How to Choose a Tree and Shrub Fertilizer

In the forest, soil nutrition comes from decaying organic matter on the ground, but in urban and suburban environments, soil composition and water drainage has been significantly disturbed, and gardens and yards are cleaned of organic debris. This is why tree and shrub owners might consider using fertilizers annually or as needed. Choosing a fertilizer wisely can help you maintain a healthy landscape in a timeframe, budget and method that best suits you.

When shopping for a fertilizer, there are 3 things to decide on:

1. Ratio of N-P-K. Each macronutrient (Nitrogen, Phosphorous and Potassium) promotes different plant reactions, which is the significance of the numbers. Fertilizers with higher rates of Nitrogen encourages abundant new leaf growth, high Phosphorous encourages root growth and Potassium encourages drought tolerance and winter hardiness. For these reasons, Fertilizers that are high in N are applied in the spring and high in K in the Fall.

2. Synthetic/Chemical or Organic. Organic Fertilizers have lower N-P-K amounts than Synthetic ones. Organic fertilizers are made from composted organic materials like fish, blood, manure, etc. and can increase soil activity and structure. Synthetic fertilizers are fast acting and are sometimes blended with pesticides or have other engineered properties such as slow release biodegradable capsules.

3. Granular or Liquid formulas. Granular may be a good choice if you already have a spreader handy, whereas some liquid products are available that you can attach onto your hose end for easy spray application.

*Always follow application rates on products to avoid pollution, plant injury and/or pest problems.

Why Your Shrubs Didn’t Flower

Are you wondering why your shrubs didn’t have many flowers or any at all? Here are a handful of reasons why this can happen and some solutions to consider.

• Flower buds were pruned/sheared off last season. Many shrubs such as Lilac, Rhododendron and Azalea flower on previous season’s wood so if they are pruned in the months after their flower buds have set, there will be no/fewer flowers the following season. Prune immediately after flowers pass.
• Not enough sun. Even plants that survive in the shade may not flower as well as the same plant in a sunny spot. Prune or thin over hanging trees or transplant to a better spot.
• Buds have been frozen by a late freeze. which is often the case with Hydrangea. There are hardier Hydrangea species to choose from and some cultivars will even repeat bloom.
• Not adequate soil nutrition. Fertilize and add compost to improve soil conditions.
• Lack of vigor/energy. Usually this happens in shrubs that are very old and overgrown. A hard rejuvenation prune in spring can stimulate new growth and fresh start. Keep in mind that it most likely won’t flower during the first year of this new growth.
• Species has less showy or noticeable flowers than you would have thought. Remember some trees and shrubs have separate male and female flowers. Look closely.
• Has pests attacking it. Your shrub may be prioritizing its energy reserves to staying alive, thus sacrificing flower development.
• It can depend on the weather. The duration and harshness of each season will yield brighter or duller, numerous or fewer blooms.