January 2010 Consulting Rosarian Report

By: Sue Kirkham

This is a busy and very important time of the year for rose growers. Here I will touch briefly on the aspects of your winter care.  Throughout the year GGRS will have programs and Consulting Rosarian Reports going into some of these areas in much greater depth.

We prune our roses in the winter to ensure our bushes remain healthy and vigorous.  Winter pruning can influence the size of the blossoms, the strength of the stems and can direct growth in different directions.  A well-pruned rose bush is more likely to reward you with fresh new basal canes.  In San Francisco it is best to complete your pruning by the end of January.

Health and Vigor – removing old canes, spindly canes, and canes going in the wrong direction gives vigor to the rose bush as new growth is directed to more productive canes and the center is opened up to provide better airflow (a plus for control of fungal diseases).  Removal of all leaves remaining on the bush, and any on the ground, assists in control of fungal diseases that may over winter on the bush or in the soil.

Control Size and Direction  - as a general rule you should prune to an outward eye to open up the center of the bush. 

Tools – the correct tools are essential to good pruning.  Sturdy garden gloves are essential.  A sharp pair of by-pass pruners (Felco #2 is an excellent choice), a pruning saw and long-handled loppers will handle most situations.  I have found a battery operated Makita saw to be very helpful for access small spaces.

Assessing Your Rose Bush – if the bush has been very disease prone or performing very poorly it is probably best to remove the bush and replace it with another specimen.  There are many excellent varieties, so don’t increase your workload with a poor performer.

During the growing year visit the Rose Garden at Golden Gate Park , or other public rose gardens, to see which varieties are doing well throughout the growing year.  Consider these healthier specimens for your shopping list late in the year when the catalogs come out for winter purchases and planting.  

Your goal will be to reduce the bush to approximately 3 – 5 healthy canes, to open up the center of the bush, and to reduce the size of your bush by at least 50% in most cases.  Ideally the 3 – 5 canes would be somewhat evenly spaced (a challenge at times).  12 – 24 “ high after pruning would be the normal result. 

Remove older canes, flush with the bud union if possible (older canes are less productive than newer canes)

Remove spindly canes (less than the width of a pencil)

Remove canes that cross into the center of the bush

Remove die-back  (brown, dead areas – look at the pith of the cane, it should be white/green, not brown)

Be careful how you make your cut – it should be about ¼” above an outward eye and at a 45 degree angle (see diagram)

Do not leave “stubs” – too much space above the eye or bud union generally leads to die-back.

Know the difference between suckers and basal canes.  Basal canes are new growth coming from the bud union and this is what we really want to encourage.  Suckers are growth coming out of the soil around the base of the bush (from the root stock).  Look for suckers and pull them out with a firm pull tug.  If you are unsure if a growth is a basal cane or a sucker, just wait until it develops a little more or blooms for the first time.  A basal cane will have the flower you expected and normal cane and leaf formation for the variety. A sucker will have a long sprawling cane, different leaf formation and will ultimately bloom with small maroon/reddish flowers of the Dr. Huey root stock.  If left unchecked the rootstock will ultimately take over.

Clean Up – Sanitation is extremely important - remove all of your pruned canes and leaves, including any on the ground.  There should not be any leaves remaining on the rose bush.  Do not compost the rose cuttings at your home – they will likely harbor insect eggs and fungal spores.

Dormant Spray - if you do not have any new growth showing you can use a dormant spray (horticultural oil can be used at this time – check for products at your local nursery).  If your roses are showing some new growth use a growing year fungicide.  Be sure to read the labels carefully and only apply the amount specified (more is NOT better).  Protect yourself with goggles, respirator, rubber gloves and protective clothing and boots.  

Spray Program  - for the best control of fungal diseases you will follow the sanitation practices above, and continue to remove any diseases leaves from the bush and the ground throughout the year.  In addition you would follow the frequency of application instructions on the fungicide you purchased.  It is a good idea to alternate the products you use to that the fungi do not build resistance to a particular product.  Once you can see a fungal disease it has already been present in your garden for weeks.  It is tough to eradicate once it has taken hold.  It is best to stay ahead of fungal disease with a regular spray program.

Soil Amendment  - this is the time of year to add amendments to your soil.  Ideally you would have a professional soil analysis, but in the absence of this you could consider feeding each bush with superphospate, alfalfa meal (without molasses), Osmocote, etc (follow the directions on the label).  Gently scratch these amendments into the soil so you do not disturb the delicate feeder roots.  After amending my soil each year I put a layer of chicken manure on top (so that it breaks down during the year and does not burn the roots), and then put a layer of mulch over the manure. 

Planting New Rose Bushes – if the roses are bare root soak them for about 24 hours before planting.  Dig a large and deep hole in good soil.  Fill the hole with water and let it drain.  Put the superphosphate at the bottom of the hole.  It is a good idea to temporarily cover the bud union until the bush has taken off in the spring.  Once it has leafed out remove the soil covering the bud union.  Try to resist cutting roses from your first year bushes – they need to put their energy into the root system rather than encouraging them to create new roses.