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Gardening Answers Knowledgebase

Search Results for ' Frost'

PAL Questions: 9 - Garden Tools: 2 - Recommended Websites: 3

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Keywords: Frost, Hardy plants, Plant diseases--Diagnosis, Rhododendron

PAL Question:

A friend in Illinois has sent a photo this spring of a very healthy looking rhododendron - leaf buds fully elongated and beginning to unfurl, while the green, blunt flower buds remain unopened. The flower buds don't look brown, diseased, frozen or injured, but they remain tightly closed, foliage bud growth preceding blooming. He says he has 6 plants doing the same this month. Possible reason?

View Answer:

Though we can't diagnose plant problems by phone/email, early autumn frosts can inhibit flowering and not all buds are equally affected.

"Autumn frosts: These can lead to damage...if they either occur in early autumn or immediately after a late season warm spell. Continental climates with extremes of heat and cold are more likely to suffer sudden temperature changes than those with maritime climates...A sudden temperature drop will catch a plant before it has had a chance to reach maximum hardiness and it may suffer accordingly, even if normally perfectly able to withstand such a temperature in mid-winter...Speed of ripening varies considerably...There is also a variation in the hardiness of flower buds compared to foliage and growth buds. Commonly, flower buds may be as much as 10 F. less hardy than foliage..."
(Source: The Cultivation of Rhododendrons, by P. Cox, 1993, p. 119-120)

On the other hand, there might be something unusual about your friend's particular location. He/she might want to call a local Master Gardener and ask whether they're aware of anything abnormal. To locate Master Gardener clinics in various Illinois counties, go to http://www.extension.uiuc.edu/mg/ui-hort-links.html.

Season Fall
Date 2008-01-17
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Keywords: Failure to flower, Frost, Rhododendron, Master gardeners

PAL Question:

This is the second year in a row that my rhododendron Blue Peter has flower buds but they are dry and somewhat dark and have no flowers at all. These buds are easy to deadhead. Can you help me salvage this rhododendron, which is very old, and beautiful when it blooms?

View Answer:

In order to get an accurate diagnosis you will need to take a sample of your plant (including both healthy and affected parts if possible) to a Master Gardener clinic. If they do not know what it is, ask them to send the sample to the pathology laboratory in Puyallup. It is best to go through Master Gardeners first so you will not be charged. If you send the sample yourself there will be a fee.

Meanwhile, several sources mention frost, drought, and "bud-blast" (unlikely in the Pacific Northwest) as potential causes of bud failure. Damaged flower buds and poor bud set: It is always most disappointing when fat, healthy looking flower buds either fail to open at all or only open a percentage of their buds, the rest being black and dead. Some rhododendrons regularly abort some or even all of their buds for no apparent reason. This may be due in some cases to a deficiency, perhaps magnesium, or to drought…reports from various places give mixed results from applying magnesium (usually as Epsom salts)... By far the most usual cause of bud damage is frost. Flower buds are invariably less hardy than the rest of the plant so a really hard winter is sure to cause losses to flower buds. Early autumn frosts can damage buds that are not fully hardened off. This is a very annoying type of damage that may be overlooked and may not be noticed until the buds attempt to open in spring. Rhododendrons vary greatly in their ability to harden up enough to withstand early frost. In areas very prone to spring frosts, it is better to avoid growing plants that always burst into growth at the first sign of spring. Plants that frequently loose their first growth flush (and sometimes even their second) are liable to become stunted and rarely flower.

Source: The Cultivation of Rhododendrons, by P. Cox, 1993, p. 244.

Season Spring
Date 2006-10-26
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Keywords: Cold protection of plants, Frost, Bulbs

PAL Question:

Do the many bulbs that are rising up to 8" out of the ground need to be covered since the forecast has temperatures down to 17 degrees F these next few mornings?

View Answer:

The bulb foliage should be fine as it is. Any flowers, on the other hand will probably turn to mush. If you're feeling protective or nervous you may want to cover up the foliage with burlap, cloth rags, sheets, etc. Once the clouds come back you can remove the protection.

Here is an article on predicting frost from Organic Gardening magazine.

Season Winter
Date 2007-01-11
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Keywords: Cold protection of plants, Frost, Paeonia

PAL Question:

I have two three-year old Tree Peonies - each in a 30-inch pot. Both have buds - what can I do to protect them from the coming freeze - or will they be ok? The pots are way too heavy for me to move. They are sitting on a blacktop driveway margin. I have no dirt to bury the pots into. Do I wrap them? Would bubble wrap work?

The new one I planted Sunday is covered with an inverted pot - will that be enough?

