Q: I read that I am supposed to remove the suckers on my rose bush below the union. What is the union on a rose bush and how do I know what a sucker is?

A: Growers can propagate roses in several different ways. Some can grow from planted seeds, but most are produced by cuttings and grafts.

Grafts are common on the newer varieties. If a grower wants to obtain as many new roses in the same classification, one of the fastest ways is by using bud grafts. A rose has many buds that would grow new stems; however, these buds are removed and each individual bud is grafted onto its own new rose bush. The original top of this rose is cut off, and the new bud sends out growth that replaces the top of the bush — the bottom of the rose bush supplies the root system.

The result is a plant containing two parts. The joining of these two parts often forms a large knot of swollen tissue called the graft union, or union for short. Rootstocks, which are below the union, are often chosen for winter hardiness and vigorous growth that will be able to supply water to the top. The top portion of the grafted plant is called the scion. Sometimes, the size, hardiness or other characteristics of the scion are determined by which rootstock is used.

Each spring, new stems will hopefully develop from the scion portion of the union. Old stems and dead ones should be removed all the way to the top of the union without leaving a stub.

Occasionally, the rootstock will send up its own stems. Some can sprout from the roots and others may come from the vertical stem between the roots and the union. All new stems from the rootstock are called suckers; they should be removed as soon as possible. If left to grow, they will eventually bloom.

The flowers of the rootstock will not be similar to the flowers of the scion. When people say their rosebush suddenly has a new flower color, it is often because a sucker has gone unnoticed and grown until it bloomed. Suckers take away energy from the roots that were supposed to go to the scion. If the scion portion of the plant has died, the rootstock suckers may form the whole new plant. It is unlikely that the rootstock's flowers will be acceptable to the purchaser of the original rosebush, so it should probably be removed.

The union is usually large enough to be visibly different than the stem. In warm climates, the union is usually planted several inches above the soil. In cold climates, it is put a couple of inches below the soil for winter protection. If the union is buried, it may be hard to tell which stems are suckers, unless the leaves are different.

Unions are only found on the grafted roses. This is the common case for hybrid tea, floribunda and grandiflora roses, but doesn't include shrub and many heirloom roses. Other rose varieties vary as to their propagation method and might have a union. If the rose has a single stem for several inches and a group of stems coming from this point, consider it a union. If it contains stems coming from the roots, there is no union. No new growth from the roots will be the same as the original top; they are not suckers.

Q: I have a new arbor and I planted two climbing roses, one on each side.

When do I prune them?

A: Roses bloom on new growth of the current season or on older branches.

The roses that produce on new wood will send out a new stem that ends in a cluster of roses. Roses that bloom on old wood first grow a stem for a year, which sends out short branches of blooms in the following years.

Most climbing roses develop on stems that are two years and older. During the first year, a stem will grow out of the ground, or off the union, in the summer. It will become longer without blooming. Unless it is in the way and can't be strapped up to the arbor, don't prune it. The second year it will send out short stems, usually less than a foot long, from each of the locations that had a leaf the first year. Each short stem will produce a cluster of flowers. The original stem sends out more short stems for a couple of more years and will then decline in flower production.

At the end of four years, remove the stem at the ground level to make room for younger stems. If you take the oldest one-quarter of stems, you will always have new young flowering stems.

Many climbing roses only bloom once a year. In that case, do the pruning following growth. The expiring flower clusters can be removed and the whole plant tidied up. Climbing roses that bloom more than once during the same growing season can be cleaned after each blooming session. They can also be pruned during the dormant season. A few of the long canes may be cut up to a third, if necessary to keep the plant in bounds. Don't cut all the canes back; you will lose too many flowers.

E-mail questions to Jeff Rugg, Kendall County unit educator, University of

Illinois Extension at [email protected]. To find out more about Jeff Rugg and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.