Rose expertise

Roses (genus Rosa) are one of the many genera of the Rose family (Rosaceae). There are about 300 species of wild roses worldwide, of which approximately 20 grow in the Netherlands and Belgium. These are roses that grow in their natural environment without human intervention and reproduce by seed. In addition, there are several tens of thousands of cultivars grown by man through cross-breeding.

GARDEN ROSES VERSUS CUT ROSES (GREENHOUSE ROSES)

When breeding garden roses, the breeder has very different criteria than when breeding greenhouse roses.

Important criteria in breeding garden roses are disease resistance, floridity (continuous flowering), self-cleaning, fragrance and winter hardiness.
Important criteria in the breeding of cut roses are the number of flower stems per plant, length of the flower stems, the flower shape, the vase life and tolerance to transport.

Disease resistance is less important than with garden roses because growth is more easily controllable in the greenhouse.
This website relates to garden roses.

CLASSIFICATION OF ROSES

A generally accepted classification of rose varieties is:

1. Large-flowered roses. As the name suggests, these cultivars usually have large, well-filled flowers that grow singly or in small clusters on the stem. They are propagated by budding wild rootstocks which combines the vigour of the rootstock with the good features of the cultivar.

2. Floribunda roses. These roses flower in large clusters and usually have slightly less filled flowers. This group is also propagated by budding.

3. Polyantha roses. These roses have small flowers in often large clusters. Propagation by budding.

4. Patio or miniature roses. This group usually blooms with small roses in clusters. They are suitable as ground cover. Propagation by budding or cuttings.

5. Climbing roses. These are in fact espalier roses, they do not climb naturally but have to be tied to a frame. Propagation by budding or cuttings.

6. Shrub roses. These roses can be considered shrubs as far as pruning is concerned. They can be propagated by cuttings, which prevents wild growth. We distinguish the traditional roses (wild roses, botanical roses) and the modern shrub (landscape) roses that cannot be distinguished from the species mentioned above, but have sufficient vigour to form a good shrub on their own roots.

The distinction between the groups of roses is not strictly defined. Due to the many crossbreeds between them, the various groups merge into each other.

We also distinguish between rose varieties that flower once a year and those that continue flowering until autumn.
Once-flowering varieties bloom on branches that grew a year earlier, continuously flowering varieties bloom on branches that grew in that year.

Wild roses generally flower once a year; the flowers usually have 5 petals. The number of petals in cultivated breeds varies from 5 to more than 100. The vast majority of cultivars currently offered are continuously flowering. Some climbing roses (particularly Ramblers) flower just once a year, but very profusely.

PROPAGATION OF ROSES

Outdoor roses are propagated in 3 ways:

1. Sowing.
Wild roses can be propagated by sowing. The main application is sowing rootstocks that can be grafted. Seeds from crosses are also sown when breeding roses by crossing. Each seed produces a unique plant; through selection, new varieties are bred.

2. Budding.
This involves placing a bud with a piece of bark from the rose to be propagated under the bark of the rootstock via a T-cut. Its advantage is that the growth vigour of the rootstock is combined with the characteristics of the cultivar. Disadvantage is that the rootstock can give wild growth, which needs to be removed.

3. Cuttings.
If the cultivars naturally have sufficient vigour, they can be propagated by cuttings. A major advantage, especially for public green spaces, is that no wild growth occurs. Also, for the grower, the cost price of cuttings is lower than that of propagation by budding.

TIPS FOR BUYING ROSES

Outdoor roses come in shapes and sizes, scents and colours. When buying roses to plant in the garden, you can choose between bare root roses that can be planted from November to April in frost-free weather and roses in containers that can be planted year-round. Advantage of bare root roses is the price, they are considerably cheaper than roses in container. The advantage of containerised roses is that you can buy them in full bloom and thus immediately enjoy the floral splendour in your garden.

Flowering roses in container can be bought for use on a terrace or balcony. Of course, it is also possible to enjoy the flowers on the terrace or balcony first and plant the roses in the garden after flowering.

CHOOSING ROSES

Of course you want beautiful, healthy roses that have good resistance to the main rose diseases for your garden.

To be sure about its health, choose varieties with the German ADR certificate or the Dutch/Belgian Excellence certificate.

Whether you like a rose, is mainly a matter of personal taste.  At De Rozenhof in Lottum, you can see a large range of ADR and Excellence roses in bloom. Come take a look and make a conscious choice. The various garden centres in Lottum offer a large assortment of ADR and Excellence roses, also blooming in containers.

PLANTING ROSES

1. Roses in container for patio or balcony

These roses are usually repotted in an ornamental pot. Choose a pot with straight or inward sloping sides, considerably larger and deeper than the pot in which the rose was purchased. Do not use a pot with convex walls, it is very difficult to remove the rooted plant from it. At the bottom of the pot, add a layer of clay pellets if necessary. Carefully remove the pot from the rose and place the rose in the new pot. Fill with good potting soil.

