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Past Questions and Answers | February 2008

This month's questions concern:

How to Test Soil For Magnesium Level
Using Fresh Manure
Headless Lettuce, Cauliflower, Cabbage
Carrot Rust Fly Maggots
Plants For Septic Field
Using Pre-Emergent Weed Killer
Impatiens Cuttings
Out Of Control Weeds
What Is Heavy Soil
Too Much Manure
Leafminers on Tomatoes
Seed Potatoes
Planting Acorns
Pruning Hydrangeas
Getting Rid of Yellow Vine (Puncture Vine, Caltrop, Goathead)
Pruning Roses

Please scroll down to read the answers.

Question #1:  How to Test Soil For Magnesium Level

Question:  This question is in response to last month's emailed gardening tip. You mentioned to make sure to do a soil test to see what your magnesium level is before adding any Epsom salt to outdoor plants. You said, "Without knowing your current magnesium levels, you shouldn't apply Epsom salt at all to outdoor plants. Many areas have almost toxic proportions of magnesium present in the soil, and continually adding more will end up poisoning the plants and the soil." That's great, but how do I test for Magnesium levels?

 Jim Trueman, UK


ANSWER:  Hi Jim! Great question. Since most home "do-it-yourself" soil testing kits only test for pH, Nitrogen, Potassium, and Phosphorous, in order to find out your calcium and magnesium levels you'll have to take a sample to a local soil testing lab. Every county has one, and the cost is usually around $10 (�5). It's fast and very accurate.

Question #2:  Using Fresh Manure

Question:  Does manure have to be well rotted or can you put fresh on and leave it over the winter months?

 Sharon Taylor, Coventry, England


ANSWER:  Hi Sharon! It depends upon what you are putting it on. If you are going to put it on a fallow bed or garden area that currently isn't growing anything, and you just want to spread it out so it can decompose and age, then you're fine. In the spring you can turn it into the soil.

If however, you want to apply fresh manure to live plants, you will have a problem. Fresh manure will scorch plants because the ammonia in it hasn't broken down into nitrates yet, and the nitrates are what can be absorbed by the plants.

Actually, manures (of any kind: cow, chicken, sheep, etc.) are best when composted. The composting process stabilizes the nutrients, which might otherwise be washed out by the rain, and converts them to a form that is more readily taken up by plants, plus the heat of a compost pile can kill some weed seeds and harmful organisms.

Manure, when used properly, can be an excellent soil conditioner, and when used in conjunction with a good balanced fertilizer, will give you very healthy plants.

Question #3:  Headless Lettuce, Cauliflower, Cabbage

Question:  This is my first garden and my head lettuce, cauliflower and cabbage are not coming to any heads. My broccoli is doing GREAT! which is planted right in the middle of the rest. I am I doing something wrong? Thank you very much.

 Chrissy Altman, Lake Worth, FL, USA


ANSWER:  Hi Chrissy! Well, it could be a couple of things. First of all, and I'm not trying to sound simple here, but cabbage and lettuce both come in loose and head varieties. You clearly stated you had planted head lettuce, but did you plant a head variety of cabbage, or a loose-leaf variety, also known as "spring cabbages"?

Since your broccoli is doing fine, that can exclude the plants not getting enough light, but another consideration is soil preparation. Have you have been feeding your plants a good balanced fertilizer regularly to give them the nutrients they need to produce?

The last consideration is the weather variations.

I don't know how your weather has been, but here we have had days 30° to 40°F (1-4°C) and the next day has been 70° to 80°F (21-27°C), with nighttime temperatures going from the high 20°s F (-6.7°C) to the 40°s (4.4°C) and the cool weather crops here are not doing well at all because the temperature variations are so extreme.

So let's take a quick look at this crop by crop.


Cabbage prefers a temperate climate, preferably on the cool side. If the temperature never left the 60°s and 70°s F (15.5-21°C) , cabbages would grow to perfection. But when the weather is hot, cabbage flavor declines and the heads can split quickly if the soil is wet.

Cabbages behave like biennials: Exposed to cold below 40°F (4.4°C) they don't do well and can bolt and go to seed, and days when the temperature barely reaches 50°F (10°C), cabbage will sit there and not grow very much.

