Ten (or more) Most Frequently Asked Questions at McLennan Gardens

Plant types

What is the difference between an annual and a perennial?

An annual expends its entire life cycle in one year: from seed to flowering to development of seed heads. Most annuals produce flowers and need to be dead-headed to continue flowering. If annuals appear to return the next year, it is probably because they have self-seeded. A perennial (a category that includes perennial grasses) returns every year; however, in order to thrive, it will need to be divided in the spring or fall every three to five years. Most perennials develop as clumps that double in size each year; you know they need to be divided when flower (or in grasses, seed head) production declines.

What is the difference between a deciduous tree or shrub and an evergreen?

A deciduous tree or shrub loses its leaves in winter. An evergreen is a woody plant (shrub) or tree that generally retains its leaves or needles during the winter. Not all evergreens have needles like spruce and pine; some are broadleaf evergreens, like hollies, boxwood, and rhododendrons.

What is a semi-shrub?

A woody plant that often looks like a perennial but cannot be propagated by division (e.g., lavender and caryopteris).

Planting

Where should I plant?

Correct placement of plants is essential; it depends on sunlight, exposure to the wind, and soil type.

Sun and shade: Almost all plants need a specified number of hours of sunlight a day. Full sun means at least 6 hours of sunlight (this can be a combination of different times of day, e.g., early morning and late afternoon). Most plants prefer full sun or partial shade. Typically, the south and west sides of the house are the sunniest exposures.

Wind: Many trees and shrubs are vulnerable to high winds, which dry them out; since our winter winds tend to come from the west, these plants survive best on the east side of the house.

Soil: Most plants prefer well draining, fertile soil (although there are some that thrive in dry and/or infertile soil). Michigan soil tends to be a mixture of clay and sand, with a neutral or alkaline pH. The pH of the soil is the relative measure of alkalinity or acidity. Clay soil retains moisture, compacts, and makes it difficult for plants to breathe: it should be broken up and amended with compost, Canadian spagnum peat moss, and or gypsum (which we sell). Sandy soil is well draining, which most plants prefer, but tends to be less fertile; it should be amended with compost, topsoil, and/or Canadian spagnum peat moss. Spagnum peat moss adds acid to the soil, which is appreciated by all needled evergreens (including spruce, pines, and junipers), and broadleaf evergreens (rhododendrons, hollies, boxwood), as well as azaleas and dogwoods; it can be bought at Kleinschmidts. We have a handout on soil types if you want more information. Also, clients can take soil samples to the Washtenaw County Extension Agency on Jackson Roadin Ann Arbor (734-971-1129) for chemical analysis.

What is the difference between potting soil, topsoil, and compost?

Potting soil does not contain soil; it is composed of light-weight vermiculite, pine bark, and peat moss. It should be used only in pots, where its light weight is appreciated and it helps plants to get the air they need. Compost is 100 percent organic matter and has a higher nutrient content than topsoil. Topsoil is a combination of soil and organic matter. We sell topsoil, compost, and potting soil.

How should I plant?

Dig the hole as deep as the pot and twice as wide. Remove stones larger than 2-3”. Depending on soil type, amend with top soil, compost, and/or Canadian spagnum peat moss. Your backfill soil should be 50% native soil (in other words, the soil you just dug out) and 50% amendments. In most situations, when placing the plant in its hole, maintain the soil level of pot. In clay soils, place plants on a slight rise above the soil line to provide better drainage. Never allow the plant to sink deeper into the ground than the surrounding soil level as this will lead to rot. For balled and burlapped trees and shrubs, you don’t need to remove the burlap or wire, but you do need to remove all of the twine that is wrapped around the trunk. Remove air pockets in the soil by tamping the soil down by walking around the plant before watering. The first watering of a plant is extremely important as it helps to settle the soil, remove air pockets, and provide crucial moisture to the plant. Water deeply by turning the hose on to a steady flow between a trickle and a stream. Do not mist the plant using the nozzle, and do not turn the hose on so much that the soil or mulch is disturbed. We provide a planting sheet for trees and shrubs.

When should I plant?

You can plant whenever the soil isn’t frozen; however, most plants will do best if planted in cool (50-60 degree) and moist weather, as this reduces transpiration (loss of moisture due to transplant shock). If planting on hot summer days, try to do it early in the morning, and provide some temporary shade protection (a cardboard box lid on stakes can sometimes do the trick with small shrubs and perennials). You can also reduce transpiration by pruning off 3-4 inches from the tops of stems and by immediately feeding with a water soluble fertilizer (Miracle Grow or Mir-Acid; available at most garden supply stores).

Staking

Should I stake new trees?

