Healthy, productive roses begin with good nutrition, and there is no shortage of options to choose from to feed your roses. Whether you are drawn to organic methods, prefer the convenience of inorganic fertilizers, or enjoy a blend of both, understanding what each product offers will help you make the best choices for your roses and your soil. It is worth taking a moment to consider your own fertilizing philosophy (link to philosophy article) as well as the particular composition of your soil before selecting products. A soil test, while not essential, can be informative - more on that at the end of this article.
Roses benefit from feeding in spring, typically beginning when leaves emerge and buds start to appear. Feeding after each flush of blooms is recommended to encourage continuous flowering through the season. Always follow the recommendations provided on purchased products and take your climate and growing conditions into account. Roses growing in pots or containers, for example, benefit from more frequent feeding as regular watering carries nutrients away more quickly.
Manure - Well-aged manure provides nitrogen, improves soil structure, and enhances water retention. It is important to use only well-aged manure, as fresh manure can burn fine roots. Widely available from garden retailers or sourced directly from a local farm. Best applied in late fall or early spring while roses are still dormant, worked gently into the soil around the base of the plant.
Compost - Naturally supplies nitrogen, phosphorus and potassium along with many valuable vitamins and minerals. This decomposed organic matter improves soil structure, helping to lighten heavy clay soils and build up sandy ones. It also contributes to biodiversity and the long-term health of garden soil. Perfect for mixing into existing soil at planting time and equally beneficial as a regular top dressing throughout the season. Available from many retailers, or you can start your own compost at home. Safe to apply at any point during the growing season.
Fish Emulsion - Contains nitrogen in addition to phosphorus, potassium and other essential nutrients for plant health like calcium and magnesium. Being rich in nitrogen, it is a great support for vigorous foliar growth. It also stimulates microbial activity in the soil as the fungi, bacteria, and earthworms that break it down increase organic matter content, benefit plant health, and help loosen soil structure over time. Available in dry pellet form, known as fish meal, which is worked directly into the soil, or as a liquid concentrate mixed with water for application. Safe to apply regularly throughout the growing season, with a final application 6 to 8 weeks before your first expected frost.
Seaweed or Kelp - This is a powerhouse containing over 60 different minerals and micronutrients that play a crucial role in the plant’s essential chemical reactions. It contains naturally occurring growth hormones spurring on vigorous growth in your rose and its root system and it supports the efficiency of absorption of water and nutrients. Regular use helps correct soil deficiencies, improves the soil's liquid and gas ratio, and supports the microorganisms that contribute to overall plant health. Kelp is also known to trigger immune responses in plants, helping them better resist disease and environmental stressors. Available in powder form to be mixed with water, or in meal form to be worked directly into the soil. Safe to apply regularly throughout the growing season, with a final application 6 to 8 weeks before your first expected frost.
Alfalfa - A member of the legume family which offers the unique attribute of a symbiotic relationship with soil bacteria allowing them to convert atmospheric nitrogen into a form roses can readily absorb. This essentially fertilizes the soil and supports more vigorous growth. In addition it brings calcium, iron, and phosphorus among other vitamins and minerals to the soil.
Available in pellet or meal form. Sprinkle and mix well into the soil to prevent attracting rabbits. Pellets can also be soaked in water creating a nutrient rich tea that can be used to water roses every 4-6 weeks throughout the season with a final application 6-8 weeks before your first expected frost.
Bone Meal - High in phosphorus and calcium, it is beneficial for root health and is an excellent product to add to the soil when planting or transplanting as these nutrients are vital for early root formation and establishment. Bone meal breaks down slowly in the soil providing nutrients over several months. Available in granular or powder form that can be sprinkled and worked into planting holes or topsoil in the spring season or at the time of planting or transplanting. Note that bone meal is best not used at the same time as mycorrhizal fungi, as it can interfere with the fungi's establishment - see the note on mycorrhizal fungi below.
Mycorrhizal Fungi - Mycorrhizal fungi form a beneficial symbiotic relationship with plant roots, by acting as an extension of the root system and significantly increasing the plant's capacity to absorb water and nutrients. In exchange, the plant provides the sugars the fungi need to thrive creating a beautifully balanced partnership. Available in powder or granule form, it is applied directly into the planting hole or sprinkled onto roots at the time of planting. It is advised not to apply bone meal at the same time, as this can hinder the fungi from establishing. For best results, wait 2 to 4 weeks before introducing bone meal to the soil.
Banana Peels - An easy DIY addition to the soil. Banana peels are high in potassium which plays an important role in regulating water and nutrient transfer movement in plant cells, is critical for chemical reactions including photosynthesis and helps strengthen the plant and protect against disease. Also benefits the soil by contributing organic matter. Can be composted, chopped finely and spread around roses, or steeped in water for several days to create a potassium-rich tea that can be applied to roses throughout the growing season. There is no strict limit on application frequency, though as with all inputs, balance is key.
Coffee Grounds - Used coffee grounds contain nitrogen, potassium, and other valuable nutrients, along with antioxidant and antimicrobial properties. They add organic matter to the soil, act as a mild acidifier, and are known to help deter ants, snails, slugs, and some other insects. Allow used grounds to dry completely before applying. Sprinkle 1 to 2 tablespoons (15 to 30mL) around the base of each rose and work lightly into the soil, up to three times per growing season beginning in spring. Coffee grounds can also be added to your home compost and applied as part of composted soil throughout the season. As coffee grounds are acidic, avoid over-application, particularly if your soil is already on the acidic side.
Inorganic Fertilizers - Also known as synthetic, mineral, chemical or human-made, are convenient and easy to use. Most suggest applying once every six weeks which means around two to three times per growing season, with some slow release varieties only needing a single application per season. These products should display a series of three numbers which refer to the content of nitrogen, phosphorus and potassium. Nitrogen supports leaf growth, phosphorus promotes root development and flower production and potassium adds to the overall strength and resilience of the plant and reduces water needs. Look for fertilizers designed with roses in mind, as these will contain a well-balanced blend of nutrients specific to what roses need most. Final application should be made 6 to 8 weeks before your first expected frost to allow any late season growth to harden off before the cold arrives.
A Note on Soil pH and Testing
The availability of nutrients to your roses is highly dependent on soil pH levels, and the only way to truly know your soil's pH or whether it is deficient in a particular mineral or nutrient is to have it tested. Over-application of any nutrient can be as harmful as a deficiency, so understanding your starting point is genuinely valuable. Search in your area for professional agricultural labs or government-affiliated testing services for details on how to submit a sample and associated costs. Being well informed is one of the kindest things you can do for your garden.
Follow this link to help you determine your Rose Garden Fertilizing Philosophy.
