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Crabapple Question & Answers

Q: Are all the fruits on flowering crabapple trees edible? We have one that produces dark pink blossoms in the spring and this year it is loaded with small dark red to purple apples. Are these edible?

A: All fruits on crabapples are edible— some more than others, depending on the size and how juicy they are. Just be sure they have not been sprayed pesticides.

Q: When is the best time of year to trim flowering crabapples? How much can they be trimmed back?

A: Prune anytime before spring growth. Late winter or early spring is ideal. Prune no more than 25% — 30% of the total crown area.

Q: My old crabapples look normal, but aren't flowering like they used to.

A: When the trees were last pruned? That is often the problem. Intelligent pruning during a 2 — 3 year period should bring them back to their full show.

Q: How do I properly prune crabapple and regular apple trees. I ordered some trees from a nursery catalog and the trees I received came with quite a few branches. Should I remove most of the branches so there are only 3-4 left? Should I remove bigger branches that are closer to the ground in favor of the smaller ones up higher? The trees are roughly 4' — 5' tall.

A: At one time pruning trees at the time of transplanting was the norm, but we've found that doing so can cause more harm than good. Leaves that come out the first year on the current branches are vital as it establishes itself in its new home. Hold off pruning for 1 — 3 years until the trees get established.

For structural pruning, keep in mind:

  • Never prune more than 1/4 at any one time. The tree needs those leaves to harvest sunlight and convert it to food energy. If the tree loses too many leaves at one time, it will take a long time to recover.

  • Wide branch angles are preferred, at least 30 degrees away from the (vertical) main stem. Even better if they are between 45 — 60 degrees.

  • Keep the main structural branches spaced about 18" — 24" apart along the main stem

Q: The crabapple trees that line our street look distressed. They bloomed this spring, but now look like they're dying. They dropped leaves all summer. Are they a lost cause or can they be saved?

A: It could be apple scab, which is a plant disease caused by the fungus Venturia inaequalis. It also could be a rust fungus known as cedar-apple rust. Both cause early leaf drop.

Rust fungus is more isolated, while the apple scab fungus is more wide spread. Clean up the leaves and fruit this fall. Next spring, spray the trees with lime-sulfur while the trees are still dormant and again after leafing. Use a fungicide known as Captan. Repeat again in 10 — 14 days.

Q: We have a flowering crabapple tree that bloomed profusely this spring, but is already losing leaves. What does this indicate? Any suggestions?

A: This is a leaf spot (likely scab) disease problem. It will take a lot more than this to kill the tree. However, it will weaken the tree and make it vulnerable to other problems.

Spray with a Funginex or Bordeaux mixture right now to help prevent the spread of the spores to uninfected areas. Clean up leaf and fruit in the fall. Next spring spray the tree with lime-sulfur before leafing. As they open, spray with the aforementioned fungicides or Captan.

Q: We transplanted 3, 15 year old flowering crabs 3 years ago. The next year they looked excellent. The following year about 1/3 of the branches lost their leaves in the spring. In the fall, the bark on those branches looked like they were suffering from sun scorch or fire blister. Those branches were cut off last fall. Is there any hope? Should I cut the tops off the trees, leaving only the trunk, so new branches will sprout?

A: Topping off the trees is about the worst thing you can do to a tree and still consider it a real tree. You're better off removing the trees. Moving trees that old left many feeder roots behind that make it difficult to survive transplanting. I suggest removing the trees and replanting. Crabapples grow quickly and you’ll be happier in the long run.

Q: We grew 3 crabapple trees from small seedlings. One tree is now about 10' tall while the other 2 are about 6'. This is the third year and still no blooms. The trees have not been pruned, except to remove some suckers. Is the absence of blooms do we have to do something to promote blooms?

A: Hang in there for a couple more years! In some cases, it takes about 5 — 6 years for some trees to mature enough to produce flowers.

Q: I know you are not supposed to prune in the summer, I have a mature crabapple that's blocking light to my flowerbeds. Can I prune now, and if I can, is there anything I should put on the cuts to avoid disease?

A: The risk of disease is greater during the growing season than with dormant pruning. However, you can prune whatever you need for satisfactory growth in the flowerbeds. Dip your pruning shears and saw in alcohol prior to pruning and between each pruning cut. No wound dressing is necessary, in fact, it should be avoided. Cuts heal better and faster without this unnecessary step.

Q: There are little shoots sprouting up all over the yard from my crabapple. What do I do to stop that?

