Early spring is an exciting time in the garden. The greenhouses are full of blooming annuals. The leaves are back on the trees, my apple trees are blooming, the grass is green, and things are growing so it must be time to plant right? It depends. My Facebook feed reminded me that May 3rd six years ago I was shoveling snow. The standard wisdom is to wait until Mother's day to plant frost tender flowers and veggies. That is because our average last frost date is May 9th. However averages, are just that averages. Even though April ended amazingly warm, it looks like the start of May will be unseasonably cold. A late frost is not out of the question at this point, and the overnight temperature Friday night says we could get frost. In the pictures below you will see that five years ago we had to cover our plants on the 20th of May! The next six days the overnight temperatures look cold, we might even get frost. A frost would kill tender plants. Even if it doesn't freeze, warm season plants will still complain this week. We have been running the propane heaters again this week. They really want overnight temps in the 50's or higher. It is not a good week for frost tender vegetables like peppers, tomatoes, eggplant, squash and melons to be outside. Even if a frost doesn't kill them, they will not be happy in these temperatures. So what do you do if you already planted them out in the garden? Don't worry! We've got this covered!
How do I protect frost tender plants?
When the forecast is cold, we take tender plants in pots indoors, (a covered porch or garage is fine) and cover those that are already planted. We have learned through experience that where we are on a slope, the backyard will be colder than the front yard. That means when the forecast is 40 degrees we pretend that it might freeze. We don't want the temperature to unexpectedly dip and cause us to lose the garden plants we worked so hard on. Here are a few tips for covering tender plants during spring cold snaps.
1. Try to create and air pocket to preserve heat from the soil. The air cools down very quickly when the sun goes down, the ground stays warm longer. You want to capture some of that heat and wrap it around your plant. You can buy frost cloths, or I have used blankets, bed sheets and plastic to try to keep the frost off. A bucket turned over on top of a tender plant is usually good for a few degrees of heating. A layer of cloth,covered with a layer of plastic is good insulation too.
2. Don't let the cover touch the leaves. If we get a frost, you will damage leaves that are touching the plastic directly. The cover really isn't the most important part, what you want is to have warm air circulating around the plants. A bucket overturned over small plants works well. For rows of veggies use wire, stakes, or tomato cages to put your covering over. You want something that covers, but doesn't directly touch the plant. This will also keep you from breaking stems or tender leaves.
3. Take the covering off during the day when the warmth returns, and cover again in the afternoon. You can't just put a bucket over your plants all week. They need the light and heat from the sun. The same covering that keeps the heat in will keep the heat out if you leave it on all day. In the mornings after things warm up, take the coverings off and let the plant get the sunshine and let the soil heat. Then in the afternoon when it is still warm, cover everything back up. That way you will capture some of the day's heat to carry them through the night. IF you took your plants indoors, remember to take them back out during the day. A week in the garage with no light would be hard on them.
4. Consider supplemental heat. While we have heaters and fans to keep plants warm in a greenhouse during cold snaps, I wouldn't use a heater and fan for plants already planted in a garden. However if you have individual plants covered with a bucket and you wanted to give yourself a little peace of mind, you could activate a hand or foot warmer or fill a water bottle with hot water and place it inside the bucket as well - just make sure you time it so they are still warm in the coldest hours of the morning. Most of the time when our greenhouse alarms go off it is early morning just before sunrise. That's when it gets really cold. If you have a row of small tender plants covered you could also add a string of non-LED Christmas lights to bump the temperature up a degree or two.
May 20, 2015 - Notice that we wrapped the tomatoes and put unrolled tomato cages over the strawberries and put blankets over them just in case since it was so late in May that they were already loaded with strawberries. The wire kept the blankets from pressing down on the plants and gave them a pocket of air. We took the blankets off as soon as the day warmed up so that they could get sunshine and warmth.
How do I know which plants are frost tender?
Even trees and experienced farmers can be fooled by a warm spring that ends with an unexpected cold snap. My apple trees are in full bloom, and even my grapevines are leafing out. They usually wait to get going until it is safe. However, I lose my apricot blooms every year to a late frost. Lots of the plants we grow originated in warmer climates, and they do not know how to deal with our Midwest weather. They need special care. Basil, tomatoes, peppers, melons, cucumbers, and eggplant will not take the cold. Even if it does not freeze, they will be unhappy in these conditions. They will not grow, they might drop blossoms, their leaves will show stress. They are warm season veggies. Pretend they came from southern California. If it gets down to 45 degrees they are thinking, "where is my winter jacket? Do you want me to freeze to death?"
