The beginning of June brings better gardening weather, what a welcome change!  Although it’s been a bit dry for Vermont spring, recent rains have created a great time to get some plants into their outdoor homes for the summer.  Broccoli, cauliflower, cabbage, onions, and more salad greens can move out now but it’s still a little early for heat loving plants like basil, tomatoes, beans, cucumbers, squash, okra, & peppers.  Annual flowers like geraniums, petunias, marigolds, nasturtiums, and sweet peas will do well outside now.  Some adventuresome gardeners have already planted out their tomatoes and they might do well, but cool nights will stunt growth so I’ll wait just a little longer.  Transplanting into the garden is a major change for plants and taking some care to minimize the trauma will help plants get through transplant shock smoother and carry on with their growth.

Whether you grow your own seedlings (Congratulations!) or buy your garden plants, they will need some preparation for the transition out to the “real world”.  There are big differences between the comfortable indoors (house or greenhouse) and the tough world outside and plants need a little help to adapt to those harder conditions outside.  This process is called “hardening off” and it is easy if you follow a few basic steps. 

Hardening off is a necessary transition for plants because they have to adapt to multiple environmental factors at once.  In addition to getting direct sunlight outside vs through a window or from artificial lights, they also are dealing with new temperature swings (day to night), wind stress (flexing & dehydration), and varying moisture levels.  The best approach is to make sure plants have some time to get used to the different conditions. Think of a pale Vermonter hitting a tropical beach for all day in the sun, Ouch!

Depending on how you raised the plants indoors and the species, most plants do best with a gradual transition over 10-14 days.  Start by putting them outside on warmer, cloudy days (or in a shady spot) for 2, 4, 6, and then 8 hours per day.  After 4-5 days of this they can be placed in direct sunlight for about 4 hours per day for a 2-4 days and then full sun all day and overnight for a couple days before transplanting.  Keep them moist and protected from strong winds.  Here is a good video on hardening off plants at  https://www.almanac.com/video/how-harden-plants

All this is under optimal circumstances, assuming you have the time.  This is just a target to shoot for, few people will actually do the whole transition perfectly so do what you can.  Remember too, there is little advantage to getting plants out at the earliest possible date, so a delayed transplant is probably better to minimize transplant shock.  Previous articles on “When To Plant” provide some guidelines.

Before transplanting begins get your soil is ready.  That does not mean rototilling or turning of soil is needed, or even desirable, it is not.  It does mean the soil should be drained and as weed-free as possible.  You’ll never be 100% weed-free so stop trying!  Some gentle soil loosening and removing spring weeds to reduce the competition for space, water, nutrients, and sunshine.  I use a broad fork on raised beds which doesn’t turn the soil upside down (bad idea) but gently loosens it up without destroying important soil structure.  A basic garden fork will also work well, without turning the soil over.  Spring is also a good time to work in some mature compost (not fresh manure) to add organic matter and nutrients.  Compost is “mature” when you can no longer recognize the original ingredients or it’s full of earthworms.  The preferable time of day for transplanting is usually late afternoon (after 4 pm) on a calm day (wind dries your plants just as well as your laundry!) or on very cloudy days to reduce dehydration. 

A recent study has revealed that many commercial composts contain high levels of toxic PFAS chemicals and should not be applied to home gardens or lawns.  The particular composts all were made from sewage sludge or “biosolids” and sold at stores including Home Depot, Ace Hardware, and Walmart.  Check the labels and avoid these!

Plants are best transplanted in the ground at the same depth as they were in their containers with the except of tomatoes (they go in deeper).  Generally, no fertilizer should go in the planting hole but I do like to put in a small amount (1-2 Tbs/plant) of Phosphate (rock or colloidal phosphate, bone meal, bone char, etc.) since this is the one nutrient that does not move down through the soil to the roots when applied on the surface.  Phosphate is slow release and will help young roots grow. 

Once your plants are in the ground, they’ll need plenty of watering immediately and for a few days or more afterwards until they become established and growing.  This is a great time to offer them some liquid food in the form of fish emulsion in their water.  It’s organic and will release gradually so the plants can take it in over time.  Also, the fishy smell will repel deer and rabbits if that is a concern.  If we get warm sunny weather some shade during the day would be good too. (Think sunscreen)  I use Agribon-19 row cover held up with wire hoops or ½ inch PVC pipe to allow some air flow but it does block the direct sun on tender leaves until they are growing strongly.  Anchored cardboard propped up over plants during mid-day will also do the trick. 

Transplanting is complete after some protection is provided against hungry critters that love those tender new plants.  I have voles (field mice) that can devour a whole row overnight so I sprinkle generous amounts of MoleMax (Bonide), a castor bean repellent, along the rows and it seems to keep them away, mostly.  Also recommended for deer, rabbits, and voles are products like Shake-Away (mint, rosemary, & cedar), and Plantskydd (blood meal) as repellents that are accepted as legally Organic.  The row cover used for shade also hides plantings from deer and insect pests so provides a double benefit.  Of course, full protection with a combination barrier & electric fence is best, but that will be another topic.

There will usually be a few plant failures, it’s hard to get 100% success with anything, so I like to keep a couple spares on reserve to replace those that go missing.  It’s nice to have a full row or bed growing.  Finally, since the soil is not fully warmed yet, it is too early to apply any organic mulch just yet.  That will come in mid-June to provide weed suppression, moisture retention, and soil building. 

What experiences have you had with hardening plants?  Do you have your own tricks for transplanting to share?  Please put them in the Comments below.