How to choose and grow a tree in Laguna

The Garden Fanatic

"October is the fallen leaf ...."

-- Hal Borland

"Old gardeners never die ... they just fade away."

-- Anonymous

There have been a number of defining moments in my life: the first

kiss, leaving Laguna for college and marrying Catharine come to mind

quickly. I also recall selecting my first tree for a client, and it

was Fritz Toohey who sold it to me.

I was thinking about Fritz last week, as I noted that the

liquidambars and sycamores had begun to turn color in and around

Laguna. It had been awhile since we had last chatted, so I promised

myself that I would call him soon. Later that day, my

ever-inquisitive wife asked, "Why do some trees turn color?" And I

answered ....

Trees are planted wherever one chooses, but grow naturally only

where they can survive and prosper. In the wild, environmental

factors determine success or failure for a particular species of

trees.

Northern latitudes and higher altitudes, as on our recent mountain

visit, are characterized by cold winters and periods of winter

drought (unavailability of water due to snow). Deciduous trees

(cottonwood, maple, etc.) must shed their leaves to protect against

adverse conditions, and are native to these climes.

The desert, which has an excess of summer heat, and Laguna Beach,

which does not provide sufficient winter cold, are inhospitable to

many species of deciduous trees. Although many cultivars of trees

provide fall color in Laguna, one must travel as far away as Maine,

or as close as Idyllwild, to view the truly spectacular turning of

leaves.

Every broadleaf, deciduous leaf is attached to its tree by a stem

called the petiole. The petiole not only holds the leaf, but contains

the conducting pipelines, which carry water (xylem) to the leaf and

returns food (phloem) out of the leaf to the plant. This versatile

structure also rotates the leaf to the proper angle to receive more

sunlight and elongates to ensure that each leaf reaches enough light.

As a leaf matures, it changes in color from light green to darker

green. When temperatures become chillier and water becomes less

available, a biological signal is sent to the tree that winter is

approaching. From late summer to early fall, a ring of cork grows

across the petiole of many deciduous trees, slowly blocking the

pipelines of water and food to and from the leaf. These cork cells

are called incision cells. By early October, the conducting

structures of the leaf are completely sealed off. Depending on the

tree, leaves may hang on the stem for just a few days or remain for

several weeks.

This biological process, of abscising leaves for winter survival

and to prepare for the spring's new foliage, is the reason we enjoy

fall foliage color. With the absence of water, the leaf stops

photosynthesizing and loses its green color from chlorophyll and

instead reveals hidden chemical colors. Xanthophyll, a bright-yellow

pigment, becomes clearly visible. Another substance called carotene

(carrots contain this chemical in quantity) is brilliant with red or

orange hues. Deep reds and purples are created by anthocyanin , a

chemical that is newly formed upon the departure of chlorophyll.

The fall color of a tree depends on which of the three compounds

it has in the greatest abundance within its leaves. Birch, ginkgo and

elm turn yellow with xanthophyll. The Sugar Maple turns golden,

bright orange, or red with carotene. Liquidambar and ash turn deep

red or purplish from anthocyanin production. Frequently, multiple

presences of these chemicals will yield combinations of colors within

the leaf.

* * *

Sadly, I wasn't able to have that conversation with Fritz. He had

passed away a week earlier. Angry with myself, I thought about him as

I spotted a liquidambar leaf fall slowly, first end over end, then in

a spiral as it flipped lazily toward the ground. It joined its

brothers and sisters that already carpeted half of the sidewalk with

a brilliant yellow. I know that Fritz would have hoped that the city

gardeners wouldn't tidy up too soon. See you next time.

* STEVE KAWARATANI is the owner of Landscapes by Laguna Nursery,

1540 S. Coast Highway in Laguna Beach. He is married to local artist,

Catharine Cooper, and has three cats. He can be reached at 949 497

2438, or E-mail to plantm@lagunanursery.com.

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