Q. I planted about 12 gardenias a month ago and if them
appear to be dying. I checked the soil and it's evenly damp. It has two 2gph
emitters and they are all being watered 3x a week for 20 minutes right now.
Water is applied to the soil. The water fills all the
spaces between soil particles forcing the air which is in the soil to exit. As
this water drains or is being used by the plant, outside air above the soil
begins to enter into the soil filling the spaces that was previously filled
with water.
There is another problem that can occur which can keep
water from moving from the soil to the roots and finally to the leaves and
stems. If there is something which is choking the stem of the plant, this can
prevent water moving from the roots to the leaves. Mechanical injury to the
stem from insects which chew or bore holes into the central stem can disrupt
water moving from the roots to the top.
A. From the picture it looks like a lack of water. Just
before you tell me "no", I want to explain something. A lack of water to the
plant can be for many reasons and only one of those reasons is that not enough
water is being applied. Follow me on this.
Water is applied to the soil. The water fills all the
spaces between soil particles forcing the air which is in the soil to exit. As
this water drains or is being used by the plant, outside air above the soil
begins to enter into the soil filling the spaces that was previously filled
with water.
Roots of plants need oxygen. The above ground, green portions of
the plant need carbon dioxide and oxygen. If the soil particles are too close
together there will not be enough room to provide the oxygen needed by the
roots. This is why we add compost and other organic material to the soil so
that we can build the structure of the soil to provide that oxygen needed by the
roots. I know you have improved that soil for those gardenias so that is not
the problem.
There is another problem that can occur which can keep
water from moving from the soil to the roots and finally to the leaves and
stems. If there is something which is choking the stem of the plant, this can
prevent water moving from the roots to the leaves. Mechanical injury to the
stem from insects which chew or bore holes into the central stem can disrupt
water moving from the roots to the top.
There is also a disease problem which
can choke the stem near the soil level. This can happen on very young plants
which have stems surrounded by wet mulch. If this mulch stays wet around these
young stems, it can cause a rotting to occur at the soil to the level of the mulch.
This is frequently called collar rot. Make sure that wet mulch does not come in
contact with the trunk or stems of young plants. Young plants are very
susceptible to this problem. As they get older and developed more wood around
the trunk or stems, this problem lessens.
So from judging just from the pictures to me it looks
like water related and/or too much shade. Excessive shade can cause thin, spindly growth
that can't support itself. That is my best shot at it from the pictures.
I've planted a couple of gardenias and they are not an easy plant to grow, especially in the Mojave Desert. I would make sure that the plants have plenty of drainage and plenty of water. I use the hose a couple of times a week during the late Spring and Summer. In my case, large rocks below the surface were stopping the water from draining. Gardenias need very good drainage. The second thing is that I understand that the soil in the Las Vegas valley is very alkaline and gardenias need a soil that is acidic. Once I started giving the soil around the gardenias an acid supplement they did much, much better. I also limit the amount of sun they get to 50%.
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