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Archive for the ‘Pest Control’ Category

Common dodder covers some host plants

On a walk in the Smoky Mountains last summer, we came across a patch of plants that were covered with what looked like yellow Silly String. It was crazy looking! Strands and strands of fine golden strings were draped over and twining around these poor plants.

Common dodder (Cuscuta gronovii) covers some host plants

Common dodder (Cuscuta gronovii)
covers some host plants

Eric knew what it was right away – dodder; a parasitic vining plant also known as scaldweed, strangleweed, devil’s hair, devil’s guts, love vine, and many other equally descriptive common names.

Dodder (Cuscuta spp.) is an annual plant that is effectively leafless and has contact with the soil only as a young seedling. These plants do not manufacture chlorophyll so they are unable to produce their own food through photosynthesis like green plants can. With the exception of the first few days after germination, dodder is entirely dependent on a host plant for the water and nutrients needed to complete its life cycle – an obligate parasite!

Flowers of common dodder

Flower clusters of common dodder

Despite its lack of chlorophyll, dodder IS a flowering plant and produces many clusters of tiny flowers from June through the fall. If pollinated, the flowers will form seeds just like other like flowering plants. In fact over the course of a season, a single dodder plant is capable of producing thousands of seeds!

Dodder seeds typically germinate in the spring and the seedlings, which have thin, vine-like stems, grow upwards and twine around the first solid object they encounter. Since the dodder seeds generally drop to the ground under the mother plant, the seedlings normally germinate among suitable host plants. For the first few days of growth, the dodder seedlings survive on nutrients stored in the seed. If they do not contact a host plant within 5-10 days, they will run out of food and die.

Dodder stem produces haustoria which penetrate the host stem

Dodder stems produce haustoria
which penetrate the host stem

Once dodder contacts a host plant, it quickly twines around the stem of the plant and small structures called haustoria are produced along the dodder stem. The haustoria penetrate the vascular system of the host and begin to extract carbohydrates and water from its stem. At this point, the dodder plant is completely supported nutritionally by the host. The original (seedling) stem of the dodder eventually withers and this parasitic plant loses contact with the soil.

Once attached to a host plant, dodder continues to grow and reattach in multiple places along the host stem. Individual plants will often spread to nearby host plants creating a mass of stringy orange stems which can cover large areas. This is what we came across on our hike in the Smokies.

A tangle of dodder stems intertwine to form a stringy mat.

Many dodder plants intertwine to
form a tangle of stringy stems.

Parasitic organisms rarely kill their hosts since they rely on them for sustenance. Dodder is no exception and, though they may weaken and stunt the growth of the host plants, they generally do not kill established plants. However, if they attach to seedling plants, they can seriously weaken them and may end up killing these young plants.

If it becomes established in agricultural fields, dodder can cause a significant reduction in crop yield. Alfalfa and sugarbeets are common host plants for some species of this parasitic plant. It can also infest ornamental plants including many perennials and annuals. Japanese dodder (Cuscuta japonica) often parasitizes trees and shrubs, including many types of fruit trees.

Seed capsules of common dodder contain up to 4 seeds each.

Seed capsules of common dodder
contain up to 4 seeds each.

This is one unusual plant!

It can become a serious garden pest and unfortunately it is usually difficult to control. If you pull the stems off the host plant, any haustoria that remain embedded in the host stem will resprout and continue to parasitize the plant. If it is allowed to set seed, thousands of seeds can drop to the ground!

A pre-emergence herbicide can prevent the germination of dodder seeds but these seeds have a hard seed coat and have been found to remain viable in the ground for more that 20 years! Yikes!

One recommendation for control of dodder in the garden is to completely remove all the host plants and replace them with a non-host species. Thus any dodder seedlings that germinate will not find a suitable host and will die off.

If you find this crazy parasite in your gardens, I hope you are able to win the battle against it!

Until next time – Happy Gardening!

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Thrips in Platycodon flower

I have noticed lots of these tiny insects deep within the flowers of many of the daylilies in the gardens. As a result of their feeding, these pesky critters have caused some disfiguring of daylily flowers and foliage.

Apparently, a few years ago they were also very abundant! Here’s some info that I put together at that time …

Thrips on a daylily petal

Thrips on a daylily petal

So… what are thrips?