A: Remove the water sprouts and suckers. They are not making a positive contribution to the vigor of the tree. Cut them off at their point of origin. Excessive sucker and water sprout growth is a possible indication of tree decline, so monitor the health of the tree through the growing season.

Visit a local garden center or nursery and ask for "Sucker Stopper." Spray it on after you cut the suckers back. That should take care of them for the growing season.

Q: I have a 4 year old flowering crabapple tree, but it doesn’t seem to be growing. It flowers and gets berries, but doesn’t get any bigger. What can I do or is its growth stunted for some reason?

A: You might just have a dwarf cultivar that has reached mature size.

Q: My crabapple tree had been blooming nicely the past few years, but last year it didn’t get flowers. The leaves were eaten. I sprayed the tree, but did not get any flowers this year.

A: Flower buds have a different hardiness level than leaf buds. It could be that the tree was in a state of vulnerability when the buds were about to open and a cold snap may have killed the flower buds.

Q: I planted a crab apple tree that was flowering and looked wonderful. This year the buds seem dry and brittle like they’ve been through a drought. When I touch them, they feel hard with no sign that a soft leaf is trying to poke through or open up.

A: It sounds like the parts you examined are dead. If this is true with the entire tree and there are no buds emerging, then the tree is likely finished. Cause for this unfortunate situation is probably associated with proper planting, and over / under watering last year.

Q: We have a crabapple tree that flowers nicely, but no longer produces fruit. It starts to loose leaves in July. How can we help our tree before it is too late?

A: Get some apple scab protection spray on the tree immediately and repeat every 7 — 10 days when the bees are not active. Spray until the fruit is close to full size. Consider using benomyl, mancozeb, Fore or Bordeaux mixture. Always clean up fallen fruit and leaf litter in the fall.

Q: I’ve got a fast growing crabapple a few feet from the house. The upper branches are taller than the house and growing into the gutters. The tree is V-shaped and looks top-heavy. I would like to reduce the height of the tree. Can I do it without “topping” the tree?

A: Cut the tree back to a lateral branch. That way you won’t “top” the tree. If you can make the lateral branch an outside one rather than an inside one, and do this when you prune every spring, the tree will tend to grow more horizontally.

Q: Each year, our old crabapple bloomed beautifully. The past few years we noticed the bark peeling, and after it blooms, the leaves dry up and turn yellow. The tree drops 1/2 or more of its leaves. It had a tremendous crop of berries the last 2 years, but only a few this year. I'm afraid it is dying. What do you think?

A: Old crabapple trees can have any number of pathogens or insects that cause these symptoms. You might want to contact a local International Society of Arboriculture certified arborist to make an accurate diagnosis and discuss a possible remedy.

Q: We planted a crab tree last year that blossomed this year with small red fruit, but the leaves are small. The tree looked fine except for the bare appearance because of the small leaves. Any clue as to why the leaves were so small?

A: It is the new growth that counts. Everything will even out with time, so don’t worry. The fruit will not get much larger because it can’t go beyond its genetic potential for size and color. Last year’s environmental setting probably had an impact on the leaf size of the older growth.

Q: I have a crabapple bearing a lot of fruit, but I can’t find anyone who can tell me when the fruit is ripe and ready to make jelly.

A: Without knowing where you live, the conventional wisdom is to wait until after the first frost. Generally, late August to early September is a good time.

Q: I have 2 flowering crabs. They flowered beautifully this spring but then began to look sick. The berries and leaves had a rusty layer that could be rubbed off. Two other trees in my neighbor’s yard looked the same.

A: Sounds like cedar-apple rust. Clean the area thoroughly this fall and spray a lime-sulfur mixture early next spring while the trees are still dormant. Spray with a Bordeaux mixture after the leaves unfold. Repeat the fungicide spray again 30 days later. That should provide protection. In the meantime look for the offending alternate host: junipers. If you see an orange globular growth on the trees this fall or early next spring, pick them off and dispose of them. That is the source of infection on your crabapple trees.

Q: We had a prairiefire crab and were told it was resistant to diseases, but the leaves are turning brown and falling off. The tree looks sick. We brought a branch back to the nursery and were told the tree has been infected by spores from the arborvitae in our area. Can this be true or are they just trying to get out of replacing our tree?

