost-free place.

Because I have fairly large numbers of certain dahlia cultivars to collect from the different gardens we work in, I usually use and recycle the plastic bags that potting soil or manure comes in. I write the cultivar name in magic marker on the outside of the bag, and then collect all of those roots into the bag, soil attached. The bags then go into the cellar until the end of March, when it is time to go over them for division and potting up.

This year's favorites echo last year's: the gallery dahlia series. These dahlias are expensive, but their performance warrants it. Of the three we used, 'Rembrandt,' 'Leonardo,' and 'Salvador,' the first, a girly pink, seems to be most floriferous, but all three are stars. Despite being low-growing plants, all three have usable stems for cutting and they are early flowering.

For lovers of purple dahlias, 'Ted's Choice' is a standout in the garden row in terms of floriferousness. In annual dahlias, the series 'Bishop's Children' performed well in the border, with dark foliage and a beautiful blend of colors in floriferous plants two to two and a half feet high. Further favorites are oldies-but-goodies 'Fascination' with lavender anemone-type blossoms and dark foliage; 'A La Mode,' a formal decorative bicolor of soft apricot and white in the BB category; and 'Ringo,' a bicolor red and white formal decorative (the two colors bleed into each other instead of having distinct edges) that is in the M category.

Saturday is the Harvest Festival at the fairgrounds of the Martha's Vineyard Agricultural Society. Admission is free. From noon on there will be hayrides, games and demonstrations, culminating with a potluck dinner open to all who bring a dish to share, and a dance until 10 pm. with the Texas swing of the Blue Strangers. See you there.