So if you are having a cold snap, your cabbage won't grow much and if it gets too hot, it will not form a head.


Cauliflower is also a cool-season vegetable and more sensitive to the cold and heat variations, and more difficult to grow than other members of the cabbage family.

It is important to start cauliflower early enough that it matures before any warm temperatures begin, but not so early that it is injured by the cold.

Any interruption (extreme cold, heat, drought with not enough soil moisture, or plant damage) can abort development of edible flower head.


Crisphead varieties are extremely sensitive to heat. If an unseasonably early heat wave hits before they have matured, they almost certainly fail. In many locations, crisphead lettuce plants started in late summer to mature in the cooler weather of fall have a much better chance of success.

Now I just did a quick check via to see your weather this week, and you're having temperatures around 80°F (27°C) which is getting warm for lettuce.

Since your broccoli is doing well, and that crop is a bit more tolerant of weather swings, I would say, you, like many others lately, are a fine gardener, but a victim of the weather. I hope this helped.

Question #4:  Carrot Rust Fly Maggots

Question:  How do I control or irradicate root maggots in carrots? Would this be the results from sawflies, and if so what do I do about it?

 Betty Snow, Thunder Bay, Ontario, CA


ANSWER:  Hi Betty! Sounds like you have Carrot Rust Fly (Psila rosae), which produce creamy, white larvae that tunnel into roots of susceptible plants, carrots being one of them.

The adults are shiny, metallic, greenish-black flies that emerge in the spring, mid-April to May, and begin laying eggs in the soil close to plants. Eggs hatch in 7 to 10 days and the tiny maggots burrow in the roots for 3 to 4 weeks and then pupate. There can be 2 or 3 generations per year.

At the moment trying to discuss prevention would be hard, because you already have the problem. Not surprising, because according to Agriculture Canada, Carrot Rust Fly Maggots are most common in soils of southern Ontario and Quebec.

I think the first thing you need to do is clean up and discard any carrots that may still be around, and any other plants that Carrot Rust Fly like which are: celery, parsley, parsnip, dill, caraway, and fennel.

Rotate other crops for a few seasons and then start monitoring with yellow sticky traps to see how the adult population is doing. If you see a dramatic decrease then you can start planting carrots again with these precautions in mind:

1. Try growing the resistant variety `Flyaway" carrot.

2. Use floating row covers before seedlings emerge. This can provide excellent protection. Make sure to bury the edges under soil, and leave the crop covered until harvest. This won't allow the adults to lay their eggs, and will really help the problem. You can do this only after you have cleaned up your current problem. To put floating row covers over infested soil, will only make things worse.

3. Wait and late-plant (after mid-June) to reduce severity of attacks.

4. Never leave carrots or other susceptible plants in the ground over winter; you're just providing a nice home for them.

5. Make sure to continue to rotate your plants.

6. There is also a parasitic nematode that you can drench the soil with, but I have never used this method and can't give you personal results.

7. Last resort, you can try using Diazinon (5% granules) which is not an organic solution, and I wouldn't do this unless the problem was extreme, but it has proven effective.

Overall, Carrot Rust Fly can be a real mess to try and clean up, but it can be done with patience and diligence on your part. Good luck!

Question #5:  Plants For Septic Field

Question:  What plants are suitable to be planted on the drainage site of our septic line? The area is large and very deep but I don't want my plants to suffer root rot, any ideas would be well recieved. Thanks.

 Heather Robbie, Auckland, Waiuku, New Zealand


ANSWER:  Hi Heather! Well, I don't think you need to worry about planting anything that will get root rot. I think the main thing you need to worry about is not to plant anything that will interfere with your septic tank and lines.

In general, shallow-rooted herbaceous plants that are not excessively water-loving are best because, (for those not familiar with it) a leach field is a series of relatively shallow, a minimum of 6 inches (15 cm) below the surface, underground perforated pipes set in gravel trenches that allow septic tank effluent to drain over a large area. As the effluent seeps into the ground, it is purified by the soil. Plant roots can help remove excess moisture and nutrients thereby making the purification of the remaining effluent more efficient.

However, roots that clog or disrupt the pipes will seriously damage the drainage field. The challenge of leach field gardening is to find plants that will meet your landscape needs but not clog the drain pipes.

