Dahlia to do List
by Month
We will add to this each month until we have the entire year covered.


May is traditionally the time that we in the Northwest plant our Dahlias.  For those of you who exhibit dahlias, the
timing of planting can be a difficult undertaking as one cannot factor in the affects of climate on the development of
the Dahlia plant.  The Dahlia grower will want to start his largest varieties first, allowing them the most time as the
larger varieties require the most grooming to nurture the largest, most perfect bloom(s).  For those of you that are
planting dahlias for the first time, the general planting directions are:  Drive your stake in, then place tubers flat at
least 4” deep with the eye or sprout facing up and 2-3” from the stake.  Set out bait, as slugs consider tender young
dahlia sprouts as salad.  Plant large flowering varieties at least 2’ apart and smaller ones at least 15”.

The grower will not only be planting out tubers but also dahlia plants taken from cuttings.  Plants will be available at
this month’s meeting so if you are short on your planting, dahlia plants are excellent for taking up the slack.  They
will generally grow faster than tubers if planted out at the same time, and there is the added advantage of not
worrying about a plant rotting out.

Plants take a little more care initially.  After being hardened off, cuttings and seedlings are planted when the
weather &soil temperatures are more stable.  You need to watch the watering, because they don’t have the tuber
under the ground to provide moisture.  It works well to soak the pot in a bucket of water prior to planting.  Wait till
the bubbling stops and you will know it is completely saturated.  Break off one or two sets of lower leaves and plant
the cuttings a bit deeper than they were growing in the pot.  The will form a pair of tubers at each leaf node.  Many
times the tuber clump that forms at the bottom of the plant will be quie gnarled, but the ones that form at the leaf
nodes will be normal and easy to remove.

Here are some more planting tips from our past president, Ted Kennedy.

How much sun do dahlias need?

Dahlias need quite a bit of sun.  Most homeowners actually have some shade in all parts of their garden. Dahlias
seem to thrive in any area that receives full sun for at least 50% of the day.  When grown in more shade, dahlias
grow too tall and leggy and the quality of the blooms declines significantly. Many of the competition growers use
shade cloth for their dahlia patches. They feel that the bright colors of their competition flowers are preserved when
grown under shade cloth. (Old timers use umbrellas over their blooms to keep them from both the fading sunlight
and the rain spots caused by the rain).   Shade cloth looks a lot like a black plastic tarp. It comes in different
densities and dahlia growers use 30% through 50% sun blocking with most preferring 30% to 40%. If you do use
shade cloth, you must allow for increased height of the dahlias. A typical variety that grows 4 feet tall in full sun will
grow 6 feet tall under shade cloth. Since many varieties grow 6 feet tall in full sun, you need to install the shade
cloth to be at least 9 feet above the ground and 10' to 12' may be best.

How much water do dahlias need?

When planting tubers in our normally damp soil in the spring, dahlias need very little water until they sprout out of
the soil. Most people try to err on the dry side because a spring shower after you already watered could cause wet
warm soil and resultant tuber rot. Once they are up out of the ground they need enough water to grow quickly. If
you are planting rooted cuttings, you need to apply enough water to keep them from wilting. The plants are growing
roots for two weeks or so after planting and they need a constant source of moisture for these two weeks or so.

After the tubers or plants are a foot tall or so, water them at least weekly. As they grow taller they become a bit
more drought tolerant. Dahlias  store extra water in both the tuber clumps and in the hollow stems.

Here in the Portland area, we have three distinct growing periods for our dahlias: cool to moderate spring, hot
summer, and then early fall weather.   When we plant them in May, the weather is still reasonably cool. It stays
reasonably cool until about July 10th or so, when we really start getting our summer heat. During this spring growing
period the dahlias grow fast and look great. When the summer heat arrives, they do not grow as fast and of course
need lots more water. During these dog days of summer, the blooms develop too fast and many have open centers
and lack depth. Then on about August 10th or so the weather cools down and the dahlias start growing faster
again. Probably the best blooms in our gardens occur from about August 15th to September 15th.


Once again, Mother Nature has given us very unpredictable weather to deal with.  Last month, which is the month
most of us plant in, we faced some very trying weather.  We had a low of 42 (average 47), a high of 95 (average
69) and 4.34 inches of rain (normal 2.83).  Those that had gotten planted early found it necessary to water when
those high temps hit, and some had scorched plants. For those that didn’t get planted in that short time frame of dry
weather, it has been  very hard to get things in the ground.  I am still trying to finish.  So far this month, we are
having wetter and cooler weather than normal.  Along with dealing with this unpredictable weather, we still have our
normal chores to take care of.  I am finding that the slugs are much worse than normal.  Even my potted plants that
are on pallets and blocks are not safe.  They climb up and eat during the night, then hide on the side of the plants
during the day.  It requires one to be vigilant about their slug control.