A: They are probably thinking the problem is cedar-apple rust and the arborvitae is the alternate host. The alternate host to cedar-apple rust is the juniper, not the arborvitae, which is an entirely different species. There could be some junipers in the area that are acting as the alternate host for this disease. If they are on your property, you can control that quite easily. It’s a problem if they are on someone else’s property. This disease can be controlled with a good spray program. Use lime-sulfur in early spring while the tree is still dormant. Use a Bordeaux mixture as the new leaves unfold, and again 10 days later.

Q: Initially the fruit is clean, however in time, small dark brown spots appear on some of the apples. As the season progresses, these spots appear on most of the apples. The spots penetrate about an eighth inch deep into each apple, but don’t seem to affect the overall quality of the fruit. Is this apple scab, black rot or insects?

A: It is apple scab. It doesn’t affect the eating quality of the apples, just the aesthetics.

Q: My crab apple tree has lots of apples but they don’t get very big. Right now the apples are the size of peas. Can I remove every other apple so that the remaining ones will get bigger?

A: That is a lot of work and probably won’t make any difference! The size is mostly determined by genetics, especially with crab apples.

Q: I planted 2 crabapple trees last fall. They seemed fine until about 3 weeks ago. The dark pink looks like it has a white paint or coating on the trunk and a few of the branches. I also noticed some of the branches are bare. The white crabapple next to it now has the same symptoms.

A: It could be cottony cushion or some other species of scale insect. Take a twig with the infestation on it to a local nursery for confirmation. Purchase horticultural oil that will control these destructive pests. If they don't have the oil, see if they have a systemic insecticide that will do the job.

Q: We planted 2 prairie fire crab trees 3 weeks ago. They looked beautiful until a few days ago. The leaves turned yellow and are dropping off. There are still some green leaves toward the top of the trees. The trees have received plenty of water from rain and sprinkling.

A: They have probably been over watered. You should never have the water from a sprinkler impacting directly on the foliage of a tree. The plant could have a leaf spot or rust fungus. Back off on the water or redirect a couple of sprinkler heads. Hopefully, you will be able to save the trees.

Q: I have 3 flowering crabs, 1 white and 2 red. Last spring the white and 1 red were loaded with flowers, more than I’ve ever seen in the 15 years I’ve had them. When the flowering was done, I noticed they were really thin on leaves. This spring they were dead. The other red one is okay. They are in a row within 20' of each other. What happened?

A: When a tree puts on a heavy reproductive show, it is a pretty good indication it will soon die. The cause could be armillaria root rot.

Q: I have a flowering crab that has very few leaves. The leaves are also very small. The rest of my crab trees are doing fine.

A: It sounds like a progressive root rot disease. It is a common disease that can afflict a wide range of woody plants. It is known as armillaria mellea or simply armillaria root rot. From a plant pathology standpoint, this is an interesting disease. It is a soil-inhabiting saprophyte that spreads through vegetative mycelium. The mycelium often remains suppressed in healthy trees but can become active in trees stressed by environmental conditions such as drought, heat stress, compaction or insect infestations. The fungus actually kills the tree by girdling the crown or lower trunk and then colonizes the dead wood as a saprophyte. It can spread to healthy adjacent trees via rhizomorphs (root-like growth) or from root contact. The likely scenario with your tree is that it will continue to decline. The disease will exhaust the carbohydrates stored in the stems and trunk above the girdling fungus until the tissue is completely dead. I suggest that you remove the plant totally, including the root system. Do not replant in the same spot for a couple of years.

Q: Is there a crab apple tree that does not bear fruit? I have a friend that says she has one in her yard, but does not know what kind it is or where it came from.

A: The only tree on the market that I know of is the spring snow crabapple. It should be available in most quality garden center outlets.

Q: My mother gave me a tiny crabapple tree she received from the Arbor Day Foundation. I have no idea what kind it is. I planted it on a partially shaded side of the house. It has been there for 3 — 4 years and seems to be growing just fine, but it has never bloomed. Does it need more sun? Could I move it without killing it? When is the best time to move it?

A: You could move it, but I wouldn't recommend it. Sometimes it takes crabapple and other fruit-bearing trees 5 or more years to mature enough to flower and fruit. As long as it gets about 6 hours of direct sun each day that should be sufficient to get it to bloom eventually. Don't make the mistake of fertilizing with turf fertilizer around the tree. This highly nitrogenous fertilizer material is good for the turfgrass and will cause the tree to put on lots of vegetative growth, but it does so at the expense of flowering, and sometimes disease resistance. If you are locked in to moving it, then do it this spring before new growth emerges with as large a root ball as you can handle and be sure to set it at the same depth.

