* This is PART TWO of a two-part article about “GREENHOUSE GARDENING”. PART ONE can be found here.
# Proper Containers
Most greenhouse gardeners use either clay or plastic containers in the greenhouse. Both are relatively inexpensive and will do the job. They do have some differences, and you should understand how each container works before making your choice.
The followings are some general points to keep in mind:
– Plant containers for the greenhouse need a drainage hole in the bottom of the pot.
– Some plants grow better in one type pot than another — be aware of your plant’s special needs.
– Plant containers will need to be cleaned and sterilized between uses; do this by scrubbing the insides with a maximum of bleach and water, and leave the containers in the sun for several days to kill any fungus spores that may lurk in tiny openings.
Clay pots are porous containers that not only could absorb water but also permit air circulation through the container sides. It’s difficult to overwater plants in clay pots. If plants are over-fertilized, though, excess salts will appear as a white crust on the pot sides. In areas where the water has a heavy salt concentration, the excess salts filter out, also forming a white crust on the container sides. In humid greenhouses, a green moss or mold may also form. These crusts should be scrubbed off to keep the containers porous.
Clay pots may be quite heavy when planted. And several hundred plants in clay pots could be quite a load on your greenhouse bench.
Greenhouse gardeners seem to be using plastic pots more and more. They are easy to clean, lightweight even when watered, and available in a wide range of colors, shapes, and sizes.
Plastic containers are nonporous, a condition that could create a watering problem. The pot can’t absorb any excess moisture or permit air circulation through its sides. But there’s another side of the coin: because watered plants grown in plastic pots remain moist longer than plants in porous pots, they will need watering less frequently; this feature could be a real lifesaver to the busy greenhouse gardener. Some plastic containers have wide slits for drainage holes; for crocking, use a thin layer of stones or pebbles instead of pot shards.
# Importance of Fertilizers
Plants grown in containers will need to be fertilized, since their roots are confined and can’t search out the nutrients they need in the ground. Once the nutrients in the potting mix are used up, your plant is stranded. It’s up to you to replenish these nutrients by applying fertilizer.
Plant fertilizers usually contain 3 main ingredients: nitrogen, phosphorus, and potassium or potash. Some fertilizers also include needed trace elements. The ratio of these 3 ingredients is usually indicated on the label by 3 numbers, e.g. 5-10-5 or 18-20-16. The first number refers to the percentage of nitrogen, which stimulates leaf growth and helps leaves maintain a rich green color. The second number indicates the percentage of phosphorus, which promotes sturdy cell structure and healthy root growth and aids in flower and fruit production. The third number refers to the percentage of potassium, which aids plants in normal plant functions and development. Many fertilizers are formulated for specific types of plants. Read the labels carefully to make sure the fertilizers should be used on the plants you grow in your greenhouse.
In a greenhouse where you are dealing with a large number of plants, it’s a good idea to keep accurate watering and fertilizing records. These records will be invaluable if you must leave your greenhouse in someone else’s care. And you can check to see if your geranium actually does need more fertilizer, or if it has another problem.
If possible, clear out the greenhouse completely and wash it down. Scrub off any moss or mildew that has formed, and clean off the walls and roof, both inside and out, to provide maximum light. If your cleaning time is in the fall, this is also a good time to remove any whitewash that has survived the summer rains. And you can be sure the greenhouse is prepared for winter.
With the greenhouse empty, you can rearrange the plants in a neat. This should also make you aware of any diseased or pest-infested plants. Treat them before you return them to the greenhouse, or if they are too far gone, discard them.
Before the first frost, check for and repair any broken or torn wall coverings. Make sure the doors and vents shut tightly and have a good seal. Replace any caulk or seal that has worn out. And make certain that your various climatic equipment systems are working efficiently.
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