WEEDING As part of the survival mechanism of their species, weed seeds have the ability to delay germination for
many years. If you're tempted to slough off on the weeding, remember the old adage:

One year's seeding,
ten year's weeding!

Using some type of mulch – either natural (leaves, straw, grass, etc) or man-made (landscape fabric, burlap,
newspapers) I think by far is the best way to conquer the weeds.  If they don’t have light, most weed seeds can’t
germinate.  If you hoe them, use one of the hoes that just cuts them off at the surface and disturbs the soil as little
as possible.  Again, you don’t want to expose the seeds under the soil line to light.  There are some that use pre-
emergent herbicides.  While these work on the weeds, I feel that they can affect the soil where it is placed for a long
time to come.  If you use these, be very careful.  Some even feel it limits the tuber production.

Other dahlia chores to take care of this month are:  STOPPING –  After the plant has 2-4 sets of leaves, carefully
break off the very top. This will cause the dahlia plant to produce multiple branches and blooms.  DISBRANCHING –
This means removing some of the laterals (or branches) to concentrate all the growing energy into the remaining
blooms in order to maximize their size.  If needed, it is done several weeks after stopping the plants.

TYING – You can use baling twine, nylons, or garden twine.  The more unfavorable the growing weather, the more
one needs to tie dahlias to the stake.  Another idea that is being used by at least one grower I know of in the Seattle
area is the use of horizontal barrier fencing.  Here is how he does it:

“The orange barrier fencing is laid horizontally.  It is held in place with steel fence posts at each end of the row and
a pair in the middle of the row.  Rows average about 40 feet in length.  Longer rows would need more fence posts in
the middle.  The fencing is about 20 inches from the ground.  After the dahlia plants have worked their way through
the holes (4" by 4") in the fencing (sometimes this requires a little help on our part) and get to be about 3 - 4 feet
high we string baling twine around the posts to rein the plants in.  Usually we need two sets of the baling twine on
each row. “

I’m going to give it a try on some of my rows and will let you know how it works.

Follow the instructions in PSDA’s Dahlias: A Monthly Guide for these tasks.

v Watering: Soak the soil thoroughly because one good soaking is much better than several light sprinklings
v Spraying: One spray used over a long period enables insects to build a tolerance for that brand. Switch sprays
v Disbudding: Continue removing side buds to achieve specimen blooms. Often, it is necessary to remove more
than the top two side buds.
v Gather your show materials. Clean your containers with a bleach solution and check for leaks.


This is probably the busiest time in the dahlia garden with many, many chores to take care of:  tying, disbudding,
deadheading, collecting seed, etc.  


Enjoy your blooms!

OCTOBER Time to dig the tubers and divide them for storage.


This is the slow time of your for us dahlia lovers to take a bit of a rest.  Hopefully all your tubers are dug and stored
away for the winter.  Now is a great time to sit in front of the fireplace and peruse the catalogs and decide what we
want to add and subtract.  It is also a good time to plan next year’s garden, if it’s time to change the layout.  Tags
can be made and stakes painted.

Those of us that are ADS members are anxiously awaiting the Bulletin to see what varieties did well in all the trial
gardens, and get the new Classification Guide.  I understand it will be a little late this year.  Be sure to get your
orders in early for new varieties, as they usually sell out.  Most of all, take some time to rest, and appreciate your
family and friends.  There is so much to be thankful for and so many things to look forward to in the New Year.

If you just can’t stand to rest, here is a great idea I read in McConkey’s newsletter.  It is for a germination chamber.  
For those of you that grow dahlias from seed, or grow any other type of seed, this would be great.

Take any left over or old polyfilm and find any stainless steel container, one that holds up to 5 gallons (a steel oil
drum cleaned & cut in half could work).  You’ll also need a heating element and a thermostat to control the
temperature.  Add you water, create a frame to hold the plugs, enclose it with the polyfilm, and then insert your
heating element and thermostat.  The heating element should boil the water to create near 100% humidity without
reaching saturation.  This humidity dissolves the protective coating around the seed.  The thermostat ensures 70+
degrees temperatures.  The chamber will help seeds to germinate at the same time instead of different times, which
typically happens when germinating on the bench.  The seeds will germinate faster and be more uniform and
stronger.  Even if you have to purchase everything, this chamber should not cost you more than $150, but most of
these items you should already have in your greenhouse.  The moment the seed germinates, move it into the
sunshine and watch it grow.  Using these chambers, you can create temperature zones with a single greenhouse.