Rose Care Guide: Pests and Diseases, Pruning and Fertilizing
Pests and diseases
Some rose varieties are prone to black spot so if you are in a warm humid area you may want to avoid these and choose hardier less vulnerable plants. Any good rose catalogue or book will list whether a rose is susceptible or not.
You can choose from knockdown sprays or systemic sprays. A knockdown spray, such as pyrethrum will get rid of the pest infestation but they could come back. If you use a systemic spray the plant actually takes this up and when a bug bites a leaf of flower it dies.
Roses are not attacked by many pests but they are attacked by aphids, a sap sucking insect that will destroy new growth and stunt your bushes.
This is the main insect problem with roses. These little insects love the sap from new tender growth and will cover a bud in order to get to the sap. They suck the sap from leaves, buds and new growth. In some areas where the weather is cooler these might not be a huge problem until later in the season. Any good knockdown insecticide will get rid of aphids but if you don’t like using chemicals you don’t need to.
They come in three different colours white, green and black and you can use a pyrethrum based spray to get rid of them or they can simply be hosed off if you prefer. If you do hose them off they will gradually return.
There are many products available on the market so just choose the one you are happiest with or try a homemade remedy.
This is not a huge problem but if you see tiny webs and eggs on the underside of leaves it will be from these little insects. The leaves will look silvery as the insects destroy individual cells. Any good pyrethrum spray will get rid of them.
Scale or white scale can be seen on the stems of bushes. It looks like little white blobs but underneath the covering is a collection of eggs waiting to hatch. The tiny insects feed on the sap similar to aphids. To get of rid scale you need to smother them by spraying with white oil or eco-oil. They can also be scraped off with your fingernails or a small nail brush.
These may appear to be advantageous but they are protecting the scale. The scale produces honeydew that the ants feed on and in return the ants protect the scale. By removing scale you will lessen the chance of ants on your rose bushes.
Leaf cutting bee
This little bee has an aesthetic effect on the rose bushes as it cuts little sections off the leaves and uses them to hide in. It doesn’t really affect the plant unless you are inundated with them and they defoliate the bushes. They do not often cause any significant threat to your bushes.
There are so many varieties of roses today and they have bred for minimal problems and some show more resistant to attack from disease than others. Some of the well known and loved varieties are prone to problems like black spot but people grow them for the beautiful flowers and deal with the black spot as it arises.
Black spot is the result of moisture and humidity and even the most fastidious rose grower will get black spot in certain weather conditions. If the weather is wet and humid you have a greater chance of getting black spot. Never water your roses over the top of the foliage if it won’t dry out before nightfall. You can water over the top but you need to give the leaves enough time to dry.
If the weather is warm and not wet, it is likely to stay away. Another way to keep it at bay is to keep your rose bushes well fed and healthy. A healthy plant is less likely to suffer from any diseases.
There are many commercial preparations in the market to eliminate black spot. But if you just have a few bushes or leaves affected just take them off and dispose of in a plastic bag in the garbage bin or burn the cuttings. Don’t add them to your compost heap.
You can always try out one of our homemade remedies.
This disease is a fungus seen by the yellow patches that will appear on the leaves with orange spores on the underside. The affected leaves will fall sooner than is usual. This is spread about by the wind.
This can be a result of poor pruning or excessive black spot. The leaves with black spot will turn yellow and drop off and the small branch may die from the fungus.
If you leave too much stem above the new growth buds this will cause die back to the new growth. It is an aesthetic problem caused by poor pruning practices. Even when you are cutting flowers, look for a growth bud to cut to.
This can affect any rose bush and the healthier the plants are the less likely it will appear.
This is evidenced by patterns on the leaves that is caused by a virus. The mosaic can be in any pattern or shape.
Make up a soapy water mix and spray on all new growth, making sure you spray under the leaves. Just add a few pure soap flakes into warm water and shake til they dissolve. Let mix cool then use.
Blend 3 garlic cloves and a hot chilli with a few tablespoons of vegetable oil. Add to a litre of water and let sit overnight. Next day shake well and then strain. Use the strained liquid at a ratio of 1 to 10 in water and spray over affected plants.
Dissolve a teaspoon of baking soda in two pints of water and add a few drops of liquid soap to help it cling to leaves. Spray over leaves making sure you spray the underside as well.
Mix one part milk with two parts water and spray on the leaves on affected bushes and on those not affected to prevent black spot being a problem.
It is recommended to burn all rose prunings as black spot and rust can live in the bark and cells of the stems. If you are unable to burn prunings place in your garbage bin but never in a green waste bin.
Get yourself a good pair of well fitting leather gloves so that your hands won’t be scratched from the thorns. The tiny tip of some thorns can come off in your skin and give you a sore spot for days that will get red and may fester. Just apply a good topical antiseptic to clear it up.
A good set of tools for your roses is paramount and they need to be sharp and kept clean. There are only a few tools you will need to keep your roses in tip top shape:
- Long handled pruners
- Small saw
- Flower snippers
- Dethorner-if you wish to remove thorns from cut flowers
- Wet stone to sharpen tools
- Leather gloves
Dead heading your roses
This is possibly the most important job you need to do to keep your roses flowering. Every few weeks you need to go over your rose bushes and remove any spent flowers. In this way the bush is not pushed to produce rose hips that take more effort than flowering. It also makes the bushes look better without any dead flowers to distract from the new flowers. The bushes will produce more flowers when you dead head them regularly.