Thrips are small cigar-shaped insects with long, narrow, fringed wings. They are tiny; just visible to the naked eye. There are many different species and most of them cause injury to plant tissue. A heavy infestation of thrips can cause severe damage to foliage and even flowers and fruit as their rasping/sucking mouth parts scrape the tissue and extract plant juices.

Thrips damage on daylily foliage

Thrips damage on daylily foliage

What does thrips damage look like?

On foliage, thrips damage appears as brown stippling on the leaf surface and when damage is more severe, the leaves may appear silvery or papery in appearance. Flower buds can become distorted and sometimes fail to open. On open flowers, thrips damage appears as dead spots, blotches, or the flowers may be discolored or deformed. I find this a lot in some of my daylilies; it’s especially noticeable on the darker colored flowers like the reds and the purples.

Thrips damage on a daylily petal

Thrips damage on a daylily petal

In addition to the damage caused by their feeding, thrips are also vectors for the spread of some destructive plant diseases and viruses like tomato spotted wilt virus.
A double whammy!

You can sometimes see thrips on the flowers or foliage but you have to look carefully because they are very small. You may also notice black specks of their fecal matter on the foliage or flowers. According to Andre, though, the easiest way to tell if you have thrips is to shake the foliage or a flower just above a pad of white paper and see if any little cigar-shaped insects fall onto the paper.

Thrips tapped out of a hosta flower onto white paper.

Thrips (and pollen) tapped out of a
hosta flower onto white paper.

Controlling Thrips

In the past, thrips were controlled with applications of DDT. Yikes! There are much “safer” ways to control them now.

Minor infestations may not warrant any control measures. Healthy, vigorous plants are able to outgrow thrips damage so it is important to keep your plants healthy through proper fertilization and watering practices.

If you have a heavier infestation of thrips, one way to reduce their numbers without spraying is to prune off damaged flowers, buds, foliage, or terminal growth and discard it in the trash. This is kind of drastic and it doesn’t always get rid of the problem.

Thrips on a daylily showing their small size. Notice the damage to the petal.

Thrips on a daylily showing their small
size. Notice the damage to the petal.

A better way to control them is to spray your plants with highly refined horticultural oil such as Bonide All Seasons Oil. Horticultural oils are often used by organic gardeners and are effective in controlling thrips in the nymph (immature) and adult stages. The oil basically coats the insects and smothers them. Although oil sprays are often effective in smothering the eggs of many insects, thrips eggs are usually unaffected because they are laid inside the plant tissue where they are protected.

The nice thing about oil sprays is that they have little effect on non-target, beneficial insects like lady beetles and honeybees.

Thrips crawl deep into the flowers, good spray coverage is necessary for control.

Thrips crawl deep into the flowers.

Thrips can also be controlled using Bonide Captain Jack’s Deadbug Brew, a broad spectrum organic insect control that can be used on ornamentals and edibles. Always read and follow the label directions.

So if you have noticed small patches of color missing in your flower petals or stippling on the foliage, you may have thrips – but now you know what to do!

 

You should know!

Even natural or organic products can be deadly to pollinators like bees. Captain Jack’s Deadbug Brew is toxic to bees for three hours following treatment. If possible DO NOT spray when plants are in bloom. If this is not possible, spray early in the morning or later in the evening when bees are less likely to be foraging on the plants and ALWAYS read the label!

Until next time – Happy Gardening!

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Today is Arbor Day!

Celebrate! Plant a tree!

Show someone close to your heart that you really care about them by planting a tree in their honor or in memory of a loved one. One day it will grow to be a majestic tribute to that very special person!

A majestic oak silhouetted against the winter sky

Here are a few tips for planting trees.

 

Below is a post that I wrote on Arbor Day in 2012.

I thought I would share it today in honor of Arbor Day 2016!

 

Today is National Arbor Day!

Our new woodland garden replaces our front lawn!

Our new woodland garden replaces our front lawn! We planted a little pink dogwood, hosta, and several azaleas. Now it just needs some mulch.

It’s always the last Friday in April although some states recognize a different State Arbor Day that corresponds better with planting times in their state. Since Arbor Day was founded in 1872, it has been customary to plant a tree in observance of the holiday and on that first Arbor Day, it is estimated that about one million trees were planted.

As you celebrate Arbor Day this year, keep in mind that as important as it is to plant new trees, it is equally important to care for and protect the trees that are already growing in your landscape.

