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Cedar Leaf Miner Can Promote Lush Growth

...and other timely tips
by Marg Fleming
by Marg Fleming

1979 - BSc. Botany University of Toronto, 1981 - MSc. Forestry University of Toronto, 1982-1986 - Horticulture Teaching Master - Niagara College , St. Catherines Ontario., 1986 - 2000 - Owner/Operator of Cedar Valley Botanical Gardens - Brighton Ontario, 2000- Present - Manager of Horticulture Toronto Zoo

Public Speaking Topics - Perennials, house plants, garden design

November 2, 2003

A new landscape evolves as leaves fall from deciduous trees. Conifers (evergreens) take on visual importance as their green colour stands out against denuded surroundings no longer typically verdant as in spring and summer. We are lucky this year that ample rainfall has occurred during the summer months. As a result evergreens are a thick lush green, made even more obvious by retiring oaks and maples.

Another reason cedars are looking particularly full can be traced back to the infestation by cedar miner last year. This familiar little insect “mines out” the tasty cells of the current year’s growth. Each tiny mined-out cedar leaf then dies and turns brown. This gives a brownish cast to the entire tree that elicits concern from dedicated gardeners. But miner infestations are really not worthy of any sort of treatment. Feeding of the insect usually does not completely consume the new growth. Instead, the remaining growth is stimulated to branch repeatedly as the tree grows throughout the year. In effect, the tiny insect accomplishes the same thing we attempt to do with hedge shears by “feather pruning”. If left to grow unattended, most evergreen growth takes place at branch tips. Pruning (or mining as in this case) results in the development of many new “tips”, so recovery growth emerges dense and full.

Recent rain and wind has relieved cedars and other conifers of their old needles. So this year’s lush growth is even more obvious now – a nice way to end a successful growing season.

Last chance to retrieve sensitive houseplants from their summer vacation outdoors. Don’t despair if frost has touched a few leaves and stems. Crowns tight to the soil surface have likely been protected by the microclimate that occurs here. Temperatures at soil level and below are warmer than the surrounding air. This “warmth” radiates upward taking the chill off immediately adjacent plant parts. More remote leaves and stems may not have been so lucky after a frosty night. But those close to the soil surface will likely have escaped the chill, and the crown may still be active. Bring the plant indoors now. Prune away obvious compromised parts, and wait for the crown to re-sprout.

Start tapering off fertilizer treatments for your indoor plants now. Light levels are approaching a point that encourages hibernation or “dormancy” for our indoor tropicals. When plants become inactive like this they require much less nutrient. Otherwise, surplus minerals could accumulate and burn plant roots. If you have been feeding half the recommended dose each time you water, now reduce this by half again. Keep reducing the food you give until mid-December when all fertilizing should stop. Plants will also require progressively less water during this time because of their decreased activity. However, keep in mind that the dry winter air that defines our homes can steal soil moisture quickly. Check plant pots regularly to ensure the soil is kept barely moist at all times. Plant roots should never stand for days in dry soil.

For those of you lucky enough to have encouraged flower buds on your Christmas cactus, you are now obligated to leave the plant right where it is or sacrifice the bloom. Christmas cactus is very temperamental when it blooms. Buds will abort if growing conditions are altered. This is a timely tip that can be entered in your gardening journal.

Time is running out for repotting congested root balls and pruning excessive growth. Indoor plants prefer a reasonable amount of light and other more suitable growing conditions to convalesce after this type of surgery. Do it now. November may be too late.


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