Weeding
The more frequent the weeding is the better. Weeds grow fast and take place of wanted plants in matter of time. Weeds not only absorb most of the nutrient of soil but can cover useful plants from receiving sunlight, air, heat etc. Keep regular search for weeds and if detected remove on the spot as otherwise there will be bunch of those in few days.
Plants
Different plants absorb different nutrients from soil. So, specially for smaller window boxes it is better not to have plants of same kind. Because the particular nutrients that the plants need may run out quickly from soil, and you may soon find unhealthy plants in window boxes. Try to have variety of window box plants. Taller plants on the back, mid height ones on middle and shorter plants on front. As long as size of the container allows and well maintenance is there, many plants can grow in window boxes.
Pruning
Pruning is not a task that helps same as for trees planted in gardens or roof terraces but still is very helpful for window box plants to be healthy. Wait till plants to blossom or till you harvest the vegetables to prune. When pruning clean cuts are essential as to help plant to grow again quickly.
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