Research suggests that trees that are not staked tend to develop stronger root systems and thicker trunks more quickly than do staked trees. However, some trees do need staking, particularly if they will be sited in high-wind areas or have small or light root balls compared to the width or height of the trunk and/or canopy. Staking helps to prevent the breakage of roots—indicated by the trunk being loose in the root ball. We sell staking kits.

Watering

How much should I water?

Water immediately after planting. If planting during the summer, you may need to water every other day or so for the first few weeks. Plants need time to extend their roots outward from the pot soil to the garden soil, so it is crucial to check the soil moisture every day until the plant is established (especially in June, July, August). Remember, these plants have been watered two to three times a day at the nursery. Most plants, once established and if planted in good garden soil, need approximately 1” of water a week. Plants in sandy soil may need more water; plants in clay may need less. If you are in doubt about whether a plant needs water, remove some mulch and stick your finger into the soil to a depth of 2”. If it is completely dry, water by turning the hose on to a steady flow between a trickle and a stream for about 10 minutes on each side. Deep watering is better than frequent watering. Plants can die from too much watering: water removes the oxygen from the soil and the plants’ roots suffocate, drown, rot.

Mulch

Why should I mulch?

Mulching conserves moisture, keeps down weeds, and, as it decomposes over time, adds nutrients to the soil. It is the most important proactive step you can take to ensure the health of your plants.

When should I mulch?

Apply mulch after planting, and renew mulch level in the spring and fall. Try to mulch before June 15, when soil moisture starts being depleted by the sun and heat.

How much should I mulch?

We recommend that you mulch 3” deep.

What is the best mulch?

All the mulches we sell are fine. For new installations, we recommend shredded bark or double shredded bark as they have a higher level of microorganisms which help to amend the soil.

What causes the colors in Envirotech mulch?

The dye is made of a hydrolicized iron derivative.

What is the white fuzzy stuff on the mulch?

Part of the natural decomposition process.

Edging

Do I need edging?

Edging provides a practical and aesthetic boundary between lawn and planting beds. Because most lawn grasses have roots of less than 4”, black plastic edging helps to keep their roots out of the foundation or flower bed. An alternative is to cut out an edge with a sharp spade, and to maintain that edge twice a year.

Feeding

Do I need to fertilize my plants?

Almost every plant will appreciate a dose of time-release fertilizer in the spring and late summer or fall. Time-release fertilizers come as pellets or tree-stakes that release their nutrients as they come into contact with water. For a quick pick-me-up, to reduce transplant shock, and to maintain annuals in pots, use Miracle Grow or, for acid loving plants, Mir-Acid. Most potted plants need to be fertilized more heavily than plants growing in the garden.

What is in fertilizer?

Most fertilizers are a combination of nitrogen, phosphorous, and potash. The numbers on the bag refer to the ratio between them, always in the same order. Nitrogen stimulates leafy growth; phosphorus and potash are good for root development and blooms. Trace minerals are also important to different plants, which is partly why there are so many different fertilizers available. We sell Flower Tone for fertilizing of flowering plants; bone meal, which is high in nitrogen and phosphorous; Holly Tone and sulfur for acid loving plants; Ironite for plants that need a shot of iron (chlorosis, signified by yellow leaves, comes from an iron deficiency); and a variety of organic fertilizers made out of seaweed.

When should I fertilize?

You can fertilize as much as three times during the growing season. However, don’t use high nitrogen fertilizer on evergreens or roses after mid-July; you will stimulate new growth that won’t have time to harden off before frost.

Dead-heading Annuals, Perennials, and Roses

Why should I deadhead?

Most flowering plants need to be dead-headed in order to continue blooming; otherwise, they will set seed heads (or rose hips) and think their blooming time (or worse, their reason for living) is over. Remove the dead blossoms by clipping on an angle right above a leaf node. For roses, cut the stem below at least two groups of 5-leaved clusters.

Pruning Shrubs and Trees

Why should I prune?

There are three reasons to prune: to remove dead or diseased limbs; to enhance the shape of your plant; and to stimulate growth. Dead or diseased limbs can be removed any time. Corrective pruning involves removing crossing or rubbing branches by choosing one to keep and removing the other. Rejuvenation pruning can be used on most shrubs or multi-stemmed trees.

How should I prune?

The most important thing is to make a clean cut (see pruning handout) at the appropriate place and to know when to stop. Generally it is safe to remove one third of the plant in a given year. Rejuvenation pruning involves cutting out three-year old canes in order to stimulate new growth. Starting near the bottom of the plant, cut 1/3 of the canes away. On those canes that remain, make some more cuts about 1/3 of the way up; then make a few more cuts near the top third of the plant.