Trees and shrubs are risky to plant over or near a drain field. Their roots penetrate more deeply than grasses and flowers, and once their roots find the constant source of moisture and nutrients that a septic pipe affords, the roots will invade the pipe.

If the pipe becomes filled with roots, waste water can no longer flow down it. The water may back up into the tank and could even back up into your house! Willow, poplar and pine trees are all known to clog up drain pipes.

The best place to plant a tree is near the end of a line, where it is drier and less attractive to root growth. If you really want to plant shrubs over the drain field, the ones that have fibrous roots, such as holly, boxwood, azalea and rhododendron are fine because they are not likely to invade pipes. Even a small tree, such as dogwood or dwarf Japanese maple could be considered.

Here are other choices to think about:

Not Recommended Near Drain Fileds:

Beeches (Fagus spp.)
Birches (Betula spp.)
Elms (Ulmus spp.)
Poplars (Populus spp.)
Red Maple (Acer rubrum)
Silver Maple Acer saccharinum)
Willows (Salix spp.)

Better Choices to Plant Near Drain Fields:

Cherries (Prunus spp.)
Crabapples (Malus spp.)
Dogwoods (Cornus spp.)
Hemlock (Tsuga spp.)
Oaks (red, scarlet, white) (Quercus (rubra, coccinea, alba)
Pines (Pinus spp.)
Sourwood (Oxydendrum arboreum)

In addition, lawn, perennials and annuals are great choices, and while there are many others, this list should get you started.

Question #6:  Using Pre-Emergent Weed Killer

Question:  I am relandscaping and the gardener brought in extra dirt. It has already started to show some grass and weeds. Where I previously lived we used a product called Pre-Seed which was a pre-emergent weed killer. It was a granular product and could be used in flower beds without killing existing flowers. Can't seem to find it any more and wondered what you would recommend. I'd appreciate any help.

 Joy Hart, Camarillo, CA, USA


ANSWER:  Hi Joy! It is a bummer when weed and grass seeds are introduced into your yard, because now you have whole new set of weeds to combat! The good news is I have a great solution for you:

Corn Gluten Meal: This is a wonderful organic solution that works really well and leaves no reason to use chemical products. It's made from corn gluten, and is a 100% natural weed suppressor and slow release granular nitrogen fertilizer.

Corn gluten is a pre-emergence herbicide, so it works by inhibiting the development of small feeder roots. It does well against germinating seeds only, it won't affect established plants, and it can be applied in and around lawns, bedding plants, trees, shrubs, and vegetables.

Any nursery or home improvement center will have it, and if you've never tried it, do, you will be very happy with the results!

For more read our article on it: Corn Gluten Meal

Question #7:  Impatiens Cuttings

Question:  I'd Like to start some Impatiens from my larger, lush plants. Where do I cut? Do I place cuttings directly in water or in soil for best results? My mother did this all the time when I was a child, I wish I'd paid attention. Thanks for your advice!

 Sue White, Riverview, FL, USA


ANSWER:  Hi Sue! Yes, it's amazing what we do and don't pay attention to when growing up isn't it? The good news is that impatiens are very forgiving, and can be propagated quite easily.
  • Now both perennial impatiens and annual impatiens cuttings are very easy, but annual impatiens can sometimes be just a little more difficult to get them to root.

  • Start by choosing a strong stem with healthy leaves and remove the flowers and large flower buds.

  • Then cut the stem about 3 inches (7.6 cm) in length and just below a node.

  • You can use a smaller piece of stem, but it is much easier on the cutting if it is a little longer.

  • Next pour moist perlite in a clear container, and place the cutting in the medium. You can use rooting hormone if you want, but it's not really needed in this case.

  • Place some plastic wrap over the top and set the container where it will get lots of bright indirect light.

  • In about a week's time they should start to show signs of roots.
Now some people have found success just using a glass of water to root impatiens cuttings, and yes this does work well too. Keep in mind however, at some point you will want to plant your rooted cuttings into soil, and roots that have developed in water, often break during transplant, and those that don't break are very poor at water absorption and often die.

If you want, try it both ways, and let me know which method you preferred!

