Editor: Mike Riordan (503) 256-0425 Contacts: Larry Smith (503) 777-1857,
Jeanette Benson (503) 649-4118
Meets second Tuesday of the month at Rose City Park
United Methodist Church, 5830 N.E. Alameda
Next meeting Tuesday, July 10th, 2007 @ 7:30 PM
COOKIES FOR JULY
Cookie hosts for July are Arnie Klug and Phil Mingus.
PROGRAM FOR JULY
Our program for July will be a presentation by our own President detailing the ins and outs of
entering dahlia blooms in County Fairs in Oregon and SW Washington. Larry has been
successfully entering fairs for a number of years and also sometimes is asked to judge at the
events as is Jeanette Benson. Another member told me a few years back that he was able to
finance most of his dahlia hobby (new varieties, fertilizer, spray and water) with his winnings at
the fairs. If you know how to successfully compete, it can be financially rewarding.
TALLY VOLUNTEERS NEEDED
We need three volunteers to work on the Tally Committee at our annual show Saturday,
September 1st. Volunteers would compile show results, record winning exhibits and determine
sweepstakes winners in each competition category. Time commitment would be several hours
beginning about 11:00 AM. If you would like to help with this project, please contact Larry Smith.
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 7th Avenue between Powell and Division in Portland. Peruse their offerings
and prices at http://www.concentratesnw.com/organics_pricelist.htm 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.
We had a wonderful presentation at the June meeting on soil types and the need for lime to create
the proper pH for growing dahlias. As she said, 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-e/#anchor918073
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
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.
Using the ADS Color Chart to
determine the color of a dahlia