The fertilization of potting soil becomes depleted and must be replenished before the growing season.
Every 2 years, potting soil must be replaced.

  • The care of the rose during the growing season is aimed at growing flowers for as long as possible. As a result, some branches are insufficiently hardened and therefore freeze to death. The result is an unbalanced shrub the following year.
  • The potted rose is prone to frost because the potting soil freezes, causing the roots to dry out. It is possible but not easy for roses in pots to survive the winter, they need care throughout the winter.
  • The potting soil should not dry out.
  • There is a risk that the pot will freeze to pieces due to the expansion of the potting soil when it freezes.
  • All in all, the easiest option is to replace the rose every year. For the price of one bouquet, you can enjoy an entire season of one rose bush.

2. Planting roses in garden

Roses love the sun. They grow and bloom best in sunny spots. Partial shade is still tolerated well by most varieties, but with less than 4 hours of sunlight per day, roses are usually not the best option for your garden.
When choosing the colour of the rose, keep in mind that dark colours and especially dark red roses can burn quickly in the sun. So place them where there is shade during the afternoon sun.

Then again, yellow roses are known to be more prone to frost than other colours, but also to bloom earlier.

Make sure roses can dry properly after rainfall or irrigation to prevent infections with fungal diseases. So plant them well in the wind, but not in a draft.

Preparation of the soil

The rose is a lime-loving plant. It is important that your soil is suitable for keeping roses in terms of acidity. The ideal pH value is between 6 and 7 for sandy soil and between 6.5 and 7.5 for clay soil.

If the pH is too low: apply lime.
If the pH is too high: sprinkle peat.

You can have the pH value tested free of charge at most Boerenbond and Welkoop stores. You can also test the pH yourself; test kits are available at the higher end garden centres and from various online providers.

If you want to plant new roses in a bed where there were previously roses, there is a chance that the roses will grow poorly due to infestation by root nematodes (soil fatigue).

There are three remedies:

  1. Use Symbivit ® when planting (available at De Rozenhof and at better garden centres). Symbivit ® is a fungus that lives in symbiosis with the roots of the rose and has a very beneficial effect on the development of the root system.
  2. Replace the soil (50 x 50 x 50 cm per plant). This can be done when planting one or two roses, but is hardly an option when planting a larger bed.
  3. Sow African Marigolds (Tagetes Patula) and allow to bloom for a minimum of 3 months, then dig under as a green manure if necessary (can also be used on a large scale). African Marigolds can be sown after mid-May when the danger of night frost has passed. It is important that the soil is weed-free and kept weed-free during the germination process of about 2 weeks, otherwise the nematodes can survive in the roots of the weeds.

Planting distance
The planting distance in beds depends on the height and width of the chosen variety and is 40 to 60 cm for most varieties. Please inquire in advance at your purchase address or on this website [with a link to the encyclopaedia].

Planting container roses outdoors

  • Dig a planting hole well larger and deeper than the container.
  • Mix the excavated soil with about 1/3 potting soil or soil improver, e.g. DCM Vivimus. This promotes the growth of the root ball in the surrounding soil.
  • Carefully remove the container and place the rose in the planting hole.
    Fill the planting hole with the mixture and make sure the grafting point is about 5 cm below the soil. Press well and water generously.

Planting bare root roses in the open ground
Bare root roses can be planted from November to April in frost-free weather. The best time is November-December, so the plants can make new roots before winter.

If you cannot or do not want to plant the roses right away, you can ensilage the roses by digging an oblong trench, in which the roses are loosely spread out next to each other, the roots covered with soil. In case of severe frost, cover them, e.g. with fleece.

  • If you plan on planting the roses, put them in a bucket of water for 2 hours before planting.
  • Dig a generous planting hole.
  • The soil around the rose should be well-drained. Permeability can be improved by mixing the excavated soil with dry (perennial) horse manure, cow manure pellets or other potting soil or DCM Vivimus.
  • Treat the bare roots with Symbivit ® if necessary.
  • The bush is usually shortened. If not, prune them back to 10-15 cm from the stem.
  • Cut the roots at about 20 cm.
  • Then plant the rose in the spacious planting hole, deep enough that the grafting point is about 5 cm below ground level. Make sure the roots are spread out in the planting hole. The roots should never protrude above the ground. Add the well-mixed soil to 2/3 part and irrigate.
  • When the water has been fully absorbed, further fill in the planting hole and firmly press the soil so that the soil fits the plant well and no roots protrude above the ground after planting. Then water the rose again.
  • When planting in the autumn, it is wise to earth up the rose with ± 15 cm soil before winter. The plant that has not grounded yet, is thus better protected against severe frost. In spring remove the soil.