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Fertilize Acid-Loving Plants Differently Than Other Plants

Acid-loving perennials such as rhododendrons, azaleas, camelias, Pieris, heathers, and blueberries need a different fertilizer than other plants in your garden. Fertilizing is made much easier if you planted them all in the same area so you can maintain that acid soil without competition from basic-loving plants.


Because nutrients are released or held tightly at different rates in an acid soil, fertilizers have been developed specifically for that exchange. Read your labels closely and apply fertilizer according to the directions. More is not better. Too much fertilizer can burn your plants. It is better to divide a year’s worth of fertilizer into 2-3 different applications, allowing the plants to absorb what they need at a slow and steady rate.


Since many of these plants retain leaves year-round, time applications for early spring before new growth and flowers start and fall to support the plant through the winter. If you see nutrient deficiency signs such as light green leaves (chlorosis) or veining (darker veins on leaves), an additional application can be used to correct the symptoms. Plants need sufficient water to transport the fertilizer; if rain isn’t providing 1” per week, you need to irrigate. Nitrogen, a major nutrient, is water soluble, so don’t overwater either, e.g., you want water absorbed, not running off.

Conserve Water

Here in the Pacific NW, most of our summertime water comes from snow melt or aquifers, both of which are precious resources and should not be squandered. Plan now for those months where we don’t have 1” of rainfall per week. Sprinkling or impact-style rotating sprinklers are one of the most inefficient and wasteful ways of watering. Splashing transfers organisms from the soil to the foliage. Foliage is drenched, providing ready transport for micro-organisms. Weather is usually cool in May, making for perfect growing conditions for powdery mildew and other fungal diseases as a result of that drenching.


Drip irrigation systems or soaker hoses, combined with 2-4" of mulch, provide an ideal combination of water distribution and conservation. There are a variety of emitters, and you should choose those that best fit your needs. For instance, in the vegetable garden, soaker hoses that provide water directly to the roots of row plantings can be laid on the surface of the row. For tree fruits, feeder roots can be found at the drip line and several feet beyond. Place emitters every 2 feet around the circumference of the tree at the drip line and cover with mulch to prevent as much evaporation as possible.

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Photo used with permission

Drip irrigation on rhododendrons provides water exactly where each plant needs it. Irrigation lines can be covered in mulch if preferred.

For landscape plants getting established, set emitters at the drip line every 2 feet. Crop plants and tree/bush fruits need a consistent amount of water to produce a crop. Newly established shrubs and trees need extra water until the second or third year and in drought periods. Well-established woody plants can usually survive with a moderate amount of deep watering. Herbaceous plants such as perennials and annuals need consistent water to keep blooming.


Grass should be allowed to go dormant during warmer months to preserve water resources.

Seed and Plant Annuals and Perennials

This month is that first “big push” of planting to take advantage of the growing season. After Mother’s Day, it’s generally safe to plant bedding plants and your vegetable garden, whether from seeds or transplants. Buying or growing plants for transplant means you’ll get flowers and produce much earlier in the season than direct sowing seed.


The choice to seed or use transplants depends on the plant. Some plants such as cucurbits (melons, pumpkins, squash, and cucumber) don’t like to be transplanted so it’s better to direct seed. Some plants grow quickly enough that you can get a crop or flowers from seed and have successive plantings.


Transplants should be placed at the same soil level as they were potted in. Seeds are sown according to the size of the seed. Read the seed packet for specific depths and soil temperatures.

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Photo used with permission

Sunflowers grow easily from seed and provide cheer for you and your bird visitors.

Plant Balled and Burlapped Trees and Shrubs

Some woody plants don’t transplant well when their roots are disturbed. The balled and burlapped method assists that process. When the plants are dug up, a root ball containing the soil is left undisturbed. Burlap is wrapped around the root ball to keep it intact.


When planting balled and burlapped trees and shrubs, dig the hole deep enough so that the same soil level is maintained. Loosen the soil around the hole so roots can penetrate easily. Addition of organic matter is no longer recommended, but the soil in the root ball is probably different than your own soil. You can open the ball, gently remove excess soil (use the hose to gently wash away excess dirt) and prune out any damaged roots. Remove the burlap wrapping, since it acts like a wick and draws moisture away from the root ball, preventing new roots from moving into the surrounding soil.


Set the ball in the hole, adjusting to ensure the crown (where trunk meets soil) remains the same as it grew in the field. Look for dirt stains on the trunk to identify the crown. Sometimes dirt is added when balled up, but you want to set it at its original depth.


Water in well to facilitate good contact with the root ball and surrounding soil. Stake if necessary and cover with 2-4" of mulch. Keep mulch 2-4" away from the trunk to avoid rodents using the mulch to hide in while chewing on the bark.

Deadhead Flowering Shrubs and Annuals

Some spring-flowering shrubs, like rhododendrons and lilacs, will try to set seed. This will reduce next year’s flower set. Deadhead (remove the spent flower cluster) to prevent seed formation. Be careful to not damage adjacent leaf buds. Lilacs set their flower buds for next year shortly after flowering, so when you prune out the spent flower cluster, don’t cut into the green growth.


Annuals will bloom until the end of the growing season if you keep spent flowers picked off. This prevents the formation of seed which would tell the plant it has done its job and it is time to stop flowering.

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Photo used with permission

Deadheading the spent flower clusters on rhododendrons increases the plant's energy for more flower production the following year.

Authored by Scott Hagues, Island County Master Gardener
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