Q: I would like your recommendation about a crab apple tree that we hope to plant near our house. I have a spot that is approximately 20' x 20' with the property line fence on the north side, my house on the east, a deck attached to another portion of my house on the south, and part of the same deck (L shaped) on the west. We would like something that has a shape that would fit into the area and not over-power the house. We would like something that has nice flowers, holds its fruit to avoid a constant mess, has small red fruit and preferably red leaves as they age towards fall. I would appreciate any advice you could give us on what would be hardy for our area and come close to what we would like in that type of tree.

A: The one that comes to mind is the thunderchild crab. It gets 12' — 20' tall, has nice pink flowers, deep purple leaves and small, persistent fruit.

Q: I have an ornamental crabapple that I planted a few weeks ago. I have noticed that the leaves are always folded inwards. Could this mean the tree is over or under watered?

A: The first thing I would suggest is to look inside the folded leaf and see if there is a critter there. Some insect larvae will make a cocoon that way. It could also be responding to high temperatures as a means of conserving water. Many times the symptoms of over or under watering are exactly the same. That is a determination you will have to make. Most people tend to over water.

Q: I understand that one should avoid trimming a crab apple in June or July. I have a tree trunk that did not get leaves this year. Should I trim it now or wait until winter? Also, is this dead trunk a sign of things to come for the rest of the tree?

A: Try to avoid pruning apples or crabapples in the hot, sticky months of summer to avoid possible disease problems but if the branch is dead, it isn't a good idea to keep it around either. I would recommend cutting it back to just outside the collar. This is not necessarily a sign of things to come. It could be the branch died of a cankerous fungus or borers that may have decided to take up residency in your tree. Monitor the condition of the tree and try to catch any anomalies that may show up early so they don't become a lethal threat to your tree.

Q: We have a white flowering crab apple tree. We pruned it last fall and this summer it did not flower. Did we do something wrong? Was it pruned wrong? What is the proper way to prune this tree? When is the best time to prune it?

A: You could have pruned off too much. You didn't say whether or not it leafed out, but I assume it did. The best time to prune is early spring before new growth emerges, depending on where you live.

Q: I have 2 crabapple trees in my front yard that are around 20 years old or older. I am having a problem with limbs dying. They have been falling off all year long and one seems to be rotting from the inside. Any ideas?

A: It sounds like your trees are not long for this world. You can get someone locally, such as an arborist or county extension agent, to come out and give you a better diagnosis than I can at this distance. You might start looking through some of the spring catalogs that are beginning to arrive to make a replacement selection.

Q: I have a flowering crap apple tree that is about 2 years old. I will be moving soon and would like to take it with me. Is it possible to dig up the tree in October and transplant it somewhere else or will I have to just leave it for the new owners. The tree is pretty small right now.

A: Any tree would be better off at the same location rather than digging it up. But it can be done, especially at the stage of life it is at right now. Just make sure that the new owners didn't consider it part of the purchase price of the property.

Q: I have a 25 year old crabapple that has gotten too big. I have tried pruning branches back to thin and reduce its height, but new branches sprout densely and grow very long during the next summer. I understand there is a hormonal balance between roots and shoots, so I spaded around the tree about 6' from the trunk, 8" — 9" deep, to cut roots. Still the branches sprouted. How can I get the tree reduced in size without it becoming dense with new, long growth? When should this be done?

A: There is a basic rule of thumb: to stimulate growth, prune when dormant; to slow or reduce growth, prune after leaf out. The idea behind this is that by pruning in late spring or early summer, photosynthesis material is removed, which reduces the vigor of the tree. Doing it just once will not do the trick. It must be done annually and sometimes twice during the season.

The bad news is that pruning in summer or when the trees are actively growing, opens them to disease spore invasion. Consequently, carefully select the time to do such pruning when there is no rain or high humidity and high temperatures forecast.

Q: My mother has some type of flowering crab that has lost most of its leaves. The remaining leaves look like they are drying up. The fruit looks perfect, but seems small. I've looked up apple scab and it doesn't look like the pictures. It's planted in sandy soil. We don't like using chemicals. Any suggestions?

