How To Grow Roses In The Moist Northwest – Prevent Disease Attacks

Roses may be cut by gardeners seven months of the year in the general area referred to as the moist Pacific Northwest. Two weeks without rain brings out newspaper notices concerning the “drought” conditions. 

Winters are frequently so mild that planting operations continue from November until March without interruption. A famed visitor from Northern Ireland, Mr. Sam McGredy, stated that the climate was much like that of his own home, where roses also thrive to perfection. 

blooming Mirandy rose in the northwestPin

The many days and often weeks of gentle, mist-like precipitation are pleasantly referred to as “soft days” by this personable rosarian. 

With so much in favor of rose growing – mild climate, long growing season and plenty of natural moisture – what problems could there be for rose enthusiasts? 

Only a few, but these should be well noted.

Watch Out For Roses With Too Many Petals

First of all, while it is conceded that roses enjoy plenty of water, certain varieties do not perform at their best under the almost excessive humidity of the Pacific Northwest. 

These varieties include roses of unusually numerous petals (generally over 50). This is especially true when the petal texture is thin. In such cases, the blooms will not open well and will hang on the plant in an unsightly manner.

Growing roses with petals that overlap one another are also prone to follow this pattern. 

In addition to selecting roses of moderate petalage and heavy texture rosarians of the Pacific Northwest have one more limitation placed upon them. 

Along with plenty of moist, cool days the area has a temperature range in summer which rarely exceeds 80° degrees Fahrenheit. Nights are almost always cool (50°-60° degrees Fahrenheit). 

Roses that need warm days and nights to produce rich color have a tendency to show muddy, uninteresting blooms in the moderate climate. Such varieties rarely attract much favorable comment except in an unusually warm summer. 

Most of the roses referred to in the catalogs as apricot or peach blend fall in the class above. It is certainly no disparagement of the varieties, only a climatic factor which must be carefully considered.

The One Major Cultural Problem – Mildew

After the best cultivars are found (and there are literally hundreds of satisfactory ones) the rose grower is faced with perhaps the only major cultural problem – mildew. 

Starting with fall cleanup in late November the rose gardener will strip all foliage from the plants, rake the leaves from the beds and follow this with a dormant spray such as lime-sulphur combination. 

The plants are then left until mid-February when another weaker dormant spray solution is applied. 

It has been found that in the case of both powdery mildew and black spot – the only other fungal disease ordinarily found on roses in the Pacific Northwest – prevention is the best means of combatting the scourge effectively. 

Beginning in April, when pruning has been completed for about a month (generally around March 1 to 10) the foliage is sprayed or dusted weekly with either sulfur, powder or wettable mixture.

Timing Sprays

Timing the spray to precede rain is a wise practice. Mildew spores are most active when the humidity approaches 100 percent. Most sprays have what is termed a spreader or sticker incorporated in them by the manufacturer so that very little of the spray is washed off by a mild rainfall. 

Blacks pot, previously mentioned may also be combatted by the same lime-sulfur spray. The fungicide, captan has proved very excellent in combatting black spot specifically. 

It may be combined with some insecticides, but is generally best used alone. Rosarians sometimes feel that since no apparent evidence of mildew or blackspot is present, spraying is unnecessary. 

Nothing could be further from the truth, for it is much easier to prevent the two than to cure either of them.

In fact, in the case of blackspot all leaves showing the characteristic “ink blotch” type of evidence should be carefully picked and destroyed immediately. 

Since the fungus is within the leaf tissue itself, it cannot be reached and thereby “cured.” 

It must be prevented or held in check. While mildew, that white, downy blemish, may be cured, it will still leave the foliage marred and distorted. Prevention is the answer.

Lush Growth and Insect Pests

With such lush growth as is produced in the Pacific Northwest comes the advent of insect pests. Most of these are not a serious problems and require only a minimum amount of attention. Aphids and leafhoppers are among these. 

Any one of several contact insecticides properly used spells quick doom for them. Thrips and red spider mites do cause considerable damage in some years and are not easily controlled. 

Thrips are so small that they conceal themselves within the petals deforming the bloom and causing a brownish discoloration. Since they may appear from adjoining areas it is next to impossible to eradicate them. 

Malathion or any one of several contact insecticides proves effective (if you can reach them). Red spider only occurs when summer weather turns dry. The loss of luster on the foliage and a grayish cast signifies their presence. One of the miticides is best used here.