Question #8:  Out Of Control Weeds

Question:  We have recently moved into our house, and the gardens are full of weeds. We have tried pulling them out, we have tried both chemical and organic weed killers, and tried solarization. Is there any other way. We just can't seem to contain them.

 Brad Martin, Lismore, NSW Australia


ANSWER:  Hi Brad! I can hear and understand your frustration. Nothing is worse than a battle of the weeds. Unfortunately, the best advice I can give you is diligence, and try mixing up your techniques a bit more.

The problem with a lot of chemical weed killers is they do a great job of killing what's there, but if you simply leave that area bare, and don't do anything else, new weed and grass seeds can blow in and take root in the now clean and open area.

You also have to realize there are perennial and annual weeds, which means that at any time of the year, some kind of weed will be growing. The trick is to keep after it year-round and in a season or two, you will see a huge decrease in the problem as you kill each weed's growing cycle and start to get the upper hand.

So what I would suggest is to pick a general weed killing method, I like solarization because it's chemical free, but many people opt for RoundUp or another systemic weed killer.

Once you have killed everything back, come back in and put down some corn gluten, I mentioned this up on question # 6, see above if you didn't read it.

Corn gluten is great because it will keep any new seeds from germinating. Keep in mind, it will keep all seeds from germinating, so if you are planning on starting a vegetable garden from seed, this will be a problem.

If that is the case, and you can't put down a pre-emergent, put down a good layer of mulch, 2 to 3 inches (5.1 to 7.6 cm) to keep any new weeds smothered.

Hang in there, you have the right idea, and in time, your garden is going to look great.

Question #9:  What Is Heavy Soil

Question:  I want to start a water garden. I went and bought a Papyrus plant. I was told to repot plant and to use "heavy soil" and water plant fertilizer. Can you tell me what "heavy soil" is? And what type of fertilizer to use that can be used with fish in pond?

 Ramona Diorec, Honolulu, HI, USA


ANSWER:  Hi Ramona! Good question. Soils come in various "textures" meaning there sandy, loam, and clay soils, which some people can refer to as light, medium, and heavy soils.

Heavy soils (the same as a clay soil) are called that because they contain more clay, are sticky, and have little pore space, drain slowly and retain water and nutrients longer, which tend to make them more fertile than other soils, and are ideal for pond plants.

A medium soil (the same as a loam soil) which is considered the ideal garden soil (not for pond plants, but general gardening), because it has a nice balance of 3 particle types, clay, silt, and sand, giving it a combination of large and small pore spaces allowing it to have air for healthy root growth, and to drain well and lose nutrients at only a moderate rate.

Lastly, a light soil (the same as a sandy soil) contains particles that are fairly large and irregular, and have large pore spaces between the particles giving the soil lots of air, which drains very quickly losing nutrients and water. That's why plants in sand need watering and feeding more often.

In your situation, you will want to use a heavy clay soil, and there are such soils packaged specifically for aquatic plants, so ask for that. In a pond situation, using the wrong type of soil can cause numerous problems, so start your plants out correctly with the right soil.

Now, just a few extra tips for you. One of the problems with ponds is that they can get a brown tinge to the water. This is because the soil has come out of the pot, which can happen in a high wind when the pot blows or falls over spilling soil into the water, or the soil washes out of the bottom of the pot. To avoid this problem here are a couple of things you can do:

1. Use a shorter wider pot (sometimes called a "pan") because it is less likely to blow over than a taller pot, especially if it is a taller growing plant (like some Papyrus); and make sure that you add some medium sized stones on top of the soil to keep the soil in the pot. The stones will also add extra weight which will keep the pot from tipping over in the pond in the wind.

2. Line the pot with burlap, weed barrier mat or a few layers of damp newspaper. After the bottom of the pot is lined then add your soil and plant. This helps keep the soil from washing out the drainage holes into the pond. Once the plant is potted up, soak the entire pot in a bucket that is large enough to cover the top of the pot for about 24 hours. This will allow any loose soil to be washed off into the bucket of water and not in your pond.

3. When you are putting the plant in the pond make sure that you slowly lower the pot into the water rather than just plunge the pot into the water. By lowering the pot slowly this will keep the force of the water from washing the soil out of the pot and into the water.