Damage to mature trees due to insects and diseases (many introduced from other countries) can be devastating to your landscape as well as the surrounding areas and adjoining forests. Diseases such as the Chestnut blight and Dutch elm disease and exotic insects like the emerald ash borer and the Asian long-horned beetle have killed tens of millions of trees across the U.S.

Chestnut blight canker on the stems of a young American Chestnut. Photo by Eric Jones

Chestnut blight canker on the stem of a young American Chestnut.
Photo by Eric Jones

The chestnut blight, caused by a fungus (Cryphonectria parasitica), was introduced to North America from Asia in the early 1900’s either on infected lumber or through diseased trees. Within 40 years of its introduction, virtually all the chestnut trees in North America were wiped out. Although mature American chestnut trees have disappeared from our forests, small trees often grow from stump sprouts since the blight doesn’t kill the roots. Unfortunately, these small trees rarely grow to reproductive age before they are attacked and killed by the fungus. Such a sad ending for these once majestic trees which often reached 200 feet tall and 14 feet across! There is no cure for this disease but much work has been done to genetically engineer a disease resistant American chestnut using genetic material from a few stump sprouts that managed to produce seeds and a bit of DNA (as little as 3%) from Asian species that show resistance to the blight. The American Chestnut Foundation is at the forefront of this research with a mission …

…to restore the American chestnut tree to our eastern woodlands to benefit our environment, our wildlife, and our society. The American Chestnut Foundation is restoring a species – and in the process, creating a template for restoration of other tree and plant species.”

How’s that for a great Arbor Day message!

Woolly adelgids on the branch of a young hemlock.

Woolly adelgids on the branch of a young hemlock. Photo by Eric Jones

Another pest that is doing its best to wipe out whole a species of trees is the hemlock woolly adelgid (Adelges tsugae). This past Sunday on a wonderful but rainy walk in the George Washington National Forest, Eric and I saw evidence of this destructive pest on a young hemlock. The hemlock woolly adelgid was also an accidental introduction from Asia and is devastating populations of eastern hemlock (Tsuga canadensis) and Carolina hemlock (Tsuga caroliniana) throughout eastern North America. The insect damages the trees by feeding at the base of the needles causing them to desiccate and eventually drop off. Heavy infestations have been known to kill trees in as little as four years but healthy trees can sometimes survive an attack for a longer period of time. Luckily, there are products that the homeowner can use to help control hemlock woolly adelgids but sadly in our hemlock forests, these pests are causing the destruction of large numbers of these beautiful trees. Read more about the woolly adelgid.

As they have with the American chestnut, researchers have developed an adelgid-resistant hybrid by crossing the Carolina hemlock with an Asian hemlock which is resistant. While this is great progress – it does nothing to save the trees that are already infected!

Seen these hanging around?

Seen these hanging around? These purple structures are Emerald Ash Borer traps used to evaluate populations of the pest.

Another group of insects that causes widespread damage to established trees is the wood-boring insects including the emerald ash borer, the Asian long-horned beetle (both introduced from Asia), and a wide variety of the bark beetles.

The emerald ash borer, first reported in Michigan in 2002, has already killed millions of ash trees and is a potential threat to all the ash trees in North America.

The Asian long-horned beetle is one of the most destructive of the wood borers because it is not selective and attacks a wide variety of hardwood trees.

Bark beetles, like the spruce beetle, the mountain pine beetle, and the southern pine beetle, have killed millions of conifers in North American forests especially during severe outbreaks.

Bark beetles attacked this weakened pine and contributed to its death.

Bark beetles attacked this weakened pine and contributed to its death.

I remember when we were in Alaska several years ago seeing where the spruce beetle had killed entire forests of Sitka Spruce. Although bark beetles generally attack trees that are weak, dying, or already dead, the species listed above are particularly destructive because they will attack live, seemingly healthy trees.

For the homeowner, there are products that can be used to help control some of these pests. Horticultural oils can help control the woolly adelgid if they are sprayed at the correct times.

Some systemic insecticides may help control adelgids, emerald ash borers, Asian long-horned beetles, and pine borers. Bayer Advanced 12 Month Tree & Shrub Protect & Feed II and Bonide Annual Tree & Shrub Insect Control are products that can be mixed and poured at the base of the tree according to the label directions. These products are not available in all states. Always read and follow the label directions when using any pesticides. Read more about borers.

On this Arbor Day, The Nature Conservancy reminds us of some important tips to help protect our trees.

