Meets second Tuesday of the month at Rose City Park
United Methodist Church, 5830 N.E. Alameda
Editor: Mike Riordan (503) 256-0425
Portland Dahlia Society Bulletin
Meets second Tuesday of the month at Rose City Park United Methodist Church, 5830 N.E. Alameda
Editor: Mike Riordan (503)256-0425 Contacts: Larry Smith email@example.com, Jeanette Benson
Next meeting Tuesday, July 8th, 2008 @ 7:30 PM
COOKIES FOR JULY
Cookie hosts for July are Arnie Klug and Max Ollieu.
PROGRAM FOR JULY
Our program for July will feature a presentation on the ins and outs of dahlia crossing, saving viable seed and
originating new varieties. The program will include a video with Wayne Shantz and a show and tell approach
to dahlia hybridization. Wayne taught high school English for a number of years, so the presentation promises
to be interesting and well organized. Ted Kennedy will follow up with a few “tricks of the trade” that he and
Margaret have gleaned through their experience in creating the Hollyhill stable of cultivars.
We encourage members to bring in blooms to the July meeting so others can admire and enjoy. We know it’
s still very early, so anything we can feast our eyes on is much appreciated.
Special thanks to last month’s speaker, Vicky Molino and Rain or Shine who contributed $26.84 from her
sales to PDS.
In preparation for our annual show Labor Day Weekend, we need to ask for volunteers to help with some of
the show functions. Thursday afternoon, August 28 we need members to help with the set up of the exhibit
hall. This includes assembly of the head table, draping the tables and setting out the size/form/division
Friday night we need a few to help with classification as blooms are entered. On Saturday late morning and
early afternoon we need some members to help with the tally process. Both Saturday and Sunday we need
volunteers to help with hospitality and answer general questions from the public.
At 6:30 PM on July 8th we would like to have a short Board Meeting to discuss plans for our annual show.
The meeting will take place at our regular meeting venue and all interested members are welcome to attend.
MENTOR PROGRAM CONTINUES
Our guest mentor for the month of July is Max Ollieu. ; He will be at the meeting hall a half hour early at 7:00
PM to answer any growing questions. If you have leaf samples of some disease or bug chew, feel free to
bring it in for examination and diagnosis.
HOW DO I FERTILIZE MY DAHLIAS
By Ted Kennedy
Sometimes the shortest, most basic questions are the most difficult to answer. Rather than just saying how I
do it, here are some ideas from other growers.
One club member got a soil analysis to determine what his garden needed. He has always used a lot of
organic compost and a bit of sheep manure on his garden. In addition he has used commercial garden
fertilizers such as 10-20-20 and 16-16-16 in the past. His soil report indicated that he needed only nitrogen
and he decided to buy a time release product that only has nitrogen. I believe he bought a product called
Nitroform and it is 38% nitrogen
Another member of the club is strictly an organic gardener who uses lots of compost along with such products
as bat guano, blood meal and green sand. Such products are available at Concentrates on SE 8th Avenue
between Powell and Division in Portland. Peruse their offerings and prices at http://spreadsheets.google.
com/pub?key=pJrWEmwyrO76JtBhzIRWDcQ Other organic choices include alfalfa and chicken manure.
An English grower swore by cow manure and added a full six inches to his garden every year. The dahlias
grew wonderfully, but in the long run the high nitrogen content and probably high levels of bacteria and soil
fungi caused the tubers to rot in storage. That did not deter him and he kept pot tubers of all his dahlia
varieties and planted rooted cuttings from them.
One grower in the Seattle area who has won very many best in show awards uses the very best Osmocote
fertilizer. I was told that she uses the product that has an 8 to 9 month dissipation rate and an analysis of 13-
13-13 and includes micronutrients. There are numerous choices in the Osmocote line but the biggest
drawback is the expense. I have been told it runs about $1.00 per pound, even in the 50 pound bags.
Osmocote releases all of the plant nutrients slowly along with all of the trace nutrients throughout the entire
growing season. This should not be confused with come cheaper products that release only the nitrogen
slowly and really over-dose the plants with phosphorus and potassium when first applied.
One grower now deceased grew dahlias on the coast in sandy soil. She swore by chicken manure and a
product derived from seaweed (probably no longer available). That seaweed product probably provided
micro-nutrients and some potassium. By the way, the word potassium derives from potash and that was
produced by burning seaweed to produce a nutrient laden ash. Later, chemists determined that the potash
was mostly one chemical element and named it potassium.
Another grower in Washington swore by the liquid fish products that he sprayed on the plants. Fish fertilizer
used to be very popular but its downfall was that it smelled so bad. There are fish pellets being sold as a time
release fertilizer for organic gardeners. Their drawback is that dogs and other animals like to eat them and
will dig them out of the soil.
