Category: The Gardening Guy

What to do about invasives

Since ancient times, explorers have brought back seeds and plants from exotic lands. Some, like the apple, have been a boon to the citizens of their adoptive home. Others, like the notorious Japanese knotweed (a.k.a. “bamboo”), have been more headache than boon.

New England, with its cold climate, is blessed with a natural defense against some invasives: our winters. But many others have settled in and are taking over —‌ or trying to. It is up to us, the gardeners, to be responsible; we need to learn what the problem plants are, and we need to get rid of any we have growing on our property.

Invasive plants are those that reproduce rapidly and take over wild habitats, out-competing the plants that Mother Nature provided, stealing light, water and nutrients from less aggressive plants. By definition, they are alien species, plants that have come here from other countries.

Most invasives produce large numbers of seeds that are distributed by birds, by the wind, or by water. In most cases, invasives are also difficult to remove or eradicate once established and have extensive root systems that preclude simply pulling them up.

Back home, in their country of origin, most invasives have predators —‌ insects or diseases —‌ that keep their numbers in check. They may have come inadvertently or been brought by well-intentioned people who thought they were pretty or had some use for them. Some, like burning bush, barberry and Norway maple, have been introduced and sold because they are essentially indestructible —‌ and pretty.

For starters, you can learn to identify the prohibited species in your state, and eliminate them on your own land. Check with your local University Extension service to obtain a list for your state.

Getting rid of invasives, however, may not be easy for two reasons: you may like the invasive species, and may have planted it before you knew better. Secondly, it may not be easy to eliminate —‌ even with the use of herbicides (which you probably don’t want to use anyhow).

The Norway maple, for example, is a lovely-looking tree that grows fast and survives well even in urban areas. It will grow in sun or partial shade and is not bothered by road salt. If you have one that is shading your house, I can understand why you might be unwilling to cut it down.

If you are a city dweller, you may assume that since there are no forests nearby, it shouldn’t matter if you keep your Norway maple (or other invasive species). But it’s not just wind or birds that distribute seeds. Runoff can carry seeds to an outlet in a natural environment. Seed from your tree can end up in streams, rivers, ponds. Thus even city dwellers can make a difference, helping to control the propagation of this invasive tree by cutting down theirs.

To see if maple trees growing wild near you are Norway maples, do this simple test: Snap off a leaf at its attachment point, and look at the stem. If it oozes a milky sap, it’s a Norway maple. The leaves also tend to be broader and larger than sugar or red maple leaves.

For organic gardeners, getting rid of invasives is not easy. For herbaceous weeds, think lawnmower. Once you have the stalks (and as much of the root mass as possible) removed, plant grass seed. Mow it every week and the roots will not get recharged. Stems will continue to grow for years, but if you mow it, you can win.

Digging the stump of an invasive shrub like barberry, bush honeysuckle or burning bush is a pain in the neck, but you probably can do it. Digging the stump of a large Norway maple is not practical. But there are folks with backhoes and stump grinders, and the expertise to do it.

If your woods are full of small seedlings of invasive trees or shrubs, you may wish to get a tool for pulling saplings called a weed wrench. This tool has a gripping mouth-like part and a long handle to provide the leverage. A weed wrench of the proper size allows a 150-pound office worker to pull out shrubs and small trees that otherwise would not be possible to yank.

Why bother digging out invasives? You may decide to do it for the sake of your grandchildren, or for the environment. Even in states with good laws prohibiting the sale of invasive plants, no one can force you to cut down or pull out your invasive plants. But being a little selfish is OK, too. Think of all the great plants you can buy and plant if you get rid of those invasives. And think how wonderful it would be if wildflowers and native plants started flourishing in your woods.

Featured photo: Purple loosestrife is beautiful, but can take over a wetland, but will also grow in dry places if given a chance. Courtesy photo.

What to use and how to use it

Mulch is commonly used to help suppress weeds and to hold in soil moisture in dry times. There are many different kinds of mulch and it is important to get the right kind, and to apply it properly if you wish to get the benefits of mulch.

