As with standard roses, there are many different varieties of miniature roses, varying in flower colour, dispersal, size, shape and texture. Flower colours range from red and pink to orange, yellow, and even green. For the most part, however, care of all varieties is standard.
CONDITIONS PREFERRED:
Miniature roses are actually quite hard to kill. They do well in varying amounts of light. Their primary requirement is constantly moist, but well drained and nutrient rich soil. Miniature roses are becoming more and more commonly seen indoors, unfortunately many people simply keep the plants until they stop blooming, then throw them away. To keep miniature roses potted, repot from the original container. Chose a pot appropriate to the size of the miniature rose you have. Place horticultural charcoal in the bottom of the pot to absorb water and preserve the freshness of the soil. Then fill the pot with soil to within 1/2" of the rim. Dig a hole for the roses. Carefully (remember the thorns!), remove the roses from their original packaging and loosen the rootball, removing as much of the original soil as you can without damaging the roots. Then plant in the new pot, compacting the soil well to keep the plants stable. Water immediately by filling a sink to just above the top of the pot. Let the plants soak until bubbles stop rising from the soil, then drain well. Put them under a fluorescent light (they do fantastically under fluorescents, the closer to the light the better), or near a window. Water the plant regularly, do not let the soil dry out. Be careful when watering not to let water touch the leaves or splash up from the soil. This will help prevent black spot (a common rose malaise).
PROPAGATION:
Miniature roses are becoming quite a popular grocery store item. Propagation can be done using standard rose methods (hardwood cuttings, primarily) but generally isn't worth the bother. There generally isn't enough hardwood on miniature roses to make this a succesful endeavour, and even if you have enough hardwood, it's quicker just to go get some more plants from the store (and guaranteed to work!).
PRUNING AND GENERAL CARE:

Pruning:
Pruning of miniature roses is a matter of removing yellowing leaves and any branches which cross others or which have grown too tall. Many consider even this too much. The miniature rose will generally do very well left on it's own. They tend towards being naturally bushy and leafy, and most varieties sold in grocery stores have been hybridized to have many flowers, ensuring an appearance that most people can enjoy without any extra work.

The only mandatory pruning is deadheading. Deadheading is removing the flowers as soon as they are past their prime. This keeps the flower from wasting nutrient resources to produce a "hip" (the fruit of the rose plant). Once the flower is no longer at it's peak, cut it off where the flower stem meets a 5-leaf cluster.

Some people prefer that their minis have all the same desireable characteristics as it's full sized counterparts. This will require pruning exactly like that of larger bushes, but on a smaller scale. To sum up the pruning needs:
  • Remove any branches which cross over another.
  • Remove any branches which are too spindly and have few branches of their own (the more branching, the more leaves).
  • Remove branches which crowd the center of the plant -- it is desirable to have airflow there (when cutting branches, look for buds, and cut just above them. Ideally, cut above a bud which grows outward from the center of the plant).
  • Remove any "suckers". Suckers are branches which grow directly from the root system instead of the main stem. Also, branches which do not terminate in a flower bud are often considered suckers, and these should be cut too. They are called suckers because they use nutrients without having flowers to make them worth the nutrients they use. If you are not so concerned about flower development, you can leave these suckers if they add to the bushiness of the plant.
  • Plants which are always kept indoors can be pruned as needed.
  • Plants which are kept outdoors during the warm months and indoors during winter should be pruned just after being replanted outside in the springtime.
  • Hard pruning, a process which involves cutting all the branches back by 1/2 to 1/3, can be done periodically. While this does improve the branching and bushiness of the plant, it will reduce the number of flowers (but the flowers will be of higher quality). To do a hard prune, defoliate the plant. A few days later, examine the branches and cut them just above newly formed buds which face outward from the center of the plant.
Tips:
  • Water every day, but just enough to keep the soil moist.
  • Water with a watering can that has a narrow spout. This will help keep water off the leaves, reducing the risk of fungus.
  • Fertilize with a specific rose fertilizer or other houseplant fertilizer every two weeks. Use at 1/2 the recommended strength.
Problems:
As an indoor plant, your miniature roses are not likely to suffer too much from plant pests. More common, however, is fungi. These are often not the owners fault, rather the mass production of miniature roses involves conditions which can encourage fungus. Rose fungi are often visible as black spots or black smokey fuzz on leaves which have yellowed. The best way to handle this is to remove all affected leaves and buy a gentle commercial fungicide.

Evidence of under-watering should be visible immediately, leaves will dry, turn yellow, and fall off. Over-watering is difficult -- so long as you don't turn the soil into mud daily, you should be fine. Water enough to keep the soil moist, not wet.
CARE FOR OUTDOOR PLANTS:
Roses will do well outdoors so long as they have soil which retains enough water to stay constantly moist. Do not plant in sandy soil, and be wary of placement of roses on hillsides, as the water may just move down the hill rather than staying near your plant. If you plant on a hill, build a water retaining wall of soil on the downhill side of the rose bush.

Such small rose plants generally can not overwinter the same way larger roses can. This is primarily because there isn't enough hardwood (bark covered branches versus green branches) to ensure survival. It is best to bring outdoor miniature roses indoors out of inclemental weather.

For roses kept outdoors, the winter time can be used as a dormant period, so you can keep the roses in a cool garage with some mulch at the base of the main stem. Plants can be brought into a the household, but there may be some initial shock at the change of environment. Make sure to provide adequate light. As well, outdoor plants will probably be used to more humidity than you will have inside your home. To provide humidity, place the pot of roses on a tray of gravel to which water has been added.

Once there is no danger of hard frosts, the plants can be moved back outside. This is the perfect time to do a hard prune if you wish. You can cut back all branches by 1/2 to 1/3 if you wish to encourage more branching growth during it's active spring growing period.

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