Q & A: Vegetable seeds and early crops

Every Thursday from 1:00-1:30 join us for Ask a Virtual Master Gardener. Thanks to everyone who participated in this week’s call. Here’s a summary of some of the key discussion topics.

When to plant

Predicted last frost date for this year: April 21 to 30

Soil temperature for early crops

Check soil temperature before planting early crops using a soil thermometer.

  • 5º to 10º C for cold hardy crops.
  • at least 10º C for semi-hardy crops

If crops are planted too early the seeds may rot.

(Good quality thermometers are available online. Get one with a stainless steel stem.)

Cold hardy crops for Kingston area

Mid-March start seeds indoors: peas, lettuce, turnips, mustard greens and spinach. Harden off for a week then plant outside the second week of April.

First week of April: planted directly outdoors arugula & watercress

Use good quality regionally grown seed

Use good quality seed – Ideally regionally grown so that it is locally adapted. Certified organic…these are grown without pesticides or herbicides and are often open pollinated varieties which means you can save the seed. Local sources are online: Kitchen Table Seed House (Wolfe Island)

Greta’s Organic Gardens (Ottawa) and Hawthorn Farm Organic Seeds (Palmerston)

Hardening off seedlings

When seedlings are 1 to 2 inches tall, harden off for a week – gradually expose to the outdoors.

Soil care over the winter

Never leave the soil bare. Plant cover crops in late summer/early fall for winter cover, like rye, clover, buckwheat, winter peas and tillage radish. Peas are beneficial to the soil as they help to fix nitrogen. Radishes have deep taproots so they loosen up the soil. All crops add organic matter to the soil if they are not removed. Straw can also be used to cover the ground in the winter, and moved aside as the weather changes to warm the soil more quickly in spring.

Note, pea sprouts and radishes can be eaten – a winter “salad” !

A no-till method used when planting retains organic matter and beneficial soil organisms.

Questions were also asked about specific crops/methods – some key points


Potatoes are a great starter plant. Just clear a 1m by 2m area in full sun for 2kg organic seed potatoes (try https://www.seedpotatoes.ca/ for online or Quattrochi’s (not organic) and plant any time now until mid-June for a 20kg yield… great fun and good value.

Get organic seed potatoes and then you can save some for planting the next year (select only your best ones to save for planting out next year, about the size of a golf ball to lemon).

Seed potatoes can be planted whole but to stretch out your seed, you can cut each tuber into pieces with 2 to 3 eyes, to grow more plants, but it’s higher risk for rotting once planted.

If you do cut your seed potatoes, place them in the sunshine where they will develop a protective compound called solanine, before planting.

Commercial potatoes are sprayed to reduce sprouting so they won’t grow very well, if at all.

Potatoes can be planted in bags full of decaying leaves. The tubers (potatoes) will grow off the main stem. (A tuber is a part of the stem that stores food for the plant). As the main stem grows, it can be covered with more decaying leaves and further tubers will be produced. (This method is not recommended in rural areas where mice and moles will eat the potatoes. Best to plant them in the soil).

Gardening with straw bales

An old straw bale would be ideal as the straw has gradually decomposed creating rich organic matter. The same principle is at work when using an old bag of leaves. If the straw bale is fresh, holes can be made into the bale and composted manure added to the hole before planting.

Mustard greens

These can be used instead of spinach – can “cut and come again” at least three times before it wants to bolt (go to seed) so let it and collect the seed for planting next year!


Rhubarb is a cold hardy perennial. Despite the variable weather at this time of year, it doesn’t need protection from the cold. The rhubarb plant stores lots of sugar in the root and as the new leaves emerge they also have a high sugar content. This protects them from the frost.

Divide rhubarb once the plant begins to die back in summer. Dividing in spring sets back its growth.


Garlic scapes should be cut to encourage good bulb growth. If not, the plant resources are shared between the bulb and the flower/seeds. Ideally garlic should be planted in the fall and harvested in July. As it is being harvested the best cloves should be saved to plant in the fall.

Growing garlic from seed takes longer (two seasons).

Starting a vegetable garden from scratch

Ideally start small and get to know your vegetable plants (weeds can be an overwhelming pressure in a new garden because they often grow faster than vegetable seeds!)

For a new bed, dig down one shovel depth and turn the sod over. Grass should be face down at the bottom of your cleared space. Cover the area with cardboard /newspaper and wet. Then add compost and plant, mulch and water as needed.

If you plan to plant root vegetables you need to “double dig”.

Smiling Gardener demonstrates how to double dig to prepare soil for root crops


Vegetable gardens need 6 to 8 hours of sun a day. A few possibilities if you only have a few hours of sun are parsley, chives and lettuce.

Recommended Books for the novice vegetable gardener

Thought for the day

Grow it….Don’t mow it 😊

And plant vegetables instead of flowers this year.

Happy gardening!

Reporting by Colette McKinnon, Master Gardener in Training, Rideau 1000 Island Master Gardener April 16th