The most commonly used type in flower and shrub borders is sold as bark mulch. It is sold in bags, or by the scoop at garden centers to people who have access to pickup trucks. Bulk mulch is less expensive than bagged mulch if you have a truck or can borrow one from your brother-in-law.

I’m an organic gardener, so I avoid the orange and black mulches. Read the bag before you buy any to see what is in it. According to a report from the University of Massachusetts, the dyes themselves are probably not toxic, but the wood is usually recycled wood from pallets, old decks and scrap. Those sources are dry and accept dye more easily than fresh bark or chipped branches. Recycled pressure-treated wood, if older stuff, may contain arsenic; pallets may have been exposed to spilled toxins.

I often see deep layers of mulch to keep weeds down. However, a layer 4 inches deep will also keep a short rain shower from getting to the soil and your plants. I use an inch or two of mulch, maximum. Yes, some aggressive weeds will poke through a thin layer of mulch, so I try to do a good weeding first.

Chopped leaves are wonderful mulch. Last fall we raked up our leaves and stored them outdoors in a pile. This summer we ran that pile through a chipper/shredder and turned it into a fine product we use as mulch. You can also use your mower to chop fall leaves before raking them. I have friends who store the chopped leaves in bags in the barn until needed. Chopped leaves rarely blow away after they have been rained on.

In addition to weed suppression, a layer of mulch keeps soils from drying out quickly in the hot summer sun. Essentially, it shades the soil, keeping it moist and cool. In the spring I do not mulch my vegetable garden until after soil temperatures have reached their summer level — say, 60 degrees or more.

In May, I want the sun to heat up the soil as my plants need warm soil to grow in, and seeds need warm soil to germinate. And yes, that means weed seeds will germinate too. But weeding or hoeing the early weeds is not bad and goes quickly — just be sure to get the weeds before they get too big.

Mulch gets broken down over time by soil microbes. That is a good thing — wood chips or leaves that break down add organic matter to your soil and encourage earthworms to aerate the soil and add their castings to the soil, and they are rich in minerals.

Some gardeners tell me that they worry about soil microbes using up nitrogen in the soil as they break down mulch. A nitrogen-starved plant has yellowish leaves, not dark green leaves. But I doubt that you‘ve seen that occur, even in flower beds with plenty of mulch. If it has been a problem, or you worry it will occur, apply some slow-release organic fertilizer on the soil surface before mulching.

In the vegetable garden I mulch with straw or hay. Straw is sold as seed-free and is often grown and cut before seeds are formed. Nonetheless, straw often does have seeds, much to the dismay of gardeners who have paid a premium price for it. Buy it from a source you trust!

Hay is just grass grown for animal feed that has gotten wet after cutting. Those pampered cows or horses won’t eat it, so it is sold as mulch for a few bucks a bale.

I always lay down two to four layers of newspaper on the ground before applying hay or straw. This accomplishes two things: it keeps light away from any weeds that germinate even with a layer of hay, and it slowly breaks down and adds more organic matter to the soil.

In the old days newspapers used dyes with heavy metals, including lead. But now inks are made with soy products and are said to be non-toxic, or at least free of heavy metals. The newspaper itself is made from cellulose derived from trees, though some chemicals are used in producing the paper.

Black plastic will keep weeds from germinating, but it breaks down and goes into the landfill. It’s also ugly, and I avoid it. There are various “landscape fabrics” to put under mulch that do help, though pernicious weeds can grow through some kinds. The woven kind is more susceptible to that.

What about papers that have been through a shredder? I don’t find them easy to use or aesthetically pleasing. What about coffee grounds? These are quite acidic, and if you collect them at your local coffee shop, use them only for acid-loving plants like blueberries, hollies or azaleas.

I use no mulch in my mature flower beds. By letting perennials mature and spread, they will choke out almost any weeds, except perhaps in early spring. But by now, they shade out all but the most difficult of weeds.

Featured photo: This new bed needs mulch to keep down weeds and hold in moisture. Courtesy photo.

Vines offer special features

The story of Jack, of Bean Stalk fame, appealed to me as a boy, and still does. I love climbing vines and grow many, including those that are perennial or annual flowers, and some vegetables. Vines are a great way to save space and to get blossoms up and visible.

