Small Acreage: Gardening tips
June 13, 2014
Ah, the first days of spring! My calendar says I can plant my peas, spinach, and lettuce St. Patrick's Day.
So I did.
And I waited and I waited and nothing came up.
One month later (around mid-April), I replanted all my cool season crops and two weeks later they were up. I also started cucumbers and melons in my greenhouse the first of May.
One month later they had their first true leaf.
A couple weeks ago I threw some compost in my garden which included some melon seeds and they germinated within 10 days.
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What made the difference between my greenhouse and my garden?
Soil temperature is a huge factor in seed germination and something all gardeners should be aware of.
The soil warmed up by at least 10 degrees between March 15 when I first planted and April 15 when I did the second planting.
My soil was a bit cooler because I had a foot of mulch on it and hadn't removed it before I planted the first crop.
Mulch is something you should add after planting, but it can also keep the soil abnormally cool after a long winter.
Two weeks before planting, spread or remove the mulch.
Raised beds also help elevate soil temperature.
Refer to Colorado Master Gardener Garden Notes #143 for more information on the effects of soil temperature on seed germination at http://www.cmg.colostate.edu.
Q: I am starting to see black spots and yellowing of the leaves on my roses. What should I do?
A: Due to the current wet weather we are experiencing this spring and early summer, your roses may be suffering from a disease aptly named black spot (Diplocarpon rosae).
According to Wallis and Lewandowski in the Department of Pathology at Ohio State University, black spot is a common fungal disease that occurs on roses under warm, humid, wet conditions.
Certain types of roses such as grandifloras, hybrid teas and miniatures are more susceptible while some of the shrub and Rugosa types have shown some resistance.
Black spot begins as dark, roughly circular spots on the upper side of the leaves. The leaves will turn yellow and eventually fall off. This weakens the rose and can affect flower production. Severe infestations can also affect petals, canes, fruit and petioles.
The fungus reproduces by spores, which on fallen leaves can splash up to contaminate new leaves and spread the disease. The spores can also be spread by wind.
Wallis and Lewandowski state black spot spores can germinate and infect new leaves in as little as one day under ideal conditions. Symptoms will occur in four or five days and spores will be produced in 10 to 11 days. This life cycle will continue as long as the perfect conditions continue.
Luckily for us, Colorado is a semi-arid state and these wet periods are not as prevalent as in other parts of the country.
Wallis and Lewandowski list several ways to manage this disease. When applying fungicides, read the label and follow the directions. These chemicals can cause plant stress and death if used incorrectly.
• Avoid overhead irrigation, water in the morning and provide adequate air circulation to the plants by proper spacing and pruning.
• Remove and dispose of infected leaves and canes as they occur (do not put infected plants in the compost bin; throw them in the trash). A thorough cleaning of all debris is also recommended in the fall. Spores will overwinter in fallen leaves and damaged canes.
• Purchase black spot resistant roses whenever possible. A list of resistant roses can be found at http://ohioline.osu.edu/hyg-fact/3000/pdf/3072.pdf.
• Fungicide controls are effective if used in conjunction with proper sanitation practices. These chemicals prevent new spores from germinating on unaffected leaves; they will not protect already infected leaves. These fungicides will need to be reapplied every 7-10 days in rainy weather.
Fungicides labeled for the control of black spot of rose include: Captan, Chlorothalonil (Ortho Garden Disease Control, Bonid Fung-onil Multipurpose Fungicide), Mancozeb, Myclobutanil (Spectracide Immunox Multipurpose Fungicide), Potassium bicarbonate (Bonide Remedy), Propiconazole (Bonide Infuse, Ferti-lome Systemic Fungicide), Thiophanate-methyl (Ferti-lome Halt Systemic Fungicide), Copper hydroxide (Hi-Yield Copper Fungicide), Copper salts (Bonide Liquid Copper Fungicide), Lime sulfur, neem oil and sulfur.
Black spot can be controlled on Colorado roses. Look for the symptoms, remove diseased leaves, treat with a fungicide if necessary and hope for sunny days. ❖