Garden Notes: Trees in winter

Don’t send leaves to the dump.

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Runaway ivy poses a risk for trees year-round, but especially in winter. —Susie Safford

Gardens are mostly gone or blank, and we regard trees, which have been background all along anyhow, with renewed appreciation. The newly mown fields at Polly Hill Arboretum give the eye a rest and draw attention to the trees.

The recent mild weather has probably enhanced the reproductive success of the winter moths fluttering about, but that is another topic. Trees must face winter challenges first: mighty winds and heavy snow and ice. The ancient carol celebrates the holly and the ivy, quite seasonably and logically. They are highly noticeable at this time of year in the recently bare woods, and may be looked at in several ways, focusing here particularly on ivy.

How “romantic” a semiwild garden looks with ivy dripping off everything! The idea of ivy is seductive: its deep green tendrils, marbled with lighter veining, produce a beautifully textured tapestry. Ivy-clad trees unquestionably supply greenery and a great deal of cover for wildlife: birds and small animals. The berries produced by vines, which have morphed into the adult phase and thus produced flowers and fruit, will become welcome food for these animals.

So far so good; however, the reality of ivy is a downside for the tree supporting all this. Tree bark performs a photosynthesizing function for trees (bit.ly/BarkFacts), and when it is smothered by ivy foliage, the tree suffers. Ivy is not so much a strangler vine, such as honeysuckle and bittersweet; it grows little hold-tight root hairs that attach themselves to surfaces, but over time the roots and vines become very large and heavy, and their foliage becomes dense, blocking all light from the bark of the trunk. This produces considerable weight and stress for the host tree.

So far not too bad; however, once an ice storm or heavy wet snowstorm arrives, poor host tree is suddenly supporting an even greater weight than it is accustomed to. Something eventually gives, and a large limb or entire tree, whose ivy cladding may have also disguised structural flaws, comes down. Or a heavy rain, waterlogging the ground, may cause the tree to keel right over from all that additional ivy weight.

Long story short: Clear trees you value of ivy burden, for no good comes of it to the tree.

Large trees are valuable landscape assets. With a great deal of construction and renovation taking place on Island properties, care must be given to avoiding soil compaction and the cutting of tree roots, both of which I regularly witness, I regret to report. Sizable trees are not easily replaced, although failure may be slow, and hard to connect to the initial event.

There is other work to be done in the winter garden, when greenery has gone to sleep and framework and structure become more apparent. Inspect for rubbing or crossing growth that has occurred over the summer. In the training of young trees and saplings, usually a single leader and well-formed, wide-angled branch structure off the trunk is desirable for structural strength.

This would be the time to thin trunks of smaller, multi-stemmed trees such as chionanthus, dogwoods, or witch hazels, as well as the shrubs that grow similarly, such as forsythia and bush honeysuckles. Note that experts advise against magnolia pruning except when these are in active growth.

When performing renewal pruning of shrubs such as forsythia, take out the largest old shoots — not more than about one-third of the canes — right down to the base. Replacements grow in quickly.

In all pruning, avoid creating stubs, those abrupt, full-stop endings that uglify and mutilate the silhouettes of trees and shrubs in winter and permit the entry of disease.

Turf and arboreal research has shown that these two vegetation types are not really compatible, and that turf is a strong competitor with trees. Large mulch rings under mature trees are preferable to attempting to have the trees arise from turf right up to the root flair. Thoughtfully chosen underplantings protect the root zone as well.

Tree leaves are almost all dead and ready for collection, finally. I cannot possibly rake all the leaves blowing around my place, so I grab the ones that collect in accessible corners and clean those out. In a day or two, more will have lodged for easy removal.

Please do not send this valuable biomass to the dump! Stockpile in biodegradable leaf bags or corral them in wire surrounds; perhaps share them with a friend if you do not use them. For anyone gardening on the Vineyard’s (mostly lean) soils, this leaf compost is an effective soil conditioner, like black gold, and will be rapidly digested in ornamental and vegetable gardens alike.

Brilliant days like Dec. 3, blue-sky-sunshiny and mild, disguise the fact that they are very short. Sunrise is after 7 am, and sunset is just after 4 pm, but even before the winter solstice, by Dec. 15 the sun is setting later in the pm.

Holiday plants

Indoor humidity levels are typically very low now, and a poinsettia or cyclamen will dry and wilt sooner than you might expect. Try not to let this happen, because part of the plant may not fully revive, and the overall life of the display is shortened. Water from the bottom, do not let sit in excess water, and display out of direct sunlight, if possible.

Tell Congress

Congress made little progress on the Farm Bill last year. From Organic Consumers Association: “As we head into 2019, we have an opportunity to let new members of Congress know that it’s time to fix the Farm Bill, so that it helps the farmers who grow food responsibly.”