In the vegetable garden I have had great luck growing cucumbers on trellises. I made a simple frame to support my cukes, and you can, too. You can use four 6-foot-long 2-by-2 pieces of lumber for the framework. Attach them in pairs with simple gate hinges from the hardware store. Then space them 5 feet apart with pieces of strapping at the top and bottom, and attach chicken wire for the vines to grab on to.

I used a cordless drill and short sheet rock screws to put it all together. I made it sturdier by cutting short pieces of strapping to go from the front legs to the back legs. To ensure it doesn’t blow over, I drove a hardwood-grade stake into the ground on each end, and screwed it to that strapping. Once the vines are long enough, lift them up onto the chicken wire, and they will quickly attach to it and grow up.

Other vines will grow up on trellises, too, including squashes and gourds of all sorts. For heavier fruits you may want to build your trellis with two-by-fours, and perhaps to use stronger wire mesh or the stuff used to reinforce concrete that comes in 4-foot by 8-foot pieces.

If you have only grown bush beans, you should also try pole beans. As the name implies, these will encircle a pole and grow up 8 feet or more. The great thing about them is that if you keep on picking them, they will produce beans all summer. Bush beans produce just one load of beans over a three-week period, and then they are done.

Beans fix nitrogen, taking it from the air and storing it in usable form in nodes in the roots, but only if the soil has a certain bacteria to work with your beans. You can buy inoculants to make sure your beans do fix nitrogen, and can add some to the soil and water it in, even now.

Climbing hydrangea is a perennial woody vine that looks good all year. It is slow to get started, but once established (after a few years) it grows quickly. It does well on the shady north side of a building, a place often difficult for flowers. It will attach to brick or stone, but needs to be attached to a wood building, either with a trellis or with individual ties. It blooms in June, but the large white panicles look good long after, even into winter.

There are many types of clematis but all have wonderful blossoms, some 6 inches wide or more, others small but profuse. Most will grow 6 to 10 feet tall; some die back to the ground each year while others have woody vines that send out new shoots and flowers each year. The key to success is to give the vines plenty of sunshine, but to protect the roots with shade from other plants to keep them cool. There are spring, summer and fall bloomers. Some are fragrant, others not.

If you have lived in a warmer part of the country you may long for wisteria, a woody vine that blooms profusely with blue or purple flowers, and occasionally in shades of pink and white. Each blossom is actually a cluster of blossoms that hang down like a cluster of grapes. Although most wisteria varieties will survive our winters, most bloom on “old wood” and the flower buds get killed in winter.

I grow two varieties that do bloom in Zone 4 because they bloom on “new wood,” or this year’s growth. One is called Blue Moon, a hybrid developed in Minnesota. The other is Amethyst Falls, a native variety with smaller leaves and blossoms. Both bloom for me in late June or early July, and re-bloom lightly throughout the summer.

Annual vines are vigorous and delightful, too. We generally grow morning glories from seed. These come in many colors: reds, pinks, blue, purple and white. My favorite is called Grampa Ott. It is a deep purple, and can grow up to 15 feet in a season. It was one of two heritage plants that inspired the creation of the Seed Saver organization and seed company. They grow quickly so it’s not too late to plant some by seed.

Two decorative flowering beans that I like are purple hyacinth bean and scarlet runner bean. The purple hyacinth bean is a beautiful plant: The leaves are purple, along with the flowers and seed pods. It is slow to germinate and get up a pole or trellis, so it is best started in pots indoors before it can be planted outdoors. The young beans are edible raw or cooked, but the mature pods have seeds better used as dry beans.

Scarlet runner beans, like the hyacinth bean, can climb up a support and grow 10 feet in a season. They are quicker to grow than hyacinth beans, and I often start them in the soil near my hexagon cedar shade structure where I also grow wisteria. The bean has bright orange flowers and standard bean leaves. Plant four to six seeds around a pole and watch them grow — just like Jack, the bean stalk kid.

Featured photo: This fall-blooming clematis had hundreds of blossoms. Courtesy photo.