  • Keep your trees healthy and vigorous! Many destructive insect pests and diseases are attracted to trees that are stressed due to poor nutrition, drought conditions, and mechanical injury such as lawn mower or weed whacker nicks in the trunk.
  • When purchasing trees, purchase certified, pest-free nursery stock.
  • To avoid inadvertently spreading invasive pests or diseases, NEVER transport firewood when you travel, always obtain it locally!

So make a pledge this Arbor Day to pay attention to your existing trees and strive to keep them strong and healthy!

… and plant a tree!

Until next time – Happy Gardening!

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Autumn olive

This was the title of a question posted on our Discussion Board several weeks ago. Here is the post:

Autumn olive

Autumn olive in fall

What is the name of the invasive species of small bush/tree with thousands of little red berries, and is spreading like kudzu? It grows two or three inches a day seems like, and is dominating every hedge row in my area. I live near Stuart, Virginia. What is the best way to eradicate them?

My guess was autumn olive but I asked for some additional information to be sure of the identification:

The silvery undersides of the autumn olive leaves

The silvery undersides and
alternate arrangement of 
autumn olive leaves

Are the undersides of the leaves silvery in color and are the leaves arranged alternately on the branches? If the leaves are arranged opposite each other on the branches and the leaves are green, then it would be a bush honeysuckle. In either case, they are both invasive and hard to control.

He replied back that the leaves were silvery underneath and they were arranged in an alternate pattern on the stem.

Autumn Olive – as I suspected.

Autumn olive (Elaeagnus umbellata) is a deciduous shrub that is native to China, Japan, and Korea. It was introduced to the United States in 1830 as a fast growing shrub that could be used to quickly revegetate disturbed areas and provide erosion control as well as habitat and food for wildlife. It certainly did the job but unfortunately did it so well that the shrub has now become invasive in much of the eastern and central US.

Pale yellow autumn olive flowers

Pale yellow autumn olive flowers

Autumn olive is very prolific and is as happy growing on dry, rocky, infertile slopes as it is growing in rich garden soil. It is drought tolerant, salt tolerant, and even grows in very acidic soil.

This is one tough plant!

One of the reasons that autumn olive is able to thrive in nutrient-poor soils is its ability to produce its own nitrogen with nitrogen-fixing root nodules. This can become a problem for many of the native species that are adapted to areas with infertile soil because it interferes with the natural nutrient cycle.

In addition, because of its vigorous growth and quick spreading habit, autumn olive can easily outcompete and displace these native plants.

Autumn olive laden with fruit

Autumn olive laden with fruit

The other problem is that these shrubs produce a tremendous number of small red fruits all along their branches and each of these contains a seed. Birds and other animals apparently scarf up the fruit and are responsible for dispersing the seeds far and wide!

Autumn olive fruit contains a lot of lycopene and is apparently quite tasty when it is perfectly ripe. Before that time, it has a very bitter taste due to high levels of tannin – similar to unripe persimmon fruit. The few that I tried the other day, though deep red in color, really made me pucker up! Definitely not ripe yet! The tannin content decreases as the fruit ripens and it becomes sweeter. If you look online, you can find quite a few recipes which use autumn olive fruit to make jam, juice, and other things!

BUT …

These shrubs ARE invasive and efforts should be made to control them. However, this is no easy task! If you cut them down or burn them, they quickly sprout vigorous new growth from the base. Seedlings pop up everywhere the fruit/seeds drop.

Deep red fruit is speckled with silvery scales

The deep red fruit of autumn olive is
speckled with silvery scales

Seedlings can be hand pulled but it is best to do this when the ground is moist so you increase the chances of removing the entire root.

Seedlings and young shrubs can be controlled by spraying the foliage with triclopyr (found in many brush killers) or glyphosate (the active ingredient in Roundup) according to the label directions.

Large, mature shrubs are harder to kill. One of the best methods is to cut them down and then immediately apply an herbicide containing glyphosate or triclopyr directly to the freshly cut stump according to the label directions for stump treatment. You can use a paint brush or a spray bottle to apply the herbicide and if you add a dye to the mix, you can easily see when you have good coverage on the stump.

One of the best times to do this is in the early fall before the fruit (with seeds!) matures. At this time, the plants are beginning to prepare for winter by moving nutrients and stored starches from their leaves into their roots. Spraying systemic herbicides at this time (for any perennial weed) means that these chemicals get transported down to the roots more quickly thereby increasing their efficacy.