View Answer:

Your peony (Paeonia) buds will probably be fine, but don't take any chances! Protect the pots with bubble wrap and cover the tops with bed sheets or some other cloth. I think the inverted pot over your new plant should be sufficient. Tree Peonies are quite hardy. The frost would be much more damaging if it came in March or April when plants have leafed out.

Here is an article on predicting frost from Organic Gardening magazine.

University of California's Marin Master Gardeners also has useful tips on how to protect plants from damage by low temperatures. Tree peonies are not among the plants most liable to be harmed by the cold.

Season Winter
Date 2007-01-16
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Keywords: Cold protection of plants, Frost, Camellia

PAL Question:

How can I protect my camellia shrubs from very low temperatures?

View Answer:

The website of the International Camellia Society has a discussion of camellias and their cold tolerance, indicating that most spring-blooming Camellia japonica and fall-blooming Camellia sasanqua cultivars will survive a Washington, D.C. winter (zone 7, compared to our zone 8), but there is some concern about extreme cold and drying winds, and sudden drops in temperature (see excerpt below on winter protection, from the University of Georgia Cooperative Extension Service):

Winter Protection

“Covering a camellia plant provides frost protection but does little good in a severe freeze. If plants are covered with cloth, plastic or paper, prop up the cover so that it does not touch the buds. Put the cover on after the sun goes down and remove it before mid-morning the next day.

There are additional approaches to providing winter protection against plant damage. Maintain good soil moisture, especially just before freezes. Maintain adequate nutrition by following current fertilizer recommendations. Plant in locations that provide moderate winter shade. Select varieties with good winter hardiness.”

The article below from the North Carolina State University Extension has a good general discussion of winter protection for evergreens such as camellias.

Season Winter
Date 2007-01-16
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Keywords: Shrubs--Wounds and injuries, Effect of storms, Arbutus unedo, Frost

PAL Question:

I live in Monroe (Zone 7). Two years ago I planted 3 Arbutus 'Compacta'. I have never pruned them. This year they took the cold winter pretty hard: over half of the leaves are golden/brown/black, with some already falling off. Will the leaves be replaced or do I need to cut the branches and stems to those leaves and hope for the best? The tree/shrubs are in well-drained soil, mulched, facing south/southwest. The leaves hurt the worst were on the upper and north facing side.

View Answer:

It sounds like you are seeing winter damage on your plant. You should probably wait and see if the plant returns to more robust health, and to see if new growth develops where those leaves have dropped before deciding whether to prune it at all. The local web site Great Plant Picks indicates that Arbutus unedo 'Compacta' can be cold-sensitive. Arbutus unedo 'Compacta' tolerates a wide variety of soil conditions. It grows best in part or full sun and is drought tolerant once established. There are few insect and disease problems, though it can occasionally get aphids and there may be fungal spotting on older leaves if grown in very poor soil. Foliage and flowers may be damaged in extremely cold winters. If you think that there is something else going on besides winter injury, I would recommend taking a sample to a Master Gardener Clinic for diagnosis.

Below is information on winter injury from Washington State Extension and the Pacific Northwest Plant Disease Management Handbook.

Season All Season
Date 2007-04-13
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Keywords: Frost, Seeds

PAL Question:

This year is my first in a house with a yard. I'm very excited to try my hand at growing some food this year. Many of my seed packets say to plant after the last frost or when the soil reaches certain temperatures. Having never planted anything at the beginning of a season before, I have no idea when any of these temperatures happen around here! Can someone give me some temperatures and approximate times when they are normally reached?

View Answer:

The last frost date in Seattle can be as early as March 22, but to be on the safe side, April 15-20 would be more definitive. This information can also be found on the web site of local gardening expert, Ed Hume. The web site also provides further details. Excerpt:
" The last frost date for an area is the last day in the spring that you could have a frost. The average last frost day is the date on which in half of the previous years the last frost had already occurred (so about half of the time it will not frost again and it will be safe to plant tender plants). Most planting directions are based on the average last frost date. The calendar based directions I give (Now it is time to... etc.) are usually based on an average last frost date of April 1st. An important thing to realize about last frost dates is that the actual date of the last frost is different every year. It can be much earlier than the average or much later. This is especially important for tender plants that can be killed by a frost. For hardier plants, the average last frost date is more an indicator of general growing conditions than a danger sign. "

The closer to the water the garden is, the milder the temperatures. The moderating effect of Puget Sound or Lake Washington, for instance, which results in milder winter temperatures, extends inland for some distance. If your garden is more than a mile or so from water, that moderating influence could vary. The last frost date for Vashon Island is April 5; for the Sea-Tac area, April 9. Again, add at least a week and check your own garden temperatures and patterns.