It’s a quiet time for flowers

Mid-summer is often a quiet time for flowers; many gardens have fewer dramatic blossoms than in the spring. I have made an effort to have plenty blooming now. It’s true that my Japanese primroses, peonies and Siberian iris have gone by. But I have many others, both old favorites and lesser-known beauties.

Bee balm has started early this year for me. Contrary to what most gardening books say, bee balm does not need full sun. In fact, full sun makes it dry out and go by more quickly. It does well in moist, rich soil but will grow anywhere. This year I planted some wild bee balm, a native prairie plant. Its scientific name is Monarda fistulosa, and some better garden centers are selling it now, even though it is not as flashy as its domesticated cousin. It’s a light lavender in color, and shorter than the standard varieties. It is terrific for butterflies and bees.

Just finishing up for me is one of the bellflowers, clustered bellflower. It stands about 24 inches tall with purplish-blue globes of small blossoms. It is a fast spreader but pulls easily if it gets out of its place. A relative, peach-leaved bellflower, is preferred by some as it is better-behaved. It has flowers growing up its tall stems and comes in blue or white. Both species are good cut flowers.

Feverfew has been used traditionally to cure many things, but I like it as a white cut flower with a yellow center. Each blossom is small — say half an inch — but there can be hundreds on a big plant. It is rambunctious. It sows seeds and shows up around my garden, but it is easily pulled. It keeps well in an arrangement.

Betony is in bloom now, too. It is in the same genus as lamb’s ears but has green, not silvery, leaves and sends up lovely purplish flowers on stiff stalks that look great in a vase. The best variety is one called Hummelo, named after the Dutch hometown of Piet Oudolf, designer of the High Line Gardens in NYC. But Hummel means bumblebee in German, which is appropriate — it attracts bees over its long bloom time. Small flowers appear all along its tall stems.

An uncommon flower in bloom for me now is called false hydrangea because the leaves are similar to those of the PeeGee hydrangea, although the flowers are totally different. This gem grows in full to part shade in moist, rich soil. It has small bluish-lavender cup-shaped flowers.

There is another false hydrangea, Deinanthe bifida, which has white flowers. Both are rated as hardy to Zone 5. I am in Zone 4 and have lost some plants, but others have survived.

A huge, dramatic plant is the giant fleece flower. The blooms are a bit like astilbe flowers on steroids. The hollow stems stand up to 8 feet tall, and flower panicles are sometimes 18 inches from top to bottom. It does not spread by root, but each year the clump gets larger. I just cut back a good portion of mine, as the plant was shading out nearby plants. It would take a pickax and a strong back to dig it up – which I have, on one occasion. It likes moist soil and full sun,

Moist soil is also good for Japanese iris. In fact, it is often grown in shallow water. I have one clump that has just begun blooming, after all the others. Its foliage is similar to Siberian iris, but the “falls” or petals lie back flat, looking up. It does not like the competition of weeds, I have learned, as we weeded it well early on, and it is going to bloom dramatically this year.

Great masterwort has small domed blossoms in white or pinky-purple that look like pins stuck in a small pincushion, surrounded by delicate bracts (petal-like structures). Deer won’t eat it, and it blooms for weeks, preferably in moist, sunny locations. Each year my clumps get bigger and more wonderful.

At the front of a prominent flower bed I have installed lady’s mantle, a tidy plant with lacy clusters of chartreuse flowers, a color that accents others nicely in a vase, or in the garden. It is probably best known for its tidy foliage which traps rain drops or dew and shows them off. It works as a ground cover, spreading a bit each year and providing dense foliage that helps reduce weeds. It will grow in full sun or light shade but does not thrive in hot, dry soil.

In addition to perennials, each year I grow some annuals. Last year we started many dahlia tubers for their big, colorful blossoms, and saved the tubers indoors to reuse this year, and to share with others.

This year we bought some canna lilies for their interesting foliage — one variety has deep purple leaves — and bright orange or yellow flowers. They stand from 2 to 6 feet tall and have been blooming consistently for a month so far.

If your garden is a bit short of flowers just now, try some of those mentioned above. There is always space for a few more.

Featured photo: Betony ‘Hummelo’is a good cut flower. Photo courtesy of Henry Homeyer.

