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A common question I get asked occasionally as a professional gardener is, ‘Why are my roses growing so tall’. My answer is they usually need pruning as they haven’t been pruned in years, or you might have purchased a climbing or rambling rose without realising. Sometimes, they don’t realise they need to prune their roses every spring to maintain a certain height, usually between 4-5ft. Roses are best pruned back to 20-30cm every year.
The issue starts with plant labels too. They provide the eventual height on the label of that particular rose, maybe 3ft, for example. The problem is, with roses, this height is if you main a pruning schedule and cut them back every spring to around 1ft above ground level like you should with most roses. The rose will then grow to about 3ft every year. If you leave the rose not pruned, they keep growing and growing to as tall as 10ft.
The problem with tall and leggy roses is that the wind that loosens the roots in the ground or snaps tall stems causing damage.
Read on to learn more about this and other reasons that roses sometimes become leggy.
Types of roses (natural causes)
If you’ve inherited your roses or moved into a new home with an established rose bed, you may not know what varieties of roses you have. Your tall roses may be designed to grow that way. Maybe you have a species of rose that has a tall variety.
The key here is to look and see if your rose is in proportion or if it seems leggy and spindly. If it’s spindly, then it’s probably not intended to be that tall. But if it looks well-put together, then you have a naturally tall rose, but you should still prune them every spring.
Or maybe you’re the unexpected owner of a climbing or rambling rose. These rose types put out long, spindly canes and stems. They frequently cannot stand up right unaided and need support. If your rose tree or bush looks like this and is tending to grow along the ground, you need to provide a framework (wires up a fence or a trellis, for example) and train the climbing or rambling rose up it. Your roses growing so tall turns out to be a good thing for climbing roses.
For more information about climbing roses, see How to train climbing roses and How to prune climbing roses in this series of articles.
The growing environment
Maybe your rose tree is growing tall because it’s in a difficult growing environment. Roses grow tall when they’re not getting enough sunlight. You can tell this is the case with your rose by looking at its lower leaves.
If all the growth seems to be at the top of the plant and the lower leaves and buds look as if they’re dormant, then you have a problem with a lack of sunlight. The rose plant is sending all its limited energy and resources to the top part for development and ignoring the bottom sections. They are in essence reaching for the light.
You need to get more sunlight to your rose. If it’s a container, that’s easy enough. Just move it to a sunnier place. If it’s in a rose bed, check around and see if you can cut back or move any other plants that are overshadowing your rose bed.
What you’re doing or not doing
If your getting lots of green foliage but no flowers, you may be giving your rose tree too much or the wrong mix of fertiliser. Too much fertiliser encourages the plant to grow in unsustainable ways and in unexpected directions, including upwards. You may also be giving your plant a fertiliser that’s too high in nitrogen which is a common reason for lots of fresh tall green growth. This encourages the development of foliage to the loss of the development of flowers.
Check the fertiliser you’re using and that you’re using it appropriately. A rule of thumb is to use a balanced general-purpose fertiliser until the flower buds develop. Then select one that’s higher in potassium for flower development. Use the fertiliser about every fortnight but be sure to mix it in with the soil if it’s granular or to dissolve it thoroughly in water if it’s soluble.
Your rose may also have grown so tall because you’ve been neglectful in pruning it. You need to prune the rose to keep it healthy, in shape and to encourage the right kind of growth. Left to itself, a rose tree will grow spindly in all directions.