Good luck if you have this stuff! It is growing in dense thickets around our little orchard and every year it seems to close in a bit more!

Until next time – Happy Gardening!

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Corn crop destroyed by critters

We have had more trouble with critters enjoying our garden this year than ever before!

It is being a challenge to say the least.

End of June - pre-woodchucks

End of June – pre-woodchucks

Healthy pole beans and sweet potato vines

Healthy pole beans and sweet potatoes

It started back in the spring when cucumber beetles infected many of my small cucumber plants with bacterial wilt. I lost probably 50 percent of my original crop before I realized what the problem was and sprayed the plants with Bonide Eight. I had to reseed and also buy some plants to replace the ones that were lost. I kept on top of them after that and ended up with a great crop of cucumbers until disease finally destroyed the vines in mid August. At least I was able to enjoy lots of delicious cucumbers and make lots of pickles!

Most of the lower leaves were eaten

Most of the lower leaves were eaten

Woodchucks have been the worst problem this year. Despite the fence and wildlife netting we have around the garden, somehow at least one managed to get in. We first noticed it when all the leaves of our sweet potato vines were chewed off. Then the lower leaves of the pole beans began to disappear! At least it didn’t bite off the growing tip of the bean vine and they continued to climb up the poles. The plants were just leafless at the bottom.

We searched the perimeter of the garden and found a spot or two where it looked like some critter might have been getting under the fence. In those areas, we took some old fencing, bent it at a right angle, and pinned it down so that it extended about 2 feet out along the ground on the outside of the main fence. We hoped that would do the trick.

The beans had begun to recover by the time I took this photo

The beans had begun to recover
by the time I took this photo

After that, all was well for a while … until one day when Eric noticed that the leaves along the top of the bean trellis were being eaten! Our bean trellis is sort of like a pergola made out of bamboo poles. There are two rows of 8 uprights and then bamboo cross pieces join the two rows along the top. This allows the vines to grow between the poles at a manageable height (once they reach to top of the poles) so that I can easily reach the beans to pick.

It’s a great system but we were baffled as to how the foliage at the top was being eaten! Certainly if a woodchuck tried to climb the poles to get at the top leaves, they would have knocked the poles over or at a minimum torn down many of the vines in the process. Plus, I don’t think the cross pieces could support even the weight of a small woodchuck. Yet the leaves were chewed right off!

The only critter we could think of that might be able (and willing) to do this was a squirrel. Squirrels have been enjoying the foliage and flowers of the petunias on our deck for years. Actually, they have recently switched to the coleus and tomato leaves since there are no petunias left! So it seems entirely possible that squirrels are the bean robbers. How in the world could you keep them out?

They left us only the cobs!

They left us only the cobs!

A few weeks later just as the Silver Queen corn was beginning to ripen, we went out to the garden and found that about two thirds of the corn in the Three Sisters garden had been pulled down and the ears were chewed down to the cob. Normally I would blame this on raccoons but I’m wondering if it was the woodchuck(s) again. To make matters worse, since it’s the Three Sisters garden, when they tore down the corn, they also tore down the rattlesnake beans that were climbing up the corn stalks! We can’t see where they might be getting in – it’s very frustrating.

Destruction in the Three Sisters garden!

Destruction in the Three Sisters garden!

Not much left of this butternut squash!

Not much left of this
butternut squash!

After the corn, the woodchuck started in on the butternut squash. He just got one or two before we discovered this latest attack! Luckily we were able to protect the rest of the squash from being eaten. It was too early to harvest so Eric pulled the squash (still on the vines) together in groups and we were able to set them in plastic crates with another crate wired on top like a little cage. A few of the squash were off by themselves so I just put one crate upside down over them and pinned it down with landscaping pins. This seems to have kept the critters at bay – for now. Hopefully it will last until it’s time to harvest the squash.

Our improvised squash protection cage!

One of our improvised squash protection cages! So far so good!

Oh boy! What next? So far everyone has mostly left the tomatoes and peppers alone. Guess I’d better knock on wood! And at this point the beans seem to be recovering and producing new foliage and flowers. Perhaps the acorns and hickory nuts are beginning to ripen!

Until next time – Happy Gardening!