The final part of your question was about fertilizer. There are many made especially for ponds, just ask for fertilizer for Pond Plants. It will be safe for all aquatic life, and it won't turn water green from algae growth.

Good luck to you!

Question #10:  Too Much Manure

Question:  I have clay soil which I treated to plenty of manure last year. I planted a wide selection of vegetables which had plenty of foilage but no veg! Could I have used too much manure or is it something else?

 Marie Finney, Ireland


ANSWER:  Hi Marie! Overall, manure is great to use to help improve soil texture. In your case, since you have a clay soil, in addition to the manure, I would add more varied organic matter like a good composted soil that has some straw, sand, peat, or something to help give more pore space and air for your plant's roots to breath, and for the soil to drain well.

Now, I don't know what kind of manure you added, or how much, but generally, cow manure is about a 2-1-1 fertilizer. Other manures available at retail outlets, such as sheep, turkey or horse, have similarly low nutrient percentages, so try not to use manure as your only nutrient source because rapidly growing vegetables require a high level of available nutrients.

In addition to any manure you put down, you should also use a fertilizer whose nutrient profile closely matches what was recommended on your soil test. If you didn't test the soil this last year, try doing it this year. You can get a home soil test kit and it's fast and easy to do.

It sounds to me like your plants had plenty of nitrogen, but not enough phosphorus, which is necessary for good root development and for fruit and seed production. When you see lots of healthy, green foliage and no flowers or fruit, that is a telltale sign of plants that needed more phosphorus.

Sounds like you're on the right track, just make a few adjustments this next growing season and you'll have wonderful vegetables!

Question #11:  Leafminers on Tomatoes

Question:  I have 5 pots of "patio" tomotoes growing in large pots on my balcony. All 5 plants have tan "schrigely" marks on them, as you can see in the picture. Not all leaves have these marks. Also, the newest growth leaves on top of plants do not have these marks (yet??). Any suggestions as to the problem? Thanks.

 Bob Coyne, FL, USA


ANSWER:  Hi Bob! First of all, thank you for sending a picture with your question. It always is so helpful to be able to see exactly what you are talking about.

What you have are called Leafminers. They like to feed on bean, beet, cabbage, chard, lettuce, pepper, tomato, and other vegetables; also many ornamentals, especially chrysanthemum and nasturtium.

The larvae tunnel through the leaf tissue making hollowed-out, winding mines. They can kill seedlings, but the good news is that on older plants, such as your tomatoes, the larvae are more of a nuisance, and a cosmetic issue, than a serious problem.

There are a few things you can do:

1. Handpick and destroy mined leaves.

2. Remove any egg clusters you may see on the undersides of the leafs as soon as they are visible in the spring.

3. You can also spray neem oil. Read more about neem oil.

Your plants might not look great, but Leafminers won't affect the taste of your tomatoes, so enjoy!

Question #12:  Seed Potatoes

Question:  I have brought some seed potatoes and it doesnt show any directions on the back but what do you do to the seed potatoes before they go in the ground do I put them in the dark or in the light and do I water them or not?

 Brandon Tracey, Borehamwood, Hertfordshire, UK


ANSWER:  Hi Brandon! Potatoes are hardy creatures and don't really need a lot of help. The only thing I ever do with potatoes is to dust them in sulfur before I plant.

You can buy soil sulfur at any garden center, and simply put some in a paper bag, and put in your seed potatoes and gently shake. Your potatoes will now have a light coating of sulfur.

This is done for a couple of reasons: sulfur helps prevent rotting, and it also makes the soil around the potato seed a bit more acid, which potatoes like. In fact potatoes like a pH of around 5.0 so a little sulfur is a good thing. You are now ready to plant.

If you want to read a bit more, read our story on How To Start A Vegetable Garden. We have an entire section on potatoes with many tips on how to plant them for the best results.

Keep in mind, you can also plant potatoes in containers, you can watch our video how to do this: How To Plant Potatoes In A Container

Have fun and enjoy your potatoes!

Question #13:  Planting Acorns

Question:  My son-in-law gave me 3 small acorns and asked me to plant them and grow 3 trees. Is this possible? And if it is, how do I do this? Thank you for your help.

