Pollination
The approach to rose plant breeding at Northern Hybrid Roses is quite simple. We choose a hardy female with good flower form and disease resistance and cross it with a male of similar qualities. Using the old time-tested technique, we remove the stamens from the female or seed parent with tweezers. Stamens are also gathered from a desired male, placed in a petri dish or baby food jar, and allowed to dry for 24 hours. The pollen is then used immediately or stored in a freezer. Once stamens have been removed from the seed parent, we cover the hip with a circular swath of voile secured with a twist tie, and identified with a colored dot as a next day pollination. After 24 hours, the swath is removed and fresh or stored pollen applied with a small water color brush. The cross is tagged for parental identification and the swath replaced over the hip.
Seed stratification
Pollination begins with the first flowering (beginning to mid-June) and continues until the end of July. In mid-October, the mature orange or red-colored hips are collected, seeds removed and washed under cold running water. The seeds are subsequently placed in coarse sand moistened with sterilized water and stored in Ziploc quart (945 ml) freezer bags. The seeds/sand combination is kept at room temperature (68oF or 20o C) for 60 days. The seeds are then washed and strained, introduced into a fresh combination of moistened sand in Ziploc freezer bags and stored in a refrigerator used exclusively for seed cold treatment for about two to three months.
Seedlings
After cold treatment, the seeds are planted in a sterile moistened substrate in plastic trays and covered with a small amount of vermiculite which is moistened daily. Germination begins within one-to-three weeks, at which time the seedlings are placed 3 to 5 inches (8 to 13 centimeters) under cool white fluorescent lighting for 16 hours a day. The seedling to light distance should be maintained as the plant(s) grow. GroLux or other comparable lighting can also be used. A timer is used to switch the lights on and off.
Damping-off is controlled with daily sprays of hydrogen peroxide (3%)/water (50 ml/950ml) solution* and a fan which operates 24 hours a day until the second or third true leaves develop. The frequency of watering is also reduced. Rootshield, a biological product, mixed with the substrate is reported to give good control of this soil-born disease.
Water and feeding
Watering is quite important from seed germination to outdoor transplant. The substrate is moistened several times a day. When the first true leaves appear very light feedings with soluble fertilizer is given once a week and then followed with feedings on even days. The substrate is leached with water only on odd days to avoid salt buildup. Seedling transplant to multipot trays (45 seedlings per tray) occurs after the second or third true leaves appear.
Hardening off
To harden off the seedlings for the outdoors, we withdraw water and gradually decrease the ambient temperature. Once outdoors, the seedlings in the multipots are placed in a nursery and covered with netting to reduce sunlight by about 40 to 50 percent. The netting is slowly drawn back two to three weeks later and the seedlings well watered throughout each day. Initially, small amounts of rose fertilizer are given every other day and the concentration slowly increased to the recommended level(s) for roses. Magnesium sulphate (Epsom Salts) and chelated iron are also included with the feedings. We do not exceed the amount of iron recommended on the package as this may cause iron toxicity in the seedlings. The first symptom of iron toxicity is necrotic spots on the leaves.
Protection
Although the young rose plants are generally derived from the crossing of two hardy roses, they require winter protection during the first year. To accomplish this, the plants are covered with about 8 to 12 inches of soil and 12 inches of leaves. Leaves and soil are removed by hand as soon as thawing begins in the spring (about the first week of April). A Shop-vac is used to remove the fallen leaves between the closely spaced seedlings in the multipots. No further winter protection is required.
The seedlings generally flower during their first summer outdoors and selection can begin. However, some plants only bloom the second or third summer so we wait three to six years before discarding unwanted plants.
* Kuska, Henry. Consult Internet for more information