Do I need to shear my boxwoods and yews?

No; for a more natural look, you can do rejuvenation pruning which, over time, will allow the plant to get the sunlight it needs for healthy bottom growth.

When should I prune?

Spring-flowering shrubs bloom on old wood: Prune immediately after blooming (generally May/June) so that you don’t remove the flower buds that will form during the summer to bloom the next spring.

Summer/Fall flowering shrubs bloom on new wood: Prune in early spring.

Broadleaf evergreens: Rhododendrons are pruned by carefully twisting off the flower cluster immediately after bloom.

Needled evergreens: These need little pruning; however, if you want a denser plant, in June snip the candles in half with pruners.

Pruning Grasses

Cut down to 6-8” tall with lawn or hedge trimmers or pruners in late fall or, if you want the panicles for winter interest, in March.

Winter protection

What should I do to protect my plants?

Protect all your plants with a renewal layer of mulch which will help them deal with our freeze-thaw cycles. Some plants, like marginally hardy perennials, roses, and shrubs, need extra mulch to make it through our winters: mound up to 8” after the first hard frost, and slowly remove it in the spring. Protect young trees from deer damage with tree wrap in fall. In late fall but before a hard frost, spray evergreens (both needled and broadleaf) with Wilt Pruf (which we sell) to reduce moisture loss. If you live near a busy road, particularly a high-speed road, put up a burlap screen to protect your evergreens from road salt. And water all of your plants thoroughly in the late fall if we haven’t had a lot of rain; they need to go into the winter freeze with sufficient moisture.

Hydroseed

What is hydroseed?

Hydroseed is a slurry of seed, water, and mulch that is sprayed to create or repair a lawn. After hydroseeding, it is imperative that the homeowner water very frequently for several weeks to keep the moisture content constant.

Plant problems

Most plant problems occur because the plant is under stress. It is important to try to diagnose the problem before attacking with pesticides or fungicides. First check to see if you are over- or under-watering. Is the soil dead-dry or soggy? Drooping or yellow leaves can signify either too much or too little water, or an iron deficiency. Have you seen insects? Check the undersides of the leaves, and check at night as well as during the day. If you are very concerned or confused, bring a sample of your plant for analysis to the Washtenaw County Extension Service on Jackson Roadin Ann Arbor.

Fungus

Powdery Mildew (white fuzzy look on leaves) and black spot (just how it sounds) disfigure the plant by eventually turning the leaves yellow and making them drop off. Treat with copper fungicide.

Common Insects

Slugs and snails: attack hostas, creating holes. Use beer in saucers (they drown), diatomacious earth (ground up sea shells), or the snail bait, Rain Tough Deadline, which we sell.

Saw-fly caterpillar: tiny green worms with big eyes attack pines. Use any insecticide for caterpillars (e.g., Safer Insecticide or NEEM).

Mites: attack spruce. Stick your hand in and shake the plant; if it looks like you’ve put pepper all over your hand, you have mites; use any insecticide (e.g., Safer Insecticide or NEEM).

Aphids: tiny lime-green flying insects: attack roses and spirea. Use any insecticide (e.g., Safer Insecticide or NEEM).

Japanese Beetles: attack roses. Pick off and put into a can of kerosene; or use a pesticide like Sevin.

Critters

Deer: Many plants are delectable to deer, particularly during snowy winters when deer can’t graze. Put soap in nylon bags in susceptible trees, and sprinkle blood meal around your shrubs. Use deer repellent (we sell this). Plant plants that the deer aren’t interested in (foxgloves). Protect the bark of young trees from the rubbing of antlers with tree wrap or flexible, perforated drain tile; wrap from ground level to 3 feet above snow cover and be sure to remove it in early spring.

Rabbits: The deer repellent we sale may be effective in deterring rabbits. Probably the most foolproof method is to put chicken-wire fencing 36” high around the plant (adjust the height to accommodate for snow drifting). Placing a food source in another location may keep rabbits at a distance from your plants. However, even if rabbits gnaw your shrubs during a snowy winter, this may affect certain plants like a heavy pruning, serving to rejuvenated them.

Mice, Moles and Gophers: Unfortunately, the radio-wave vibrators that are placed under the soil or the smoke bombs you put in their holes only send the gophers to another area of the yard. We sell mole and gopher repellent. As a last resort, you can also put poison pellets in their holes.

Black Walnut

Black Walnuts produce a poison, juglone, which is emitted by the roots, nuts, leaves and branches of the tree. Certain plants are resistant to it; we have a detailed information sheet: Black Walnut Survival Guidelines.