"How to" articles to help gardeners.
summer turns to fall and you are out surveying your garden, learn how
to spot your next year's flowers on your rhododendrons. This
article will also teach you how you can encourage more blooms on these
King of Shrubs with food or light.
Flower Bud IdentificationMid-spring
blooming rhododendrons make their flower buds in July to September, but
will not open until the following year. Many customers ask "Why
didn't my rhododendron bloom? They had flower buds!" If you
know what the difference between a flower bud and a leaf bud, you will
not be surprised come spring as you will be able to recognize which
plants have made flower buds the year before they bloom. On most
rhododendrons, flower buds are larger, and round like a marble.
Leaf buds are small and pointed. There are exceptions, for
example, on the Big Leafed rhododendrons, the leaf buds are large,
causing confusion. And, on the tiny leaved lepidote rhododendrons like
the species Augustinii, the flower buds are small and pointed.
Read on for some examples.
Big Leaf Rhododendron's Leaf BudsFewer people grow these giants of the rhododendron family, and they are not to be confused with the more commonly grown hybrids.
species plants have big leaf buds, fooling those hopeful gardeners into
thinking they will see flowers next year. Sorry...the real flower
buds are usually bigger than golf balls that open to large trusses of
light yellow, pink or white flowers. Most of the Big Leaf
Rhododendrons take at least 10 years to first flower, and many times
much longer. An old timer rhody enthusiast once told me that if you put a
bucket full of alfalfa pellets at the bottom of the hole, your Big Leaf
Rhododendron will bloom in 5 years. I haven't tried it yet.
Small Leaved Rhododendrons have small flower buds
confuse you even more, the small leaved rhododendrons, many dwarfs,
have little pointed flower buds, but they are larger and more plump than
the leaf buds. On these types of rhododendrons, it is common to
have mostly flower buds developing, however, in deep shade there will be
fewer flower buds created.
Factors affecting Flower Bud Development in Rhododendrons - LightWe
all want more flowers on our rhododendrons, so it is useful to know
what to do to enhance flower bud development. Light is the primary
factor that will stimulate flower bud development. You can dump a
lot of fertilizer on a rhododendron that resides in a very shady spot,
and not influence flower bud production at all. It is not necessary that
your plants get direct sun, but they do need good light from the
sky. A rhododendron planted on the edge of a forested area
will flower nicely as long as above the plant you can see open
sky. If the plant is planted back under the tree branches where it
is dark, it will not bloom much if at all. Pruning tree limbs up
so more light from the sky is available may cause your plant to start
blooming more, then feeding and adequate watering will be useful.
Another thing to keep in mind is that your mid-spring blooming
rhododendrons will need the adequate light in July through
September, when they make their buds. If they are in shade at other
times, that is not so crucial. And one last thing, adequate water is
also important for flower bud development, especially if your
rhododendrons are planted near greedy roots from large trees.
Other Blooming Behaviors
1. Very few flowers for 2-3 years after planting:
Some rhododendrons that have been growing in a container for most of
their life will find the freedom of a rich soil mix, plenty of water and
good drainagesoooo good that they just want to grow some
foliage for awhile. Also, flowering is the way plants makes seed to
procreate, so if the plant is not feeling very threatened for survival
thus needing to make offspring, then it may tend to produce more leaves.
2. Rhododendrons that bloom every other year:
There are some varieties that bloom so heavily in the spring, they take
a year off for a breather. This seems to be varietal dependent. In the
"off" years, they have spotty blooming. This doesn't seem to have
anything to do with light or food.
3.Wetter than normal winters make for more flowers:
We have noticed that our rhododendrons make more flowers after a wetter
than normal winter. This may be due to the overall plant health
being enhanced, adding vigor. This is unlike fruit production where a
wetter than normal spring keeps the bees away, resulting in a drop in
4. Old established rhododendrons flower like crazy with no attention what so ever:
You may have noticed, if you live in an area with old established
rhododendrons, that they flower every year, and usually heavily with no
extra food or water given to them. This is partially due to the
genetics of these old hybrids, but mostly it is because they have
established a dense, strong root system and can flower without much
care. However, some of these older plants will become trees with fewer
leaves and flowers over time, while other always look perfect. The
gangly ones will need occasional pruning, food and water. In the
photo below, taken in Queen's Park, New Zealand, you can see the old
rhododendron on the left blooming heavily, while the other is 'spot'
blooming. This could be either a genetic difference, or a food
Factors affecting Flower Bud Development in Rhododendrons - FoodWe
recommend that you feed your rhododendrons twice a year. The
first feeding in early spring gives the plants some energy for the
upcoming bloom. We usually suggest Valentine's Day as an easy date to
remember. We have been told that this early feeding will promote
larger flowers with more vibrant colors. Whether this is true or
not is not confirmed. The other feeding we recommend is right
after blooming. This feeding is the most important for flowering
as it is the one that will stimulate flower bud production. So if your
plants are in good light, this feeding will give you more
blooms...guaranteed! We suggest using Father's Day as an easy date
Before and after in Flower Bud Development
first photo was taken in late May of this year of a new growth emerging
just after the bloom. At this time, there is no indication of this bud
being a leaf or flower bud. The same bud is shown in the second photo as
a definite flower bud. This plant received just what it needed.
This photo was taken in mid August. This flower bud will
continue to become rounder and fatter as the season turns from summer to
fall. By late October the bud will be complete and will sit
dormant waiting for the warmer spring days that will cause it to open
and reveal the beautiful flowers within.
hope this discussion was of some help to all of you rhododendron
enthusiasts out there, and that you will pour a glass of your favorite
wine and take a tour of your rhododendron collection this October to see
which plants have flower buds for the upcoming spring.
Don S. Wallace
Singing Tree Gardens & Nursery
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