In our area it is necessary to add lime to the soil to maintain proper pH. Lime is not technically a fertilizer but
it sure works to make your flowers grow. If the soil has the proper pH, the plants can utilize the nutrients in
the soil. One needs to test the pH of your garden and lime regularly to keep the pH at proper levels. If
should be noted that commercial fertilizers tend to make the soil more acid. If you have been adding only
fertilizer and no lime to your garden, you have probably made the soil acid (reduced the pH number, over 6.0
is needed for dahlias and 6.5 is considered ideal). There is a chart on a university web page that showed how
much each fertilizer component acidified the soil. For example, for every 100 pounds of urea (46% nitrogen,
very common ingredient in fertilizer), you add to your soil, you need to add 71 pounds of lime to keep the soil
pH the same. Here is a link to that chart: http://extension.oregonstate.edu/catalog/html/fg/fg52-
Many dahlia growers like to use the water soluble products such as Miracle Grow to fertilize their dahlias.
These products can be applied with a hose end sprayer and the product is sprayed on the foliage on a weekly
basis. A more economical alternative to Miracle Grow is the use of commercial greenhouse fertilizers such as
Peters or Plant Marvel 20-20-20 that cost about $25 for a 25 pound bag. All of these products have the
advantage of giving the plants a feeding of fertilizer that takes effect almost immediately. These products are
very useful in hot weather, when dahlias seem to have problems getting enough fertilizer from the soil.
JULY IN THE GARDEN
Besides fertilizing, spraying, tying, topping, disbranching, disbudding, and irrigating (my, we are a busy lot!),
one needs to consider the benefits of mulching and with what type mulching of material. Mulching benefits
plants in three ways. By shading the soil, mulch keeps the soil cooler and reduces moisture evaporation.
Thick mulch discourages weed growth. And finally, most organic mulches provide some plant nutrients and
over time improve the texture and water retention capacity of the soil. A nearly ideal mulch is screened
compost available from your local yard debris recycler. The Portland Dex Yellow Pages has 13 listings for
compost purveyors. If you are considering having it delivered (as opposed to hauling it yourself), keep in
mind that transportation costs can add up quickly. So look for suppliers close to your location.
Another thought for mulch would be grass clippings (sans Weed and Feed only). When applying any mulch
be careful not to smother the dahlia stalks. Remember it is a soil blanket, not a plant blanket. One grower
down in the valley had a rabbit farmer contact. The rabbit farm used mint silage as litter for the rabbits. So
not only did the mulch smell like Doublemint, it had the rabbit manure kick. Some growers have used straw
or stable bedding mixed with manure. With the manure think light dressing (see Ted’s previous discussion).
Other growers have used spoiled silage or spoiled or unspoiled bales of Alfalfa. Your local Feed and Seed
store would most likely be able to direct you to nearby sources.
Another type of mulch is the in-organic type. Here I’m thinking of “landscape fabric”. The landscape fabric
is porous enough to let water, nutrients and air through and yet forms an effective weed barrier. It is sold by
the lineal foot at most garden centers. Other types of barriers;e.g., layers of newspapers or black plastic are
not recommended since they generally don’t allow good moisture and air exchange with the soil.
Side dressing the plants with fertilizer is generally done in June or early July. Be sure to place the fertilizer no
closer than around the drip line of the plants and in all instances at least 6” away from the dahlia stalk.
Growers that continue to side dress later than mid July run the risk of causing an increased incidence of
oblong, double, misshapen or “bull” centers.
Into every garden a little rain must fall.
This is great for plant growth, but sadly promotes some fungus diseases. Powdery Mildew (as well as other
fungus diseases) is much easier to prevent than to cure. Organic preventatives include 1 Tbs. Baking Soda
with 1 tsp. Ivory Liquid in 1 gallon water sprayed on the garden weekly. Another is skim milk with the same
spreader-sticker (Ivory). Home garden approved chemicals include Daconil and Funginex which are
available at most garden centers. Good garden sanitation seems to help. Also take a look at other vegetation
around the dahlia plot. Does it show evidence of mildew? If so, consider treating it along with the dahlias.
Dahlia Smut seems more active this year. It starts out as lighter discolorations in round circles on the leaves,
looking almost like mosaic virus. Later, these circles in the leaves completely rot through leaving a “shot hole”
perforation in the leaves. Daconil seems to be the best control. Best photo I could find on the net is at the
below link. Be sure to scroll down to find the two photos of early and advanced infection.
Some growers like to combine insecticides and fungicides. This is a great timesaver and a good idea as long
as both labels say this is permissible. Still others have been known to combine liquid fertilizer with insecticides
or fungicides. My experience has been this combination sometimes will cause some leaf burn. Saying this
another way…if you are experiencing leaf burn with a combination fertilizer spray, you might want to try
applying your liquid feeding separately from your other garden chemicals. For years I was kidding myself
and blaming the burning on relatively high daytime temperatures. Applying separately solved the leaf burn
problem. Be sure to thoroughly shower after using garden chemicals.