Why you need to prune roses each year
A rose grows unlike other plants that get bigger and stronger after each year’s growth. The longer a rose branch is left on the bush the weaker it becomes and the fewer flowers it will produce. Roses flower best on new growth to two to three years old. Each year you will notice strong new growth coming from low down on the bush or from the graft point on standards. This is called a water shoot and this will be the new growth. If the old growth is not cut out the bush will become a tangled mess with fewer flowers and a greater chance of becoming diseased.
We want the water shoots to be strong and that is why we cut out the old growth so the sap is diverted into the new growth so it will grow and flower.
Many years ago roses were pruned back to a few stumpy branches but this is no longer the case and the branches are kept to a reasonable size for the bush. Some of the bigger growing varieties will produce shoots up to 6 feet tall, so the height you cut them back to becomes a personal preference.
The summer prune of your roses is just a tidying up project for the rose bushes. Any growth that had not produced flowers or grown much can be removed. If you cut flowers for use indoors you can do pruning at the same time. Cut the flowering branch back to an outward facing bud so the new growth points in the right direction.
Many bushes, especially floribundas will help you recognise where to prune as they usually produce new shoots after the flush of flowers. Just trim the branches to just above this new growth and tidy the bush up.
This is when you prune your roses back in order for the new growth in growth in spring. All spindly and twiggy branches are removed and any dead wood. Any intersecting branches that cross the middle of the bush need to be removed before cutting back other branches.
Remove any old and worn out branches that did not flower this year. Cut branches back at least 50% to an outward facing bud. You want all growth to be away from the centre of the bush. If the centre of the bush becomes congested there is a greater chance of black spot and pest invasion. There needs to be good air flow around and through the bushes.
When you select a branch to prune you need to look for the new buds forming along the stem. All new growth wants to be directed away from the middle of the bush, this is why you prune the branch just above an outward facing bud.
This term applies to the new growth that is just leaves and does not contain any buds in the new growth. The way to deal with is to prune back a few leaves from the new growth and hope that the subsequent shoots will flower. This does work but you may need to be vigilant for a while to get the bushes to flower.
Pruning for climbers is much the same as any rose at first. Remove all dead, spindly and poor growing branches and then decide how much you are going to cut the branches back. As these are usually tied to a frame you may need to untie the branches as you prune. The main thing to remember with climbing roses is to keep the branches in a fan shape against the fence or trellis and don’t have any branches coming down too low to the ground as they will not grow well.
These rose flower on new growth and they can be pruned back to a clump of branches. Remove any old and twiggy branches and cut all the new green branches back to a bud. They may throw out a long branch that seems disparate to the bush, this needs to be removed to keep the plant a low growing mound. Some people prune these roses with hedge clippers, shortening the branches back to roughly the same length. This can work for younger plants but you may need to be more selective as the plant gets older.
Like any plant roses need to be fertilised regularly to be at their best and most productive. You can buy a commercial rose food that will have all of the necessary ingredients and they like organic matter dug into the soil before planting. A good layer of composted material around the plants will help them to get lots of nutrients and to save water evaporating from the soil.
Fertilise your plants with a good slow release fertiliser as soon as you see new shoots emerging in spring. You can then fertilise again after the first flush of flowers and the summer pruning to promote more flowers and healthy growth. You don’t want to fertilise to close to winter as you want to prune the plant so it comes back in spring. Too much fertiliser here and the rose will want to keep growing.
You can also use a good foliar plant feeder over the leaves and you do it early in the morning so the leaves have time to dry. This can be done every fortnight during spring/summer to promote new growth and flowers.
Roses are a very hardy plant and do not need a lot of water if they are getting sufficient rain. If the summer is dry you can deep water your roses once a week to keep them in prime condition. If the water is not getting into the soil you can use a soil wetting agent such as fabric softener. Another way is to push your large gardening fork into the ground around the plants to let water get into the soil.
During the colder months the rose bushes won’t need as much water as they are dormant and waiting for the warmer weather.
Snow and very cold winters
If you live in area that has permanent snow in winter and consistent low temperatures you need to care for your roses and protect them from the severe conditions. There are a few different ways you can go about protecting the bushes depending on how sever the conditions are.
- Cover the crown of the rose bushes with dry bark mulch to protect the growing area from snow and cold temperatures.
- Wrap the entire bush in burlap by first loosely tying together the branches. This will stop the cold and wind from drying the branches out. You can then cover the burlap in a layer of conifer cuttings in severe conditions to further protect the plant.
- Buy a commercial rose cone with an open top to cover your roses.
- A standard rose is harder to protect. Some people advise you to dig them up and then lay them down in a trench. And fill the part of the trench with the growing top with mulch and the rest with soil.
- You can try to warp a standard rose with burlap that is filled with an insulating material such as oak leaves.
- Dig up your standard rose and cover the roots and let them winter in the shed or garage
- For roses in pots you can cover the rose with burlap and then heap mulch around the pot to protect it from the cold.
Moving a rose bush
Roses are one plant that can be quite easily moved with little ill effects. The best time to move a rose is in winter when it is in a dormant phase. If you live in a tropical climate this can be tricky as the rose will want to flower and grow all year round. The best time to move then is after the winter prune when the bush has no leaves or new growth.
The best method takes a few weeks as you cut down vertically into the soil about 12 inches away from the plant, in a circle around the bush. This severs all lateral roots. If you are able, leave the rose in the ground for two to three weeks and then dig under the root ball and transplant to new location. If you don’t have this time, as we all make sudden choices in our garden don’t worry. Just dig the bush up and transplant. The new hole needs to be bigger than the root ball so you can firm soil in around the bush. Never plant a rose deeper than it was before and don’t plant it higher than before.
After you have moved the plant you will need to water it well so the stems don’t shrivel from lack of water. Keep the water up to it and you will have a rose bush that looks like it has never been moved.