I am starting a new theme for the month of May covering garden tasks that need to happen this month. There is a lot going on in the month of May for most gardeners in the northern hemisphere. Here in Denver we reach our last frost date, over night temps start to reach the sweet spot to transplant tomatoes and we transition into the warm season with highs averaging 72-73°F. Warm season temperatures are between 65°F to 85°F (18.3°C to 29.4°C). We average about 6 days of rain in May. 

Some garden tasks we have to do this month include adding soil amendments to your raised beds if you didn’t add any at the end of the previous season. You can add aged compost, finished manure, worm castings, etc. If you haven’t already wash and prep all containers for growing and add new soil specific to container growing to your containers.

What To Direct Sow In May In Denver (zone 5b)

• Beets
• Lettuces
• Radishes
• Anise
• Chervil
• Cilantro
• Dill
• Basil 
• Cucumbers 
• Squash
• Melons
• Arugula
• Okra
• Bush beans
• Pole beans
• Summer savory
• Potatoes
• Carrots
• Corn
• Mustard greens
• Chard
• Brussels sprouts 
• Cauliflower 
• Cabbage 
• Rutabaga 
• Turnips
• General leafy greens
• Bok choy
• Tatsoi 
• Edible flowers
• Chives
• Any herbs that are easy to grow from seed *purchase starts for herbs like sage, thyme, etc because they can be tricky or take a long time to establish. 

What To Transplant In May In Denver (zone 5b)

You can purchase any of the above listed vegetables, fruits and herbs as “starts” and transplant them into the garden. Some will transplant better than others. Always be careful with cucumbers and squash and anything that has a tap root, they prefer direct sowing. For any warm weather fruit, vegetable and herb wait until night time temperatures are consistently 55°F and above or cover at night with frost cloth or another protective heat saving barrier. Cooler night time temperatures can stunt the growth of warm weather plants and may lead to them not maturing. Herbs and other plants that take a long time to mature optimally should be started well before the last frost date so they are a good size when temperatures are right for them to be added to the garden. This will help you harvest sooner or at all. Peppers and tomatoes are two food crops that I always suggest that you either start from seed on your own or purchase from a reliable organically grown source to get a head start on in the garden. I have grown both from seed straight in the garden vs transplanting, while hey both grow fine, I could have been able to harvest much more when using transplants. With that said here is a list of what to transplant in May:

• Tomatoes
• Peppers
• Herbs
• Edible flowers
• Kohlrabi
• Chard
• Cucumbers
• Celery

Now is the time to start daily checks for garden pests and nipping weeds as soon as you see any. (You can do this every 3-4 days if needed, but I prefer daily garden walks.) If you intensively plant, weeds should not be an issue, especially in raised beds. It is better to attack weeds now while they are small and their roots are not well established. If you are not intensively planting adding mulch to your garden is recommended. I prefer to intensively plant to get the most out of my growing spaces. You can fill in any bare areas around kales and cabbages or other larger and longer plants with fast growing plants like radishes or quick growing beets like the “Early Wonder variety. This helps you get the most you of your space, bu the time you need the room for those bigger plants the quick growing smaller ones will be ready for harvesting. I eat a lot of salads and toss salad seeds of any variety (mostly loose leaf) in bare areas too. I treat them almost like a cover crop, except I harvest from them daily.

Other garden maintenance includes deeply watering your garden after checking each bed with the finger method. Just stick your finger into the soil and if it comes out dry or almost dry it’s time to water, if it comes out moist you can wait and check again the next day. Colorado weather in May can be all over the place, we may get rain for days and nothing for even longer. It is important to make sure your garden is getting 1 inch of water per week. Especially when establishing new transplants or starting seeds. Seeds need the moisture to germinate, if it is inconsistent the seed may start to germinate them stop growing. Check to make sure your watering method, if not by hand, doesn’t have any leaks, that timers are ready and that you watch the weather for rain. (No need to run the irrigation system if it has rained a bunch.) Make sure that you have some sort of hail protection at the ready! Hail season in Colorado can last from May to July, sometimes August. You can use pretty much anything you can to cover your plants that won’t smush them. I have used sheets, tarps, umbrellas, lightweight blankets, tables, etc. I now leave my hoops ups and have my thick frost cloth and sheets on stand by. I always check the weather and make sure everything is prepped just in case. (I have lost so many plants over the years to freak hailstorms.)

This is a short overview of somethings we need to do or start in May. There are many, many garden tasks in May and each week I plan to go over different ones with you to follow along with me in the garden. 

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