Also serving the communities of De Luz, Rainbow, Camp Pendleton, Pala and Pauma

Fungus and fertilizer in the rose garden

Frank Brines

ARS Master Rosarian

Boy, has it been crazy weather? Depending on your location – or more specifically, that of your garden – you may have experienced frost damage to your roses and tender young plants recently. Keep an eye on your roses: If you see that frost has actually killed new growth that came out after pruning, you may need to reprune, making your cuts just above the next outward-facing bud down the cane. But don't be too hasty – wait until the threat of frost damage has likely passed.

The thing is, even gardens in the same general vicinity may have different effects due to their prevailing micro-climates. The next few days of March have slightly below-normal nighttime temperatures, with predicted daytime temperatures near average. Overall, temperatures predicted for March are near average and rain is likely. Roses enjoy this weather – it encourages them to jump into life.

If your roses experienced fungal diseases last year and you haven't yet done so, you might think of applying a copper dormant spray soon – but only if you can be fairly certain it won't rain for 24 hours. You can mix Horticultural Oil with the dormant spray for better adherence – but read the label to make sure you can mix different sprays. These will reduce the likelihood of early fungal and pest issues. Oh, and as a note of caution: Be prepared for chilli thrips as temperatures warm up!

Steps to take when ready to spray: First, make sure the garden is free of left-over debris and dispose of it in the green garden waste bin – do not compost rose debris in your yard. Backyard composting doesn't get hot enough to kill any pathogens. Second, if you didn't do it already for pruning, remove all old leaves that may be left on the bush. This cleanliness will help keep down disease.

Third, read the spray label completely to ensure the proper strength of the mixture for “growing season instructions” as the new growth has begun. Fourth, saturate all canes and the soil surface of the entire bed.

Fifth, maintain a minimum of 2” to 4” of organic composted mulch over the entire garden surface to insulate the upper 8” to 12” of the soil zone where most rose roots feed, and to reduce evaporation and conserve water, while still providing sufficient moisture. This will also supply nutrients to build the soil for your roses over the season.

Take time now to inspect and make any necessary repairs to your irrigation system while there is little to no new foliage. Then you'll be prepared to begin a regular irrigation schedule. Drip systems are the most efficient and they avoid problems created by above-ground sprayers and sprinklers, which waste water and can foster molds (e.g., mildew and rust).

If possible, avoid any over-spray or misting applied elsewhere in your garden that may hit your roses; but if you use overhead watering systems, avoid doing so when there is any wind to avoid moisture evaporating or collecting on leaves which could result in sunburn or add to conditions favorable for fungal diseases.

For best results and efficiency, be sure to schedule irrigation so it is complete before the day gets hot (preferably by mid-morning, that is, 8-9 a.m.). Avoiding afternoon or evening watering prevents excess ground moisture into night time. Too wet soil can lead to unhappy roots and/or fungal diseases.

Roses do love food and water for the best blooms. Rule of thumb: When new growth is 2-3 inches long, it is time to begin a fertilizing program. I suggest an initial feeding be higher in nitrogen (N) to encourage new stem and leaf growth. In about two weeks, apply fertilizer that is higher in phosphate (P) and potassium (K) to give roots a boost at the start of season.

New information suggests that continued use of fertilizer higher in P and K will foster greater root development and lead to better growth, disease resistance and healthier plants. Look for fertilizers rated as 8-10-8 that include micro elements for greater results. Also, you can apply worm castings (available at garden stores and nurseries).

I highly recommend organic type fertilizers vs. inorganic or “chemical” ones. Organics foster better soil development, a richer, livelier, more viable community of soil organisms that break the elements into easily absorbed form and release them slowly. They will “build” soil structure into a healthy component and when used regularly will develop a soil rich in reserve energy, allowing you to use less product with the same results.

If you have completed your pruning, it is likely all your pruning tools need sharpening. Sharp pruners make for clean cuts and the prevention of diseases or otherwise damaged weak canes. The best files to use are thin flat types with diamond grit material. This type allows easier sharpening for the tight spaces between the cutting blade and bar.

Attempt to follow the current/original bevel/angle of the sharp blade. Felco said that the angle for their pruners is 23 degrees. Keeping pruners clean can be done using 70% isopropyl alcohol,WD40 soak, or Lysol sheets. If heavy plant “juice” is a problem a small brass bristle brush will help remove it. Lubricate the mechanism with a light oil like 3-in-0ne.

There will be an American Rose Society (ARS) Pacific Southwest District Rose Show and Convention April 22 and 23 in San Diego. As in past years, it will be at the Ronald Reagan Center, 195 E. Douglas Avenue in El Cajon.

Be sure to visit the Rose Haven Heritage Garden located at 30500 Jedediah Smith Road (the cross street is Cabrillo Avenue) in Temecula, a 3.4-acre rose garden owned and maintained by the Temecula Valley Rose Society, a (501c3) organization, supported with donations from kind people like you. (Look for the donation box when you visit!) Also, visit regularly for great information and schedule of events.


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