• If you cultivate boxwoods, start getting into the habit of scouting them on a regular basis for signs of Boxwood blight. Look for plants that are thinning out with a large amount of dead leaves at their base, leaves with brown spots, and black lesions on the stems.
• Spray horticultural oil on trees and shrubs that had soft scale last year to kill any over-winter insects.
• Boxwoods can be sprayed with horticultural oil for leaf miners and psyllids. They are tough inspects to control and better results may be obtained using chemical systems.
• Overseed/re-seed/spot-seed your lawn and apply mulching hay or Penn-mulch to aid germination.
• Test the pH in your garden to see if soil pH needs to be altered. Each plant has a different pH preference range. Limestone or garden sulphur may be needed.
• Amend your soil with compost, cow manure, peat moss, sand, vermiculite or perlite based on your garden’s needs.
• Apply a dress coat of bark mulch to existing beds, being careful not to pack it against the trunk and/or branches of shrubs and trees.
• Recycle wood ashes from your fireplace. Scratch a small amount of ashes into the soil around Lilacs, Lavenders, and Peonies, as these plants thrive in sweet alkaline soils.
• Begin fertilizing roses now. Upon leaf-break, you can start your preventive maintenance spraying, especially for disease problems like black spot and powdery mildew.
• Spray hemlocks (saturate both sides of branches) with dormant oil spray to control wooly adelgid and hemlock scale.
• Spray deer-attracting plants with Bobbex, a deer repellent and 100% organic fertilizer. On fast-growing plants, like tulips, remember to spray new growth every seven days.
• Divide fibrous-rooted (i.e. several small roots but no dominant root) perennials if they have fully matured. Phlox, coreopsis, scabiosa and other fibrous-rooted perennials respond best to being divided in April.
• Prune summer-blooming shrubs, removing any dead wood and any branches that are not desirable. Spring blooming shrubs will also respond best to pruning now, but you will be sacrificing some blooms! They can be pruned after they flower, but shrubs do not have as many accumulated reserves as they do right after winter. If rosebushes and perennials were not pruned in the fall, now is the time to prune those as well.
• Transplant shrubs and perennials so the plants have a full season in their new sites before having to endure winter.
• Clean out the dead leaves and branches from your ground cover beds to help prevent disease and insect problems.
A frequently asked question by many gardeners in the early spring is “When are the impatiens coming in?” That’s a good indication of the popularity and importance of this bedding plant. Normally a reliable flowering annual, impatiens (Impatiens walleriana) are at risk of contracting a disease called Impatiens Downy Mildew (Plasmopara obducens).
Impatiens Downy Mildew has shown up in isolated areas through-out the United States and southeast Canada. It is sometimes confused with spider mite damage. Young plants and new growth are most susceptible to this disease. Symptoms begin with leaves that look pale green, yellowish, or speckled. The leaves will exhibit a downward curling along the edges and become distorted. As the disease progresses, a white to light gray growth occurs on the undersides of the leaves. Eventually the leaves and flowers drop off the plant leaving bare stems.
Conditions that favor the development of this disease are: high humidity or leaves that remain moist for long periods, overcrowded plantings, cool temperatures, excessive fertilization, and heavily shaded locations. Since prevention is the best management strategy, the above conditions should be avoided. Do not plant impatiens in an area where disease problems have been experienced before, leave enough space between plantings to allow for proper air flow, never water at night, and use a mild organic fertilizer for feeding. Check plantings on a regular basis for this disease and remove any affected plants immediately, including any fallen leaves and flowers. Spores can remain in the soil for years.
Fungicides do not provide much in the way of a cure, but are more effective when applied preventively. They are best used when conditions favor disease development or when diseased impatiens have been removed and the remaining plants need protection. Rotation among fungicides with different modes of action increases effectiveness. Chemical fungicides that can be used are mancozeb, daconil (Bonide’s Fung-onil), and phosphorous acid (Monterey’s Agri-Fos). Organic options are Actinovate (Streptomyces lydicus) and copper sprays. Spraying fungicides are an important part of a prevention program, especially if planting in an area where there were disease problems in the past.
There is a bit of good news in all of this. New Guinea impatiens (Impatiens hawkerii) have shown a high degree of tolerance to Impatiens Downy Mildew. They can be grown in gardens where the disease was present in the past. If New Guinea impatiens are not desired, there are many shade loving annuals that can be employed.