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Asparagus beetle damage

Asparagus beetles cause mostly cosmetic damage

Asparagus beetles

The other day I had a call from a gardener who was having trouble with asparagus beetles chewing on his asparagus. These beetles don’t usually do a lot of damage but they can make the spears look a bit ragged especially at the tip. If not controlled, however, a heavy infestation of beetles and their larvae can cause defoliation of the asparagus ferns during the summer. This can weaken the plants and reduce spear production the following spring.

Asparagus beetle eggs and stem damage

Asparagus beetle eggs and stem damage

One of the worst parts about having asparagus beetles is that they lay their eggs all over the asparagus stems. These black cigar-shaped eggs are very prominent, sticking out at a right angle up and down the stalk like little prickers. Not very appetizing to say the least! If you have asparagus beetles, you will have the eggs and lots of them! There are two types of asparagus beetles in our area; the common asparagus beetle (Crioceris asparagi) and the spotted asparagus beetle (Crioceris duodecimpunctata).

Common asparagus beetle

Common asparagus beetle

Spotted asparagus beetle

Spotted asparagus beetle

Asparagus beetle eggs stick out from the stem. Damage to the stem from feeding is also evident.

Damage to the stem from feeding

The common asparagus beetle is the most prevalent and unfortunately is the one that does the most damage to the plant. Most of the time, unless there is a heavy infestation, the damage is purely cosmetic. The beetles feed on the stem leaving shallow grooves and scars on the surface. In some cases, the spears can become disfigured, ragged, and bent over like a shepherd’s crook. However, it’s the presence of those little black eggs sticking out all over the spears that is often the most objectionable part of an asparagus beetle invasion! Luckily, they are fairly easy to rub or scrape off when you are preparing the spears for consumption.

Control of Asparagus Beetles

Our asparagus patch is relatively small so I normally just hand pick the beetles and squish them when I find them. If you have a larger bed, this can become an overwhelming job. If you cut the spears when they are still pretty short (about 8″ or so), they normally don’t have much damage and early harvesting has the added benefit of removing any eggs before they have a chance to hatch.

Lady beetle adult

Lady beetle adult

Natural predators in your garden can reduce asparagus beetle eggs and the caterpillar-like larvae. A small parasitic wasp will attack and destroy the eggs. Lady beetles, which are similar in coloration to the spotted asparagus beetle but are round rather than oval in shape, will consume both eggs and larvae of the asparagus beetle. Another trick is to leave a few of the asparagus unharvested. Asparagus beetles are attracted to mature plants with a lot of foliage so these plants can become “trap” plants and the emerging spears are more likely to be left alone. In large plantings or when there are more severe infestations, pesticide applications may be warranted.

Bonide Neem Oil and Pyrethrin are good organic controls for asparagus beetles. These can be used pre-harvest or post-harvest according to the label directions.

For organic control post-harvest only, Bonide Captain Jack’s Deadbug Brew which contains spinosad is a good option.

Chemical insecticides to control asparagus beetles include Bonide Eight (permethrin) and Sevin (carbaryl). Be sure to apply according to the label instructions and ALWAYS follow the pre-harvest interval recommendations.

NEVER spray an insecticide (organic OR chemical) when the bees are active. Just because a pesticide is listed as organic doesn’t mean it isn’t toxic to bees and other pollinators. The best time to spray is in the early morning or in the evening when they are less likely to be collecting nectar. Once the foliage begins to yellow in the fall, cut the plants to the ground and throw the foliage in the trash rather than into the compost pile. Weed and rake up all plant debris around the asparagus bed. This will reduce overwintering sites and help lower populations of these beetles the following spring.

Until next time – Happy Gardening!

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Grafted melon at Merrick Farm, Wilbraham, MA. Photo: Megan Poljacik

When I first heard about grafted tomato plants several years ago, I thought the idea was crazy. I was very aware of the great cultural benefits of grafted trees and shrubs but why in the world would you spend the time and effort to graft a vegetable that only grows for a season then dies with the first frost?

Grafted tomato

Grafted tomato; Cornell University Cooperative Extension

It didn’t dawn on me at the time that the same disease resistance and increased overall vigor that the rootstock imparts to a grafted fruit tree could also work for a grafted tomato plant. When you think about it, this is a brilliant concept because tomatoes and many other vegetable crops have a plethora of disease and pest problems that we as gardeners are constantly battling.

It turns out that grafting vegetables is not a new practice at all – they’ve been doing it in Asia for a long time!

What is grafting?

