This Month in Your Garden: Fertilizing and Weed Control

Reader Contribution by Raintree Nursery

This Raintree Nursery post is by horticulturist and plant propagator Theresa Knutsen


Apply a half-strength dose of fertilizer to acid loving plants — such as blueberries, lingonberries and cranberries— as buds start to swell on the plants. Use a fertilizer that is specifically for blueberry or rhododendron. Raintree Nursery offers a great balanced organic blueberry fertilizer. Follow with a light mulch of wood chips or pine needles under the blueberries. Apply a second half dose of fertilizer when the flowers fall.

Raspberries and rhubarb appreciate a mulch of cow or steer manure applied before new growth emerges in the spring.

A one-inch layer of compost spread under the edge of the leaf canopy of most fruiting plants will help maintain fertility. If your plants seem less vigorous than they should be, a little fish fertilizer with kelp (seaweed) may be helpful.

Controlling Weeds

Keep weeds controlled around trees and shrubs, especially those that were planted within the last few years.

Be careful when working around blueberries. Their shallow roots are easily damaged by vigorous digging and weed removal. If your blueberries have a lot of weeds under them, you might try cutting the weeds to the ground, putting down a 1/2 -1″ layer of peat moss, several layers of newspaper or a layer of cardboard, and then wood chips on top. Most weeds will be smothered. More persistent perennials that eventually come back through the mulch, can be repeatedly cut off (every 10-14 days) until their roots starve out.

New plantings of ground covers — such as cranberry, lingonberry, or wintergreen — need regular weeding. Even after they have filled the space, some weeds may still come through.

Installing biodegradable mulch at the time of planting will help control weeds until your groundcovers are established.

This mulch is not porous, so make sure you provide water where the plants are until the mulch biodegrades, about 1-2 years depending on product and conditions. A layer of wood chips or pine needles will hide the black color. You could also put down cardboard or layers of newspaper covered with mulch between the new plants to help reduce weeds and contribute to building the soil organic matter.

Permanent weed barrier fabrics may seem to be a good solution for controlling weeds, but only if used for just a year or two, or only just near the trunk of the tree. Longer use in the active root zone area of the plant interferes with organic matter rebuilding in the soil, which can have a negative impact on the general health of your trees. Instead try biodegradable mulch squares under your newly planted trees to keep grass and weeds from competing until those new trees are established (2-3 years). Top with bark mulch to keep it looking nice as well.


If you have had problems with adequate pollination or fruit set in the past, the following are some factors to consider:

  • Look at your fruiting plants as they come into bloom, especially those that did not set fruit well last year. Are you seeing a lot, or just a few flowers. If there are only a few, did the tree produce a lot of fruit the previous year? Or do the trees receive enough shade in July or August to reduce their time in direct sun to less than 8 hours?

  • Notice if there are plenty of bees in the flowers. If you have bees and flowers, are the varieties that should be providing pollen for each other blooming at the same time?

  • What is the weather doing? Is there a lot of cool wet weather that will support brown rot disease in the blossoms, effectively interfering with pollination? Frost can cause physical damage that interferes with pollination, or provide a site for a secondary infection that damages the flower. Sometimes misting overnight or smudge pots are used to protect blossoms from frost damage. Another possible technique is to run a string of outdoor Christmas lights in the tree, and turn them on when hard frost threatens.

  • Do you see ants or earwigs in the flowers? Both insects can cause significant damage and interfere with fruit set. If you are growing kiwi, look at the blossoms and compare them to the pictures in our catalog. Make sure you have both male and female flowers.