The
fragrance of gardenias, a mix of vanilla, jasmine
and nutmeg, is well known to most gardeners. The
unmistakable scent floods a person's senses so
thoroughly that, once smelled, it is forever
remembered.
Originating in China, where it was grown and admired
for more than 1,000 years, gardenias were first
described by botanists in 1761. "Gardenia" was
chosen as the name for this fragrant group of
plants, not on behalf of a garden, but in honor of
Alexander Garden, a well-known naturalist living in
the Carolinas at the time.
Although named to honor a great naturalist, it is in
our gardens where it has gained its fame.
Some plants just perform better in the coastal
gardens of Orange County than they do inland.
Gardenias are one of these. But even in our nearly
perfect coastal climate, gardenias struggle in some
gardens while thriving in others. If the climate of
our Newport-Mesa area is ideal for gardenias, why
the discrepancy of the many gardenias planted in our
gardens?
The basic needs of gardenias in coastal Orange
County are rich organic soil; quick drainage; even
and consistent soil moisture, especially during
summer; at least a half a day of direct sunlight;
and a soil pH between 5 and 6.5. All of these can be
achieved with a bit of planning, the proper location
in the garden and the use of acidic soil amendments
and fertilizers.
Coastal gardeners struggling to grow and flower
gardenias usually complain of similar troubles:
Either the buds are dropping prematurely, or the
plants are pale, woody, thin and sickly looking.
The causes of buds turning brown and dropping before
opening is usually caused by poorly drained, overly
wet soils or by excessive watering, but sometimes by
unfavorable weather. If your gardenias are otherwise
growing well, with good color to the leaves, but
buds are dropping off, water or weather are the
likely cause.
Following excessively hot, dry weather, bud drop is
prevalent because the plant cannot absorb water
rapidly enough to compensate for what it is losing
through its leaves. Keeping the soil evenly moist as
well as frequent light syringing of the foliage will
go a long way toward reducing bud drop under these
conditions. Gardenias may also drop their buds
following a rapid change in temperature, such as an
unseasonably cold or hot spell.
If your gardenias are pale or woody, with lots a
leaf drop, there may be additional causes. In my
experience, an incorrect soil pH is the place to
begin. The soils in our gardens are naturally
somewhat alkaline. Gardenias like an acidic soil,
not alkaline. If the soil pH is too high,
fertilizing, especially with iron and trace
minerals, will be ineffective. For these nutrients
to be absorbed by a gardenia the pH has to be
corrected first. Acidic mulches and fertilizers like
cottonseed meal, will bring the pH down, but it will
take a few months, so be patient.
Many gardenias in local gardens that are pale, iron
deficient, woody and miserable will green up, put on
new growth and began flowering once the soil pH is
corrected.
If you are providing the correct culture, including
soil, water and pH and your gardenias are still
unhappy, your problem may be more serious. Tiny
microscopic pests, known as root-knot nematodes,
find gardenias a favorite host. These invisible
pests feed on the roots of gardenias and slowly
drain them of their vigor, damaging roots and
preventing the normal uptake of water and nutrients.
Root-knot nematodes are difficult to diagnose on a
gardenia growing in a landscape, but an examination
of the roots of a dead or dying plant will provide
certain confirmation. If root-knot nematodes are the
culprit, small irregular nodules, about the size of
a pea, will be obvious along the roots. Until
recently, if nematodes were present there was
nothing a gardener could do short of giving up on
gardenias altogether and planting something that was
resistant to nematodes.
Several years ago a few nursery workers in Florida,
where nematodes are even more prevalent than
California, began producing grafted gardenias. These
grafted plants, now available in limited numbers in
California, are nearly immune to root-knot nematode
attacks. The grafted rootstocks of these "super
gardenias" are also more tolerant to our higher soil
pH and irrigation mistakes. When selecting new
gardenias to add to your garden, it is often worth
searching for the more vigorous grafted plants.
One of the special pleasures of gardening in the
mild coastal climate of Orange County is the
fragrance of blooming gardenias. Gardenias are a
special gardening pleasure afforded to us because
here, as in few other areas of the country,
gardenias can be outstanding garden plants.
RON VANDERHOFF is the nursery
manager at Roger's Gardens in Corona del Mar.
I am planting tulip bulbs for the first time. How
deep should they be planted?
DAVE
Costa Mesa
Whoa, Dave. I hope you're not planting them quite
yet. Every year suppliers race to offer flower bulbs
earlier and earlier in hopes of being the first on
the market, but it's way too early for these to go
into our Orange County gardens. It's OK to make your
choices now, while the selection is good, but keep
them in a paper bag for a while.
For tulips I suggest waiting until late November or
early December for planting in our area. About six
to eight weeks prior to planting, place the bag into
the crisper of the refrigerator, away from any
fruit, to provide them with a bit of a false winter.
ASK RON your gardening questions,
and the nursery staff at Roger's Gardens will come
up with an answer. Please include your name, phone
number and city, and limit queries to 30 words or
fewer. E-mail stumpthegardener @rogersgardens.com,
or send to Plant Talk at Roger's Gardens, 2301 San
Joaquin Hills Road, Corona del Mar, CA 92625.