 Mary Vella, Staten Island, NY, USA


ANSWER:  Hi Mary! Yes, it's possible, but I have no idea how old or dry the acorns have become by now. Normally you want fresh acorns to work with, but regardless, here are some instructions to get you started.


Choose swollen or plump-looking, mature acorns from healthy trees or pick them off the ground as soon as possible. Some acorns start sprouting soon after they fall, and even if they have started a shoot, you can still collect them. Also don't collect any acorns that have holes, insect damage, or are cracked. The acorn is perfect when you can easily remove the cap.


Remove the caps, and put acorns in a plastic bag with an equal amount of leaf mold or peat mix and barley dampen. Close the bag loosely and store in the refrigerator at between 35° to 40°F (1.7-4.4°C). Check acorns throughout the winter and keep just barely damp.

Acorns need about 1000 hours (about 42 days) of low temperature dormancy. Plan to plant your acorns in late April or early spring. You can leave them in the refrigerator and plant as late as July, but an early start will produce stronger seedlings.


If you want, you can plant out in the garden or in a container.

In the garden: Plant the acorn on its side and cover with 1 inch (2.5 cm) of soil. If the acorn has started to sprout, plant it pointed downward. If your garden has rodents or squirrels around, you may want to line and cover your hole and seed with wire mesh to keep them out. If you want to plant in containers, you can do that too.

For containers: use a good quality potting soil mixed with the same amount of milled sphagnum moss. You want a porous, sponge-like soil. Choose a container that has good drainage holes in the bottom. Fill to the top and tap to settle the soil leaving about an inch watering space.

Place the acorn horizontally, about 1 inch (2.5 cm) under the surface. If the acorn has started to sprout, plant it pointed downward. Water until it comes out the bottom and place the containers in direct light. Never let the soil get completely dry, you don't want the acorn to dry out, keep it moist. Check moisture daily or more often if necessary.

When the stalk has reached 5 to 6 inches (13-15 cm), and the first set of leaves will have spread, plant it out into the garden. Oak trees have a tap root that you don't want to start spiraling around in the container, in fact some growers intentionally cut the taproot when moving the seedling so that the young tree will develop a branching root system.

Water regularly for the first season until the trees are settled, then taper the water off. Oaks typically don't like a lot of water once they are established, so try not to plant them near lawns or other high water areas, or they will simply die over time.

Acorns are super easy to grow, and I hope you can try this with what your son-in-law gave you. If not, go out and collect your own acorns and try some anyway!

Question #14:  Pruning Hydrangeas

Question:  I have a hydrangea in a container that I cut back, was to big, only get leaves, now know I cut it back too hard, anything I can do to bring back flowers?

 Susan Crawford, Edinburgh, Midlothian, Scotland


ANSWER:  Hi Susan! No not really, because it sounds like you have a hydrangea that likes to flower on older wood. The good news is however, that hydrangeas are very forgiving plants and in time the flowers will come back.

I personally have always pruned my hydrangeas back after the flowers have faded in the fall, and when they have gone dormant, and they have always come back looking fantastic with tons of flowers.

This way I don't really worry about cutting before or after bloom, because my way, no matter what type of hydrangea (some flower on new wood, some on old wood) I always get flowers.

So next time, make sure to leave some older wood when pruning, and prune after the flowers have faded in the fall, and you'll be just fine.

Question #15:  Getting Rid of Yellow Vine

Question:  Thanks for the very interesting site. We have a problem which may be commen to this area. The veggie garden was left abandoned for several years and is now covered in Catseyes or yellow vine. The thorns from these weeds stick into everything and are very difficult to remove. Poisons only kill the plant but the thorns live on.

 Peter Taylor, Gunnedah, NSW Australia


ANSWER:  Hi Peter! First of all, let me say how sorry I am that you have this noxious plant to deal with. Bear with me for a moment while I give some background information on this plant for others who have been lucky enough not to run into this plant.

The botanical name for this vine is Tribulus terrestris and it's a flowering plant in the family Zygophyllaceae, native to warm temperate and tropical regions in southern Europe, southern Asia, throughout Africa, and in northern Australia. It can thrive even in desert climates and poor soil.

