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Search Results for: Leaves | Search the catalog for: Leaves

Plant Answer Line Question

Keywords: Leaves, Acer palmatum

I planted an Acer palmatum a year ago spring. It has healthy leaves in spring then they all curl and turn brown in summer: not a pretty sight. I feed and water regularly. It gets late-morning and afternoon sun. It doesn't get very hot, maybe in the 70s to low 80s on average in summer with an evening fog rolling in from San Francisco Bay. Any ideas?


Acer palmatum sometimes displays this foliage problem. According to Japanese Maples by J.D. Vertrees and Peter Gregory (Timber Press, 2009), root weevils can cause this type of damage. Also, Verticillium wilt as well as other fungi can cause leaves (and often branches) to die. Leaf scorch seems to me the most likely cause, and your fertilizer may be contributing to it: Vertrees says excess nitrogen in the soil can lead to leaf scorch, as can watering so that the leaves become wet in the hottest part of the day.

I recommend that you contact the Alameda County Master Gardeners for more information and a more specific diagnosis.

Date 2017-05-04
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Plant Answer Line Question

Keywords: Plant phenology, Leaves, Trees

Can you direct me to a list of deciduous trees whose leaves generally emerge in early spring, or a list of trees ranked in order of their leaf emergence? I know this will vary from year to year and from individual tree to individual tree due to climate and genes, but if there is a list out there with a general sequenced time schedule, it would be a great tool for design.


An early American observer of the varying timing of leaf emergence was Henry David Thoreau, whose journals list leaf-out dates for the trees and shrubs he saw in Massachusetts in 1854. In fact, his data is now being used in climate change research. Though it's a subject that hasn't been much approached from a garden design standpoint, the increased interest in climate change means that more research on phenology and the leafing out sequence is becoming available. See the following article, "Turning Over New Leaves" by Richard Primack in the Arnold Arboretum newsletter. Primack (of Boston University) is the author of many articles on this topic. Primack and Caroline Polgar co-authored "Leaf-out phenology of temperate woody plants: from trees to ecosystems" (New Phytologist, Volume 191, Issue 4, pages 926-941, September 2011) which states that "maples (Acer spp.), birches, alders (Alnus spp.), and poplars" tend to leaf out earlier, while "oaks, ashes (Fraxinus spp.), and hickories (Carya spp.)" are among the later-leafing trees.

The article "Why Do Temperate Deciduous Trees Leaf Out at Different Times? Adaptation and Ecology of Forest Communities," (The American Naturalist December 1984, Martin J. Lechowicz) has a chart (p. 825) showing the tree species the author studied leafing out in this order:

  • Acer rubrum
  • Populus tremuloides
  • Betula papyrifera
  • Sorbus americana
  • Acer saccharinum
  • Betula alleghaniensis
  • Ulmus americana
  • Tilia americana
  • Quercus macrocarpa
  • Fraxinus pennsylvanica
  • Populus grandidentata
  • Fraxinus nigra

Another chart on the same page compares 1980 and 1981 leafout dates, with Populus tremuloides and P. balsamifera and Betula species consistently leafing early, followed by Acer and Prunus, then Fagus and Populus grandidentata, then Fraxinus and Tilia, and finally Carya and Juglans.

You may want to read a short article in the March 11, 2015 online version of Conservation Magazine on predicting the future of forests, based on two centuries of data from citizen scientists in England. Here is an excerpt:
"It is likely that the variation in each species' sensitivities to both spring forcing and winter chilling will mean that forests will look quite different in the future. Those species for whom spring forcing is most important will grow leaves earlier in the year; those for whom the autumn and winter chill is more critical could leaf later in the year. Eventually, a late-leafing species like oak might wind up growing its leaves earlier than an early-leafing species like birch."

Another resource that may help you determine the leaf-out date of specific trees is The Botanical Garden: volume 1: Trees & Shrubs by Roger Phillips and Martyn Rix (Firefly, 2002). The book presents photos of branch samples from many tree species, often showing the young leaves associated with a date (though not with the geographical location; bear in mind that the authors reside in England). While it doesn't have such a photo for every tree, it might have enough trees for you to get useful data.

Date 2017-01-12
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Garden Tip

Keywords: Leaves, Mulching

Treat fallen leaves like the resource they are. Under the dripline of a tree, let leaves lay where they fall so nature can recycle the nutrients back to the tree. Yes, the leaves may kill the grass, but tree roots don't like the competition from grass anyway. Outside of the dripline shred leaves with your lawnmower. Mixed in with grass clippings the shredded leaves will break down fairly fast and feed the lawn.

Still feel compelled to rake those leaves? Fill a few black plastic garbage bags, add a shovel-full of soil and then stash the bags for about 9 months. You'll be rewarded with what the British refer to as "leaf mould." Use leaf mould as mulch or as an earth-friendly substitute for peat moss. Stash the bags under the deck or porch or even under the shrubbery. Just mark your calendar for next July so you don't forget. If individual leaves can still be recognized wait a few more months or use it as a mulch around perennials. For a good article on leaf mould go to the Irish Peatland Conservation Council

Date: 2007-04-03
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Garden Tip

Keywords: Leaves, Mulching, Lawns--Care and maintenance

Research from Purdue and Cornell University shows that autumn leaves can simply be left where they fall, shredded by a mower and allowed to mulch the lawn. Fertilize as you normally would. The shredding is essential, so don't skip that step. If the leaf mulch is too thick, move some into your flowerbeds or compost bin. Read the research report.

Date: 2007-04-03
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August 01 2017 12:36:01