If you can wait to plant them, wait until the overnight temperatures are in in 50's. If they are already planted, help them out on cold nights with a covering.
Some plants are more hardy. We hit 60 degrees and they break out in shorts because they think it is so warm. My snow peas literally grew through our last spring snow. So did my onions garlic, parsley, and thyme. Oregano is hardy, tarragon can take some cold. Strawberries like the cool spring weather. Chives show up in my garden early and don't mind the cold. Rhubarb, kale, chard, spinach, beets, carrots, cabbage and celery will not flinch in the cool spring weather. They like it. Lettuce likes it cool too. Unless we get down to freezing temps these plants will be fine, and most of them will stand a light frost just fine. I won't worry about them this week.
Do I have wait for Mother's Day?
“When should I plant my tomatoes?” A common answer in central Iowa is “any time after Mother’s Day”. But does that rule of thumb still apply this year? The best planting time for tomatoes depends on your weather conditions, but here are a few guidelines that can help you decide when to plant regardless of where you live.
The first thing to understand about planting tomatoes (and peppers, eggplants, melons, and squash) is that they are warm weather plants. Tomatoes will not grow in temperatures below 50 F. The first sign that it is warm enough to plant is the night time temperature stays consistently above 50 F. The ten-day weather forecast for my town in central Iowa indicates we won’t reach those temperatures in the next 10 days.
Why should I care about the soil temperature?
The second thing to consider is the temperature of the soil about 4" deep. Ideally, tomatoes should be planted when the soil temperature is at least 60 F in the early morning. You can use a soil thermometer, a kitchen thermometer, or just stick your finger in the soil for a minute and see if it feels cold (if it feels uncomfortably cold it is probably below 60 F). So far this year, even the maximum temperature at the closest station taking soil temperatures hasn’t reached 60 F.
Why should I care about the weather forecast?
The third thing to consider is the weather forecast. Even if there have been a few warm days and nights and the soil temperature warms to 60 F, a forecast for significant cold weather indicates it may be better to wait to plant until warmer temperatures are in the forecast.
What about this year?
So where does my garden in central Iowa stand on these 3 considerations? Our night time low temperatures this week have been in the upper 40's most nights. The soil temperature in my west-facing raised garden beds this morning has warmed, but the night time lows in the 10-day forecast has a mix of 40's and 50's. All of that suggests I should wait another week or two, which puts us pretty close to….Mother’s Day.
What about Peppers, Eggplants, Squash and Melons?
If you are like us, tomatoes are not the only type of plant we like to grow. We also grow peppers, eggplant, squash, and melons. Add 10 degrees to all of the tomato temperatures above when deciding when to plant peppers, eggplant, squash, and melons. Cool season plants like peas, potatoes, onions, celery, kale, carrots, broccoli, and cabbage can be planted now if not already done.
If you haven’t purchased tomato, pepper, strawberries, herbs, or squash plants yet, check out our plant sale page at https://www.iowabackyardfarmer.org/springplantsale.html
Don't let the pretty flowers and greening grass fool you, early spring is a rollercoaster event. There are unexpected freezes, snow, rain, and ice. There are sunny warm and windy days too. We keep what I affectionately call "farm hours" this time of year. Farm hours is that time of year where you work not until quitting time, but until the job gets done. Usually there is more work to do than can reasonably fit in a 24 hour period. I'm unusually grateful for a long hot shower after a hard day in the dirt. Steven gets up many nights in April somewhere between 1-2 am to start or restart the propane heaters in the greenhouses. It has been a challenging week. The high winds earlier this week made us rethink the structure of the in-the-garden greenhouse. The design was for a mythical somewhere that never gets wind at more than 10 mph. We ended up needing to frame everything in and screw everything down to keep the greenhouse from flying away.
