April is the ideal time to get on top of your tree care. After the long hard winter, your trees likely have been neglected and it is time to pay them more attention to gear up for the summer months ahead.
Tip 1. Planting and Moving
• In colder regions of the US, you can also still plant container-grown deciduous hedging plants, shrubs, trees and climbers. We recommend the use of stakes and rabbit guards. Use these at the time of planting to prevent damage to the rootball and bark. As the weather becomes warmer and often times dryer too, watering and establishment could become problematic. If you can, we suggest waiting until the fall to plant. October is a great month for those in the colder regions to plant.
Tip #2 - Mulch and Fertilizer
• Now is a great time to mulch rose and shrub beds with 2-3 inches of organic matter. This will help retain moisture during dry spells, reduce weed build-up and over time improve soil structure. Pay particular attention to your rhododendrons, azaleas and camellias, Be meticulous with your mulch around these plants as flowering is impaired if they are allowed to dry out during late summer.
• Don't forget to fertilize as well. Feed trees, shrubs and hedges with a balanced fertilizer, sprinkling it over the root area before hoeing into the soil surface. This will particularly benefit young, weak, damaged or heavily pruned plants.
Tip #3 - Pruning and Training
• If not completed last month or before, winter-stemmed shrubs such as Salix and Cornus can still be cut back at the beginning of the month. Prune back hard all the previous year's growth to within 1/2 to 3/4 inch of the framework.
• Other shrubs that are routinely cut back hard in spring, to keep their larger or more brightly colored juvenile foliage – such as smokebushes (Cotinus) and elders (Sambucus), can be cut back this month. You can leave a couple of branches un-pruned if you are reluctant to lose all the height gained last year.
• Remove any frost damaged shoots from evergreens damaged by earlier cold weather.
• Remove any reverted green shoots on hardy variegated evergreens, to prevent reversion taking over.
• Lightly cut back lavenders to prevent them getting too leggy and woody. Treat Helichrysum (curry plant) and Santolina (cotton lavender) similarly.
• Loosen any tree ties that are digging into the bark, or could do so soon as the trunk girth expands.
• Twining climbers (such as honeysuckle and clematis) need regular tying in and twining around their supports.
• Tie in climbing and rambling roses as near to horizontal as possible. This will restrict sap flow, causing more sideshoots to grow along the length of stem, and so producing more flowers.
Tip #4 - Propagation
• Check hardwood cuttings taken last year. They may need planting out or potting on.
• Take cuttings of your favourite conifers.
• Layering is a good way to propagate climbers and lax-stemmed shrubs. Layers should root by next spring, especially if attention to watering is given during dry weather. Examples to try include Philadelphus, Forsythia, Hydrangea and Lonicera.
Tip #5 - Watch for Pests and Diseases
• Phytophthora root rots can cause die back on mature trees and shrubs. Wet winter weather and poorly drained soils are likely to encourage this problem on susceptible woody plants.
• Check for damage or cankers on deciduous trees.
• Be aware that insects emerge as temperatures rise. Caterpillars, aphids, and other fly pests may all become problematic during mild spells. Early infestations can often be managed by hand removal, making insecticides unnecessary.
• Put rabbit guards around newly planted trees and shrubs to protect the bark.
• Avoid planting new roses in areas where roses were previously growing otherwise the new plants may suffer from replant disease.
• Inspect sick-looking box and holly trees for signs of blight.