Grafting involves taking the top of a plant (the scion) that has very desirable fruit qualities like superior taste (but low vigor and disease resistance) and attaching it to the bottom of a plant (the rootstock) that is known for its vigorous growth and disease resistance.

Getting ready to graft a melon (scion) to a gourd rootstock at Merrick Farm, Wilbraham, MA

Getting ready to graft a melon (scion)
to a gourd rootstock at Merrick Farm,
Wilbraham, MA  Photo: Megan Poljacik

One of the main advantages of grafted vegetables is their resistance to soil-borne pests and diseases.

Remember my whole diatribe on crop rotation? There are a lot of people with small backyard gardens that don’t have the space to rotate their crops. Planting grafted vegetables reduces the need for crop rotation. The rootstock that is used for the graft is selected for its resistance to a wide range of soil-borne diseases, including those that persist in the soil for many years. So even if diseases like Verticillium wilt, Fusaruim, bacterial wilt, or tobacco mosaic virus are lurking in your soil, grafted tomatoes are less likely to be affected because of their vigorous, disease resistant rootstock. You have a super plant!

Completed melon graft; Merrick Farm, photo: Megan Poljacik

Completed melon graft; Merrick Farm, photo: Megan Poljacik

What about diseases like early blight and late blight that travel to the plants via wind and rain? Are grafted plants protected from these devastating diseases? Unfortunately, these diseases attack the above ground parts of the plants – the foliage, stems, and fruit and the rootstock of grafted plants cannot directly provide resistance to these foliar diseases. However, as I have said many times before, healthy, vigorous plants are much less susceptible to disease and pest pressure.

An heirloom tomato grafted on a superior rootstock will theoretically be more vigorous, healthy, and productive than if it were growing on its own roots. The root system of the “super rootstock” will be much more extensive, thus providing more surface area for absorption of water and nutrients. This should lead to a healthier plant. Many of the grafted tomatoes that you will find are heirloom varieties. These very tasty tomatoes can be more prone to disease problems than hybrid tomatoes so grafting may offer a healthier, more productive plant.

Conversely, if a blight resistant tomato such as Defiant is grafted onto a hearty, disease resistant rootstock, you could end up with a seriously disease resistant tomato! Actually, this is a popular grafted tomato that is available!

Tips for growing grafted tomatoes

Grafted tomato planted with the graft well above the soil line.

Grafted tomato planted with the graft well above the soil line.

Remember how you have always been told to plant your tomatoes as deeply as possible because they will develop roots all along the buried stem and you will end up with a more robust plant? Deep planting is a no-no for grafted plants. It is extremely important to keep the graft above the soil line when you plant. If the graft ends up below ground, roots will develop above the graft, which totally defeats the purpose of having a grafted plant! When the scion roots into the soil, the disease resistance of the rootstock is bypassed and the plant is no longer protected. Money wasted! This may be the reason why some people are not successful with grafted plants and feel that they are not worth the expense to purchase.

Keep the graft at least an inch above the soil when you plant.

As the plant grows, provide it with a good support system to keep it off the ground. Any stems or branches that touch the ground can take root – again, bypassing the disease resistance of the rootstock. We grow our tomatoes on a trellis and keep all the side shoots tied up as well as the main stem. You can also tie them to stakes or a fence or grow them in cages – anything that keeps the plant from sprawling on the ground where it can take root.

It is also important to remove any growth that develops below the graft.

Many different vegetables are being grafted these days.

Melons are commonly grafted to improve disease resistance and yield.

Melons are commonly grafted to improve disease resistance and yield.

Although tomatoes are the most common, you can also find (or create your own) grafted peppers, eggplants, cucumbers, squash, melons, and watermelons. Each of these is grafted onto vigorous rootstocks that are developed specifically for that particular vegetable type and the specific diseases that attack it.

Grafted vegetables not only have increased vigor and resistance to soil-borne diseases but, because of the superior root system that develops in these plants, they also show an increased tolerance to environmental stresses like drought, temperature extremes, and nutrient deficiencies. The extensive root system increases the area that the plant can exploit for the water and nutrients needed for growth. The result is a healthier plant that not only bears well, but potentially requires less fertilizer, is drought tolerant, and has a reduced need for pesticide applications.

This may be the year that we give grafted plants a try. We may try to pick up a tomato plant or two at a local garden center. It will be especially interesting if we can find a grafted version of one of the varieties that I plan to grow from seed. That would be a cool experiment! I will keep you posted!

Until next time – Happy Gardening!

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