The propane tanks needed to be filled, but the store we get propane from was having problems of their own. Already short on propane, we found that we were also down our newest heater which stopped lighting as well as and propane hose when the thermal safety bushing cracked and fell off. We made do with some electric heaters for one night, but they tripped a breaker at 2:30 am and it took Steven some time to get everything back on and warm. He bought another propane heater yesterday, and the forecast has warmed so that we haven't needed propane for a few nights, but we always have to stay alert.
I get the daytime hours. Temperatures that get too low at night switch to temperatures that can get too high during the day. A nice sunny 60 degree day can turn into a 100 degree oven in the greenhouse. I watch the thermostats, opening and closing windows and doors, trying to keep everything at a happy temperature. With plants stuffed into the aisles and under the lights downstairs, and strawberries everywhere, it takes some care to make sure all the plants get the attention they need. The plants however, are blissfully unaware of all the drama. They keep growing confident that we have everything under control. They are growing at an accelerating pace and will be ready for pick up as early as Friday.
I can hear you thinking that this all sounds like work - long hours, sleepless nights, dirt everywhere. We have reached a point in our spring projects where even we start to ask ourselves if this is all worth it. Don't worry, it is. But I think it's important to remember that everything that is good and worthwhile to do has moments where you have to struggle. For example, my girls set goals to get up and exercise early, so yesterday they did a Jillian Michael's workout. I love hearing her give encouragement at that moment of fatigue where you are thinking of stopping. It's almost like she can tell exactly where you are thinking of quitting. Cheerfully, but firmly she encouraged them to the end of the workout, where she congratulated them on a job well done and promised that if they were diligent and worked hard amazing things would happen.
I am a big fan of hard work, but sometimes even diligent effort is not enough. A pair of young robins built a nest under my deck again this year. I try to tell them that it is not a successful spot, but they are undeterred. The wind caught their nest and it crashed to the ground eggs and all. They will build again, this time in a more secure place. Where you build your nest matters. It is discouraging to do all that hard work only to find that a small wind can dislodge everything you worked on.
Gardening is like nest building, What seems like a reasonably straightforward task has many details that if not attended to can lead to disaster. Here are some common April garden mistakes. If you can avoid these, your chances of success and enjoyment in gardening go way up!
1. Planting too early. Everyone is anxious to get growing in the spring. With the pandemic we have seen a big increase in people interested in growing their own food. Planting as soon as possible seems like the fastest way to food. Our average last frost date in central Iowa is around April 26th, but the "safe time" where you are very unlikely to see another frost for the season is closer to May 9th. Even if it doesn't freeze again this year, peppers and tomatoes and squash really do not like to grow at temperatures less than 55 degrees, and they don't have jackets to put on when they feel cold. The old wisdom is to wait until Mother's Day to plant warm season vegetables like tomatoes and peppers. This year Mother's day is May 10th, that's a great time to plant. The weather this year looks like it will be warm between now and then, but be ready to cover tender crops if you put them out early and the temperature drops. Add 10 degrees of heat for squash and melons eggplant and other warm season plants. They like to be warm. There is plenty of time for everything you want to grow there is no worry at this point. Remember that daytime temps are nice, but your plants are sleeping outside all night. Look for a good forecast where the overnight temperatures stay over 50 degrees at night and there is not too much rain. Read "Can I Plant Tomatoes and Peppers Now?" for more details.
2. Knowing what to start from seed and what to buy as plants. When you buy tomato, herb and pepper, and onion seedlings to plant in your garden, what you are really buying is time. Yes, you can start them from seed May 10th, but you will be a good two months behind my seedlings that I planted in March. To maximize the amount of food we get from the garden, I always start these seeds early inside or buy them. Rosemary can take more than 200 days to grow from seed to harvest. We only have about 160 frost free days here. I always buy a plant. On the other hand, lettuce, peas, carrots, beets, and beans, either do not like being transplanted or grow quickly from seeds. Can you transplant them, yes, does it save you money or time, not really. Things like squash and melons fall into a grey area. They are easy enough to start from seeds, but getting a little jump on the season is nice as you can get a harvest before the insects try to take over, and getting a headstart on long season melons like watermelons is nice too. If you are on a tight budget, save your money for those plants that take the longest to grow, or that will give you a much bigger harvest if planted early. That would be peppers, tomatoes, onions, and some herbs. Some herbs like tarragon, thyme, chives, sage, and oregano are perennial here, so you can plant them once and have them come back next year.