Control the size of trees and shrubs

By now your rhododendrons, lilacs and other spring bloomers have bloomed and are ready to prune. By pruning now, you will not damage buds that will form later this summer and bloom next spring. This is also a good time to prune evergreens like pines and hemlocks if you are trying to control their size.

Let’s start with rhododendrons and azaleas, as many gardeners seem to put off pruning them until they are blocking the view out the windows. If you just want to keep your rhododendrons the same size this year as they were last year, pruning is easy: you just look at the color of the stems, and cut off the new growth, which is bright green. Older growth is tan or brown.

Make your cuts just into the green growth. By doing so you are leaving a growing point for new growth next spring. Most rhododendrons blossom on old wood, which is to say growth that occurred the year before.

But what if you want to seriously reduce the size of your azalea or rhododendron? You can make your cuts farther down the stems. Make cuts just above a fork or place where branches grow in two or more directions. You will be cutting away the growth of two or even three years’ growth. There are dormant buds on those bare stems, and they will start new growth. The farther down the stem you cut, the longer it will take for growth to begin.

Most rhododendrons keep their leaves all year, but many azaleas drop their leaves and grow all new leaves each year. The old leaves of evergreen species will be a darker color than new leaves, making it easy to see new growth. By the time you read this — depending on your climate — some evergreen rhododendrons will have sent out new shoots after the flowers bloomed. In the middle of a cluster of light green leaves you may see a small very pointed bud. That is next year’s flower.

If you want to shape or reduce the size of your shrub and see new leaves and flower buds, you must make a decision: which is more important? Next year’s show of flowers, or getting your shrub under control? I say (as the Red Queen said in Alice in Wonderland), “Off with its head!” Since pruning is so easily put off for another year, just do it now — even if it means sacrificing some blossoms. There should always be more blossom buds that will appear later this summer.

Lilacs should ideally be pruned two to three weeks after blooming but can be done now, too. Buds are developed over the summer at the tips of branches to bloom next spring.

If your lilacs are not blooming as well now as they have in the past, it may be because the soil pH has gotten acidic from acid rain, or from pine needles. You can collect a soil sample and send it off to your state Extension Service for testing, but if you only want to know the pH, you can buy a simple test kit at your local garden center or hardware store.

Lilacs perform best with a soil that is near neutral (pH 7.0), or slightly higher and more alkaline. The soil test or pH kit will tell you how many pounds of lime to add per 100 square feet, but that is difficult to translate into action. So often I just wing it: I add lime around the base of a lilac and out 3 or 4 feet all around. I measure it out in a one-quart yogurt container. One quart for small lilacs, two for big ones. Not precise, but it helps. Do that now — lime takes time to change the pH.

If you have a pine, hemlock or spruce in your yard or up against your house, you would probably prefer it to stay the same size, or at least not to tower over the house. It’s easy to do: You must prune off the new growth every year. Just look at the tips of the branches now. You will see that this year’s growth is a slightly different color than the rest of the branch. Just snip that off. Do it right away — this is the time to do it.

British gardeners — and hence, many American gardeners — love boxwoods. They love hedges and portly round balls. Some even create rabbits and other silly sculptures called topiary. If you have boxwoods, they need a light haircut every year in June or July. Never prune them after August, because pruning stimulates new growth and it will be tender, and turn brown and ugly in winter.

Prune your boxwoods with a good pair of hedge shears. Mine are about 24 inches long, with 9-inch-long blades. Don’t use old rusty ones — buy a good pair such as those made by Fiskars or Barnell. Most Fiskars tools are good quality and sold at a reasonable price. I don’t recommend electric hedge shears because they can ruin a shrub in the time it takes you to sneeze. I like lightweight shears for big jobs.

When pruning boxwoods, just take a little off with each snip. You can work quickly, but just take a little at a time so you can get the exact shape you want and don’t create holes with a big cut.

Pruning can be fun. You can create a lovely piece of art if you take your time and step back to look at it as you go along. And if you goof and create an “oops,” well, it will all grow back. So go for it!

Featured photo: This young boxwood needs a light haircut. Courtesy photo.

