Yarrow is a great perennial to grow in containers on a sunny deck or patio. They can effectively be used as a filler element in a mixed seasonal planting or used singly as part of a container garden grouping. Perennials in pots will grow quite happily with just a little more attention than they need when planted in the garden. Plants in pots are not able to spread their roots in search of food or water and survive on what is provided by the gardener.
Planting Yarrow in Pots
Planting in containers is best done as early in the spring as possible. This gives the Yarrow time to establish fairly well before the heat of the summer comes on. The container needs to be in a full sun spot or somewhere that receives full sun for 6 or more hours during the day. Yarrow will survive in part shade conditions, but tends to have very tall and leggy growth and much less blooming. Pests and diseases are also more likely to attack this spindly growth. Full sun will keep all varieties of Yarrow sturdy and compact.
The container that is used needs to have excellent drainage and be at least 12 inches in diameter, depending on how many other plants are included. Yarrow needs sharply drained soil and will not tolerate any standing water. The potting soil mix can be an all-purpose, peat-free mix that has vermiculite or perlite added to keep the soil light, loose and well drained.
Best Soil for Yarrow in Pots
The best and easiest soil to use for potting up perennials is a pre-mixed, all-purpose potting soil that does not have fertilizer added. Yarrow really thrives in lean, loose soil. Potting soils with added fertilizer are generally too rich for a native plant like Yarrow. Adding a slow-release, granular fertilizer for acid-loving plants is a better idea. Following the manufacturer's directions, add the fertilizer to the soil and mix well before filling the container.
Using soil out of the garden is not recommended for container-grown perennials. The soil will be much too heavy and prone to compacting in the pot. Potting soil is formulated to be light and free draining while also retaining moisture. Peat-free potting soil is the best choice for plants and the environment. Using a layer of rocks or pebbles at the bottom of a container does not increase the drainage ability.
As long as there are plenty of drainage holes in the pot, water will drain through soil much better than rocks. Too thick of a bottom layer of rocks will also encourage shallower root growth that is likely to dry out even though there may be a layer of water trapped under the rock layer.
Caring for Yarrow in Pots
Growing Yarrow in containers is a very effective way to grow this perennial in the smaller garden or as part of a container garden. The most important tasks for pot grown perennials are proper watering, fertilizing and over-wintering.
Watering Yarrow in Pots
Watering is one of the most important parts to growing perennials in pots. Yarrow likes to be on the drier side, so these plants will tolerate a bit less watering than other potted plants. When mixing Yarrow with other plants to make a mixed container, make sure that all of the plants like the same moisture conditions. Yarrow pairs best with other Mediterranean-type plants such as smaller varieties of Lavender, prostrate Rosemary, or Thyme. Annuals like Moss Rose or Licorice plant and succulents would all make great planting partners. Let the soil dry out a bit between watering.
Water containers when the top 2 inches of soil feel dry to the touch. Depending on the position of the plant and the heat and humidity of the climate, Yarrow may need to be watered several times during the week. During periods of high heat, watering will need to be checked on a daily basis. Water the soil long enough that excess water comes out of the drainage holes and then water a few more seconds longer. This will ensure that the soil is evenly damp all of the way to the bottom and help the roots to reach down into the pot. Also, any dry soil soil in the pot will act like a sponge and take water away from the damper soil resulting in a pot that is drier than you think.
Fertilizing Yarrow in Pots
Plants grown in pots need more attention to fertilizing, as a rule. Fortunately, Yarrow requires little supplemental fertilizer in the garden. The leaner the soil, the better for this native. When grown in a pot, the story is a little different. Every time the pot is watered, nutrients are leached out and the soil can quickly become inert. Using a mulch or top dressing of organic compost or worm castings early in the spring is a great way to incorporate nutrients and beneficial microbes into the soil for the season.
A diluted liquid feed of kelp, seaweed or fish emulsion can be applied once a month from spring to summer, ending in August. Look for a fertilizer that has relatively low NPK content, which is less likely to burn plants. A fertilizer with a higher phosphorous content (middle number) indicates that it is beneficial for heavy blooming or fruiting plants.
Winter Care of Yarrow in Pots
Perennials in pots will survive the winter quite easily. The container needs to be able to withstand freezing and thawing without cracking, flaking or shattering. Plastic and composite materials are much better suited for colder climates and have all of the good looks of glazed pottery. Terra cotta and glazed pots are better suited to the warmest of the hardiness zones, although moving the pots to a frost-free, sheltered location for the winter may be a good solution.
A garage or unheated greenhouse makes a good temporary home. Yarrow are herbaceous perennials that die back all of the way to the ground in the winter, whether planted in the ground or a pot. The root ball is dormant over the winter and requires far less watering than when the plant is actively growing. Too much water in winter will lead to root rot and death.
Make sure that pots left outdoors are draining freely and not holding water in winter. Keeping the container in a spot where it will get watered naturally through the winter is best. If the pot needs to be covered or in a spot without natural rainfall, like under the eaves of a house, check it once a month or so for dryness, and water only if it is not freezing.
Growing Yarrow Indoors
Yarrow is an herbaceous perennial that needs a period of dormancy and some cold to perform its best. Bringing Yarrow indoors during the winter will not prevent it from dying back. The plant may get stressed from too much light, heat, dry air and watering indoors. Yarrow is best left outside to rest for the winter.