Season Spring
Date 2008-03-15
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Keywords: Failure to flower, Magnolia grandiflora, Frost

PAL Question:

I have a Magnolia grandiflora 'Little Gem' - I've noticed it is not flowering very much any more and when it does produce flower buds, they turn brown and start to die before they have fully bloomed. Can you tell me what causes this and what I can do to keep this from happening. The tree itself seems quite healthy and is growing very well.

View Answer:

There are a number of reasons that plants may fail to flower, and it may be difficult to pinpoint precisely why for your Magnolia grandiflora.

If this is a newly planted Magnolia, it may be too young to flower. Magnolias are somewhat notorious for being slow to flower.

Sometimes, cold temperatures kill off flower buds. This could cause bud browning and failure to flower. Magnolias can be quite sensitive to cold temperatures and to wind, in particular (see the picture of another Magnolia species with frost damaged flowers here In some cases, frost damage can be severe enough that the flower buds die entirely.

There is a chance that the M. grandiflora's failure to flower could be related to fertilizers, as well [source: This Old House website]. Making more phosphorus and micronutrients available to the tree, or avoiding adding nitrogen, can help balance this out. Rankin's book says that a Magnolia which is mulched once or twice a year does not need supplemental fertilizer, and adding it can encourage excessive vegetative growth at the expense of flowers. When there is a high quantity of nitrogen, plants tend to grow leaves rather than flowers. For example, flowering trees planted in lawns that are heavily fertilized with nitrogen may flower much less or not at all.

Finally, M. grandiflora tends to need a fair amount of sun in order to blossom. On one gardening web page, I found an anecdote where the author talks about a M. grandiflora tree they own, half of which is shaded and flowerless, and the other half of which gets sun and flowers profusely. According to Magnolias: A Care Manual by Graham Rankin (Laurel Glen, 1999), any Magnolia planted in heavy shade will flower very weakly at best.

Season All Season
Date 2008-05-28
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Keywords: Cold protection of plants, Frost

PAL Question:

I have some newly planted small shrubs and trees which are now in 3 inches of hard frozen snow. Everything was mulched well before it snowed. Yesterday I covered the plants with large inverted plastic pots, sheets, rice bags, and whatever I had at hand. The plants that are completely under pots will get no light. Can they stay in the dark through this entire cold snap (a week to ten days)? I'm not worried they will overheat under the pots, with the sun so low in the sky, and the temperatures so cold, but should I be concerned with lack of light?

View Answer:

I have some personal experience with using just such pots to protect perennials, leaving the pots in place (and the plants in the dark) for a week or more. I would expect your plants to be fine. They will not overheat, though drainage holes help with air circulation. Sheets and rice or burlap bags are fine as well, though the weight of snow (in addition to the cold) can damage or break plants. You might want to check the status of the covers if more snow falls. In addition, your mulching will help protect the roots. If the shrubs and trees are deciduous, they do not photosynthesize in the winter (low light and low moisture levels serve as the limiting factors, in general), so your plants will not suffer from the dark environment in the short term. If the trees and shrubs are evergreen, they do photosynthesize in the winter, but the process is subject to the same limitations mentioned above. Again, no worries in the short term--frost can cause more damage to most plants than a few days in the dark.

Once temperatures are above freezing (32 degrees F or 0 degrees C)--and don't forget to consider nighttime temperatures--you can uncover the plants. Usually our cold weather doesn't last too long, so I think you can adopt the philosophy "better safe than sorry" and leave the pots in place until you are sure the cold weather has passed.

Below are some helpful links for additional information about predicting frost and protecting your plants:

Season Winter
Date 2008-12-17
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Keywords: Frost, Cold protection of plants

Garden Tool: Seattle's average last frost date is April 20, but with signs of the garden coming to life all around us it's tempting to ignore that distant date. With a little knowledge a gardener can predict frost and take measures to temporarily protect tender plants. If the sky is clear and the wind is blowing from the northwest, get ready to take action. One simple technique is covering a tender plant with an old sheet. For more frost prediction signs and protection tips go online to A Gardener's Guide to Frost

Season: Winter
Date: 2007-04-03
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Keywords: Recycling (Waste, etc.), Frost, Cold protection of plants, Christmas trees, Attracting wildlife

Garden Tool: Before you send your Christmas tree away to be chipped for mulch, consider how the tree can be used in your own garden. Cut the branches off the main trunk to place around plants or emerging bulbs that could use extra frost protection. The main trunk could then be used as a stout stake for annual vines planted in the spring. Another idea is to use it as a temporary bird feeding station. Tie on orange slices, suet balls, peanut butter and birdseed smeared pine cones and then stand back and watch the feeding frenzy.

Season: All Season
Date: 2005-10-21
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June 24 2013 12:55:25