3. Starting seeds indoors too early or too late without enough light. Lots of people want to know if it is too late to start seeds now. That depends on your goals and your budget. Ideally things like peppers and tomatoes would be started 6-8 weeks before the last frost. That is about the middle of March. We start ours a little earlier because I have a great set up and greenhouses, and I really like being able to eat fresh ripe tomatoes at the end June instead of the beginning of August. Starting them now is better than later, but you'll be even further ahead to buy a plant that was started a month ago. I see lots of pictures of sad spindly seedlings grown inside by anxious gardeners. You need lots of light to start seeds well. Without light and heat, and a breeze, seeds will grow tall and thin reaching for light they can't find, and the damp soil is prone to molding without good airflow. It is discouraging, and these etiolated plants have a hard time transplanting outdoors. Don't give up! Starting seeds is a very good thing, but to do it well, you need enough time, good light, heat, and airflow. If you don't have the setup for that and haven't started yet this year, just buy good tomato and pepper starts and plant the rest as seeds. For more tips on starting seeds read seedling-starting-strategies.html on our blog.
4. Growing stuff your family won't eat. I love to try new things. I like variety. My family is not that adventurous. We recently did a minimal spending pantry challenge. One of the things that I learned is that we didn't eat stuff we don't like. Not even when it was all our budget offered. During a time of stress kids don't like to try new foods. Parents don't either. I know that the pictures of full gardens look amazing. The colors and shapes. Harvest bounty is amazing. But if you have limited time, space, money, or energy, focus on what your family likes. Don't feel obligated to grow tomatoes just because everyone else does if your family won't eat them. There are hundreds of other options.
5. New garden troubles. If you are new to gardening this year, you might not even have a garden space picked out or prepared. Here is my advice. Pick a good sunny fairly level spot that is not in the low spot of your yard where it floods when it rains. You don't need fancy or expensive garden boxes. Our first garden was just a patch of dirt. That gets muddy, but it works. We used upcycled deck boards that we got free off Craigslist for another garden. That worked too, but we could have used some topsoil or compost. In the community garden we just have a 10x15 plot of land that we rake up into raised soil beds. In our formal garden now we have blocks. Things we have learned. Raised garden beds work best here in Iowa where we get lots of rain. Compost is great and inexpensive. We can get a ton (literally) of compost from the Metro Waste Authority at the landfill for $10. Before we had a trailer, we just rented one from Uhaul. We also have gotten topsoil from Terry's Services. You can pick it up, or he can deliver it. He's busy, so plan ahead and watch the weather. Wet soil is too heavy to haul. We used to rip up all the grass with a rototiller, but you really don't need to. Just lay down a nice thick overlapping layer of cardboard where you want the garden, and then put the topsoil and compost over that. If you are in a hurry, you can spray the grass with Roundup wait a few days, and then cover with cardboard to speed up the process. The cardboard blocks light from the grass, and eventually just composts with the grass into the soil. Ideally you would do this in the fall so the grass would have time to break down, but I'll be making new first year garden beds to plant in this year as soon as the greenhouses come down. We'll try to put 8-12 inches of compost mixed with topsoil down where we plant to plant. It will work just fine. There is plenty of time.
6. Don't Give Up! Just like my young robin friends, you will probably have some setbacks. We still have troubles every year. Not enough rain, too much rain, rabbits, insects, hail, a pet dog who loves to sleep in the strawberries like my Sam did. There are too many possibilities to list. When one of these setbacks come to you, have your moment, but keep going! Remember to do the small things. Great things can happen with such small efforts. Be out in your garden for a few minutes each day. Pick weeds early and often, water regularly. The great thing about gardening is that living things want to grow! They will give you 100% effort every time. The sun provides all the light and heat you need, and there is plenty of fresh air outside, so growing outside is not nearly as hard as growing inside plants. Here is central Iowa we usually get a nice amount of rain too. You can do this! Just do the very best you can each day to do the basic things, and you will find in time that these small and simple things, combined with daily effort bring a very rewarding harvest. You will be amazed at what you can accomplish! Let's get growing!