It happens to even the best gardeners

If you are a regular reader of this column, you know that I kill plants (just like you probably do). Houseplants. Annuals. Flowers in the ground. And yes, even trees. Although some oaks live 400 years, most plants naturally have a much shorter life span. And although some die due to my negligence, most do not. But I do push the limits of zone hardiness, trying plants that rather would winter in Pennsylvania — and occasionally killing them.

I have a native dogwood tree that shows up all over my property. It is called the pagoda dogwood and is one of my favorites. This small tree never gets much taller than 10 feet, has just finished blooming with understated white blossoms and has blue berries loved by birds in July or August.

But it has a short lifespan for a tree; 25 years is a good run for this one, even in the wilds. Fortunately it seeds in, so I always have plenty. When one dies, I can cut it down, thank it, and get rid of it. No mourning.

For the last 20 years or more, I have had a hazelnut tree called Harry Lauder’s walking flower stick (“Purple Majesty”) in one of my flower beds. This tree is a naturally occurring freak: Its stems twist and turn in unusual ways. Great in winter for its silhouette, mine also had purple leaves and was a great tree. I pruned it to keep it just 6 feet tall. But last summer it showed signs of distress, and this spring it did not leaf out. It is dead.

But because it is striking in profile, I decided not to cut it down. Not yet, anyway. I planted annual vines around its base and I am training them to climb up into the tree. If all goes as planned, in a month or so I will have purple hyacinth beans blooming in the tree.

In the meantime my wife Cindy and I decorated it with colorful strips of cloth. Each is just a couple of inches wide and perhaps a foot long. She attached threads to the top of each so we could tie them on like Christmas ornaments. Even the slightest breeze has them fluttering and twisting. It’s lovely.

Although nowadays I buy almost exclusively native plants, last summer I was tempted by a lovely Japanese clethra and brought her home. This spring it did not leaf out, a major disappointment. My test for a dead branch is to rub my fingernail on the bark, scraping off the outer layer. If it is alive, it will show some green. But this clethra showed brown everywhere, and I decided it was dead.

As I was lopping off the branches prior to digging it out, I noticed a few leaves growing at the very base of the tree. Life! So I am letting it stay. Unfortunately, I do not know if the tree was grafted onto a different rootstock, which is common in the landscape trade.

So, for example, a branch or branches of a Japanese clethra might have been grafted to a summersweet clethra. This avoids having to start a new plant from seed and ensures that the new plant has the desirable characteristics of the plant grafted to rootstock. If the rootstock grows, one gets a plant different from the purchased plant.

All apples are grafted onto rootstock because the seeds are hybrids and will not breed true. The rootstock used for apples determines the size of the tree. Some will produce miniatures, others full-sized trees. So if your apple was killed by rodents last winter and the roots sent up new shoots, what you get will probably not be interesting to eat. Yes, Johnny Appleseed traveled around America with a sack of apple seeds, but those apples were for making hard cider, America’s beverage of choice, not for eating apples.

If your rose died last winter, you might be able to bring it back to life. Most roses are sold on roots that are different than the flowering portion. You should be able to see a scar, the graft union, on your rose. If the union was planted below the soil line, the rose may sprout from the fancy rose you bought, not the rootstock. So wait and see what happens. By now, this late in the season, a “dead” rose should have sent up shoots if it is going to.

Most plants we grow are vigorous and seem to have an innate “desire” to keep their genetic lines viable. That is why they produce seeds, and many (especially weeds) send out roots that can send up new plants. So if a perennial plant dies, you may be in luck. A baby plant may replace the mother plant. It’s what they do.

A few words of warning, however. Any plant that starts from seeds dropped by a hybrid plant will probably not breed true, although it can. A hybrid is a cross between two genetic lines, and seed producers develop them in carefully isolated circumstances to protect their lineage.

I like to think that if I never kill any plants, I am not trying hard enough. I try to grow new and different plants, often things that would rather grow a few hundred miles south. When those rare (for here) plants do survive and bloom, I feel like a million bucks. Hopefully they did not cost that much, as I will probably lose them at some point.

Featured photo: Pagoda Dogwood berries are loved by birds. Courtesy photo.