Indoor Oak seedlings when to plant outside


I have been successful at planting 20 acorns from two different oak tree I starting in September collecting acorns refrigerated then until November where I transplanted after germinating I now have 20 plants ranging from 4 to 12 inches

All in 12 “ sleeves

When should I place them in the ground it’s now January 2024


Dear Gardener

Thank you for contacting Toronto Master Gardeners about the ongoing care of your oak (botanical name – Quersus sp) saplings. From the photo of your well-grown saplings, it is not possible to accurately identify the species you are growing. In Ontario, there are 11 native oak species. Oaks are a great choice since they are a keystone species supporting many living organisms, e.g. oaks are host plants for 436 caterpillar species. That your saplings are in 30 cm (12 inch) sleeves and that oaks are rapid growers with deep tap roots, you might consider repotting in larger diameter square deep grower’s pots as needed to promote healthy growth. With your LED lighting set-up, it is difficult to accurately determine the colour of your sapling’s leaves, but the colour of a few might suggest a nitrogen deficit. Perhaps assessing these in daylight would give a more accurate assessment than can be determined from your photo.

The optimum times for planting out seedlings is early spring and early fall. Since it is now winter and the seedlings are actively growing and not dormant, they will need to continue to be grown indoors until the weather warms up. Continue careful watering with ½ strength all-purpose fertilizer to ensure health while observing for deficiencies. To promote optimum nutrient uptake, you may also wish to adjust the pH of the water to 4.5-7.

After the last frost (average last frost date in Toronto – May 4/24), these can be moved outdoors into a sheltered location to acclimatize for 4-6 weeks before planting in the ground. Gradually harden off saplings before full sun exposure. Select suitable sites, and dig holes about three times the diameter and the same depth of the containers. Backfill the holes with the soil, which was excavated from digging the hole, and spread a 5 to 8 cm deep layer  of organic mulch not closer than 5 cm from the trunk and outward around the sapling  for about 60 cm. Since wildlife love feeding on oak seedlings, protect the saplings with a mesh tree guard for at least three years.

For further information on:

– on ongoing sapling care, please see How to handle my oak saplings

– planting your oak saplings, please see the Gardening Guide: Planting a Tree for Life

– identifying oak species, see Oaks Group and Growing Trees in Eastern Ontario and West Quebec

Wishing you much success with your oak saplings!