This plant has many common names. Puncture Vine, Caltrop, Yellow Vine, and Goathead are the most widely used; others include automobile-weed, bindy eye, bindii, bullhead, burnut, burra gokhroo, calthrops, cat's head, common dubbeltjie, devil's thorn, devil's weed, doublegee, dubbeltje, gokshura, ground bur-nut, isiHoho, land caltrop, Maltese cross, Mexican sandbur, puncture weed, rose, small caltrops, sticker, tackweed, and Texas sandbur.

It is a taprooted, herbaceous, perennial plant that grows as a summer annual in colder climates. The stems radiate from the crown to a diameter of about 4 inches (10 cm) to over 3 feet (1 m), often branching. They are usually prostrate, forming flat patches, though they may grow more upwards in shade or among taller plants.

The flowers are lemon-yellow with five petals, and a week after each flower blooms, it is followed by a fruit that easily falls apart into 4 or 5 single-seeded nutlets. The nutlets or "seeds" are hard and bear two sharp spines, 1/2 inch (10 mm) long and 1/4 inch (4 to 6 mm) broad point-to-point.

These nutlets strikingly resemble goats' or bulls' heads, and the "horns" are sharp enough to puncture bicycle tires and to cause painful injury to bare feet.

In fact one person said, "Its caltrop-like seeds always have one wicked thorn pointing straight up to impale your foot."

The plant is widely naturalized in the Americas and also in Australia south of its native range. In some states in the United States, it is considered an invasive species. There are both physical and herbicidal solutions to the problem but neither of them provide a quick long lasting solution because T. terrestris seeds remain viable for and average of up to 3-7 years.

So, how do we get rid of it?


In smaller areas puncture vine is best controlled with manual removal using a hoe to cut the plant off at its taproot. This requires monitoring the area and removing the weed before it sets any seed in late spring and early summer. This will greatly reduce the prevalence of the weed the following year. Mowing is not an effective method of eradication because the plant grows flat against the ground.

You can also try and crowd out this plant by providing good competition from favorable plants. Aerating compacted sites and planting competitive desirable plants, including broad leaf grasses, can reduce the impact of puncture vine by reducing resources available to the weed.


Chemical control is generally recommended for home control of Puncturevine. There are few preemergent herbicides that are effective, we mentioned an organic Corn Gluten Meal above in Question #6. Products containing oryzalin, benefin, or trifluralin will provide partial control of germinating seeds. These must be applied prior to germination (late winter to midspring) of the seeds.

After plants have emerged from the soil (postemergent), products containing 2,4-D and glyphosate (Roundup),are effective on puncturevine. Another aggressive product is Brush-B-Gon, which is very effective. Keep in mind most postemergent chemcials, like glyphosate (RoundUp) will kill or injure most plants so it should only be used as spot treatments or on solid stands of the weed only.

There are organic products out there, but in a case like this where the plant is so noxious, the organic products will only kill back the top growth, and not be systemic and travel down and kill the root too.

I am a huge proponent of using organic controls as much as possible, but sometimes a very careful, and judicious use of a chemical can be helpful.

OK, so here is the bottom line.

You are going to have to be tenacious about keeping after this vine for a few years. If it were me, I would use as small an amount as possible of Brush-B-Gon to kill the entire plant back, and then use hand weeding and organic preemergent products like Corn Gluten to keep it from re-establishing, and avoiding any possibility that it can go to seed again, because once it sets seed, you start the entire process all over again.

You can do this!

Question #16:  Pruning Roses

Question:  When should I prune my roses & how do I do it? (I'm a new gardener)

 Patricia Cameron, Glasgow, Scotland


ANSWER:  Hi Patricia! The best answer I can give is to go and read our full Rose Pruning Tutorial in our "How To" section!

Here is a link to it: How To Prune Roses

It has pictures and step-by-step instructions. Pruning roses is easy once you get the hang of it, and your plants and flowers will look gorgeous every year!

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Fertilize Container Plants

Because container gardens are usually grown to show off a lot color, the plants in them require more frequent fertilizing.

It's good to feed them every two weeks with a water-soluble complete fertilizer like a 20-20-20 or a hyrdolized fish fertilizer.

Regular feeding will help them fill in faster, and produce more flowers.

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