A: With no chemicals being used, you are then limiting yourself to very few choices: Put up with what is happening and hope the weather improves so the disease doesn't manifest itself to such an extent. You can lessen the impact of the disease by cleaning up all fallen leaves in the autumn. Spraying with lime-sulfur (approved for organic use) will help sanitize the tree when dormant but is not listed as a control for the disease. Or, remove the present tree and replace with a more resistant cultivar, which depends on where you live.

Q: I have several crab apple trees, all are about 40 years old. They continue to bloom every other year but need to be trimmed. What is the best time of the year to trim.

A: The best time to trim is in the early spring, when the trees are still dormant. Trimming now would predispose the trees to disease entry, especially fireblight, so it is not recommended during the summer unless necessary to prevent breakage or to correct a hazardous situation.

Q: I have two Japanese crabapple trees that I bought 2 years ago as very small trees, Now they are about 9' tall but this year had no blooms on either of them. Do I need to fertilize them or prune them to get them to bloom? I am very new to this and want them to bloom next year.

A: Not needed. Lack of blooming is more likely related to weather conditions than to fertilization or pruning. Contact your local extension horticulturist and ask for a publication on care of crabapples in your region.

Q: We have 2 large flowering crabapple trees that canopy our back yard. They are very beautiful with vibrant pink blossoms. Each year they seem to get very large cocoons of caterpillars on the ends on the branches. What are they? and how can we get rid of them? Are they destroying our trees?

A: Those are tent caterpillars, and they love fruit trees! While they are unsightly and can be locally destructive, they seldom cause sufficient damage to be worried about. If you can, cut off the ends of the branches they are on and burn them. Next spring, spray the tree with dormant oil while it is still dormant, and the oil will kill the over wintering eggs.

Q: I have 4 Spring Snow crabapple trees (about 8 — 10 years old) planted in a line about 10' apart in a flower bed. 3 of the trees have always been good with flowers and leaves. One tree (a middle tree) is not growing as vigorously, and although it blooms, it gets very few leaves in the summer. It has been doing this for about 4 years. What should I check for to determine why this tree is not thriving like the others?

A: It sounds like it could be a canker, root rot or borer problem. My first suspicion is canker. Look for a darkening or ring around the affected branches. Cankers (dead tissue) are often caused by fungal organisms and gradually girdle the branch, killing it completely. In the meantime, the vigor of the tree declines. Having said that, it is unusual for a crabapple tree to be afflicted with such a disease.

Another possibility is root rot. If you can, dig down around the base of the tree and see if you can find any decay. In either case, there is not much one can do. If the tree doesn't pull out of this funk this year, then I suggest replacing it ASAP to keep the disparity between the established trees and the new planting from being too great.

Borers attack mostly stressed trees starting with small branches. If branch tips seem to be dying back, follow the dead parts back to see if you can find small holes in the stems. If you do, remove it and slice into the stem around the hole. You will find galleys where the borer has fed and likely girdled the branch, killing it. They are difficult to control once they get started, and I would rather see you replace the tree than to put a lot of pesticide into the environment attempting to control them.

Q: Do flowering crab trees have a life cycle or age limit? We are fighting leaf spot and/or apple scab on a very large tree, about 20' tall. I'm going to buy better fungicide delivery equipment but only if there is a chance to save it. The tree is about 23 years old.

A: There is a probability that you can save it, but if it is prone to apple scab or other diseases, it will be an annual fight, and one that usually get worse as time passes. You are better off having the tree removed and replacing it with one that has resistance bred into it.

Q: Can you tell me why the leaves on my crab apple trees have a wilted and blotchy appearance? I began using a fungicide for leaf scab at 7 — 10 day intervals, but I think I may have been too late. When is a good time to spray them and should I use a fertilizer this fall? I heard that fertilizing apple trees can promote rapid growth and fireblight. Is that true?

A: Fungicidal sprays should be applied as the leaves open. You can use chlorothalonil, which is probably the best selection. I find that using lime-sulfur as a dormant spray prior to leaf-out can also aid. You are right— fertilizer can cause excess growth and lead to fireblight.

Q: An idea I've heard about driving nails into apple trees to stimulate them to bear fruit is very interesting. How do you do it and how does it work?

A: Yes, driving nails into trees may stimulate them to bear fruit, but it is also injures the tree, so it's not advised. A less traumatic practice would be the take a square-tip spade and drive it into the soil out around the drip-line of the tree (the outer edge of the canopy) to sever some of the roots. This usually makes a pretty clean cut, which heals faster, and often results in the tree bearing fruit the following season.

 


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