The Carlisle Mosquito Online

Friday, May 25, 2001


TreeTalk: Plant stress, tough times

Extreme weather events have been brutal on the local flora lately. This past winter wasn't too bad with respect to low temperatures but think back to the early winter when there were a couple of very sudden deep drops. Damage occurred to plants that had not yet "hardened off" prior to these freezes. The persistent snow cover was beneficial in general but for many exposed plants the snow reflected a lot more sun than usual. These plants suffered increased drying as a result. This drying effect would have been extra tough on recent transplants with limited root systems. The combination of a delayed spring with an early heat-wave followed by a late frost was a rough start for many plants. Some trees such as oak and ash had their entire first string of newly emerging leaves wiped out.

Remember that glorious summer of '99? Many plants still remember it too but not so fondly. Surprisingly the drought of '98-'99 is being blamed for the severe rhododendron decline that has only become apparent this spring. The drought might not have been record breaking for total rainfall but it was very poorly spaced from a plant's perspective. Root systems were hit hard and had not fully recovered before last winter.

What can you do? Pray for a lot of rain but water what you can in the meantime. The rule of thumb for shrubs and trees is one inch of water once a week. This is tough to do by hand. Best to set up a hose on a slow drip and maybe use an inline water timer so you don't have to tend the line constantly. Discourage fungi and bacterial blights by keeping foliage as dry as possible during watering. Don't forget to mulch. Postpone any fertilization plans until you are sure that the plant has been getting plenty of water for a few months. Fertilization can actually exacerbate a drought by raising the salt content and promoting unwanted growth.

The good news is that we do not have much in the way of pests and disease this spring. Most dieback has been caused by drought or freezing. Since many plants have delayed bud break or need to develop replacement leaf buds in the next few weeks pruning should be put off until you're certain of what is actually deadwood. Severely damaged plants such as many rhododendrons will require extensive pruning or complete replacement. This decision really depends on your time and budget. My suggestion is that you give them the benefit of the doubt if they are showing signs of life. Give them plenty of water and prune all dead wood in late June.

If you are considering replacement keep in mind that the plant might never have been all that happy with its location relative to sun/shade, soil, pH, moisture, drainage, wind etc. Every plant has its own preferences and some such as rhododendrons can be pretty fussy. They evolved as understory plants and most are a bit uncomfortable in the middle of a lawn. Matching plants to their environment is crucial to surviving tough times.

John Bakewell is a Massachusetts Certified Arborist.

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